avfilter/vf_idet: add a "half_life" option for statistics

[ffmpeg.git] / doc / filters.texi

@chapter Filtering Introduction
@c man begin FILTERING INTRODUCTION

Filtering in FFmpeg is enabled through the libavfilter library.

In libavfilter, a filter can have multiple inputs and multiple
outputs.
To illustrate the sorts of things that are possible, we consider the
following filtergraph.

@example
                [main]
input --> split ---------------------> overlay --> output
            |                             ^
            |[tmp]                  [flip]|
            +-----> crop --> vflip -------+
@end example

This filtergraph splits the input stream in two streams, then sends one
stream through the crop filter and the vflip filter, before merging it
back with the other stream by overlaying it on top. You can use the
following command to achieve this:

@example
ffmpeg -i INPUT -vf "split [main][tmp]; [tmp] crop=iw:ih/2:0:0, vflip [flip]; [main][flip] overlay=0:H/2" OUTPUT
@end example

The result will be that the top half of the video is mirrored
onto the bottom half of the output video.

Filters in the same linear chain are separated by commas, and distinct
linear chains of filters are separated by semicolons. In our example,
@var{crop,vflip} are in one linear chain, @var{split} and
@var{overlay} are separately in another. The points where the linear
chains join are labelled by names enclosed in square brackets. In the
example, the split filter generates two outputs that are associated to
the labels @var{[main]} and @var{[tmp]}.

The stream sent to the second output of @var{split}, labelled as
@var{[tmp]}, is processed through the @var{crop} filter, which crops
away the lower half part of the video, and then vertically flipped. The
@var{overlay} filter takes in input the first unchanged output of the
split filter (which was labelled as @var{[main]}), and overlay on its
lower half the output generated by the @var{crop,vflip} filterchain.

Some filters take in input a list of parameters: they are specified
after the filter name and an equal sign, and are separated from each other
by a colon.

There exist so-called @var{source filters} that do not have an
audio/video input, and @var{sink filters} that will not have audio/video
output.

@c man end FILTERING INTRODUCTION

@chapter graph2dot
@c man begin GRAPH2DOT

The @file{graph2dot} program included in the FFmpeg @file{tools}
directory can be used to parse a filtergraph description and issue a
corresponding textual representation in the dot language.

Invoke the command:
@example
graph2dot -h
@end example

to see how to use @file{graph2dot}.

You can then pass the dot description to the @file{dot} program (from
the graphviz suite of programs) and obtain a graphical representation
of the filtergraph.

For example the sequence of commands:
@example
echo @var{GRAPH_DESCRIPTION} | \
tools/graph2dot -o graph.tmp && \
dot -Tpng graph.tmp -o graph.png && \
display graph.png
@end example

can be used to create and display an image representing the graph
described by the @var{GRAPH_DESCRIPTION} string. Note that this string must be
a complete self-contained graph, with its inputs and outputs explicitly defined.
For example if your command line is of the form:
@example
ffmpeg -i infile -vf scale=640:360 outfile
@end example
your @var{GRAPH_DESCRIPTION} string will need to be of the form:
@example
nullsrc,scale=640:360,nullsink
@end example
you may also need to set the @var{nullsrc} parameters and add a @var{format}
filter in order to simulate a specific input file.

@c man end GRAPH2DOT

@chapter Filtergraph description
@c man begin FILTERGRAPH DESCRIPTION

A filtergraph is a directed graph of connected filters. It can contain
cycles, and there can be multiple links between a pair of
filters. Each link has one input pad on one side connecting it to one
filter from which it takes its input, and one output pad on the other
side connecting it to one filter accepting its output.

Each filter in a filtergraph is an instance of a filter class
registered in the application, which defines the features and the
number of input and output pads of the filter.

A filter with no input pads is called a "source", and a filter with no
output pads is called a "sink".

@anchor{Filtergraph syntax}
@section Filtergraph syntax

A filtergraph has a textual representation, which is
recognized by the @option{-filter}/@option{-vf} and @option{-filter_complex}
options in @command{ffmpeg} and @option{-vf} in @command{ffplay}, and by the
@code{avfilter_graph_parse()}/@code{avfilter_graph_parse2()} functions defined in
@file{libavfilter/avfilter.h}.

A filterchain consists of a sequence of connected filters, each one
connected to the previous one in the sequence. A filterchain is
represented by a list of ","-separated filter descriptions.

A filtergraph consists of a sequence of filterchains. A sequence of
filterchains is represented by a list of ";"-separated filterchain
descriptions.

A filter is represented by a string of the form:
[@var{in_link_1}]...[@var{in_link_N}]@var{filter_name}=@var{arguments}[@var{out_link_1}]...[@var{out_link_M}]

@var{filter_name} is the name of the filter class of which the
described filter is an instance of, and has to be the name of one of
the filter classes registered in the program.
The name of the filter class is optionally followed by a string
"=@var{arguments}".

@var{arguments} is a string which contains the parameters used to
initialize the filter instance. It may have one of two forms:
@itemize

@item
A ':'-separated list of @var{key=value} pairs.

@item
A ':'-separated list of @var{value}. In this case, the keys are assumed to be
the option names in the order they are declared. E.g. the @code{fade} filter
declares three options in this order -- @option{type}, @option{start_frame} and
@option{nb_frames}. Then the parameter list @var{in:0:30} means that the value
@var{in} is assigned to the option @option{type}, @var{0} to
@option{start_frame} and @var{30} to @option{nb_frames}.

@item
A ':'-separated list of mixed direct @var{value} and long @var{key=value}
pairs. The direct @var{value} must precede the @var{key=value} pairs, and
follow the same constraints order of the previous point. The following
@var{key=value} pairs can be set in any preferred order.

@end itemize

If the option value itself is a list of items (e.g. the @code{format} filter
takes a list of pixel formats), the items in the list are usually separated by
'|'.

The list of arguments can be quoted using the character "'" as initial
and ending mark, and the character '\' for escaping the characters
within the quoted text; otherwise the argument string is considered
terminated when the next special character (belonging to the set
"[]=;,") is encountered.

The name and arguments of the filter are optionally preceded and
followed by a list of link labels.
A link label allows one to name a link and associate it to a filter output
or input pad. The preceding labels @var{in_link_1}
... @var{in_link_N}, are associated to the filter input pads,
the following labels @var{out_link_1} ... @var{out_link_M}, are
associated to the output pads.

When two link labels with the same name are found in the
filtergraph, a link between the corresponding input and output pad is
created.

If an output pad is not labelled, it is linked by default to the first
unlabelled input pad of the next filter in the filterchain.
For example in the filterchain
@example
nullsrc, split[L1], [L2]overlay, nullsink
@end example
the split filter instance has two output pads, and the overlay filter
instance two input pads. The first output pad of split is labelled
"L1", the first input pad of overlay is labelled "L2", and the second
output pad of split is linked to the second input pad of overlay,
which are both unlabelled.

In a complete filterchain all the unlabelled filter input and output
pads must be connected. A filtergraph is considered valid if all the
filter input and output pads of all the filterchains are connected.

Libavfilter will automatically insert @ref{scale} filters where format
conversion is required. It is possible to specify swscale flags
for those automatically inserted scalers by prepending
@code{sws_flags=@var{flags};}
to the filtergraph description.

Here is a BNF description of the filtergraph syntax:
@example
@var{NAME}             ::= sequence of alphanumeric characters and '_'
@var{LINKLABEL}        ::= "[" @var{NAME} "]"
@var{LINKLABELS}       ::= @var{LINKLABEL} [@var{LINKLABELS}]
@var{FILTER_ARGUMENTS} ::= sequence of chars (possibly quoted)
@var{FILTER}           ::= [@var{LINKLABELS}] @var{NAME} ["=" @var{FILTER_ARGUMENTS}] [@var{LINKLABELS}]
@var{FILTERCHAIN}      ::= @var{FILTER} [,@var{FILTERCHAIN}]
@var{FILTERGRAPH}      ::= [sws_flags=@var{flags};] @var{FILTERCHAIN} [;@var{FILTERGRAPH}]
@end example

@section Notes on filtergraph escaping

Filtergraph description composition entails several levels of
escaping. See @ref{quoting_and_escaping,,the "Quoting and escaping"
section in the ffmpeg-utils(1) manual,ffmpeg-utils} for more
information about the employed escaping procedure.

A first level escaping affects the content of each filter option
value, which may contain the special character @code{:} used to
separate values, or one of the escaping characters @code{\'}.

A second level escaping affects the whole filter description, which
may contain the escaping characters @code{\'} or the special
characters @code{[],;} used by the filtergraph description.

Finally, when you specify a filtergraph on a shell commandline, you
need to perform a third level escaping for the shell special
characters contained within it.

For example, consider the following string to be embedded in
the @ref{drawtext} filter description @option{text} value:
@example
this is a 'string': may contain one, or more, special characters
@end example

This string contains the @code{'} special escaping character, and the
@code{:} special character, so it needs to be escaped in this way:
@example
text=this is a \'string\'\: may contain one, or more, special characters
@end example

A second level of escaping is required when embedding the filter
description in a filtergraph description, in order to escape all the
filtergraph special characters. Thus the example above becomes:
@example
drawtext=text=this is a \\\'string\\\'\\: may contain one\, or more\, special characters
@end example
(note that in addition to the @code{\'} escaping special characters,
also @code{,} needs to be escaped).

Finally an additional level of escaping is needed when writing the
filtergraph description in a shell command, which depends on the
escaping rules of the adopted shell. For example, assuming that
@code{\} is special and needs to be escaped with another @code{\}, the
previous string will finally result in:
@example
-vf "drawtext=text=this is a \\\\\\'string\\\\\\'\\\\: may contain one\\, or more\\, special characters"
@end example

@chapter Timeline editing

Some filters support a generic @option{enable} option. For the filters
supporting timeline editing, this option can be set to an expression which is
evaluated before sending a frame to the filter. If the evaluation is non-zero,
the filter will be enabled, otherwise the frame will be sent unchanged to the
next filter in the filtergraph.

The expression accepts the following values:
@table @samp
@item t
timestamp expressed in seconds, NAN if the input timestamp is unknown

@item n
sequential number of the input frame, starting from 0

@item pos
the position in the file of the input frame, NAN if unknown

@item w
@item h
width and height of the input frame if video
@end table

Additionally, these filters support an @option{enable} command that can be used
to re-define the expression.

Like any other filtering option, the @option{enable} option follows the same
rules.

For example, to enable a blur filter (@ref{smartblur}) from 10 seconds to 3
minutes, and a @ref{curves} filter starting at 3 seconds:
@example
smartblur = enable='between(t,10,3*60)',
curves    = enable='gte(t,3)' : preset=cross_process
@end example

@c man end FILTERGRAPH DESCRIPTION

@chapter Audio Filters
@c man begin AUDIO FILTERS

When you configure your FFmpeg build, you can disable any of the
existing filters using @code{--disable-filters}.
The configure output will show the audio filters included in your
build.

Below is a description of the currently available audio filters.

@section adelay

Delay one or more audio channels.

Samples in delayed channel are filled with silence.

The filter accepts the following option:

@table @option
@item delays
Set list of delays in milliseconds for each channel separated by '|'.
At least one delay greater than 0 should be provided.
Unused delays will be silently ignored. If number of given delays is
smaller than number of channels all remaining channels will not be delayed.
@end table

@subsection Examples

@itemize
@item
Delay first channel by 1.5 seconds, the third channel by 0.5 seconds and leave
the second channel (and any other channels that may be present) unchanged.
@example
adelay=1500|0|500
@end example
@end itemize

@section aecho

Apply echoing to the input audio.

Echoes are reflected sound and can occur naturally amongst mountains
(and sometimes large buildings) when talking or shouting; digital echo
effects emulate this behaviour and are often used to help fill out the
sound of a single instrument or vocal. The time difference between the
original signal and the reflection is the @code{delay}, and the
loudness of the reflected signal is the @code{decay}.
Multiple echoes can have different delays and decays.

A description of the accepted parameters follows.

@table @option
@item in_gain
Set input gain of reflected signal. Default is @code{0.6}.

@item out_gain
Set output gain of reflected signal. Default is @code{0.3}.

@item delays
Set list of time intervals in milliseconds between original signal and reflections
separated by '|'. Allowed range for each @code{delay} is @code{(0 - 90000.0]}.
Default is @code{1000}.

@item decays
Set list of loudnesses of reflected signals separated by '|'.
Allowed range for each @code{decay} is @code{(0 - 1.0]}.
Default is @code{0.5}.
@end table

@subsection Examples

@itemize
@item
Make it sound as if there are twice as many instruments as are actually playing:
@example
aecho=0.8:0.88:60:0.4
@end example

@item
If delay is very short, then it sound like a (metallic) robot playing music:
@example
aecho=0.8:0.88:6:0.4
@end example

@item
A longer delay will sound like an open air concert in the mountains:
@example
aecho=0.8:0.9:1000:0.3
@end example

@item
Same as above but with one more mountain:
@example
aecho=0.8:0.9:1000|1800:0.3|0.25
@end example
@end itemize

@section aeval

Modify an audio signal according to the specified expressions.

This filter accepts one or more expressions (one for each channel),
which are evaluated and used to modify a corresponding audio signal.

It accepts the following parameters:

@table @option
@item exprs
Set the '|'-separated expressions list for each separate channel. If
the number of input channels is greater than the number of
expressions, the last specified expression is used for the remaining
output channels.

@item channel_layout, c
Set output channel layout. If not specified, the channel layout is
specified by the number of expressions. If set to @samp{same}, it will
use by default the same input channel layout.
@end table

Each expression in @var{exprs} can contain the following constants and functions:

@table @option
@item ch
channel number of the current expression

@item n
number of the evaluated sample, starting from 0

@item s
sample rate

@item t
time of the evaluated sample expressed in seconds

@item nb_in_channels
@item nb_out_channels
input and output number of channels

@item val(CH)
the value of input channel with number @var{CH}
@end table

Note: this filter is slow. For faster processing you should use a
dedicated filter.

@subsection Examples

@itemize
@item
Half volume:
@example
aeval=val(ch)/2:c=same
@end example

@item
Invert phase of the second channel:
@example
aeval=val(0)|-val(1)
@end example
@end itemize

@section afade

Apply fade-in/out effect to input audio.

A description of the accepted parameters follows.

@table @option
@item type, t
Specify the effect type, can be either @code{in} for fade-in, or
@code{out} for a fade-out effect. Default is @code{in}.

@item start_sample, ss
Specify the number of the start sample for starting to apply the fade
effect. Default is 0.

@item nb_samples, ns
Specify the number of samples for which the fade effect has to last. At
the end of the fade-in effect the output audio will have the same
volume as the input audio, at the end of the fade-out transition
the output audio will be silence. Default is 44100.

@item start_time, st
Specify the start time of the fade effect. Default is 0.
The value must be specified as a time duration; see
@ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}
for the accepted syntax.
If set this option is used instead of @var{start_sample}.

@item duration, d
Specify the duration of the fade effect. See
@ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}
for the accepted syntax.
At the end of the fade-in effect the output audio will have the same
volume as the input audio, at the end of the fade-out transition
the output audio will be silence.
By default the duration is determined by @var{nb_samples}.
If set this option is used instead of @var{nb_samples}.

@item curve
Set curve for fade transition.

It accepts the following values:
@table @option
@item tri
select triangular, linear slope (default)
@item qsin
select quarter of sine wave
@item hsin
select half of sine wave
@item esin
select exponential sine wave
@item log
select logarithmic
@item par
select inverted parabola
@item qua
select quadratic
@item cub
select cubic
@item squ
select square root
@item cbr
select cubic root
@end table
@end table

@subsection Examples

@itemize
@item
Fade in first 15 seconds of audio:
@example
afade=t=in:ss=0:d=15
@end example

@item
Fade out last 25 seconds of a 900 seconds audio:
@example
afade=t=out:st=875:d=25
@end example
@end itemize

@anchor{aformat}
@section aformat

Set output format constraints for the input audio. The framework will
negotiate the most appropriate format to minimize conversions.

It accepts the following parameters:
@table @option

@item sample_fmts
A '|'-separated list of requested sample formats.

@item sample_rates
A '|'-separated list of requested sample rates.

@item channel_layouts
A '|'-separated list of requested channel layouts.

See @ref{channel layout syntax,,the Channel Layout section in the ffmpeg-utils(1) manual,ffmpeg-utils}
for the required syntax.
@end table

If a parameter is omitted, all values are allowed.

Force the output to either unsigned 8-bit or signed 16-bit stereo
@example
aformat=sample_fmts=u8|s16:channel_layouts=stereo
@end example

@section allpass

Apply a two-pole all-pass filter with central frequency (in Hz)
@var{frequency}, and filter-width @var{width}.
An all-pass filter changes the audio's frequency to phase relationship
without changing its frequency to amplitude relationship.

The filter accepts the following options:

@table @option
@item frequency, f
Set frequency in Hz.

@item width_type
Set method to specify band-width of filter.
@table @option
@item h
Hz
@item q
Q-Factor
@item o
octave
@item s
slope
@end table

@item width, w
Specify the band-width of a filter in width_type units.
@end table

@section amerge

Merge two or more audio streams into a single multi-channel stream.

The filter accepts the following options:

@table @option

@item inputs
Set the number of inputs. Default is 2.

@end table

If the channel layouts of the inputs are disjoint, and therefore compatible,
the channel layout of the output will be set accordingly and the channels
will be reordered as necessary. If the channel layouts of the inputs are not
disjoint, the output will have all the channels of the first input then all
the channels of the second input, in that order, and the channel layout of
the output will be the default value corresponding to the total number of
channels.

For example, if the first input is in 2.1 (FL+FR+LF) and the second input
is FC+BL+BR, then the output will be in 5.1, with the channels in the
following order: a1, a2, b1, a3, b2, b3 (a1 is the first channel of the
first input, b1 is the first channel of the second input).

On the other hand, if both input are in stereo, the output channels will be
in the default order: a1, a2, b1, b2, and the channel layout will be
arbitrarily set to 4.0, which may or may not be the expected value.

All inputs must have the same sample rate, and format.

If inputs do not have the same duration, the output will stop with the
shortest.

@subsection Examples

@itemize
@item
Merge two mono files into a stereo stream:
@example
amovie=left.wav [l] ; amovie=right.mp3 [r] ; [l] [r] amerge
@end example

@item
Multiple merges assuming 1 video stream and 6 audio streams in @file{input.mkv}:
@example
ffmpeg -i input.mkv -filter_complex "[0:1][0:2][0:3][0:4][0:5][0:6] amerge=inputs=6" -c:a pcm_s16le output.mkv
@end example
@end itemize

@section amix

Mixes multiple audio inputs into a single output.

Note that this filter only supports float samples (the @var{amerge}
and @var{pan} audio filters support many formats). If the @var{amix}
input has integer samples then @ref{aresample} will be automatically
inserted to perform the conversion to float samples.

For example
@example
ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex amix=inputs=3:duration=first:dropout_transition=3 OUTPUT
@end example
will mix 3 input audio streams to a single output with the same duration as the
first input and a dropout transition time of 3 seconds.

It accepts the following parameters:
@table @option

@item inputs
The number of inputs. If unspecified, it defaults to 2.

@item duration
How to determine the end-of-stream.
@table @option

@item longest
The duration of the longest input. (default)

@item shortest
The duration of the shortest input.

@item first
The duration of the first input.

@end table

@item dropout_transition
The transition time, in seconds, for volume renormalization when an input
stream ends. The default value is 2 seconds.

@end table

@section anull

Pass the audio source unchanged to the output.

@section apad

Pad the end of an audio stream with silence.

This can be used together with @command{ffmpeg} @option{-shortest} to
extend audio streams to the same length as the video stream.

A description of the accepted options follows.

@table @option
@item packet_size
Set silence packet size. Default value is 4096.

@item pad_len
Set the number of samples of silence to add to the end. After the
value is reached, the stream is terminated. This option is mutually
exclusive with @option{whole_len}.

@item whole_len
Set the minimum total number of samples in the output audio stream. If
the value is longer than the input audio length, silence is added to
the end, until the value is reached. This option is mutually exclusive
with @option{pad_len}.
@end table

If neither the @option{pad_len} nor the @option{whole_len} option is
set, the filter will add silence to the end of the input stream
indefinitely.

@subsection Examples

@itemize
@item
Add 1024 samples of silence to the end of the input:
@example
apad=pad_len=1024
@end example

@item
Make sure the audio output will contain at least 10000 samples, pad
the input with silence if required:
@example
apad=whole_len=10000
@end example

@item
Use @command{ffmpeg} to pad the audio input with silence, so that the
video stream will always result the shortest and will be converted
until the end in the output file when using the @option{shortest}
option:
@example
ffmpeg -i VIDEO -i AUDIO -filter_complex "[1:0]apad" -shortest OUTPUT
@end example
@end itemize

@section aphaser
Add a phasing effect to the input audio.

A phaser filter creates series of peaks and troughs in the frequency spectrum.
The position of the peaks and troughs are modulated so that they vary over time, creating a sweeping effect.

A description of the accepted parameters follows.

@table @option
@item in_gain
Set input gain. Default is 0.4.

@item out_gain
Set output gain. Default is 0.74

@item delay
Set delay in milliseconds. Default is 3.0.

@item decay
Set decay. Default is 0.4.

@item speed
Set modulation speed in Hz. Default is 0.5.

@item type
Set modulation type. Default is triangular.

It accepts the following values:
@table @samp
@item triangular, t
@item sinusoidal, s
@end table
@end table

@anchor{aresample}
@section aresample

Resample the input audio to the specified parameters, using the
libswresample library. If none are specified then the filter will
automatically convert between its input and output.

This filter is also able to stretch/squeeze the audio data to make it match
the timestamps or to inject silence / cut out audio to make it match the
timestamps, do a combination of both or do neither.

The filter accepts the syntax
[@var{sample_rate}:]@var{resampler_options}, where @var{sample_rate}
expresses a sample rate and @var{resampler_options} is a list of
@var{key}=@var{value} pairs, separated by ":". See the
ffmpeg-resampler manual for the complete list of supported options.

@subsection Examples

@itemize
@item
Resample the input audio to 44100Hz:
@example
aresample=44100
@end example

@item
Stretch/squeeze samples to the given timestamps, with a maximum of 1000
samples per second compensation:
@example
aresample=async=1000
@end example
@end itemize

@section asetnsamples

Set the number of samples per each output audio frame.

The last output packet may contain a different number of samples, as
the filter will flush all the remaining samples when the input audio
signal its end.

The filter accepts the following options:

@table @option

@item nb_out_samples, n
Set the number of frames per each output audio frame. The number is
intended as the number of samples @emph{per each channel}.
Default value is 1024.

@item pad, p
If set to 1, the filter will pad the last audio frame with zeroes, so
that the last frame will contain the same number of samples as the
previous ones. Default value is 1.
@end table

For example, to set the number of per-frame samples to 1234 and
disable padding for the last frame, use:
@example
asetnsamples=n=1234:p=0
@end example

@section asetrate

Set the sample rate without altering the PCM data.
This will result in a change of speed and pitch.

The filter accepts the following options:

@table @option
@item sample_rate, r
Set the output sample rate. Default is 44100 Hz.
@end table

@section ashowinfo

Show a line containing various information for each input audio frame.
The input audio is not modified.

The shown line contains a sequence of key/value pairs of the form
@var{key}:@var{value}.

The following values are shown in the output:

@table @option
@item n
The (sequential) number of the input frame, starting from 0.

@item pts
The presentation timestamp of the input frame, in time base units; the time base
depends on the filter input pad, and is usually 1/@var{sample_rate}.

@item pts_time
The presentation timestamp of the input frame in seconds.

@item pos
position of the frame in the input stream, -1 if this information in
unavailable and/or meaningless (for example in case of synthetic audio)

@item fmt
The sample format.

@item chlayout
The channel layout.

@item rate
The sample rate for the audio frame.

@item nb_samples
The number of samples (per channel) in the frame.

@item checksum
The Adler-32 checksum (printed in hexadecimal) of the audio data. For planar
audio, the data is treated as if all the planes were concatenated.

@item plane_checksums
A list of Adler-32 checksums for each data plane.
@end table

@section astats

Display time domain statistical information about the audio channels.
Statistics are calculated and displayed for each audio channel and,
where applicable, an overall figure is also given.

It accepts the following option:
@table @option
@item length
Short window length in seconds, used for peak and trough RMS measurement.
Default is @code{0.05} (50 miliseconds). Allowed range is @code{[0.1 - 10]}.
@end table

A description of each shown parameter follows:

@table @option
@item DC offset
Mean amplitude displacement from zero.

@item Min level
Minimal sample level.

@item Max level
Maximal sample level.

@item Peak level dB
@item RMS level dB
Standard peak and RMS level measured in dBFS.

@item RMS peak dB
@item RMS trough dB
Peak and trough values for RMS level measured over a short window.

@item Crest factor
Standard ratio of peak to RMS level (note: not in dB).

@item Flat factor
Flatness (i.e. consecutive samples with the same value) of the signal at its peak levels
(i.e. either @var{Min level} or @var{Max level}).

@item Peak count
Number of occasions (not the number of samples) that the signal attained either
@var{Min level} or @var{Max level}.
@end table

@section astreamsync

Forward two audio streams and control the order the buffers are forwarded.

The filter accepts the following options:

@table @option
@item expr, e
Set the expression deciding which stream should be
forwarded next: if the result is negative, the first stream is forwarded; if
the result is positive or zero, the second stream is forwarded. It can use
the following variables:

@table @var
@item b1 b2
number of buffers forwarded so far on each stream
@item s1 s2
number of samples forwarded so far on each stream
@item t1 t2
current timestamp of each stream
@end table

The default value is @code{t1-t2}, which means to always forward the stream
that has a smaller timestamp.
@end table

@subsection Examples

Stress-test @code{amerge} by randomly sending buffers on the wrong
input, while avoiding too much of a desynchronization:
@example
amovie=file.ogg [a] ; amovie=file.mp3 [b] ;
[a] [b] astreamsync=(2*random(1))-1+tanh(5*(t1-t2)) [a2] [b2] ;
[a2] [b2] amerge
@end example

@section asyncts

Synchronize audio data with timestamps by squeezing/stretching it and/or
dropping samples/adding silence when needed.

This filter is not built by default, please use @ref{aresample} to do squeezing/stretching.

It accepts the following parameters:
@table @option

@item compensate
Enable stretching/squeezing the data to make it match the timestamps. Disabled
by default. When disabled, time gaps are covered with silence.

@item min_delta
The minimum difference between timestamps and audio data (in seconds) to trigger
adding/dropping samples. The default value is 0.1. If you get an imperfect
sync with this filter, try setting this parameter to 0.

@item max_comp
The maximum compensation in samples per second. Only relevant with compensate=1.
The default value is 500.

@item first_pts
Assume that the first PTS should be this value. The time base is 1 / sample
rate. This allows for padding/trimming at the start of the stream. By default,
no assumption is made about the first frame's expected PTS, so no padding or
trimming is done. For example, this could be set to 0 to pad the beginning with
silence if an audio stream starts after the video stream or to trim any samples
with a negative PTS due to encoder delay.

@end table

@section atempo

Adjust audio tempo.

The filter accepts exactly one parameter, the audio tempo. If not
specified then the filter will assume nominal 1.0 tempo. Tempo must
be in the [0.5, 2.0] range.

@subsection Examples

@itemize
@item
Slow down audio to 80% tempo:
@example
atempo=0.8
@end example

@item
To speed up audio to 125% tempo:
@example
atempo=1.25
@end example
@end itemize

@section atrim

Trim the input so that the output contains one continuous subpart of the input.

It accepts the following parameters:
@table @option
@item start
Timestamp (in seconds) of the start of the section to keep. I.e. the audio
sample with the timestamp @var{start} will be the first sample in the output.

@item end
Specify time of the first audio sample that will be dropped, i.e. the
audio sample immediately preceding the one with the timestamp @var{end} will be
the last sample in the output.

@item start_pts
Same as @var{start}, except this option sets the start timestamp in samples
instead of seconds.

@item end_pts
Same as @var{end}, except this option sets the end timestamp in samples instead
of seconds.

@item duration
The maximum duration of the output in seconds.

@item start_sample
The number of the first sample that should be output.

@item end_sample
The number of the first sample that should be dropped.
@end table

@option{start}, @option{end}, and @option{duration} are expressed as time
duration specifications; see
@ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}.

Note that the first two sets of the start/end options and the @option{duration}
option look at the frame timestamp, while the _sample options simply count the
samples that pass through the filter. So start/end_pts and start/end_sample will
give different results when the timestamps are wrong, inexact or do not start at
zero. Also note that this filter does not modify the timestamps. If you wish
to have the output timestamps start at zero, insert the asetpts filter after the
atrim filter.

If multiple start or end options are set, this filter tries to be greedy and
keep all samples that match at least one of the specified constraints. To keep
only the part that matches all the constraints at once, chain multiple atrim
filters.

The defaults are such that all the input is kept. So it is possible to set e.g.
just the end values to keep everything before the specified time.

Examples:
@itemize
@item
Drop everything except the second minute of input:
@example
ffmpeg -i INPUT -af atrim=60:120
@end example

@item
Keep only the first 1000 samples:
@example
ffmpeg -i INPUT -af atrim=end_sample=1000
@end example

@end itemize

@section bandpass

Apply a two-pole Butterworth band-pass filter with central
frequency @var{frequency}, and (3dB-point) band-width width.
The @var{csg} option selects a constant skirt gain (peak gain = Q)
instead of the default: constant 0dB peak gain.
The filter roll off at 6dB per octave (20dB per decade).

The filter accepts the following options:

@table @option
@item frequency, f
Set the filter's central frequency. Default is @code{3000}.

@item csg
Constant skirt gain if set to 1. Defaults to 0.

@item width_type
Set method to specify band-width of filter.
@table @option
@item h
Hz
@item q
Q-Factor
@item o
octave
@item s
slope
@end table

@item width, w
Specify the band-width of a filter in width_type units.
@end table

@section bandreject

Apply a two-pole Butterworth band-reject filter with central
frequency @var{frequency}, and (3dB-point) band-width @var{width}.
The filter roll off at 6dB per octave (20dB per decade).

The filter accepts the following options:

@table @option
@item frequency, f
Set the filter's central frequency. Default is @code{3000}.

@item width_type
Set method to specify band-width of filter.
@table @option
@item h
Hz
@item q
Q-Factor
@item o
octave
@item s
slope
@end table

@item width, w
Specify the band-width of a filter in width_type units.
@end table

@section bass

Boost or cut the bass (lower) frequencies of the audio using a two-pole
shelving filter with a response similar to that of a standard
hi-fi's tone-controls. This is also known as shelving equalisation (EQ).

The filter accepts the following options:

@table @option
@item gain, g
Give the gain at 0 Hz. Its useful range is about -20
(for a large cut) to +20 (for a large boost).
Beware of clipping when using a positive gain.

@item frequency, f
Set the filter's central frequency and so can be used
to extend or reduce the frequency range to be boosted or cut.
The default value is @code{100} Hz.

@item width_type
Set method to specify band-width of filter.
@table @option
@item h
Hz
@item q
Q-Factor
@item o
octave
@item s
slope
@end table

@item width, w
Determine how steep is the filter's shelf transition.
@end table

@section biquad

Apply a biquad IIR filter with the given coefficients.
Where @var{b0}, @var{b1}, @var{b2} and @var{a0}, @var{a1}, @var{a2}
are the numerator and denominator coefficients respectively.

@section bs2b
Bauer stereo to binaural transformation, which improves headphone listening of
stereo audio records.

It accepts the following parameters:
@table @option

@item profile
Pre-defined crossfeed level.
@table @option

@item default
Default level (fcut=700, feed=50).

@item cmoy
Chu Moy circuit (fcut=700, feed=60).

@item jmeier
Jan Meier circuit (fcut=650, feed=95).

@end table

@item fcut
Cut frequency (in Hz).

@item feed
Feed level (in Hz).

@end table

@section channelmap

Remap input channels to new locations.

It accepts the following parameters:
@table @option
@item channel_layout
The channel layout of the output stream.

@item map
Map channels from input to output. The argument is a '|'-separated list of
mappings, each in the @code{@var{in_channel}-@var{out_channel}} or
@var{in_channel} form. @var{in_channel} can be either the name of the input
channel (e.g. FL for front left) or its index in the input channel layout.
@var{out_channel} is the name of the output channel or its index in the output
channel layout. If @var{out_channel} is not given then it is implicitly an
index, starting with zero and increasing by one for each mapping.
@end table

If no mapping is present, the filter will implicitly map input channels to
output channels, preserving indices.

For example, assuming a 5.1+downmix input MOV file,
@example
ffmpeg -i in.mov -filter 'channelmap=map=DL-FL|DR-FR' out.wav
@end example
will create an output WAV file tagged as stereo from the downmix channels of
the input.

To fix a 5.1 WAV improperly encoded in AAC's native channel order
@example
ffmpeg -i in.wav -filter 'channelmap=1|2|0|5|3|4:channel_layout=5.1' out.wav
@end example

@section channelsplit

Split each channel from an input audio stream into a separate output stream.

It accepts the following parameters:
@table @option
@item channel_layout
The channel layout of the input stream. The default is "stereo".
@end table

For example, assuming a stereo input MP3 file,
@example
ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv
@end example
will create an output Matroska file with two audio streams, one containing only
the left channel and the other the right channel.

Split a 5.1 WAV file into per-channel files:
@example
ffmpeg -i in.wav -filter_complex
'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]'
-map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]'
front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]'
side_right.wav
@end example

@section compand
Compress or expand the audio's dynamic range.

It accepts the following parameters:

@table @option

@item attacks
@item decays
A list of times in seconds for each channel over which the instantaneous level
of the input signal is averaged to determine its volume. @var{attacks} refers to
increase of volume and @var{decays} refers to decrease of volume. For most
situations, the attack time (response to the audio getting louder) should be
shorter than the decay time, because the human ear is more sensitive to sudden
loud audio than sudden soft audio. A typical value for attack is 0.3 seconds and
a typical value for decay is 0.8 seconds.

@item points
A list of points for the transfer function, specified in dB relative to the
maximum possible signal amplitude. Each key points list must be defined using
the following syntax: @code{x0/y0|x1/y1|x2/y2|....} or
@code{x0/y0 x1/y1 x2/y2 ....}

The input values must be in strictly increasing order but the transfer function
does not have to be monotonically rising. The point @code{0/0} is assumed but
may be overridden (by @code{0/out-dBn}). Typical values for the transfer
function are @code{-70/-70|-60/-20}.

@item soft-knee
Set the curve radius in dB for all joints. It defaults to 0.01.

@item gain
Set the additional gain in dB to be applied at all points on the transfer
function. This allows for easy adjustment of the overall gain.
It defaults to 0.

@item volume
Set an initial volume, in dB, to be assumed for each channel when filtering
starts. This permits the user to supply a nominal level initially, so that, for
example, a very large gain is not applied to initial signal levels before the
companding has begun to operate. A typical value for audio which is initially
quiet is -90 dB. It defaults to 0.

@item delay
Set a delay, in seconds. The input audio is analyzed immediately, but audio is
delayed before being fed to the volume adjuster. Specifying a delay
approximately equal to the attack/decay times allows the filter to effectively
operate in predictive rather than reactive mode. It defaults to 0.

@end table

@subsection Examples

@itemize
@item
Make music with both quiet and loud passages suitable for listening to in a
noisy environment:
@example
compand=.3|.3:1|1:-90/-60|-60/-40|-40/-30|-20/-20:6:0:-90:0.2
@end example

@item
A noise gate for when the noise is at a lower level than the signal:
@example
compand=.1|.1:.2|.2:-900/-900|-50.1/-900|-50/-50:.01:0:-90:.1
@end example

@item
Here is another noise gate, this time for when the noise is at a higher level
than the signal (making it, in some ways, similar to squelch):
@example
compand=.1|.1:.1|.1:-45.1/-45.1|-45/-900|0/-900:.01:45:-90:.1
@end example
@end itemize

@section earwax

Make audio easier to listen to on headphones.

This filter adds `cues' to 44.1kHz stereo (i.e. audio CD format) audio
so that when listened to on headphones the stereo image is moved from
inside your head (standard for headphones) to outside and in front of
the listener (standard for speakers).

Ported from SoX.

@section equalizer

Apply a two-pole peaking equalisation (EQ) filter. With this
filter, the signal-level at and around a selected frequency can
be increased or decreased, whilst (unlike bandpass and bandreject
filters) that at all other frequencies is unchanged.

In order to produce complex equalisation curves, this filter can
be given several times, each with a different central frequency.

The filter accepts the following options:

@table @option
@item frequency, f
Set the filter's central frequency in Hz.

@item width_type
Set method to specify band-width of filter.
@table @option
@item h
Hz
@item q
Q-Factor
@item o
octave
@item s
slope
@end table

@item width, w
Specify the band-width of a filter in width_type units.

@item gain, g
Set the required gain or attenuation in dB.
Beware of clipping when using a positive gain.
@end table

@subsection Examples
@itemize
@item
Attenuate 10 dB at 1000 Hz, with a bandwidth of 200 Hz:
@example
equalizer=f=1000:width_type=h:width=200:g=-10
@end example

@item
Apply 2 dB gain at 1000 Hz with Q 1 and attenuate 5 dB at 100 Hz with Q 2:
@example
equalizer=f=1000:width_type=q:width=1:g=2,equalizer=f=100:width_type=q:width=2:g=-5
@end example
@end itemize

@section flanger
Apply a flanging effect to the audio.

The filter accepts the following options:

@table @option
@item delay
Set base delay in milliseconds. Range from 0 to 30. Default value is 0.

@item depth
Set added swep delay in milliseconds. Range from 0 to 10. Default value is 2.

@item regen
Set percentage regeneneration (delayed signal feedback). Range from -95 to 95.
Default value is 0.

@item width
Set percentage of delayed signal mixed with original. Range from 0 to 100.
Default valu is 71.

@item speed
Set sweeps per second (Hz). Range from 0.1 to 10. Default value is 0.5.

@item shape
Set swept wave shape, can be @var{triangular} or @var{sinusoidal}.
Default value is @var{sinusoidal}.

@item phase
Set swept wave percentage-shift for multi channel. Range from 0 to 100.
Default value is 25.

@item interp
Set delay-line interpolation, @var{linear} or @var{quadratic}.
Default is @var{linear}.
@end table

@section highpass

Apply a high-pass filter with 3dB point frequency.
The filter can be either single-pole, or double-pole (the default).
The filter roll off at 6dB per pole per octave (20dB per pole per decade).

The filter accepts the following options:

@table @option
@item frequency, f
Set frequency in Hz. Default is 3000.

@item poles, p
Set number of poles. Default is 2.

@item width_type
Set method to specify band-width of filter.
@table @option
@item h
Hz
@item q
Q-Factor
@item o
octave
@item s
slope
@end table

@item width, w
Specify the band-width of a filter in width_type units.
Applies only to double-pole filter.
The default is 0.707q and gives a Butterworth response.
@end table

@section join

Join multiple input streams into one multi-channel stream.

It accepts the following parameters:
@table @option

@item inputs
The number of input streams. It defaults to 2.

@item channel_layout
The desired output channel layout. It defaults to stereo.

@item map
Map channels from inputs to output. The argument is a '|'-separated list of
mappings, each in the @code{@var{input_idx}.@var{in_channel}-@var{out_channel}}
form. @var{input_idx} is the 0-based index of the input stream. @var{in_channel}
can be either the name of the input channel (e.g. FL for front left) or its
index in the specified input stream. @var{out_channel} is the name of the output
channel.
@end table

The filter will attempt to guess the mappings when they are not specified
explicitly. It does so by first trying to find an unused matching input channel
and if that fails it picks the first unused input channel.

Join 3 inputs (with properly set channel layouts):
@example
ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT
@end example

Build a 5.1 output from 6 single-channel streams:
@example
ffmpeg -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex
'join=inputs=6:channel_layout=5.1:map=0.0-FL|1.0-FR|2.0-FC|3.0-SL|4.0-SR|5.0-LFE'
out
@end example

@section ladspa

Load a LADSPA (Linux Audio Developer's Simple Plugin API) plugin.

To enable compilation of this filter you need to configure FFmpeg with
@code{--enable-ladspa}.

@table @option
@item file, f
Specifies the name of LADSPA plugin library to load. If the environment
variable @env{LADSPA_PATH} is defined, the LADSPA plugin is searched in
each one of the directories specified by the colon separated list in
@env{LADSPA_PATH}, otherwise in the standard LADSPA paths, which are in
this order: @file{HOME/.ladspa/lib/}, @file{/usr/local/lib/ladspa/},
@file{/usr/lib/ladspa/}.

@item plugin, p
Specifies the plugin within the library. Some libraries contain only
one plugin, but others contain many of them. If this is not set filter
will list all available plugins within the specified library.

@item controls, c
Set the '|' separated list of controls which are zero or more floating point
values that determine the behavior of the loaded plugin (for example delay,
threshold or gain).
Controls need to be defined using the following syntax:
c0=@var{value0}|c1=@var{value1}|c2=@var{value2}|..., where
@var{valuei} is the value set on the @var{i}-th control.
If @option{controls} is set to @code{help}, all available controls and
their valid ranges are printed.

@item sample_rate, s
Specify the sample rate, default to 44100. Only used if plugin have
zero inputs.

@item nb_samples, n
Set the number of samples per channel per each output frame, default
is 1024. Only used if plugin have zero inputs.

@item duration, d
Set the minimum duration of the sourced audio. See
@ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}
for the accepted syntax.
Note that the resulting duration may be greater than the specified duration,
as the generated audio is always cut at the end of a complete frame.
If not specified, or the expressed duration is negative, the audio is
supposed to be generated forever.
Only used if plugin have zero inputs.

@end table

@subsection Examples

@itemize
@item
List all available plugins within amp (LADSPA example plugin) library:
@example
ladspa=file=amp
@end example

@item
List all available controls and their valid ranges for @code{vcf_notch}
plugin from @code{VCF} library:
@example
ladspa=f=vcf:p=vcf_notch:c=help
@end example

@item
Simulate low quality audio equipment using @code{Computer Music Toolkit} (CMT)
plugin library:
@example
ladspa=file=cmt:plugin=lofi:controls=c0=22|c1=12|c2=12
@end example

@item
Add reverberation to the audio using TAP-plugins
(Tom's Audio Processing plugins):
@example
ladspa=file=tap_reverb:tap_reverb
@end example

@item
Generate white noise, with 0.2 amplitude:
@example
ladspa=file=cmt:noise_source_white:c=c0=.2
@end example

@item
Generate 20 bpm clicks using plugin @code{C* Click - Metronome} from the
@code{C* Audio Plugin Suite} (CAPS) library:
@example
ladspa=file=caps:Click:c=c1=20'
@end example

@item
Apply @code{C* Eq10X2 - Stereo 10-band equaliser} effect:
@example
ladspa=caps:Eq10X2:c=c0=-48|c9=-24|c3=12|c4=2
@end example
@end itemize

@subsection Commands

This filter supports the following commands:
@table @option
@item cN
Modify the @var{N}-th control value.

If the specified value is not valid, it is ignored and prior one is kept.
@end table

@section lowpass

Apply a low-pass filter with 3dB point frequency.
The filter can be either single-pole or double-pole (the default).
The filter roll off at 6dB per pole per octave (20dB per pole per decade).

The filter accepts the following options:

@table @option
@item frequency, f
Set frequency in Hz. Default is 500.

@item poles, p
Set number of poles. Default is 2.

@item width_type
Set method to specify band-width of filter.
@table @option
@item h
Hz
@item q
Q-Factor
@item o
octave
@item s
slope
@end table

@item width, w
Specify the band-width of a filter in width_type units.
Applies only to double-pole filter.
The default is 0.707q and gives a Butterworth response.
@end table

@section pan

Mix channels with specific gain levels. The filter accepts the output
channel layout followed by a set of channels definitions.

This filter is also designed to remap efficiently the channels of an audio
stream.

The filter accepts parameters of the form:
"@var{l}:@var{outdef}:@var{outdef}:..."

@table @option
@item l
output channel layout or number of channels

@item outdef
output channel specification, of the form:
"@var{out_name}=[@var{gain}*]@var{in_name}[+[@var{gain}*]@var{in_name}...]"

@item out_name
output channel to define, either a channel name (FL, FR, etc.) or a channel
number (c0, c1, etc.)

@item gain
multiplicative coefficient for the channel, 1 leaving the volume unchanged

@item in_name
input channel to use, see out_name for details; it is not possible to mix
named and numbered input channels
@end table

If the `=' in a channel specification is replaced by `<', then the gains for
that specification will be renormalized so that the total is 1, thus
avoiding clipping noise.

@subsection Mixing examples

For example, if you want to down-mix from stereo to mono, but with a bigger
factor for the left channel:
@example
pan=1:c0=0.9*c0+0.1*c1
@end example

A customized down-mix to stereo that works automatically for 3-, 4-, 5- and
7-channels surround:
@example
pan=stereo: FL < FL + 0.5*FC + 0.6*BL + 0.6*SL : FR < FR + 0.5*FC + 0.6*BR + 0.6*SR
@end example

Note that @command{ffmpeg} integrates a default down-mix (and up-mix) system
that should be preferred (see "-ac" option) unless you have very specific
needs.

@subsection Remapping examples

The channel remapping will be effective if, and only if:

@itemize
@item gain coefficients are zeroes or ones,
@item only one input per channel output,
@end itemize

If all these conditions are satisfied, the filter will notify the user ("Pure
channel mapping detected"), and use an optimized and lossless method to do the
remapping.

For example, if you have a 5.1 source and want a stereo audio stream by
dropping the extra channels:
@example
pan="stereo: c0=FL : c1=FR"
@end example

Given the same source, you can also switch front left and front right channels
and keep the input channel layout:
@example
pan="5.1: c0=c1 : c1=c0 : c2=c2 : c3=c3 : c4=c4 : c5=c5"
@end example

If the input is a stereo audio stream, you can mute the front left channel (and
still keep the stereo channel layout) with:
@example
pan="stereo:c1=c1"
@end example

Still with a stereo audio stream input, you can copy the right channel in both
front left and right:
@example
pan="stereo: c0=FR : c1=FR"
@end example

@section replaygain

ReplayGain scanner filter. This filter takes an audio stream as an input and
outputs it unchanged.
At end of filtering it displays @code{track_gain} and @code{track_peak}.

@section resample

Convert the audio sample format, sample rate and channel layout. It is
not meant to be used directly.

@section silencedetect

Detect silence in an audio stream.

This filter logs a message when it detects that the input audio volume is less
or equal to a noise tolerance value for a duration greater or equal to the
minimum detected noise duration.

The printed times and duration are expressed in seconds.

The filter accepts the following options:

@table @option
@item duration, d
Set silence duration until notification (default is 2 seconds).

@item noise, n
Set noise tolerance. Can be specified in dB (in case "dB" is appended to the
specified value) or amplitude ratio. Default is -60dB, or 0.001.
@end table

@subsection Examples

@itemize
@item
Detect 5 seconds of silence with -50dB noise tolerance:
@example
silencedetect=n=-50dB:d=5
@end example

@item
Complete example with @command{ffmpeg} to detect silence with 0.0001 noise
tolerance in @file{silence.mp3}:
@example
ffmpeg -i silence.mp3 -af silencedetect=noise=0.0001 -f null -
@end example
@end itemize

@section silenceremove

Remove silence from the beginning, middle or end of the audio.

The filter accepts the following options:

@table @option
@item start_periods
This value is used to indicate if audio should be trimmed at beginning of
the audio. A value of zero indicates no silence should be trimmed from the
beginning. When specifying a non-zero value, it trims audio up until it
finds non-silence. Normally, when trimming silence from beginning of audio
the @var{start_periods} will be @code{1} but it can be increased to higher
values to trim all audio up to specific count of non-silence periods.
Default value is @code{0}.

@item start_duration
Specify the amount of time that non-silence must be detected before it stops
trimming audio. By increasing the duration, bursts of noises can be treated
as silence and trimmed off. Default value is @code{0}.

@item start_threshold
This indicates what sample value should be treated as silence. For digital
audio, a value of @code{0} may be fine but for audio recorded from analog,
you may wish to increase the value to account for background noise.
Can be specified in dB (in case "dB" is appended to the specified value)
or amplitude ratio. Default value is @code{0}.

@item stop_periods
Set the count for trimming silence from the end of audio.
To remove silence from the middle of a file, specify a @var{stop_periods}
that is negative. This value is then threated as a positive value and is
used to indicate the effect should restart processing as specified by
@var{start_periods}, making it suitable for removing periods of silence
in the middle of the audio.
Default value is @code{0}.

@item stop_duration
Specify a duration of silence that must exist before audio is not copied any
more. By specifying a higher duration, silence that is wanted can be left in
the audio.
Default value is @code{0}.

@item stop_threshold
This is the same as @option{start_threshold} but for trimming silence from
the end of audio.
Can be specified in dB (in case "dB" is appended to the specified value)
or amplitude ratio. Default value is @code{0}.

@item leave_silence
This indicate that @var{stop_duration} length of audio should be left intact
at the beginning of each period of silence.
For example, if you want to remove long pauses between words but do not want
to remove the pauses completely. Default value is @code{0}.

@end table

@subsection Examples

@itemize
@item
The following example shows how this filter can be used to start a recording
that does not contain the delay at the start which usually occurs between
pressing the record button and the start of the performance:
@example
silenceremove=1:5:0.02
@end example
@end itemize

@section treble

Boost or cut treble (upper) frequencies of the audio using a two-pole
shelving filter with a response similar to that of a standard
hi-fi's tone-controls. This is also known as shelving equalisation (EQ).

The filter accepts the following options:

@table @option
@item gain, g
Give the gain at whichever is the lower of ~22 kHz and the
Nyquist frequency. Its useful range is about -20 (for a large cut)
to +20 (for a large boost). Beware of clipping when using a positive gain.

@item frequency, f
Set the filter's central frequency and so can be used
to extend or reduce the frequency range to be boosted or cut.
The default value is @code{3000} Hz.

@item width_type
Set method to specify band-width of filter.
@table @option
@item h
Hz
@item q
Q-Factor
@item o
octave
@item s
slope
@end table

@item width, w
Determine how steep is the filter's shelf transition.
@end table

@section volume

Adjust the input audio volume.

It accepts the following parameters:
@table @option

@item volume
Set audio volume expression.

Output values are clipped to the maximum value.

The output audio volume is given by the relation:
@example
@var{output_volume} = @var{volume} * @var{input_volume}
@end example

The default value for @var{volume} is "1.0".

@item precision
This parameter represents the mathematical precision.

It determines which input sample formats will be allowed, which affects the
precision of the volume scaling.

@table @option
@item fixed
8-bit fixed-point; this limits input sample format to U8, S16, and S32.
@item float
32-bit floating-point; this limits input sample format to FLT. (default)
@item double
64-bit floating-point; this limits input sample format to DBL.
@end table

@item replaygain
Choose the behaviour on encountering ReplayGain side data in input frames.

@table @option
@item drop
Remove ReplayGain side data, ignoring its contents (the default).

@item ignore
Ignore ReplayGain side data, but leave it in the frame.

@item track
Prefer the track gain, if present.

@item album
Prefer the album gain, if present.
@end table

@item replaygain_preamp
Pre-amplification gain in dB to apply to the selected replaygain gain.

Default value for @var{replaygain_preamp} is 0.0.

@item eval
Set when the volume expression is evaluated.

It accepts the following values:
@table @samp
@item once
only evaluate expression once during the filter initialization, or
when the @samp{volume} command is sent

@item frame
evaluate expression for each incoming frame
@end table

Default value is @samp{once}.
@end table

The volume expression can contain the following parameters.

@table @option
@item n
frame number (starting at zero)
@item nb_channels
number of channels
@item nb_consumed_samples
number of samples consumed by the filter
@item nb_samples
number of samples in the current frame
@item pos
original frame position in the file
@item pts
frame PTS
@item sample_rate
sample rate
@item startpts
PTS at start of stream
@item startt
time at start of stream
@item t
frame time
@item tb
timestamp timebase
@item volume
last set volume value
@end table

Note that when @option{eval} is set to @samp{once} only the
@var{sample_rate} and @var{tb} variables are available, all other
variables will evaluate to NAN.

@subsection Commands

This filter supports the following commands:
@table @option
@item volume
Modify the volume expression.
The command accepts the same syntax of the corresponding option.

If the specified expression is not valid, it is kept at its current
value.
@item replaygain_noclip
Prevent clipping by limiting the gain applied.

Default value for @var{replaygain_noclip} is 1.

@end table

@subsection Examples

@itemize
@item
Halve the input audio volume:
@example
volume=volume=0.5
volume=volume=1/2
volume=volume=-6.0206dB
@end example

In all the above example the named key for @option{volume} can be
omitted, for example like in:
@example
volume=0.5
@end example

@item
Increase input audio power by 6 decibels using fixed-point precision:
@example
volume=volume=6dB:precision=fixed
@end example

@item
Fade volume after time 10 with an annihilation period of 5 seconds:
@example
volume='if(lt(t,10),1,max(1-(t-10)/5,0))':eval=frame
@end example
@end itemize

@section volumedetect

Detect the volume of the input video.

The filter has no parameters. The input is not modified. Statistics about
the volume will be printed in the log when the input stream end is reached.

In particular it will show the mean volume (root mean square), maximum
volume (on a per-sample basis), and the beginning of a histogram of the
registered volume values (from the maximum value to a cumulated 1/1000 of
the samples).

All volumes are in decibels relative to the maximum PCM value.

@subsection Examples

Here is an excerpt of the output:
@example
[Parsed_volumedetect_0 @ 0xa23120] mean_volume: -27 dB
[Parsed_volumedetect_0 @ 0xa23120] max_volume: -4 dB
[Parsed_volumedetect_0 @ 0xa23120] histogram_4db: 6
[Parsed_volumedetect_0 @ 0xa23120] histogram_5db: 62
[Parsed_volumedetect_0 @ 0xa23120] histogram_6db: 286
[Parsed_volumedetect_0 @ 0xa23120] histogram_7db: 1042
[Parsed_volumedetect_0 @ 0xa23120] histogram_8db: 2551
[Parsed_volumedetect_0 @ 0xa23120] histogram_9db: 4609
[Parsed_volumedetect_0 @ 0xa23120] histogram_10db: 8409
@end example

It means that:
@itemize
@item
The mean square energy is approximately -27 dB, or 10^-2.7.
@item
The largest sample is at -4 dB, or more precisely between -4 dB and -5 dB.
@item
There are 6 samples at -4 dB, 62 at -5 dB, 286 at -6 dB, etc.
@end itemize

In other words, raising the volume by +4 dB does not cause any clipping,
raising it by +5 dB causes clipping for 6 samples, etc.

@c man end AUDIO FILTERS

@chapter Audio Sources
@c man begin AUDIO SOURCES

Below is a description of the currently available audio sources.

@section abuffer

Buffer audio frames, and make them available to the filter chain.

This source is mainly intended for a programmatic use, in particular
through the interface defined in @file{libavfilter/asrc_abuffer.h}.

It accepts the following parameters:
@table @option

@item time_base
The timebase which will be used for timestamps of submitted frames. It must be
either a floating-point number or in @var{numerator}/@var{denominator} form.

@item sample_rate
The sample rate of the incoming audio buffers.

@item sample_fmt
The sample format of the incoming audio buffers.
Either a sample format name or its corresponging integer representation from
the enum AVSampleFormat in @file{libavutil/samplefmt.h}

@item channel_layout
The channel layout of the incoming audio buffers.
Either a channel layout name from channel_layout_map in
@file{libavutil/channel_layout.c} or its corresponding integer representation
from the AV_CH_LAYOUT_* macros in @file{libavutil/channel_layout.h}

@item channels
The number of channels of the incoming audio buffers.
If both @var{channels} and @var{channel_layout} are specified, then they
must be consistent.

@end table

@subsection Examples

@example
abuffer=sample_rate=44100:sample_fmt=s16p:channel_layout=stereo
@end example

will instruct the source to accept planar 16bit signed stereo at 44100Hz.
Since the sample format with name "s16p" corresponds to the number
6 and the "stereo" channel layout corresponds to the value 0x3, this is
equivalent to:
@example
abuffer=sample_rate=44100:sample_fmt=6:channel_layout=0x3
@end example

@section aevalsrc

Generate an audio signal specified by an expression.

This source accepts in input one or more expressions (one for each
channel), which are evaluated and used to generate a corresponding
audio signal.

This source accepts the following options:

@table @option
@item exprs
Set the '|'-separated expressions list for each separate channel. In case the
@option{channel_layout} option is not specified, the selected channel layout
depends on the number of provided expressions. Otherwise the last
specified expression is applied to the remaining output channels.

@item channel_layout, c
Set the channel layout. The number of channels in the specified layout
must be equal to the number of specified expressions.

@item duration, d
Set the minimum duration of the sourced audio. See
@ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}
for the accepted syntax.
Note that the resulting duration may be greater than the specified
duration, as the generated audio is always cut at the end of a
complete frame.

If not specified, or the expressed duration is negative, the audio is
supposed to be generated forever.

@item nb_samples, n
Set the number of samples per channel per each output frame,
default to 1024.

@item sample_rate, s
Specify the sample rate, default to 44100.
@end table

Each expression in @var{exprs} can contain the following constants:

@table @option
@item n
number of the evaluated sample, starting from 0

@item t
time of the evaluated sample expressed in seconds, starting from 0

@item s
sample rate

@end table

@subsection Examples

@itemize
@item
Generate silence:
@example
aevalsrc=0
@end example

@item
Generate a sin signal with frequency of 440 Hz, set sample rate to
8000 Hz:
@example
aevalsrc="sin(440*2*PI*t):s=8000"
@end example

@item
Generate a two channels signal, specify the channel layout (Front
Center + Back Center) explicitly:
@example
aevalsrc="sin(420*2*PI*t)|cos(430*2*PI*t):c=FC|BC"
@end example

@item
Generate white noise:
@example
aevalsrc="-2+random(0)"
@end example

@item
Generate an amplitude modulated signal:
@example
aevalsrc="sin(10*2*PI*t)*sin(880*2*PI*t)"
@end example

@item
Generate 2.5 Hz binaural beats on a 360 Hz carrier:
@example
aevalsrc="0.1*sin(2*PI*(360-2.5/2)*t) | 0.1*sin(2*PI*(360+2.5/2)*t)"
@end example

@end itemize

@section anullsrc

The null audio source, return unprocessed audio frames. It is mainly useful
as a template and to be employed in analysis / debugging tools, or as
the source for filters which ignore the input data (for example the sox
synth filter).

This source accepts the following options:

@table @option

@item channel_layout, cl

Specifies the channel layout, and can be either an integer or a string
representing a channel layout. The default value of @var{channel_layout}
is "stereo".

Check the channel_layout_map definition in
@file{libavutil/channel_layout.c} for the mapping between strings and
channel layout values.

@item sample_rate, r
Specifies the sample rate, and defaults to 44100.

@item nb_samples, n
Set the number of samples per requested frames.

@end table

@subsection Examples

@itemize
@item
Set the sample rate to 48000 Hz and the channel layout to AV_CH_LAYOUT_MONO.
@example
anullsrc=r=48000:cl=4
@end example

@item
Do the same operation with a more obvious syntax:
@example
anullsrc=r=48000:cl=mono
@end example
@end itemize

All the parameters need to be explicitly defined.

@section flite

Synthesize a voice utterance using the libflite library.

To enable compilation of this filter you need to configure FFmpeg with
@code{--enable-libflite}.

Note that the flite library is not thread-safe.

The filter accepts the following options:

@table @option

@item list_voices
If set to 1, list the names of the available voices and exit
immediately. Default value is 0.

@item nb_samples, n
Set the maximum number of samples per frame. Default value is 512.

@item textfile
Set the filename containing the text to speak.

@item text
Set the text to speak.

@item voice, v
Set the voice to use for the speech synthesis. Default value is
@code{kal}. See also the @var{list_voices} option.
@end table

@subsection Examples

@itemize
@item
Read from file @file{speech.txt}, and synthetize the text using the
standard flite voice:
@example
flite=textfile=speech.txt
@end example

@item
Read the specified text selecting the @code{slt} voice:
@example
flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
@end example

@item
Input text to ffmpeg:
@example
ffmpeg -f lavfi -i flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
@end example

@item
Make @file{ffplay} speak the specified text, using @code{flite} and
the @code{lavfi} device:
@example
ffplay -f lavfi flite=text='No more be grieved for which that thou hast done.'
@end example
@end itemize

For more information about libflite, check:
@url{http://www.speech.cs.cmu.edu/flite/}

@section sine

Generate an audio signal made of a sine wave with amplitude 1/8.

The audio signal is bit-exact.

The filter accepts the following options:

@table @option

@item frequency, f
Set the carrier frequency. Default is 440 Hz.

@item beep_factor, b
Enable a periodic beep every second with frequency @var{beep_factor} times
the carrier frequency. Default is 0, meaning the beep is disabled.

@item sample_rate, r
Specify the sample rate, default is 44100.

@item duration, d
Specify the duration of the generated audio stream.

@item samples_per_frame
Set the number of samples per output frame, default is 1024.
@end table

@subsection Examples

@itemize

@item
Generate a simple 440 Hz sine wave:
@example
sine
@end example

@item
Generate a 220 Hz sine wave with a 880 Hz beep each second, for 5 seconds:
@example
sine=220:4:d=5
sine=f=220:b=4:d=5
sine=frequency=220:beep_factor=4:duration=5
@end example

@end itemize

@c man end AUDIO SOURCES

@chapter Audio Sinks
@c man begin AUDIO SINKS

Below is a description of the currently available audio sinks.

@section abuffersink

Buffer audio frames, and make them available to the end of filter chain.

This sink is mainly intended for programmatic use, in particular
through the interface defined in @file{libavfilter/buffersink.h}
or the options system.

It accepts a pointer to an AVABufferSinkContext structure, which
defines the incoming buffers' formats, to be passed as the opaque
parameter to @code{avfilter_init_filter} for initialization.
@section anullsink

Null audio sink; do absolutely nothing with the input audio. It is
mainly useful as a template and for use in analysis / debugging
tools.

@c man end AUDIO SINKS

@chapter Video Filters
@c man begin VIDEO FILTERS

When you configure your FFmpeg build, you can disable any of the
existing filters using @code{--disable-filters}.
The configure output will show the video filters included in your
build.

Below is a description of the currently available video filters.

@section alphaextract

Extract the alpha component from the input as a grayscale video. This
is especially useful with the @var{alphamerge} filter.

@section alphamerge

Add or replace the alpha component of the primary input with the
grayscale value of a second input. This is intended for use with
@var{alphaextract} to allow the transmission or storage of frame
sequences that have alpha in a format that doesn't support an alpha
channel.

For example, to reconstruct full frames from a normal YUV-encoded video
and a separate video created with @var{alphaextract}, you might use:
@example
movie=in_alpha.mkv [alpha]; [in][alpha] alphamerge [out]
@end example

Since this filter is designed for reconstruction, it operates on frame
sequences without considering timestamps, and terminates when either
input reaches end of stream. This will cause problems if your encoding
pipeline drops frames. If you're trying to apply an image as an
overlay to a video stream, consider the @var{overlay} filter instead.

@section ass

Same as the @ref{subtitles} filter, except that it doesn't require libavcodec
and libavformat to work. On the other hand, it is limited to ASS (Advanced
Substation Alpha) subtitles files.

This filter accepts the following option in addition to the common options from
the @ref{subtitles} filter:

@table @option
@item shaping
Set the shaping engine

Available values are:
@table @samp
@item auto
The default libass shaping engine, which is the best available.
@item simple
Fast, font-agnostic shaper that can do only substitutions
@item complex
Slower shaper using OpenType for substitutions and positioning
@end table

The default is @code{auto}.
@end table

@section bbox

Compute the bounding box for the non-black pixels in the input frame
luminance plane.

This filter computes the bounding box containing all the pixels with a
luminance value greater than the minimum allowed value.
The parameters describing the bounding box are printed on the filter
log.

The filter accepts the following option:

@table @option
@item min_val
Set the minimal luminance value. Default is @code{16}.
@end table

@section blackdetect

Detect video intervals that are (almost) completely black. Can be
useful to detect chapter transitions, commercials, or invalid
recordings. Output lines contains the time for the start, end and
duration of the detected black interval expressed in seconds.

In order to display the output lines, you need to set the loglevel at
least to the AV_LOG_INFO value.

The filter accepts the following options:

@table @option
@item black_min_duration, d
Set the minimum detected black duration expressed in seconds. It must
be a non-negative floating point number.

Default value is 2.0.

@item picture_black_ratio_th, pic_th
Set the threshold for considering a picture "black".
Express the minimum value for the ratio:
@example
@var{nb_black_pixels} / @var{nb_pixels}
@end example

for which a picture is considered black.
Default value is 0.98.

@item pixel_black_th, pix_th
Set the threshold for considering a pixel "black".

The threshold expresses the maximum pixel luminance value for which a
pixel is considered "black". The provided value is scaled according to
the following equation:
@example
@var{absolute_threshold} = @var{luminance_minimum_value} + @var{pixel_black_th} * @var{luminance_range_size}
@end example

@var{luminance_range_size} and @var{luminance_minimum_value} depend on
the input video format, the range is [0-255] for YUV full-range
formats and [16-235] for YUV non full-range formats.

Default value is 0.10.
@end table

The following example sets the maximum pixel threshold to the minimum
value, and detects only black intervals of 2 or more seconds:
@example
blackdetect=d=2:pix_th=0.00
@end example

@section blackframe

Detect frames that are (almost) completely black. Can be useful to
detect chapter transitions or commercials. Output lines consist of
the frame number of the detected frame, the percentage of blackness,
the position in the file if known or -1 and the timestamp in seconds.

In order to display the output lines, you need to set the loglevel at
least to the AV_LOG_INFO value.

It accepts the following parameters:

@table @option

@item amount
The percentage of the pixels that have to be below the threshold; it defaults to
@code{98}.

@item threshold, thresh
The threshold below which a pixel value is considered black; it defaults to
@code{32}.

@end table

@section blend

Blend two video frames into each other.

It takes two input streams and outputs one stream, the first input is the
"top" layer and second input is "bottom" layer.
Output terminates when shortest input terminates.

A description of the accepted options follows.

@table @option
@item c0_mode
@item c1_mode
@item c2_mode
@item c3_mode
@item all_mode
Set blend mode for specific pixel component or all pixel components in case
of @var{all_mode}. Default value is @code{normal}.

Available values for component modes are:
@table @samp
@item addition
@item and
@item average
@item burn
@item darken
@item difference
@item divide
@item dodge
@item exclusion
@item hardlight
@item lighten
@item multiply
@item negation
@item normal
@item or
@item overlay
@item phoenix
@item pinlight
@item reflect
@item screen
@item softlight
@item subtract
@item vividlight
@item xor
@end table

@item c0_opacity
@item c1_opacity
@item c2_opacity
@item c3_opacity
@item all_opacity
Set blend opacity for specific pixel component or all pixel components in case
of @var{all_opacity}. Only used in combination with pixel component blend modes.

@item c0_expr
@item c1_expr
@item c2_expr
@item c3_expr
@item all_expr
Set blend expression for specific pixel component or all pixel components in case
of @var{all_expr}. Note that related mode options will be ignored if those are set.

The expressions can use the following variables:

@table @option
@item N
The sequential number of the filtered frame, starting from @code{0}.

@item X
@item Y
the coordinates of the current sample

@item W
@item H
the width and height of currently filtered plane

@item SW
@item SH
Width and height scale depending on the currently filtered plane. It is the
ratio between the corresponding luma plane number of pixels and the current
plane ones. E.g. for YUV4:2:0 the values are @code{1,1} for the luma plane, and
@code{0.5,0.5} for chroma planes.

@item T
Time of the current frame, expressed in seconds.

@item TOP, A
Value of pixel component at current location for first video frame (top layer).

@item BOTTOM, B
Value of pixel component at current location for second video frame (bottom layer).
@end table

@item shortest
Force termination when the shortest input terminates. Default is @code{0}.
@item repeatlast
Continue applying the last bottom frame after the end of the stream. A value of
@code{0} disable the filter after the last frame of the bottom layer is reached.
Default is @code{1}.
@end table

@subsection Examples

@itemize
@item
Apply transition from bottom layer to top layer in first 10 seconds:
@example
blend=all_expr='A*(if(gte(T,10),1,T/10))+B*(1-(if(gte(T,10),1,T/10)))'
@end example

@item
Apply 1x1 checkerboard effect:
@example
blend=all_expr='if(eq(mod(X,2),mod(Y,2)),A,B)'
@end example

@item
Apply uncover left effect:
@example
blend=all_expr='if(gte(N*SW+X,W),A,B)'
@end example

@item
Apply uncover down effect:
@example
blend=all_expr='if(gte(Y-N*SH,0),A,B)'
@end example

@item
Apply uncover up-left effect:
@example
blend=all_expr='if(gte(T*SH*40+Y,H)*gte((T*40*SW+X)*W/H,W),A,B)'
@end example
@end itemize

@section boxblur

Apply a boxblur algorithm to the input video.

It accepts the following parameters:

@table @option

@item luma_radius, lr
@item luma_power, lp
@item chroma_radius, cr
@item chroma_power, cp
@item alpha_radius, ar
@item alpha_power, ap

@end table

A description of the accepted options follows.

@table @option
@item luma_radius, lr
@item chroma_radius, cr
@item alpha_radius, ar
Set an expression for the box radius in pixels used for blurring the
corresponding input plane.

The radius value must be a non-negative number, and must not be
greater than the value of the expression @code{min(w,h)/2} for the
luma and alpha planes, and of @code{min(cw,ch)/2} for the chroma
planes.

Default value for @option{luma_radius} is "2". If not specified,
@option{chroma_radius} and @option{alpha_radius} default to the
corresponding value set for @option{luma_radius}.

The expressions can contain the following constants:
@table @option
@item w
@item h
The input width and height in pixels.

@item cw
@item ch
The input chroma image width and height in pixels.

@item hsub
@item vsub
The horizontal and vertical chroma subsample values. For example, for the
pixel format "yuv422p", @var{hsub} is 2 and @var{vsub} is 1.
@end table

@item luma_power, lp
@item chroma_power, cp
@item alpha_power, ap
Specify how many times the boxblur filter is applied to the
corresponding plane.

Default value for @option{luma_power} is 2. If not specified,
@option{chroma_power} and @option{alpha_power} default to the
corresponding value set for @option{luma_power}.

A value of 0 will disable the effect.
@end table

@subsection Examples

@itemize
@item
Apply a boxblur filter with the luma, chroma, and alpha radii
set to 2:
@example
boxblur=luma_radius=2:luma_power=1
boxblur=2:1
@end example

@item
Set the luma radius to 2, and alpha and chroma radius to 0:
@example
boxblur=2:1:cr=0:ar=0
@end example

@item
Set the luma and chroma radii to a fraction of the video dimension:
@example
boxblur=luma_radius=min(h\,w)/10:luma_power=1:chroma_radius=min(cw\,ch)/10:chroma_power=1
@end example
@end itemize

@section codecview

Visualize information exported by some codecs.

Some codecs can export information through frames using side-data or other
means. For example, some MPEG based codecs export motion vectors through the
@var{export_mvs} flag in the codec @option{flags2} option.

The filter accepts the following option:

@table @option
@item mv
Set motion vectors to visualize.

Available flags for @var{mv} are:

@table @samp
@item pf
forward predicted MVs of P-frames
@item bf
forward predicted MVs of B-frames
@item bb
backward predicted MVs of B-frames
@end table
@end table

@subsection Examples

@itemize
@item
Visualizes multi-directionals MVs from P and B-Frames using @command{ffplay}:
@example
ffplay -flags2 +export_mvs input.mpg -vf codecview=mv=pf+bf+bb
@end example
@end itemize

@section colorbalance
Modify intensity of primary colors (red, green and blue) of input frames.

The filter allows an input frame to be adjusted in the shadows, midtones or highlights
regions for the red-cyan, green-magenta or blue-yellow balance.

A positive adjustment value shifts the balance towards the primary color, a negative
value towards the complementary color.

The filter accepts the following options:

@table @option
@item rs
@item gs
@item bs
Adjust red, green and blue shadows (darkest pixels).

@item rm
@item gm
@item bm
Adjust red, green and blue midtones (medium pixels).

@item rh
@item gh
@item bh
Adjust red, green and blue highlights (brightest pixels).

Allowed ranges for options are @code{[-1.0, 1.0]}. Defaults are @code{0}.
@end table

@subsection Examples

@itemize
@item
Add red color cast to shadows:
@example
colorbalance=rs=.3
@end example
@end itemize

@section colorchannelmixer

Adjust video input frames by re-mixing color channels.

This filter modifies a color channel by adding the values associated to
the other channels of the same pixels. For example if the value to
modify is red, the output value will be:
@example
@var{red}=@var{red}*@var{rr} + @var{blue}*@var{rb} + @var{green}*@var{rg} + @var{alpha}*@var{ra}
@end example

The filter accepts the following options:

@table @option
@item rr
@item rg
@item rb
@item ra
Adjust contribution of input red, green, blue and alpha channels for output red channel.
Default is @code{1} for @var{rr}, and @code{0} for @var{rg}, @var{rb} and @var{ra}.

@item gr
@item gg
@item gb
@item ga
Adjust contribution of input red, green, blue and alpha channels for output green channel.
Default is @code{1} for @var{gg}, and @code{0} for @var{gr}, @var{gb} and @var{ga}.

@item br
@item bg
@item bb
@item ba
Adjust contribution of input red, green, blue and alpha channels for output blue channel.
Default is @code{1} for @var{bb}, and @code{0} for @var{br}, @var{bg} and @var{ba}.

@item ar
@item ag
@item ab
@item aa
Adjust contribution of input red, green, blue and alpha channels for output alpha channel.
Default is @code{1} for @var{aa}, and @code{0} for @var{ar}, @var{ag} and @var{ab}.

Allowed ranges for options are @code{[-2.0, 2.0]}.
@end table

@subsection Examples

@itemize
@item
Convert source to grayscale:
@example
colorchannelmixer=.3:.4:.3:0:.3:.4:.3:0:.3:.4:.3
@end example
@item
Simulate sepia tones:
@example
colorchannelmixer=.393:.769:.189:0:.349:.686:.168:0:.272:.534:.131
@end example
@end itemize

@section colormatrix

Convert color matrix.

The filter accepts the following options:

@table @option
@item src
@item dst
Specify the source and destination color matrix. Both values must be
specified.

The accepted values are:
@table @samp
@item bt709
BT.709

@item bt601
BT.601

@item smpte240m
SMPTE-240M

@item fcc
FCC
@end table
@end table

For example to convert from BT.601 to SMPTE-240M, use the command:
@example
colormatrix=bt601:smpte240m
@end example

@section copy

Copy the input source unchanged to the output. This is mainly useful for
testing purposes.

@section crop

Crop the input video to given dimensions.

It accepts the following parameters:

@table @option
@item w, out_w
The width of the output video. It defaults to @code{iw}.
This expression is evaluated only once during the filter
configuration.

@item h, out_h
The height of the output video. It defaults to @code{ih}.
This expression is evaluated only once during the filter
configuration.

@item x
The horizontal position, in the input video, of the left edge of the output
video. It defaults to @code{(in_w-out_w)/2}.
This expression is evaluated per-frame.

@item y
The vertical position, in the input video, of the top edge of the output video.
It defaults to @code{(in_h-out_h)/2}.
This expression is evaluated per-frame.

@item keep_aspect
If set to 1 will force the output display aspect ratio
to be the same of the input, by changing the output sample aspect
ratio. It defaults to 0.
@end table

The @var{out_w}, @var{out_h}, @var{x}, @var{y} parameters are
expressions containing the following constants:

@table @option
@item x
@item y
The computed values for @var{x} and @var{y}. They are evaluated for
each new frame.

@item in_w
@item in_h
The input width and height.

@item iw
@item ih
These are the same as @var{in_w} and @var{in_h}.

@item out_w
@item out_h
The output (cropped) width and height.

@item ow
@item oh
These are the same as @var{out_w} and @var{out_h}.

@item a
same as @var{iw} / @var{ih}

@item sar
input sample aspect ratio

@item dar
input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}

@item hsub
@item vsub
horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.

@item n
The number of the input frame, starting from 0.

@item pos
the position in the file of the input frame, NAN if unknown

@item t
The timestamp expressed in seconds. It's NAN if the input timestamp is unknown.

@end table

The expression for @var{out_w} may depend on the value of @var{out_h},
and the expression for @var{out_h} may depend on @var{out_w}, but they
cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are
evaluated after @var{out_w} and @var{out_h}.

The @var{x} and @var{y} parameters specify the expressions for the
position of the top-left corner of the output (non-cropped) area. They
are evaluated for each frame. If the evaluated value is not valid, it
is approximated to the nearest valid value.

The expression for @var{x} may depend on @var{y}, and the expression
for @var{y} may depend on @var{x}.

@subsection Examples

@itemize
@item
Crop area with size 100x100 at position (12,34).
@example
crop=100:100:12:34
@end example

Using named options, the example above becomes:
@example
crop=w=100:h=100:x=12:y=34
@end example

@item
Crop the central input area with size 100x100:
@example
crop=100:100
@end example

@item
Crop the central input area with size 2/3 of the input video:
@example
crop=2/3*in_w:2/3*in_h
@end example

@item
Crop the input video central square:
@example
crop=out_w=in_h
crop=in_h
@end example

@item
Delimit the rectangle with the top-left corner placed at position
100:100 and the right-bottom corner corresponding to the right-bottom
corner of the input image.
@example
crop=in_w-100:in_h-100:100:100
@end example

@item
Crop 10 pixels from the left and right borders, and 20 pixels from
the top and bottom borders
@example
crop=in_w-2*10:in_h-2*20
@end example

@item
Keep only the bottom right quarter of the input image:
@example
crop=in_w/2:in_h/2:in_w/2:in_h/2
@end example

@item
Crop height for getting Greek harmony:
@example
crop=in_w:1/PHI*in_w
@end example

@item
Appply trembling effect:
@example
crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(n/10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(n/7)
@end example

@item
Apply erratic camera effect depending on timestamp:
@example
crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)"
@end example

@item
Set x depending on the value of y:
@example
crop=in_w/2:in_h/2:y:10+10*sin(n/10)
@end example
@end itemize

@section cropdetect

Auto-detect the crop size.

It calculates the necessary cropping parameters and prints the
recommended parameters via the logging system. The detected dimensions
correspond to the non-black area of the input video.

It accepts the following parameters:

@table @option

@item limit
Set higher black value threshold, which can be optionally specified
from nothing (0) to everything (255). An intensity value greater
to the set value is considered non-black. It defaults to 24.

@item round
The value which the width/height should be divisible by. It defaults to
16. The offset is automatically adjusted to center the video. Use 2 to
get only even dimensions (needed for 4:2:2 video). 16 is best when
encoding to most video codecs.

@item reset_count, reset
Set the counter that determines after how many frames cropdetect will
reset the previously detected largest video area and start over to
detect the current optimal crop area. Default value is 0.

This can be useful when channel logos distort the video area. 0
indicates 'never reset', and returns the largest area encountered during
playback.
@end table

@anchor{curves}
@section curves

Apply color adjustments using curves.

This filter is similar to the Adobe Photoshop and GIMP curves tools. Each
component (red, green and blue) has its values defined by @var{N} key points
tied from each other using a smooth curve. The x-axis represents the pixel
values from the input frame, and the y-axis the new pixel values to be set for
the output frame.

By default, a component curve is defined by the two points @var{(0;0)} and
@var{(1;1)}. This creates a straight line where each original pixel value is
"adjusted" to its own value, which means no change to the image.

The filter allows you to redefine these two points and add some more. A new
curve (using a natural cubic spline interpolation) will be define to pass
smoothly through all these new coordinates. The new defined points needs to be
strictly increasing over the x-axis, and their @var{x} and @var{y} values must
be in the @var{[0;1]} interval.  If the computed curves happened to go outside
the vector spaces, the values will be clipped accordingly.

If there is no key point defined in @code{x=0}, the filter will automatically
insert a @var{(0;0)} point. In the same way, if there is no key point defined
in @code{x=1}, the filter will automatically insert a @var{(1;1)} point.

The filter accepts the following options:

@table @option
@item preset
Select one of the available color presets. This option can be used in addition
to the @option{r}, @option{g}, @option{b} parameters; in this case, the later
options takes priority on the preset values.
Available presets are:
@table @samp
@item none
@item color_negative
@item cross_process
@item darker
@item increase_contrast
@item lighter
@item linear_contrast
@item medium_contrast
@item negative
@item strong_contrast
@item vintage
@end table
Default is @code{none}.
@item master, m
Set the master key points. These points will define a second pass mapping. It
is sometimes called a "luminance" or "value" mapping. It can be used with
@option{r}, @option{g}, @option{b} or @option{all} since it acts like a
post-processing LUT.
@item red, r
Set the key points for the red component.
@item green, g
Set the key points for the green component.
@item blue, b
Set the key points for the blue component.
@item all
Set the key points for all components (not including master).
Can be used in addition to the other key points component
options. In this case, the unset component(s) will fallback on this
@option{all} setting.
@item psfile
Specify a Photoshop curves file (@code{.asv}) to import the settings from.
@end table

To avoid some filtergraph syntax conflicts, each key points list need to be
defined using the following syntax: @code{x0/y0 x1/y1 x2/y2 ...}.

@subsection Examples

@itemize
@item
Increase slightly the middle level of blue:
@example
curves=blue='0.5/0.58'
@end example

@item
Vintage effect:
@example
curves=r='0/0.11 .42/.51 1/0.95':g='0.50/0.48':b='0/0.22 .49/.44 1/0.8'
@end example
Here we obtain the following coordinates for each components:
@table @var
@item red
@code{(0;0.11) (0.42;0.51) (1;0.95)}
@item green
@code{(0;0) (0.50;0.48) (1;1)}
@item blue
@code{(0;0.22) (0.49;0.44) (1;0.80)}
@end table

@item
The previous example can also be achieved with the associated built-in preset:
@example
curves=preset=vintage
@end example

@item
Or simply:
@example
curves=vintage
@end example

@item
Use a Photoshop preset and redefine the points of the green component:
@example
curves=psfile='MyCurvesPresets/purple.asv':green='0.45/0.53'
@end example
@end itemize

@section dctdnoiz

Denoise frames using 2D DCT (frequency domain filtering).

This filter is not designed for real time.

The filter accepts the following options:

@table @option
@item sigma, s
Set the noise sigma constant.

This @var{sigma} defines a hard threshold of @code{3 * sigma}; every DCT
coefficient (absolute value) below this threshold with be dropped.

If you need a more advanced filtering, see @option{expr}.

Default is @code{0}.

@item overlap
Set number overlapping pixels for each block. Since the filter can be slow, you
may want to reduce this value, at the cost of a less effective filter and the
risk of various artefacts.

If the overlapping value doesn't allow to process the whole input width or
height, a warning will be displayed and according borders won't be denoised.

Default value is @var{blocksize}-1, which is the best possible setting.

@item expr, e
Set the coefficient factor expression.

For each coefficient of a DCT block, this expression will be evaluated as a
multiplier value for the coefficient.

If this is option is set, the @option{sigma} option will be ignored.

The absolute value of the coefficient can be accessed through the @var{c}
variable.

@item n
Set the @var{blocksize} using the number of bits. @code{1<<@var{n}} defines the
@var{blocksize}, which is the width and height of the processed blocks.

The default value is @var{3} (8x8) and can be raised to @var{4} for a
@var{blocksize} of 16x16. Note that changing this setting has huge consequences
on the speed processing. Also, a larger block size does not necessarily means a
better de-noising.
@end table

@subsection Examples

Apply a denoise with a @option{sigma} of @code{4.5}:
@example
dctdnoiz=4.5
@end example

The same operation can be achieved using the expression system:
@example
dctdnoiz=e='gte(c, 4.5*3)'
@end example

Violent denoise using a block size of @code{16x16}:
@example
dctdnoiz=15:n=4
@end example

@anchor{decimate}
@section decimate

Drop duplicated frames at regular intervals.

The filter accepts the following options:

@table @option
@item cycle
Set the number of frames from which one will be dropped. Setting this to
@var{N} means one frame in every batch of @var{N} frames will be dropped.
Default is @code{5}.

@item dupthresh
Set the threshold for duplicate detection. If the difference metric for a frame
is less than or equal to this value, then it is declared as duplicate. Default
is @code{1.1}

@item scthresh
Set scene change threshold. Default is @code{15}.

@item blockx
@item blocky
Set the size of the x and y-axis blocks used during metric calculations.
Larger blocks give better noise suppression, but also give worse detection of
small movements. Must be a power of two. Default is @code{32}.

@item ppsrc
Mark main input as a pre-processed input and activate clean source input
stream. This allows the input to be pre-processed with various filters to help
the metrics calculation while keeping the frame selection lossless. When set to
@code{1}, the first stream is for the pre-processed input, and the second
stream is the clean source from where the kept frames are chosen. Default is
@code{0}.

@item chroma
Set whether or not chroma is considered in the metric calculations. Default is
@code{1}.
@end table

@section dejudder

Remove judder produced by partially interlaced telecined content.

Judder can be introduced, for instance, by @ref{pullup} filter. If the original
source was partially telecined content then the output of @code{pullup,dejudder}
will have a variable frame rate. May change the recorded frame rate of the
container. Aside from that change, this filter will not affect constant frame
rate video.

The option available in this filter is:
@table @option

@item cycle
Specify the length of the window over which the judder repeats.

Accepts any integer greater than 1. Useful values are:
@table @samp

@item 4
If the original was telecined from 24 to 30 fps (Film to NTSC).

@item 5
If the original was telecined from 25 to 30 fps (PAL to NTSC).

@item 20
If a mixture of the two.
@end table

The default is @samp{4}.
@end table

@section delogo

Suppress a TV station logo by a simple interpolation of the surrounding
pixels. Just set a rectangle covering the logo and watch it disappear
(and sometimes something even uglier appear - your mileage may vary).

It accepts the following parameters:
@table @option

@item x
@item y
Specify the top left corner coordinates of the logo. They must be
specified.

@item w
@item h
Specify the width and height of the logo to clear. They must be
specified.

@item band, t
Specify the thickness of the fuzzy edge of the rectangle (added to
@var{w} and @var{h}). The default value is 4.

@item show
When set to 1, a green rectangle is drawn on the screen to simplify
finding the right @var{x}, @var{y}, @var{w}, and @var{h} parameters.
The default value is 0.

The rectangle is drawn on the outermost pixels which will be (partly)
replaced with interpolated values. The values of the next pixels
immediately outside this rectangle in each direction will be used to
compute the interpolated pixel values inside the rectangle.

@end table

@subsection Examples

@itemize
@item
Set a rectangle covering the area with top left corner coordinates 0,0
and size 100x77, and a band of size 10:
@example
delogo=x=0:y=0:w=100:h=77:band=10
@end example

@end itemize

@section deshake

Attempt to fix small changes in horizontal and/or vertical shift. This
filter helps remove camera shake from hand-holding a camera, bumping a
tripod, moving on a vehicle, etc.

The filter accepts the following options:

@table @option

@item x
@item y
@item w
@item h
Specify a rectangular area where to limit the search for motion
vectors.
If desired the search for motion vectors can be limited to a
rectangular area of the frame defined by its top left corner, width
and height. These parameters have the same meaning as the drawbox
filter which can be used to visualise the position of the bounding
box.

This is useful when simultaneous movement of subjects within the frame
might be confused for camera motion by the motion vector search.

If any or all of @var{x}, @var{y}, @var{w} and @var{h} are set to -1
then the full frame is used. This allows later options to be set
without specifying the bounding box for the motion vector search.

Default - search the whole frame.

@item rx
@item ry
Specify the maximum extent of movement in x and y directions in the
range 0-64 pixels. Default 16.

@item edge
Specify how to generate pixels to fill blanks at the edge of the
frame. Available values are:
@table @samp
@item blank, 0
Fill zeroes at blank locations
@item original, 1
Original image at blank locations
@item clamp, 2
Extruded edge value at blank locations
@item mirror, 3
Mirrored edge at blank locations
@end table
Default value is @samp{mirror}.

@item blocksize
Specify the blocksize to use for motion search. Range 4-128 pixels,
default 8.

@item contrast
Specify the contrast threshold for blocks. Only blocks with more than
the specified contrast (difference between darkest and lightest
pixels) will be considered. Range 1-255, default 125.

@item search
Specify the search strategy. Available values are:
@table @samp
@item exhaustive, 0
Set exhaustive search
@item less, 1
Set less exhaustive search.
@end table
Default value is @samp{exhaustive}.

@item filename
If set then a detailed log of the motion search is written to the
specified file.

@item opencl
If set to 1, specify using OpenCL capabilities, only available if
FFmpeg was configured with @code{--enable-opencl}. Default value is 0.

@end table

@section drawbox

Draw a colored box on the input image.

It accepts the following parameters:

@table @option
@item x
@item y
The expressions which specify the top left corner coordinates of the box. It defaults to 0.

@item width, w
@item height, h
The expressions which specify the width and height of the box; if 0 they are interpreted as
the input width and height. It defaults to 0.

@item color, c
Specify the color of the box to write. For the general syntax of this option,
check the "Color" section in the ffmpeg-utils manual. If the special
value @code{invert} is used, the box edge color is the same as the
video with inverted luma.

@item thickness, t
The expression which sets the thickness of the box edge. Default value is @code{3}.

See below for the list of accepted constants.
@end table

The parameters for @var{x}, @var{y}, @var{w} and @var{h} and @var{t} are expressions containing the
following constants:

@table @option
@item dar
The input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar}.

@item hsub
@item vsub
horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.

@item in_h, ih
@item in_w, iw
The input width and height.

@item sar
The input sample aspect ratio.

@item x
@item y
The x and y offset coordinates where the box is drawn.

@item w
@item h
The width and height of the drawn box.

@item t
The thickness of the drawn box.

These constants allow the @var{x}, @var{y}, @var{w}, @var{h} and @var{t} expressions to refer to
each other, so you may for example specify @code{y=x/dar} or @code{h=w/dar}.

@end table

@subsection Examples

@itemize
@item
Draw a black box around the edge of the input image:
@example
drawbox
@end example

@item
Draw a box with color red and an opacity of 50%:
@example
drawbox=10:20:200:60:red@@0.5
@end example

The previous example can be specified as:
@example
drawbox=x=10:y=20:w=200:h=60:color=red@@0.5
@end example

@item
Fill the box with pink color:
@example
drawbox=x=10:y=10:w=100:h=100:color=pink@@0.5:t=max
@end example

@item
Draw a 2-pixel red 2.40:1 mask:
@example
drawbox=x=-t:y=0.5*(ih-iw/2.4)-t:w=iw+t*2:h=iw/2.4+t*2:t=2:c=red
@end example
@end itemize

@section drawgrid

Draw a grid on the input image.

It accepts the following parameters:

@table @option
@item x
@item y
The expressions which specify the coordinates of some point of grid intersection (meant to configure offset). Both default to 0.

@item width, w
@item height, h
The expressions which specify the width and height of the grid cell, if 0 they are interpreted as the
input width and height, respectively, minus @code{thickness}, so image gets
framed. Default to 0.

@item color, c
Specify the color of the grid. For the general syntax of this option,
check the "Color" section in the ffmpeg-utils manual. If the special
value @code{invert} is used, the grid color is the same as the
video with inverted luma.

@item thickness, t
The expression which sets the thickness of the grid line. Default value is @code{1}.

See below for the list of accepted constants.
@end table

The parameters for @var{x}, @var{y}, @var{w} and @var{h} and @var{t} are expressions containing the
following constants:

@table @option
@item dar
The input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar}.

@item hsub
@item vsub
horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.

@item in_h, ih
@item in_w, iw
The input grid cell width and height.

@item sar
The input sample aspect ratio.

@item x
@item y
The x and y coordinates of some point of grid intersection (meant to configure offset).

@item w
@item h
The width and height of the drawn cell.

@item t
The thickness of the drawn cell.

These constants allow the @var{x}, @var{y}, @var{w}, @var{h} and @var{t} expressions to refer to
each other, so you may for example specify @code{y=x/dar} or @code{h=w/dar}.

@end table

@subsection Examples

@itemize
@item
Draw a grid with cell 100x100 pixels, thickness 2 pixels, with color red and an opacity of 50%:
@example
drawgrid=width=100:height=100:thickness=2:color=red@@0.5
@end example

@item
Draw a white 3x3 grid with an opacity of 50%:
@example
drawgrid=w=iw/3:h=ih/3:t=2:c=white@@0.5
@end example
@end itemize

@anchor{drawtext}
@section drawtext

Draw a text string or text from a specified file on top of a video, using the
libfreetype library.

To enable compilation of this filter, you need to configure FFmpeg with
@code{--enable-libfreetype}.
To enable default font fallback and the @var{font} option you need to
configure FFmpeg with @code{--enable-libfontconfig}.
To enable the @var{text_shaping} option, you need to configure FFmpeg with
@code{--enable-libfribidi}.

@subsection Syntax

It accepts the following parameters:

@table @option

@item box
Used to draw a box around text using the background color.
The value must be either 1 (enable) or 0 (disable).
The default value of @var{box} is 0.

@item boxcolor
The color to be used for drawing box around text. For the syntax of this
option, check the "Color" section in the ffmpeg-utils manual.

The default value of @var{boxcolor} is "white".

@item borderw
Set the width of the border to be drawn around the text using @var{bordercolor}.
The default value of @var{borderw} is 0.

@item bordercolor
Set the color to be used for drawing border around text. For the syntax of this
option, check the "Color" section in the ffmpeg-utils manual.

The default value of @var{bordercolor} is "black".

@item expansion
Select how the @var{text} is expanded. Can be either @code{none},
@code{strftime} (deprecated) or
@code{normal} (default). See the @ref{drawtext_expansion, Text expansion} section
below for details.

@item fix_bounds
If true, check and fix text coords to avoid clipping.

@item fontcolor
The color to be used for drawing fonts. For the syntax of this option, check
the "Color" section in the ffmpeg-utils manual.

The default value of @var{fontcolor} is "black".

@item fontcolor_expr
String which is expanded the same way as @var{text} to obtain dynamic
@var{fontcolor} value. By default this option has empty value and is not
processed. When this option is set, it overrides @var{fontcolor} option.

@item font
The font family to be used for drawing text. By default Sans.

@item fontfile
The font file to be used for drawing text. The path must be included.
This parameter is mandatory if the fontconfig support is disabled.

@item fontsize
The font size to be used for drawing text.
The default value of @var{fontsize} is 16.

@item text_shaping
If set to 1, attempt to shape the text (for example, reverse the order of
right-to-left text and join Arabic characters) before drawing it.
Otherwise, just draw the text exactly as given.
By default 1 (if supported).

@item ft_load_flags
The flags to be used for loading the fonts.

The flags map the corresponding flags supported by libfreetype, and are
a combination of the following values:
@table @var
@item default
@item no_scale
@item no_hinting
@item render
@item no_bitmap
@item vertical_layout
@item force_autohint
@item crop_bitmap
@item pedantic
@item ignore_global_advance_width
@item no_recurse
@item ignore_transform
@item monochrome
@item linear_design
@item no_autohint
@end table

Default value is "default".

For more information consult the documentation for the FT_LOAD_*
libfreetype flags.

@item shadowcolor
The color to be used for drawing a shadow behind the drawn text. For the
syntax of this option, check the "Color" section in the ffmpeg-utils manual.

The default value of @var{shadowcolor} is "black".

@item shadowx
@item shadowy
The x and y offsets for the text shadow position with respect to the
position of the text. They can be either positive or negative
values. The default value for both is "0".

@item start_number
The starting frame number for the n/frame_num variable. The default value
is "0".

@item tabsize
The size in number of spaces to use for rendering the tab.
Default value is 4.

@item timecode
Set the initial timecode representation in "hh:mm:ss[:;.]ff"
format. It can be used with or without text parameter. @var{timecode_rate}
option must be specified.

@item timecode_rate, rate, r
Set the timecode frame rate (timecode only).

@item text
The text string to be drawn. The text must be a sequence of UTF-8
encoded characters.
This parameter is mandatory if no file is specified with the parameter
@var{textfile}.

@item textfile
A text file containing text to be drawn. The text must be a sequence
of UTF-8 encoded characters.

This parameter is mandatory if no text string is specified with the
parameter @var{text}.

If both @var{text} and @var{textfile} are specified, an error is thrown.

@item reload
If set to 1, the @var{textfile} will be reloaded before each frame.
Be sure to update it atomically, or it may be read partially, or even fail.

@item x
@item y
The expressions which specify the offsets where text will be drawn
within the video frame. They are relative to the top/left border of the
output image.

The default value of @var{x} and @var{y} is "0".

See below for the list of accepted constants and functions.
@end table

The parameters for @var{x} and @var{y} are expressions containing the
following constants and functions:

@table @option
@item dar
input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar}

@item hsub
@item vsub
horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.

@item line_h, lh
the height of each text line

@item main_h, h, H
the input height

@item main_w, w, W
the input width

@item max_glyph_a, ascent
the maximum distance from the baseline to the highest/upper grid
coordinate used to place a glyph outline point, for all the rendered
glyphs.
It is a positive value, due to the grid's orientation with the Y axis
upwards.

@item max_glyph_d, descent
the maximum distance from the baseline to the lowest grid coordinate
used to place a glyph outline point, for all the rendered glyphs.
This is a negative value, due to the grid's orientation, with the Y axis
upwards.

@item max_glyph_h
maximum glyph height, that is the maximum height for all the glyphs
contained in the rendered text, it is equivalent to @var{ascent} -
@var{descent}.

@item max_glyph_w
maximum glyph width, that is the maximum width for all the glyphs
contained in the rendered text

@item n
the number of input frame, starting from 0

@item rand(min, max)
return a random number included between @var{min} and @var{max}

@item sar
The input sample aspect ratio.

@item t
timestamp expressed in seconds, NAN if the input timestamp is unknown

@item text_h, th
the height of the rendered text

@item text_w, tw
the width of the rendered text

@item x
@item y
the x and y offset coordinates where the text is drawn.

These parameters allow the @var{x} and @var{y} expressions to refer
each other, so you can for example specify @code{y=x/dar}.
@end table

@anchor{drawtext_expansion}
@subsection Text expansion

If @option{expansion} is set to @code{strftime},
the filter recognizes strftime() sequences in the provided text and
expands them accordingly. Check the documentation of strftime(). This
feature is deprecated.

If @option{expansion} is set to @code{none}, the text is printed verbatim.

If @option{expansion} is set to @code{normal} (which is the default),
the following expansion mechanism is used.

The backslash character '\', followed by any character, always expands to
the second character.

Sequence of the form @code{%@{...@}} are expanded. The text between the
braces is a function name, possibly followed by arguments separated by ':'.
If the arguments contain special characters or delimiters (':' or '@}'),
they should be escaped.

Note that they probably must also be escaped as the value for the
@option{text} option in the filter argument string and as the filter
argument in the filtergraph description, and possibly also for the shell,
that makes up to four levels of escaping; using a text file avoids these
problems.

The following functions are available:

@table @command

@item expr, e
The expression evaluation result.

It must take one argument specifying the expression to be evaluated,
which accepts the same constants and functions as the @var{x} and
@var{y} values. Note that not all constants should be used, for
example the text size is not known when evaluating the expression, so
the constants @var{text_w} and @var{text_h} will have an undefined
value.

@item expr_int_format, eif
Evaluate the expression's value and output as formatted integer.

The first argument is the expression to be evaluated, just as for the @var{expr} function.
The second argument specifies the output format. Allowed values are 'x', 'X', 'd' and
'u'. They are treated exactly as in the printf function.
The third parameter is optional and sets the number of positions taken by the output.
It can be used to add padding with zeros from the left.

@item gmtime
The time at which the filter is running, expressed in UTC.
It can accept an argument: a strftime() format string.

@item localtime
The time at which the filter is running, expressed in the local time zone.
It can accept an argument: a strftime() format string.

@item metadata
Frame metadata. It must take one argument specifying metadata key.

@item n, frame_num
The frame number, starting from 0.

@item pict_type
A 1 character description of the current picture type.

@item pts
The timestamp of the current frame.
It can take up to two arguments.

The first argument is the format of the timestamp; it defaults to @code{flt}
for seconds as a decimal number with microsecond accuracy; @code{hms} stands
for a formatted @var{[-]HH:MM:SS.mmm} timestamp with millisecond accuracy.

The second argument is an offset added to the timestamp.

@end table

@subsection Examples

@itemize
@item
Draw "Test Text" with font FreeSerif, using the default values for the
optional parameters.

@example
drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"
@end example

@item
Draw 'Test Text' with font FreeSerif of size 24 at position x=100
and y=50 (counting from the top-left corner of the screen), text is
yellow with a red box around it. Both the text and the box have an
opacity of 20%.

@example
drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
          x=100: y=50: fontsize=24: fontcolor=yellow@@0.2: box=1: boxcolor=red@@0.2"
@end example

Note that the double quotes are not necessary if spaces are not used
within the parameter list.

@item
Show the text at the center of the video frame:
@example
drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h-line_h)/2"
@end example

@item
Show a text line sliding from right to left in the last row of the video
frame. The file @file{LONG_LINE} is assumed to contain a single line
with no newlines.
@example
drawtext="fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t"
@end example

@item
Show the content of file @file{CREDITS} off the bottom of the frame and scroll up.
@example
drawtext="fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t"
@end example

@item
Draw a single green letter "g", at the center of the input video.
The glyph baseline is placed at half screen height.
@example
drawtext="fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent"
@end example

@item
Show text for 1 second every 3 seconds:
@example
drawtext="fontfile=FreeSerif.ttf:fontcolor=white:x=100:y=x/dar:enable=lt(mod(t\,3)\,1):text='blink'"
@end example

@item
Use fontconfig to set the font. Note that the colons need to be escaped.
@example
drawtext='fontfile=Linux Libertine O-40\:style=Semibold:text=FFmpeg'
@end example

@item
Print the date of a real-time encoding (see strftime(3)):
@example
drawtext='fontfile=FreeSans.ttf:text=%@{localtime\:%a %b %d %Y@}'
@end example

@item
Show text fading in and out (appearing/disappearing):
@example
#!/bin/sh
DS=1.0 # display start
DE=10.0 # display end
FID=1.5 # fade in duration
FOD=5 # fade out duration
ffplay -f lavfi "color,drawtext=text=TEST:fontsize=50:fontfile=FreeSerif.ttf:fontcolor_expr=ff0000%@{eif\\\\: clip(255*(1*between(t\\, $DS + $FID\\, $DE - $FOD) + ((t - $DS)/$FID)*between(t\\, $DS\\, $DS + $FID) + (-(t - $DE)/$FOD)*between(t\\, $DE - $FOD\\, $DE) )\\, 0\\, 255) \\\\: x\\\\: 2 @}"
@end example

@end itemize

For more information about libfreetype, check:
@url{http://www.freetype.org/}.

For more information about fontconfig, check:
@url{http://freedesktop.org/software/fontconfig/fontconfig-user.html}.

For more information about libfribidi, check:
@url{http://fribidi.org/}.

@section edgedetect

Detect and draw edges. The filter uses the Canny Edge Detection algorithm.

The filter accepts the following options:

@table @option
@item low
@item high
Set low and high threshold values used by the Canny thresholding
algorithm.

The high threshold selects the "strong" edge pixels, which are then
connected through 8-connectivity with the "weak" edge pixels selected
by the low threshold.

@var{low} and @var{high} threshold values must be chosen in the range
[0,1], and @var{low} should be lesser or equal to @var{high}.

Default value for @var{low} is @code{20/255}, and default value for @var{high}
is @code{50/255}.

@item mode
Define the drawing mode.

@table @samp
@item wires
Draw white/gray wires on black background.

@item colormix
Mix the colors to create a paint/cartoon effect.
@end table

Default value is @var{wires}.
@end table

@subsection Examples

@itemize
@item
Standard edge detection with custom values for the hysteresis thresholding:
@example
edgedetect=low=0.1:high=0.4
@end example

@item
Painting effect without thresholding:
@example
edgedetect=mode=colormix:high=0
@end example
@end itemize

@section extractplanes

Extract color channel components from input video stream into
separate grayscale video streams.

The filter accepts the following option:

@table @option
@item planes
Set plane(s) to extract.

Available values for planes are:
@table @samp
@item y
@item u
@item v
@item a
@item r
@item g
@item b
@end table

Choosing planes not available in the input will result in an error.
That means you cannot select @code{r}, @code{g}, @code{b} planes
with @code{y}, @code{u}, @code{v} planes at same time.
@end table

@subsection Examples

@itemize
@item
Extract luma, u and v color channel component from input video frame
into 3 grayscale outputs:
@example
ffmpeg -i video.avi -filter_complex 'extractplanes=y+u+v[y][u][v]' -map '[y]' y.avi -map '[u]' u.avi -map '[v]' v.avi
@end example
@end itemize

@section elbg

Apply a posterize effect using the ELBG (Enhanced LBG) algorithm.

For each input image, the filter will compute the optimal mapping from
the input to the output given the codebook length, that is the number
of distinct output colors.

This filter accepts the following options.

@table @option
@item codebook_length, l
Set codebook length. The value must be a positive integer, and
represents the number of distinct output colors. Default value is 256.

@item nb_steps, n
Set the maximum number of iterations to apply for computing the optimal
mapping. The higher the value the better the result and the higher the
computation time. Default value is 1.

@item seed, s
Set a random seed, must be an integer included between 0 and
UINT32_MAX. If not specified, or if explicitly set to -1, the filter
will try to use a good random seed on a best effort basis.
@end table

@section fade

Apply a fade-in/out effect to the input video.

It accepts the following parameters:

@table @option
@item type, t
The effect type can be either "in" for a fade-in, or "out" for a fade-out
effect.
Default is @code{in}.

@item start_frame, s
Specify the number of the frame to start applying the fade
effect at. Default is 0.

@item nb_frames, n
The number of frames that the fade effect lasts. At the end of the
fade-in effect, the output video will have the same intensity as the input video.
At the end of the fade-out transition, the output video will be filled with the
selected @option{color}.
Default is 25.

@item alpha
If set to 1, fade only alpha channel, if one exists on the input.
Default value is 0.

@item start_time, st
Specify the timestamp (in seconds) of the frame to start to apply the fade
effect. If both start_frame and start_time are specified, the fade will start at
whichever comes last.  Default is 0.

@item duration, d
The number of seconds for which the fade effect has to last. At the end of the
fade-in effect the output video will have the same intensity as the input video,
at the end of the fade-out transition the output video will be filled with the
selected @option{color}.
If both duration and nb_frames are specified, duration is used. Default is 0.

@item color, c
Specify the color of the fade. Default is "black".
@end table

@subsection Examples

@itemize
@item
Fade in the first 30 frames of video:
@example
fade=in:0:30
@end example

The command above is equivalent to:
@example
fade=t=in:s=0:n=30
@end example

@item
Fade out the last 45 frames of a 200-frame video:
@example
fade=out:155:45
fade=type=out:start_frame=155:nb_frames=45
@end example

@item
Fade in the first 25 frames and fade out the last 25 frames of a 1000-frame video:
@example
fade=in:0:25, fade=out:975:25
@end example

@item
Make the first 5 frames yellow, then fade in from frame 5-24:
@example
fade=in:5:20:color=yellow
@end example

@item
Fade in alpha over first 25 frames of video:
@example
fade=in:0:25:alpha=1
@end example

@item
Make the first 5.5 seconds black, then fade in for 0.5 seconds:
@example
fade=t=in:st=5.5:d=0.5
@end example

@end itemize

@section field

Extract a single field from an interlaced image using stride
arithmetic to avoid wasting CPU time. The output frames are marked as
non-interlaced.

The filter accepts the following options:

@table @option
@item type
Specify whether to extract the top (if the value is @code{0} or
@code{top}) or the bottom field (if the value is @code{1} or
@code{bottom}).
@end table

@section fieldmatch

Field matching filter for inverse telecine. It is meant to reconstruct the
progressive frames from a telecined stream. The filter does not drop duplicated
frames, so to achieve a complete inverse telecine @code{fieldmatch} needs to be
followed by a decimation filter such as @ref{decimate} in the filtergraph.

The separation of the field matching and the decimation is notably motivated by
the possibility of inserting a de-interlacing filter fallback between the two.
If the source has mixed telecined and real interlaced content,
@code{fieldmatch} will not be able to match fields for the interlaced parts.
But these remaining combed frames will be marked as interlaced, and thus can be
de-interlaced by a later filter such as @ref{yadif} before decimation.

In addition to the various configuration options, @code{fieldmatch} can take an
optional second stream, activated through the @option{ppsrc} option. If
enabled, the frames reconstruction will be based on the fields and frames from
this second stream. This allows the first input to be pre-processed in order to
help the various algorithms of the filter, while keeping the output lossless
(assuming the fields are matched properly). Typically, a field-aware denoiser,
or brightness/contrast adjustments can help.

Note that this filter uses the same algorithms as TIVTC/TFM (AviSynth project)
and VIVTC/VFM (VapourSynth project). The later is a light clone of TFM from
which @code{fieldmatch} is based on. While the semantic and usage are very
close, some behaviour and options names can differ.

The @ref{decimate} filter currently only works for constant frame rate input.
Do not use @code{fieldmatch} and @ref{decimate} if your input has mixed
telecined and progressive content with changing framerate.

The filter accepts the following options:

@table @option
@item order
Specify the assumed field order of the input stream. Available values are:

@table @samp
@item auto
Auto detect parity (use FFmpeg's internal parity value).
@item bff
Assume bottom field first.
@item tff
Assume top field first.
@end table

Note that it is sometimes recommended not to trust the parity announced by the
stream.

Default value is @var{auto}.

@item mode
Set the matching mode or strategy to use. @option{pc} mode is the safest in the
sense that it won't risk creating jerkiness due to duplicate frames when
possible, but if there are bad edits or blended fields it will end up
outputting combed frames when a good match might actually exist. On the other
hand, @option{pcn_ub} mode is the most risky in terms of creating jerkiness,
but will almost always find a good frame if there is one. The other values are
all somewhere in between @option{pc} and @option{pcn_ub} in terms of risking
jerkiness and creating duplicate frames versus finding good matches in sections
with bad edits, orphaned fields, blended fields, etc.

More details about p/c/n/u/b are available in @ref{p/c/n/u/b meaning} section.

Available values are:

@table @samp
@item pc
2-way matching (p/c)
@item pc_n
2-way matching, and trying 3rd match if still combed (p/c + n)
@item pc_u
2-way matching, and trying 3rd match (same order) if still combed (p/c + u)
@item pc_n_ub
2-way matching, trying 3rd match if still combed, and trying 4th/5th matches if
still combed (p/c + n + u/b)
@item pcn
3-way matching (p/c/n)
@item pcn_ub
3-way matching, and trying 4th/5th matches if all 3 of the original matches are
detected as combed (p/c/n + u/b)
@end table

The parenthesis at the end indicate the matches that would be used for that
mode assuming @option{order}=@var{tff} (and @option{field} on @var{auto} or
@var{top}).

In terms of speed @option{pc} mode is by far the fastest and @option{pcn_ub} is
the slowest.

Default value is @var{pc_n}.

@item ppsrc
Mark the main input stream as a pre-processed input, and enable the secondary
input stream as the clean source to pick the fields from. See the filter
introduction for more details. It is similar to the @option{clip2} feature from
VFM/TFM.

Default value is @code{0} (disabled).

@item field
Set the field to match from. It is recommended to set this to the same value as
@option{order} unless you experience matching failures with that setting. In
certain circumstances changing the field that is used to match from can have a
large impact on matching performance. Available values are:

@table @samp
@item auto
Automatic (same value as @option{order}).
@item bottom
Match from the bottom field.
@item top
Match from the top field.
@end table

Default value is @var{auto}.

@item mchroma
Set whether or not chroma is included during the match comparisons. In most
cases it is recommended to leave this enabled. You should set this to @code{0}
only if your clip has bad chroma problems such as heavy rainbowing or other
artifacts. Setting this to @code{0} could also be used to speed things up at
the cost of some accuracy.

Default value is @code{1}.

@item y0
@item y1
These define an exclusion band which excludes the lines between @option{y0} and
@option{y1} from being included in the field matching decision. An exclusion
band can be used to ignore subtitles, a logo, or other things that may
interfere with the matching. @option{y0} sets the starting scan line and
@option{y1} sets the ending line; all lines in between @option{y0} and
@option{y1} (including @option{y0} and @option{y1}) will be ignored. Setting
@option{y0} and @option{y1} to the same value will disable the feature.
@option{y0} and @option{y1} defaults to @code{0}.

@item scthresh
Set the scene change detection threshold as a percentage of maximum change on
the luma plane. Good values are in the @code{[8.0, 14.0]} range. Scene change
detection is only relevant in case @option{combmatch}=@var{sc}.  The range for
@option{scthresh} is @code{[0.0, 100.0]}.

Default value is @code{12.0}.

@item combmatch
When @option{combatch} is not @var{none}, @code{fieldmatch} will take into
account the combed scores of matches when deciding what match to use as the
final match. Available values are:

@table @samp
@item none
No final matching based on combed scores.
@item sc
Combed scores are only used when a scene change is detected.
@item full
Use combed scores all the time.
@end table

Default is @var{sc}.

@item combdbg
Force @code{fieldmatch} to calculate the combed metrics for certain matches and
print them. This setting is known as @option{micout} in TFM/VFM vocabulary.
Available values are:

@table @samp
@item none
No forced calculation.
@item pcn
Force p/c/n calculations.
@item pcnub
Force p/c/n/u/b calculations.
@end table

Default value is @var{none}.

@item cthresh
This is the area combing threshold used for combed frame detection. This
essentially controls how "strong" or "visible" combing must be to be detected.
Larger values mean combing must be more visible and smaller values mean combing
can be less visible or strong and still be detected. Valid settings are from
@code{-1} (every pixel will be detected as combed) to @code{255} (no pixel will
be detected as combed). This is basically a pixel difference value. A good
range is @code{[8, 12]}.

Default value is @code{9}.

@item chroma
Sets whether or not chroma is considered in the combed frame decision.  Only
disable this if your source has chroma problems (rainbowing, etc.) that are
causing problems for the combed frame detection with chroma enabled. Actually,
using @option{chroma}=@var{0} is usually more reliable, except for the case
where there is chroma only combing in the source.

Default value is @code{0}.

@item blockx
@item blocky
Respectively set the x-axis and y-axis size of the window used during combed
frame detection. This has to do with the size of the area in which
@option{combpel} pixels are required to be detected as combed for a frame to be
declared combed. See the @option{combpel} parameter description for more info.
Possible values are any number that is a power of 2 starting at 4 and going up
to 512.

Default value is @code{16}.

@item combpel
The number of combed pixels inside any of the @option{blocky} by
@option{blockx} size blocks on the frame for the frame to be detected as
combed. While @option{cthresh} controls how "visible" the combing must be, this
setting controls "how much" combing there must be in any localized area (a
window defined by the @option{blockx} and @option{blocky} settings) on the
frame. Minimum value is @code{0} and maximum is @code{blocky x blockx} (at
which point no frames will ever be detected as combed). This setting is known
as @option{MI} in TFM/VFM vocabulary.

Default value is @code{80}.
@end table

@anchor{p/c/n/u/b meaning}
@subsection p/c/n/u/b meaning

@subsubsection p/c/n

We assume the following telecined stream:

@example
Top fields:     1 2 2 3 4
Bottom fields:  1 2 3 4 4
@end example

The numbers correspond to the progressive frame the fields relate to. Here, the
first two frames are progressive, the 3rd and 4th are combed, and so on.

When @code{fieldmatch} is configured to run a matching from bottom
(@option{field}=@var{bottom}) this is how this input stream get transformed:

@example
Input stream:
                T     1 2 2 3 4
                B     1 2 3 4 4   <-- matching reference

Matches:              c c n n c

Output stream:
                T     1 2 3 4 4
                B     1 2 3 4 4
@end example

As a result of the field matching, we can see that some frames get duplicated.
To perform a complete inverse telecine, you need to rely on a decimation filter
after this operation. See for instance the @ref{decimate} filter.

The same operation now matching from top fields (@option{field}=@var{top})
looks like this:

@example
Input stream:
                T     1 2 2 3 4   <-- matching reference
                B     1 2 3 4 4

Matches:              c c p p c

Output stream:
                T     1 2 2 3 4
                B     1 2 2 3 4
@end example

In these examples, we can see what @var{p}, @var{c} and @var{n} mean;
basically, they refer to the frame and field of the opposite parity:

@itemize
@item @var{p} matches the field of the opposite parity in the previous frame
@item @var{c} matches the field of the opposite parity in the current frame
@item @var{n} matches the field of the opposite parity in the next frame
@end itemize

@subsubsection u/b

The @var{u} and @var{b} matching are a bit special in the sense that they match
from the opposite parity flag. In the following examples, we assume that we are
currently matching the 2nd frame (Top:2, bottom:2). According to the match, a
'x' is placed above and below each matched fields.

With bottom matching (@option{field}=@var{bottom}):
@example
Match:           c         p           n          b          u

                 x       x               x        x          x
  Top          1 2 2     1 2 2       1 2 2      1 2 2      1 2 2
  Bottom       1 2 3     1 2 3       1 2 3      1 2 3      1 2 3
                 x         x           x        x              x

Output frames:
                 2          1          2          2          2
                 2          2          2          1          3
@end example

With top matching (@option{field}=@var{top}):
@example
Match:           c         p           n          b          u

                 x         x           x        x              x
  Top          1 2 2     1 2 2       1 2 2      1 2 2      1 2 2
  Bottom       1 2 3     1 2 3       1 2 3      1 2 3      1 2 3
                 x       x               x        x          x

Output frames:
                 2          2          2          1          2
                 2          1          3          2          2
@end example

@subsection Examples

Simple IVTC of a top field first telecined stream:
@example
fieldmatch=order=tff:combmatch=none, decimate
@end example

Advanced IVTC, with fallback on @ref{yadif} for still combed frames:
@example
fieldmatch=order=tff:combmatch=full, yadif=deint=interlaced, decimate
@end example

@section fieldorder

Transform the field order of the input video.

It accepts the following parameters:

@table @option

@item order
The output field order. Valid values are @var{tff} for top field first or @var{bff}
for bottom field first.
@end table

The default value is @samp{tff}.

The transformation is done by shifting the picture content up or down
by one line, and filling the remaining line with appropriate picture content.
This method is consistent with most broadcast field order converters.

If the input video is not flagged as being interlaced, or it is already
flagged as being of the required output field order, then this filter does
not alter the incoming video.

It is very useful when converting to or from PAL DV material,
which is bottom field first.

For example:
@example
ffmpeg -i in.vob -vf "fieldorder=bff" out.dv
@end example

@section fifo

Buffer input images and send them when they are requested.

It is mainly useful when auto-inserted by the libavfilter
framework.

It does not take parameters.

@anchor{format}
@section format

Convert the input video to one of the specified pixel formats.
Libavfilter will try to pick one that is suitable as input to
the next filter.

It accepts the following parameters:
@table @option

@item pix_fmts
A '|'-separated list of pixel format names, such as
"pix_fmts=yuv420p|monow|rgb24".

@end table

@subsection Examples

@itemize
@item
Convert the input video to the @var{yuv420p} format
@example
format=pix_fmts=yuv420p
@end example

Convert the input video to any of the formats in the list
@example
format=pix_fmts=yuv420p|yuv444p|yuv410p
@end example
@end itemize

@anchor{fps}
@section fps

Convert the video to specified constant frame rate by duplicating or dropping
frames as necessary.

It accepts the following parameters:
@table @option

@item fps
The desired output frame rate. The default is @code{25}.

@item round
Rounding method.

Possible values are:
@table @option
@item zero
zero round towards 0
@item inf
round away from 0
@item down
round towards -infinity
@item up
round towards +infinity
@item near
round to nearest
@end table
The default is @code{near}.

@item start_time
Assume the first PTS should be the given value, in seconds. This allows for
padding/trimming at the start of stream. By default, no assumption is made
about the first frame's expected PTS, so no padding or trimming is done.
For example, this could be set to 0 to pad the beginning with duplicates of
the first frame if a video stream starts after the audio stream or to trim any
frames with a negative PTS.

@end table

Alternatively, the options can be specified as a flat string:
@var{fps}[:@var{round}].

See also the @ref{setpts} filter.

@subsection Examples

@itemize
@item
A typical usage in order to set the fps to 25:
@example
fps=fps=25
@end example

@item
Sets the fps to 24, using abbreviation and rounding method to round to nearest:
@example
fps=fps=film:round=near
@end example
@end itemize

@section framepack

Pack two different video streams into a stereoscopic video, setting proper
metadata on supported codecs. The two views should have the same size and
framerate and processing will stop when the shorter video ends. Please note
that you may conveniently adjust view properties with the @ref{scale} and
@ref{fps} filters.

It accepts the following parameters:
@table @option

@item format
The desired packing format. Supported values are:

@table @option

@item sbs
The views are next to each other (default).

@item tab
The views are on top of each other.

@item lines
The views are packed by line.

@item columns
The views are packed by column.

@item frameseq
The views are temporally interleaved.

@end table

@end table

Some examples:

@example
# Convert left and right views into a frame-sequential video
ffmpeg -i LEFT -i RIGHT -filter_complex framepack=frameseq OUTPUT

# Convert views into a side-by-side video with the same output resolution as the input
ffmpeg -i LEFT -i RIGHT -filter_complex [0:v]scale=w=iw/2[left],[1:v]scale=w=iw/2[right],[left][right]framepack=sbs OUTPUT
@end example

@section framestep

Select one frame every N-th frame.

This filter accepts the following option:
@table @option
@item step
Select frame after every @code{step} frames.
Allowed values are positive integers higher than 0. Default value is @code{1}.
@end table

@anchor{frei0r}
@section frei0r

Apply a frei0r effect to the input video.

To enable the compilation of this filter, you need to install the frei0r
header and configure FFmpeg with @code{--enable-frei0r}.

It accepts the following parameters:

@table @option

@item filter_name
The name of the frei0r effect to load. If the environment variable
@env{FREI0R_PATH} is defined, the frei0r effect is searched for in each of the
directories specified by the colon-separated list in @env{FREIOR_PATH}.
Otherwise, the standard frei0r paths are searched, in this order:
@file{HOME/.frei0r-1/lib/}, @file{/usr/local/lib/frei0r-1/},
@file{/usr/lib/frei0r-1/}.

@item filter_params
A '|'-separated list of parameters to pass to the frei0r effect.

@end table

A frei0r effect parameter can be a boolean (its value is either
"y" or "n"), a double, a color (specified as
@var{R}/@var{G}/@var{B}, where @var{R}, @var{G}, and @var{B} are floating point
numbers between 0.0 and 1.0, inclusive) or by a color description specified in the "Color"
section in the ffmpeg-utils manual), a position (specified as @var{X}/@var{Y}, where
@var{X} and @var{Y} are floating point numbers) and/or a string.

The number and types of parameters depend on the loaded effect. If an
effect parameter is not specified, the default value is set.

@subsection Examples

@itemize
@item
Apply the distort0r effect, setting the first two double parameters:
@example
frei0r=filter_name=distort0r:filter_params=0.5|0.01
@end example

@item
Apply the colordistance effect, taking a color as the first parameter:
@example
frei0r=colordistance:0.2/0.3/0.4
frei0r=colordistance:violet
frei0r=colordistance:0x112233
@end example

@item
Apply the perspective effect, specifying the top left and top right image
positions:
@example
frei0r=perspective:0.2/0.2|0.8/0.2
@end example
@end itemize

For more information, see
@url{http://frei0r.dyne.org}

@section geq

The filter accepts the following options:

@table @option
@item lum_expr, lum
Set the luminance expression.
@item cb_expr, cb
Set the chrominance blue expression.
@item cr_expr, cr
Set the chrominance red expression.
@item alpha_expr, a
Set the alpha expression.
@item red_expr, r
Set the red expression.
@item green_expr, g
Set the green expression.
@item blue_expr, b
Set the blue expression.
@end table

The colorspace is selected according to the specified options. If one
of the @option{lum_expr}, @option{cb_expr}, or @option{cr_expr}
options is specified, the filter will automatically select a YCbCr
colorspace. If one of the @option{red_expr}, @option{green_expr}, or
@option{blue_expr} options is specified, it will select an RGB
colorspace.

If one of the chrominance expression is not defined, it falls back on the other
one. If no alpha expression is specified it will evaluate to opaque value.
If none of chrominance expressions are specified, they will evaluate
to the luminance expression.

The expressions can use the following variables and functions:

@table @option
@item N
The sequential number of the filtered frame, starting from @code{0}.

@item X
@item Y
The coordinates of the current sample.

@item W
@item H
The width and height of the image.

@item SW
@item SH
Width and height scale depending on the currently filtered plane. It is the
ratio between the corresponding luma plane number of pixels and the current
plane ones. E.g. for YUV4:2:0 the values are @code{1,1} for the luma plane, and
@code{0.5,0.5} for chroma planes.

@item T
Time of the current frame, expressed in seconds.

@item p(x, y)
Return the value of the pixel at location (@var{x},@var{y}) of the current
plane.

@item lum(x, y)
Return the value of the pixel at location (@var{x},@var{y}) of the luminance
plane.

@item cb(x, y)
Return the value of the pixel at location (@var{x},@var{y}) of the
blue-difference chroma plane. Return 0 if there is no such plane.

@item cr(x, y)
Return the value of the pixel at location (@var{x},@var{y}) of the
red-difference chroma plane. Return 0 if there is no such plane.

@item r(x, y)
@item g(x, y)
@item b(x, y)
Return the value of the pixel at location (@var{x},@var{y}) of the
red/green/blue component. Return 0 if there is no such component.

@item alpha(x, y)
Return the value of the pixel at location (@var{x},@var{y}) of the alpha
plane. Return 0 if there is no such plane.
@end table

For functions, if @var{x} and @var{y} are outside the area, the value will be
automatically clipped to the closer edge.

@subsection Examples

@itemize
@item
Flip the image horizontally:
@example
geq=p(W-X\,Y)
@end example

@item
Generate a bidimensional sine wave, with angle @code{PI/3} and a
wavelength of 100 pixels:
@example
geq=128 + 100*sin(2*(PI/100)*(cos(PI/3)*(X-50*T) + sin(PI/3)*Y)):128:128
@end example

@item
Generate a fancy enigmatic moving light:
@example
nullsrc=s=256x256,geq=random(1)/hypot(X-cos(N*0.07)*W/2-W/2\,Y-sin(N*0.09)*H/2-H/2)^2*1000000*sin(N*0.02):128:128
@end example

@item
Generate a quick emboss effect:
@example
format=gray,geq=lum_expr='(p(X,Y)+(256-p(X-4,Y-4)))/2'
@end example

@item
Modify RGB components depending on pixel position:
@example
geq=r='X/W*r(X,Y)':g='(1-X/W)*g(X,Y)':b='(H-Y)/H*b(X,Y)'
@end example

@item
Create a radial gradient that is the same size as the input (also see
the @ref{vignette} filter):
@example
geq=lum=255*gauss((X/W-0.5)*3)*gauss((Y/H-0.5)*3)/gauss(0)/gauss(0),format=gray
@end example

@item
Create a linear gradient to use as a mask fo