mxf: Override faulty PreviousPartition entries

Some files set the PreviousPartition field to point to its own offset.

If we are parsing forward the Previous partition is immediately known
and its value could be used, otherwise we can safely point to the
header.

Reported-By: Jean Baptiste Kempf <jb@videolan.org>

diff --git a/libavformat/mxfdec.c b/libavformat/mxfdec.c
index 734c50a3ade4bf1700a03e991f1ce01bb37ed76c..39ab4628c23c909c88e7052ba008cc50c7c7a16f 100644 (file)
--- a/libavformat/mxfdec.c
+++ b/libavformat/mxfdec.c
@@ -478,6 +478,26 @@ static int mxf_read_partition_pack(void *arg, AVIOContext *pb, int tag, int size
     avio_read(pb, op, sizeof(UID));
     nb_essence_containers = avio_rb32(pb);
 
+    if (partition->this_partition &&
+        partition->previous_partition == partition->this_partition) {
+        av_log(mxf->fc, AV_LOG_ERROR,
+               "PreviousPartition equal to ThisPartition %"PRIx64"\n",
+               partition->previous_partition);
+        /* override with the actual previous partition offset */
+        if (!mxf->parsing_backward && mxf->last_forward_partition > 1) {
+            MXFPartition *prev =
+                mxf->partitions + mxf->last_forward_partition - 2;
+            partition->previous_partition = prev->this_partition;
+        }
+        /* if no previous body partition are found point to the header
+         * partition */
+        if (partition->previous_partition == partition->this_partition);
+            partition->previous_partition = 0;
+        av_log(mxf->fc, AV_LOG_ERROR,
+               "Overriding PreviousPartition with %"PRIx64"\n",
+               partition->previous_partition);
+    }
+
     /* some files don'thave FooterPartition set in every partition */
     if (footer_partition) {
         if (mxf->footer_partition && mxf->footer_partition != footer_partition) {