+static int ni_prepare_read(AVFormatContext *s)
+{
+ AVIContext *avi = s->priv_data;
+ int best_stream_index = 0;
+ AVStream *best_st = NULL;
+ AVIStream *best_ast;
+ int64_t best_ts = INT64_MAX;
+ int i;
+
+ for (i = 0; i < s->nb_streams; i++) {
+ AVStream *st = s->streams[i];
+ AVIStream *ast = st->priv_data;
+ int64_t ts = ast->frame_offset;
+ int64_t last_ts;
+
+ if (!st->nb_index_entries)
+ continue;
+
+ last_ts = st->index_entries[st->nb_index_entries - 1].timestamp;
+ if (!ast->remaining && ts > last_ts)
+ continue;
+
+ ts = av_rescale_q(ts, st->time_base,
+ (AVRational) { FFMAX(1, ast->sample_size),
+ AV_TIME_BASE });
+
+ av_log(s, AV_LOG_TRACE, "%"PRId64" %d/%d %"PRId64"\n", ts,
+ st->time_base.num, st->time_base.den, ast->frame_offset);
+ if (ts < best_ts) {
+ best_ts = ts;
+ best_st = st;
+ best_stream_index = i;
+ }
+ }
+ if (!best_st)
+ return AVERROR_EOF;
+
+ best_ast = best_st->priv_data;
+ best_ts = av_rescale_q(best_ts,
+ (AVRational) { FFMAX(1, best_ast->sample_size),
+ AV_TIME_BASE },
+ best_st->time_base);
+ if (best_ast->remaining) {
+ i = av_index_search_timestamp(best_st,
+ best_ts,
+ AVSEEK_FLAG_ANY |
+ AVSEEK_FLAG_BACKWARD);
+ } else {
+ i = av_index_search_timestamp(best_st, best_ts, AVSEEK_FLAG_ANY);
+ if (i >= 0)
+ best_ast->frame_offset = best_st->index_entries[i].timestamp;
+ }
+
+ if (i >= 0) {
+ int64_t pos = best_st->index_entries[i].pos;
+ pos += best_ast->packet_size - best_ast->remaining;
+ avio_seek(s->pb, pos + 8, SEEK_SET);
+
+ assert(best_ast->remaining <= best_ast->packet_size);
+
+ avi->stream_index = best_stream_index;
+ if (!best_ast->remaining)
+ best_ast->packet_size =
+ best_ast->remaining = best_st->index_entries[i].size;
+ }
+
+ return 0;
+}
+