avformat/demux: add duration_probesize AVOption

Yet another probesize used to get the durations when
estimate_timings_from_pts is required. It is aimed at users interested
in better durations probing for itself, or because using
avformat_find_stream_info indirectly and requiring exact values: for
concatdec for example, especially if streamcopying above it.
The current code is a performance trade-off that can fail to get video
stream durations in a scenario with high bitrates and buffering for
files ending cleanly (as opposed to live captures): the physical gap
between the last video packet and the last audio packet is very high in
such a case.

Default behaviour is unchanged: 250k up to 250k << 6 (step by step).
Setting this new option has two effects:
- override the maximum probesize (currently 250k << 6)
- reduce the number of steps to 1 instead of 6, this is to avoid
detecting the audio "too early" and failing to reach a video packet.
Even if a single audio stream duration is found but not the other
audio/video stream durations, there will be a retry, so at the end the
full user-overriden probesize will be used as expected by the user.

Signed-off-by: Nicolas Gaullier <nicolas.gaullier@cji.paris>

1 files changed, 14 insertions, 2 deletions

diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index de40397676..8afdcd9fd0 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -1439,7 +1439,7 @@ typedef struct AVFormatContext {
      *
      * @note this is \e not  used for determining the \ref AVInputFormat
      *       "input format"
-     * @sa format_probesize
+     * @see format_probesize
      */
     int64_t probesize;
 
@@ -1667,6 +1667,8 @@ typedef struct AVFormatContext {
      * Skip duration calcuation in estimate_timings_from_pts.
      * - encoding: unused
      * - decoding: set by user
+     *
+     * @see duration_probesize
      */
     int skip_estimate_duration_from_pts;
 
@@ -1729,7 +1731,7 @@ typedef struct AVFormatContext {
      *
      * Demuxing only, set by the caller before avformat_open_input().
      *
-     * @sa probesize
+     * @see probesize
      */
     int format_probesize;
 
@@ -1870,6 +1872,16 @@ typedef struct AVFormatContext {
      * @return 0 on success, a negative AVERROR code on failure
      */
     int (*io_close2)(struct AVFormatContext *s, AVIOContext *pb);
+
+    /**
+     * Maximum number of bytes read from input in order to determine stream durations
+     * when using estimate_timings_from_pts in avformat_find_stream_info().
+     * Demuxing only, set by the caller before avformat_find_stream_info().
+     * Can be set to 0 to let avformat choose using a heuristic.
+     *
+     * @see skip_estimate_duration_from_pts
+     */
+    int64_t duration_probesize;
 } AVFormatContext;
 
 /**