[FFmpeg-devel] [PATCH] avformat/oggparsevorbis: Ignore duration of the first packet

[Guangyu Sun]

The decoded Data is not returned from the first frame; it must be used
to 'prime' the decode engine. The duration of the first packet should
be ignored also by the container, to make sure the total duration is
trimmed correctly.

This commit fixes #6367.

dd if=/dev/zero of=./silence.raw count=1 bs=500
oggenc --raw silence.raw --output=silence.ogg
oggdec --raw --output silence.oggdec.raw silence.ogg
ffmpeg -codec:a libvorbis -i silence.ogg -f s16le -codec:a pcm_s16le silence.libvorbis.ffmpeg.raw
ffmpeg -i silence.ogg -f s16le -codec:a pcm_s16le silence.native.ffmpeg.raw
ls -l *.raw

Signed-off-by: Guangyu Sun <gsun at roblox.com>
---
 libavformat/oggparsevorbis.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/libavformat/oggparsevorbis.c b/libavformat/oggparsevorbis.c
index 289900f7cf..1f922b3c7e 100644
--- a/libavformat/oggparsevorbis.c
+++ b/libavformat/oggparsevorbis.c
@@ -479,6 +479,13 @@ static int vorbis_packet(AVFormatContext *s, int idx)
             flags = 0;
         }
         os->pduration = duration;
+        /* Data is not returned from the first frame; it must be used to 'prime'
+         * the decode engine. The duration of the first packet should be ignored
+         * also by the container, to make sure the total duration is trimmed
+         * correctly.
+         */
+        if ((!os->lastpts || os->lastpts == AV_NOPTS_VALUE) && os->segp == 1)
+            os->pduration = 0;
     }
 
     /* final packet handling
-- 
2.30.1