Opened 5 years ago

Last modified 5 years ago

#1555 open defect

WebM: Silent track not taken into account if followed by a noisy track

Reported by: cehoyos Owned by:
Priority: normal Component: undetermined
Version: git-master Keywords: mkv roundup async
Cc: Blocked By:
Blocking: Reproduced by developer: yes
Analyzed by developer: no

Description

(issue 2445)
I will upload a webm sample that plays different with Firefox and ffplay - both ffmpeg and ffplay ignore the initial silence.

$ ffmpeg -i res_silence_then_sound.webm -qscale 2 out.avi
ffmpeg version N-42605-g5784a46 Copyright (c) 2000-2012 the FFmpeg developers
  built on Jul 18 2012 20:29:06 with gcc 4.3.2
  configuration: --cc=/usr/local/gcc-4.3.2/bin/gcc --enable-gpl --enable-libopenjpeg --enable-libvorbis --enable-libspeex --enable-libmp3lame --enable-libtheora --extra-ldflags=-lm --enable-libvpx --enable-libxavs --enable-x11grab --enable-libass
  libavutil      51. 65.100 / 51. 65.100
  libavcodec     54. 41.100 / 54. 41.100
  libavformat    54. 17.100 / 54. 17.100
  libavdevice    54.  1.100 / 54.  1.100
  libavfilter     3.  2.100 /  3.  2.100
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0. 15.100 /  0. 15.100
  libpostproc    52.  0.100 / 52.  0.100
Input #0, matroska,webm, from 'res_silence_then_sound.webm':
  Metadata:
    creation_time   : 2010-12-24 06:39:05
  Duration: 00:00:35.58, start: 0.000000, bitrate: 1105 kb/s
    Stream #0:0: Video: vp8, yuv420p, 640x352, SAR 1:1 DAR 20:11, 25 fps, 25 tbr, 1k tbn, 1k tbc
    Stream #0:1: Audio: vorbis, 48000 Hz, stereo, s16
Please use -q:a or -q:v, -qscale is ambiguous
Output #0, avi, to 'out.avi':
  Metadata:
    ISFT            : Lavf54.17.100
    Stream #0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 640x352 [SAR 1:1 DAR 20:11], q=2-31, 200 kb/s, 25 tbn, 25 tbc
    Stream #0:1: Audio: mp3 (U[0][0][0] / 0x0055), 48000 Hz, stereo, s16
Stream mapping:
  Stream #0:0 -> #0:0 (vp8 -> mpeg4)
  Stream #0:1 -> #0:1 (vorbis -> libmp3lame)
Press [q] to stop, [?] for help
frame=  858 fps= 90 q=2.0 Lsize=    6666kB time=00:00:35.52 bitrate=1537.3kbits/s
video:6123kB audio:477kB subtitle:0 global headers:0kB muxing overhead 0.995196%
[libmp3lame @ 0x90c2a80] 1 frames left in que on closing

out.avi is broken / severe A/V desync.

Change History (4)

comment:2 Changed 5 years ago by cehoyos

  • Keywords mkv roundup added

comment:3 Changed 5 years ago by cehoyos

  • Keywords async added
  • Reproduced by developer set
  • Status changed from new to open

Works fine with -async 1:
$ ffmpeg -async 1 -i res_silence_then_sound.webm -qscale 2 out.avi

comment:4 Changed 5 years ago by cehoyos

Ticket #2051 looks related.

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