Opened 5 months ago

Last modified 2 days ago

#6386 new defect

Timebase is written as frame duration for mkv if framerate is unkown

Reported by: fthiery Owned by:
Priority: minor Component: avformat
Version: git-master Keywords: webm mkv
Cc: Blocked By:
Blocking: Reproduced by developer: no
Analyzed by developer: no

Description

Summary of the bug: chromium and firefox browsers can create WebM media using MediaStreamRecorder?; being live-generated, these media have no framerate in the webm header (as per specified in the spec: https://bugs.chromium.org/p/chromium/issues/detail?id=589561) nor correct duration information, making these media unseekable, but when remuxing the media (official chromium recommendation https://bugs.chromium.org/p/chromium/issues/detail?id=642012) ffmpeg falsely detects that the content is 1000 fps, then leading any subsequent transcodings to be effectively at 1000 fps.

How to reproduce:
# create a content with chromium (see attached test html -- needs to run over http, e.g. http://localhost/test_simple_record.html), download the video fragment
# remux using ffmpeg -i test.webm -c copy out.webm
# ffprobe out.webm reports 1000 fps

Firefox produced media do not have the issue, and the main difference seems to be that the EBML header from firefox has a zero duration instead of -1e-09

$ ffprobe -loglevel 56 test.webm 
ffprobe version 3.3 Copyright (c) 2007-2017 the FFmpeg developers
  built with gcc 6.3.1 (GCC) 20170306
  configuration: --prefix=/usr --disable-debug --disable-static --disable-stripping --enable-avisynth --enable-avresample --enable-fontconfig --enable-gmp --enable-gnutls --enable-gpl --enable-ladspa --enable-libass --enable-libbluray --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libiec61883 --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libv4l2 --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxcb --enable-libxvid --enable-netcdf --enable-shared --enable-version3
  libavutil      55. 58.100 / 55. 58.100
  libavcodec     57. 89.100 / 57. 89.100
  libavformat    57. 71.100 / 57. 71.100
  libavdevice    57.  6.100 / 57.  6.100
  libavfilter     6. 82.100 /  6. 82.100
  libavresample   3.  5.  0 /  3.  5.  0
  libswscale      4.  6.100 /  4.  6.100
  libswresample   2.  7.100 /  2.  7.100
  libpostproc    54.  5.100 / 54.  5.100
[file @ 0x562e987a1560] Setting default whitelist 'file,crypto'
Probing matroska,webm score:100 size:2048
Probing mp3 score:1 size:2048
[matroska,webm @ 0x562e987a0d00] Format matroska,webm probed with size=2048 and score=100
st:0 removing common factor 1000000 from timebase
st:1 removing common factor 1000000 from timebase
[matroska,webm @ 0x562e987a0d00] Before avformat_find_stream_info() pos: 181 bytes read:32768 seeks:0 nb_streams:2
[matroska,webm @ 0x562e987a0d00] All info found
[matroska,webm @ 0x562e987a0d00] stream 0: start_time: 0.060 duration: -9223372036854776.000
[matroska,webm @ 0x562e987a0d00] stream 1: start_time: 0.000 duration: -9223372036854776.000
[matroska,webm @ 0x562e987a0d00] format: start_time: 0.000 duration: -9223372036854.775 bitrate=0 kb/s
[matroska,webm @ 0x562e987a0d00] After avformat_find_stream_info() pos: 217397 bytes read:229376 seeks:0 frames:68
Input #0, matroska,webm, from 'test.webm':
  Metadata:
    encoder         : Chrome
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0(eng), 27, 1/1000: Audio: opus, 48000 Hz, mono, fltp (default)
    Stream #0:1(eng), 41, 1/1000: Video: vp8, 1 reference frame, yuv420p(progressive), 640x480, 0/1, SAR 1:1 DAR 4:3, 1k tbr, 1k tbn, 1k tbc (default)
[AVIOContext @ 0x562e987a98a0] Statistics: 229376 bytes read, 0 seeks

$ ffmpeg -i test.webm -c copy out.webm 
ffmpeg version 3.3 Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 6.3.1 (GCC) 20170306
  configuration: --prefix=/usr --disable-debug --disable-static --disable-stripping --enable-avisynth --enable-avresample --enable-fontconfig --enable-gmp --enable-gnutls --enable-gpl --enable-ladspa --enable-libass --enable-libbluray --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libiec61883 --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libv4l2 --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxcb --enable-libxvid --enable-netcdf --enable-shared --enable-version3
  libavutil      55. 58.100 / 55. 58.100
  libavcodec     57. 89.100 / 57. 89.100
  libavformat    57. 71.100 / 57. 71.100
  libavdevice    57.  6.100 / 57.  6.100
  libavfilter     6. 82.100 /  6. 82.100
  libavresample   3.  5.  0 /  3.  5.  0
  libswscale      4.  6.100 /  4.  6.100
  libswresample   2.  7.100 /  2.  7.100
  libpostproc    54.  5.100 / 54.  5.100
Input #0, matroska,webm, from 'test.webm':
  Metadata:
    encoder         : Chrome
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0(eng): Audio: opus, 48000 Hz, mono, fltp (default)
    Stream #0:1(eng): Video: vp8, yuv420p(progressive), 640x480, SAR 1:1 DAR 4:3, 1k tbr, 1k tbn, 1k tbc (default)
File 'out.webm' already exists. Overwrite ? [y/N] y
Output #0, webm, to 'out.webm':
  Metadata:
    encoder         : Lavf57.71.100
    Stream #0:0(eng): Video: vp8, yuv420p(progressive), 640x480 [SAR 1:1 DAR 4:3], q=2-31, 1k tbr, 1k tbn, 1k tbc (default)
    Stream #0:1(eng): Audio: opus, 48000 Hz, mono, fltp (default)
Stream mapping:
  Stream #0:1 -> #0:0 (copy)
  Stream #0:0 -> #0:1 (copy)
Press [q] to stop, [?] for help
frame=  128 fps=0.0 q=-1.0 Lsize=     646kB time=00:00:04.92 bitrate=1075.0kbits/s speed= 914x    
video:643kB audio:1kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.300635%

$ ffprobe -loglevel 56 out.webm 
ffprobe version 3.3 Copyright (c) 2007-2017 the FFmpeg developers
  built with gcc 6.3.1 (GCC) 20170306
  configuration: --prefix=/usr --disable-debug --disable-static --disable-stripping --enable-avisynth --enable-avresample --enable-fontconfig --enable-gmp --enable-gnutls --enable-gpl --enable-ladspa --enable-libass --enable-libbluray --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libiec61883 --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libv4l2 --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxcb --enable-libxvid --enable-netcdf --enable-shared --enable-version3
  libavutil      55. 58.100 / 55. 58.100
  libavcodec     57. 89.100 / 57. 89.100
  libavformat    57. 71.100 / 57. 71.100
  libavdevice    57.  6.100 / 57.  6.100
  libavfilter     6. 82.100 /  6. 82.100
  libavresample   3.  5.  0 /  3.  5.  0
  libswscale      4.  6.100 /  4.  6.100
  libswresample   2.  7.100 /  2.  7.100
  libpostproc    54.  5.100 / 54.  5.100
[file @ 0x5601fb87f560] Setting default whitelist 'file,crypto'
Probing matroska,webm score:100 size:2048
Probing mp3 score:1 size:2048
[matroska,webm @ 0x5601fb87ed00] Format matroska,webm probed with size=2048 and score=100
st:0 removing common factor 1000000 from timebase
st:1 removing common factor 1000000 from timebase
[matroska,webm @ 0x5601fb87ed00] Before avformat_find_stream_info() pos: 517 bytes read:32768 seeks:0 nb_streams:2
[matroska,webm @ 0x5601fb87ed00] All info found
[matroska,webm @ 0x5601fb87ed00] stream 0: start_time: 0.000 duration: -9223372036854776.000
[matroska,webm @ 0x5601fb87ed00] stream 1: start_time: 0.061 duration: -9223372036854776.000
[matroska,webm @ 0x5601fb87ed00] format: start_time: 0.000 duration: 4.980 bitrate=1062 kb/s
[matroska,webm @ 0x5601fb87ed00] After avformat_find_stream_info() pos: 197613 bytes read:229376 seeks:0 frames:64
Input #0, matroska,webm, from 'out.webm':
  Metadata:
    encoder         : Lavf57.71.100
  Duration: 00:00:04.98, start: 0.000000, bitrate: 1062 kb/s
    Stream #0:0(eng), 41, 1/1000: Video: vp8, 1 reference frame, yuv420p(progressive), 640x480, 0/1, SAR 1:1 DAR 4:3, 1k fps, 1k tbr, 1k tbn, 1k tbc (default)
    Stream #0:1(eng), 23, 1/1000: Audio: opus, 48000 Hz, mono, fltp (default)
[AVIOContext @ 0x5601fb8878a0] Statistics: 229376 bytes read, 0 seeks

$ ./libwebm/webm_info -i test.webm 
EBML Header:
  EBMLVersion       : 1
  EBMLReadVersion   : 1
  EBMLMaxIDLength   : 4
  EBMLMaxSizeLength : 8
  Doc Type          : webm
  DocTypeVersion    : 4
  DocTypeReadVersion: 2
Segment:
  SegmentInfo:
    TimecodeScale : 1000000 
    Duration(secs): -1e-09
    MuxingApp     : Chrome
    WritingApp    : Chrome
  Tracks:
    Track:
      TrackType   : 2
      TrackNumber : 1
      CodecID     : A_OPUS
      PrivateData(size): 19
      Channels         : 1
      SamplingFrequency: 48000
    Track:
      TrackType   : 1
      TrackNumber : 2
      CodecID     : V_VP8
      PixelWidth  : 640
      PixelHeight : 480

$ ffprobe -loglevel 56 test_firefox.webm 
ffprobe version 3.3 Copyright (c) 2007-2017 the FFmpeg developers
  built with gcc 6.3.1 (GCC) 20170306
  configuration: --prefix=/usr --disable-debug --disable-static --disable-stripping --enable-avisynth --enable-avresample --enable-fontconfig --enable-gmp --enable-gnutls --enable-gpl --enable-ladspa --enable-libass --enable-libbluray --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libiec61883 --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libv4l2 --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxcb --enable-libxvid --enable-netcdf --enable-shared --enable-version3
  libavutil      55. 58.100 / 55. 58.100
  libavcodec     57. 89.100 / 57. 89.100
  libavformat    57. 71.100 / 57. 71.100
  libavdevice    57.  6.100 / 57.  6.100
  libavfilter     6. 82.100 /  6. 82.100
  libavresample   3.  5.  0 /  3.  5.  0
  libswscale      4.  6.100 /  4.  6.100
  libswresample   2.  7.100 /  2.  7.100
  libpostproc    54.  5.100 / 54.  5.100
[file @ 0x558fe2164560] Setting default whitelist 'file,crypto'
Probing matroska,webm score:100 size:2048
Probing mp3 score:1 size:2048
[matroska,webm @ 0x558fe2163d00] Format matroska,webm probed with size=2048 and score=100
st:0 removing common factor 1000000 from timebase
st:1 removing common factor 1000000 from timebase
[matroska,webm @ 0x558fe2163d00] Before avformat_find_stream_info() pos: 317 bytes read:32768 seeks:0 nb_streams:2
[matroska,webm @ 0x558fe2163d00] All info found
[matroska,webm @ 0x558fe2163d00] rfps: 24.666667 0.012426
[matroska,webm @ 0x558fe2163d00] rfps: 24.750000 0.005794
    Last message repeated 1 times
[matroska,webm @ 0x558fe2163d00] rfps: 24.833333 0.002149
    Last message repeated 1 times
[matroska,webm @ 0x558fe2163d00] rfps: 24.916667 0.001491
    Last message repeated 1 times
[matroska,webm @ 0x558fe2163d00] rfps: 25.000000 0.003819
[matroska,webm @ 0x558fe2163d00] rfps: 25.083333 0.009133
[matroska,webm @ 0x558fe2163d00] rfps: 25.166667 0.017434
[matroska,webm @ 0x558fe2163d00] rfps: 50.000000 0.015275
[matroska,webm @ 0x558fe2163d00] Setting avg frame rate based on r frame rate
[matroska,webm @ 0x558fe2163d00] stream 0: start_time: 0.000 duration: -9223372036854776.000
[matroska,webm @ 0x558fe2163d00] stream 1: start_time: -0.001 duration: -9223372036854776.000
[matroska,webm @ 0x558fe2163d00] format: start_time: -0.001 duration: -9223372036854.775 bitrate=0 kb/s
[matroska,webm @ 0x558fe2163d00] After avformat_find_stream_info() pos: 482653 bytes read:491520 seeks:0 frames:123
Input #0, matroska,webm, from 'test_firefox.webm':
  Metadata:
    encoder         : QTmuxingAppLibWebM-0.0.1
  Duration: N/A, start: -0.001000, bitrate: N/A
    Stream #0:0(eng), 41, 1/1000: Video: vp8, 1 reference frame, yuv420p(progressive), 640x480, 0/1, SAR 1:1 DAR 4:3, 24.92 fps, 24.92 tbr, 1k tbn, 1k tbc (default)
    Stream #0:1(eng), 82, 1/1000: Audio: opus, 48000 Hz, mono, fltp, delay 312 (default)
[AVIOContext @ 0x558fe216c860] Statistics: 491520 bytes read, 0 seeks

$ ./libwebm/webm_info -i test_firefox.webm 
EBML Header:
  EBMLVersion       : 1
  EBMLReadVersion   : 1
  EBMLMaxIDLength   : 4
  EBMLMaxSizeLength : 8
  Doc Type          : webm
  DocTypeVersion    : 2
  DocTypeReadVersion: 2
Segment:
  SegmentInfo:
    TimecodeScale : 1000000 
    Duration(secs): 0
    MuxingApp     : QTmuxingAppLibWebM-0.0.1
    WritingApp    : QTwritingAppLibWebM-0.0.1
  Tracks:
    Track:
      TrackType   : 1
      TrackNumber : 1
      CodecID     : V_VP8
      CodecName   : VP8
      PixelWidth  : 640
      PixelHeight : 480
    Track:
      TrackType   : 2
      TrackNumber : 2
      CodecID     : A_OPUS
      CodecName   : OPUS
      PrivateData(size): 19
      Channels         : 1
      SamplingFrequency: 44100
      CodecDelay       : 6500000
      SeekPreRoll      : 80000000

Attachments (3)

test_simple_record.html (4.3 KB) - added by fthiery 5 months ago.
html test recorder
test_chrome.webm (630.0 KB) - added by fthiery 5 months ago.
sample file
0001-lavf-matroskaenc-Never-write-timebase-as-default-fra.patch (1.1 KB) - added by cehoyos 5 months ago.

Download all attachments as: .zip

Change History (10)

Changed 5 months ago by fthiery

html test recorder

comment:1 Changed 5 months ago by cehoyos

Please provide a (small) input sample.

Changed 5 months ago by fthiery

sample file

comment:2 Changed 5 months ago by cehoyos

  • Component changed from undetermined to avformat
  • Keywords mkv added; framerate removed
  • Priority changed from normal to minor
  • Version changed from unspecified to git-master

Feel free to test attached patch.

comment:3 Changed 5 months ago by cehoyos

  • Summary changed from WebM/VP8 created by chromium are incorrectly detected as 1000 fps by ffmpeg to Timebase is written as frame duration for mkv if framerate is unkown

comment:4 Changed 5 months ago by fthiery

Many thanks, will report

comment:5 Changed 5 months ago by fthiery

Hi there; applied the patch; now when i ffprobe on the sample, the detected framerate seems to be 0 fps

$ ffprobe -loglevel 56 test_chrome.webm
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:1(eng), 41, 1/1000: Video: vp8, 1 reference frame, yuv420p(progressive), 640x480, 0/1, SAR 1:1 DAR 4:3, 1k tbr, 1k tbn, 1k tbc (default)

Unfortunately, when remuxing with ffmpeg -i test_chrome.webm -c copy out.webm, the duration is now correct, but transcoding (ffmpeg -i out.webm out.mp4) still results in a 1000 fps output.

$ ffprobe -loglevel 56 out.webm
  Duration: 00:00:04.98, start: 0.000000, bitrate: 1037 kb/s
    Stream #0:0(eng), 41, 1/1000: Video: vp8, 1 reference frame, yuv420p(progressive), 640x480, 0/1, SAR 1:1 DAR 4:3, 1k tbr, 1k tbn, 1k tbc (default)

$ ffmpeg -i out.webm test.mp4
  Metadata:
    encoder         : Lavf57.71.100
    Stream #0:0(eng): Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 640x480 [SAR 1:1 DAR 4:3], q=-1--1, 1k fps, 16k tbn, 1k tbc (default)
    Metadata:
      encoder         : Lavc57.89.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
    Stream #0:1(eng): Audio: aac (LC) ([64][0][0][0] / 0x0040), 48000 Hz, mono, fltp, 69 kb/s (default)
    Metadata:
      encoder         : Lavc57.89.100 aac
More than 1000 frames duplicated     227kB time=00:00:01.08 bitrate=1716.0kbits/s dup=783 drop=0 speed=0.961x  


Last edited 5 months ago by fthiery (previous) (diff)

comment:6 Changed 3 months ago by leeoxiang

i came to this bug also

comment:7 Changed 2 days ago by terran

Also running into this. Following.

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