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• ffmpeg doesn't detect the subtitle format (webvtt) and refuses to copy it

  29 novembre 2023, par Thomas

  I am trying to re-encode the audio on some video files.
I want to copy the video and subtitles without touching them, however, ffmpeg doesn't detect the format of the subtitle (which is webvtt) and refuses to do anything.

  



  fmpeg -copy_unknown -analyzeduration 2000M -probesize 2000M -i input.mkv -map_metadata 0 -map 0 -c copy -c:a:0 aac -b:a 384k output.mkv

  



  [matroska,webm @ 0x5597558e4040] Unknown/unsupported AVCodecID S_TEXT/WEBVTT.
[matroska,webm @ 0x5597558e4040] Could not find codec parameters for stream 2 (Subtitle: none): unknown codec
Consider increasing the value for the 'analyzeduration' and 'probesize' options
Guessed Channel Layout for Input Stream #0.1 : 5.1
Input #0, matroska,webm, from 'input.mkv':
  Metadata:
    encoder         : libebml v1.3.9 + libmatroska v1.5.2
    creation_time   : 2020-03-05T09:03:02.000000Z
  Duration: 00:56:33.26, start: 0.000000, bitrate: 3597 kb/s
    Stream #0:0: Video: h264 (High), yuv420p(progressive), 1920x1080 [SAR 1:1 DAR 16:9], 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc (default)
    Metadata:
      BPS-eng         : 3340067
      DURATION-eng    : 00:56:33.140000000
      NUMBER_OF_FRAMES-eng: 81354
      NUMBER_OF_BYTES-eng: 1416664616
      _STATISTICS_WRITING_APP-eng: mkvmerge v38.0.0 ('The Silent Type') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-03-05 09:03:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:1: Audio: eac3, 48000 Hz, 5.1, fltp (default)
    Metadata:
      BPS-eng         : 256000
      DURATION-eng    : 00:56:33.248000000
      NUMBER_OF_FRAMES-eng: 106039
      NUMBER_OF_BYTES-eng: 108583936
      _STATISTICS_WRITING_APP-eng: mkvmerge v38.0.0 ('The Silent Type') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-03-05 09:03:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:2(eng): Subtitle: none (default)
    Metadata:
      BPS-eng         : 38
      DURATION-eng    : 00:54:47.388000000
      NUMBER_OF_FRAMES-eng: 514
      NUMBER_OF_BYTES-eng: 15766
      _STATISTICS_WRITING_APP-eng: mkvmerge v38.0.0 ('The Silent Type') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-03-05 09:03:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES

Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (eac3 (native) -> aac (native))
  Stream #0:2 -> #0:2 (copy)

[aac @ 0x5597b06ae000] Using a PCE to encode channel layout "5.1(side)"
[matroska @ 0x5597b06ab540] Subtitle codec 0 is not supported.
Could not write header for output file #0 (incorrect codec parameters ?): Function not implemented
Error initializing output stream 0:1 -- 
[aac @ 0x5597b06ae000] Qavg: -nan
Conversion failed!


  



  VLC shows it as WebVTT and displays the subtitles correctly :

  



  

  



  MediaInfo also detects properly as webvtt :

  



  Text
ID                                       : 3
Format                                   : S_TEXT/WEBVTT
Codec ID                                 : S_TEXT/WEBVTT
Duration                                 : 54 min 47 s
Bit rate                                 : 38 b/s
Count of elements                        : 514
Stream size                              : 15.4 KiB (0%)
Language                                 : English
Default                                  : Yes
Forced                                   : No


  



  My ffmpeg was built with webvtt :

  



  $ ffmpeg -codecs | grep VTT
ffmpeg version n4.2.2 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 9.3.0 (Arch Linux 9.3.0-1)
  configuration: --prefix=/usr --disable-debug --disable-static --disable-stripping --enable-fontconfig --enable-gmp --enable-gnutls --enable-gpl --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libdav1d --enable-libdrm --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libiec61883 --enable-libjack --enable-libmfx --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopus --enable-libpulse --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-libxml2 --enable-libxvid --enable-nvdec --enable-nvenc --enable-omx --enable-shared --enable-version3
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
 DES... webvtt               WebVTT subtitle


  



  How can I tell ffmpeg "this is webvtt, just copy it please !" ?

  



  EDIT : RESOLVED (thanks @Gyan)

  



  To force the decoder, -c:s webvtt must be set before the input :
fmpeg -analyzeduration 50M -probesize 50M -c:s webvtt -i input.mkv ...

  


• In Android, how can I display mp4 files captured by Android itself without having "sorry this video cannot be played" trouble ?

  31 octobre 2013, par fercis

  I am new in Android and have an application as follows :

  1) I record videos by my phone (Samsung Galaxy Note 2).
  2) I send video files (mp4) to a cloud (Dropbox in my example) without any change in encoding. And store the URL of the sent video on the cloud.

  And when the application is in view video mode,
  3) I want to view the videos with the URL (which may be captured by other client Applications) in videoview.

  I cannot view the videos that are captured by the phone itself. There are many discussions in SO about the encoding compatibility (H 263, H 264 etc.).

  Video recoding with ffmpeg

  However, I could not manage to find a way to CHANGE the encoding of the video to be recorded by the application. Camera.Parameters class has the encoding information only for pictures. The quality is not important, I only want to capture videos which can be directly played in the same Android application without any change.

• avformat/matroskaenc : use display aspect ratio for DisplayWidth and DisplayHeight...

  22 octobre 2016, par James Almer

  avformat/matroskaenc : use display aspect ratio for DisplayWidth and DisplayHeight when possible
  This avoids potential rounding errors and guarantees the source aspect
  
  ratio is preserved.
  
  Keep writing pixel values when Stereo 3D Mode is enabled and for WebM,
  
  as the format doesn’t support anything else.
  This fixes ticket #5743, implementing the suggestion from ticket #5903.
  Signed-off-by : James Almer <jamrial@gmail.com>
  

  • [DH] libavformat/matroskaenc.c