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• avformat/matroskaenc : Only write Tracks if there is a track

  29 décembre 2019, par Andreas Rheinhardt

  avformat/matroskaenc : Only write Tracks if there is a track
  The Matroska muxer does not write every stream as a Matroska track ;
  
  some streams are written as AttachedFile. But should no stream be
  
  written as a Matroska track, the Matroska muxer would nevertheless
  
  write a Tracks element without a TrackEntry. This is against the spec.
  
  This commit changes this and only writes a Tracks if there is a Matroska
  
  track.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskaenc.c

• Removing one audio track from a movie results in audio desync when copying, but not when reencoding --- why ?

  18 avril 2020, par chsk

  I'm trying to remove a superfluous audio track from a movie file. Specifically, this movie on archive.org has the original audio as track 2, and what appears to be a slavic (Russian ?) voiceover in track 1. I'd like to get rid of the latter.

  



  I found this question that suggested I should do the following :

  



  ffmpeg -i Benjamín\ dúfa.avi -map 0 -map -0:a:0 -c copy Benjamín\ dúfa\ \(aðeins\ íslenskt\ tal\).avi

  



  But this doesn't work : after removing the first audio track, audio and video are not in sync in the resulting file anymore (when played in VLC). Now, I was able to overcome this problem by also reencoding the remaining audio track along the way, using

  



  ffmpeg -i Benjamín\ dúfa.avi -map 0 -map -0:a:0 -c:v copy Benjamín\ dúfa\ \(aðeins\ íslenskt\ tal\).avi

  



  But while this works, I'd like to understand why copying the audio track instead does not. I suppose it's a somewhat philosophical question --- consider it a matter of intellectual curiosity, combined with an aversion to needless lossy re-encoding.

  



  So if anyone can explain this to me, I'd very grateful. Thanks !

  



  EDIT : as per Gyan's request, here's ffmpeg's output for the first command :

  



  ffmpeg version 4.2 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 9.1.1 (GCC) 20190807
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-amf --enable-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt
  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
Input #0, avi, from 'Benjam├¡n d├║fa.avi':
  Metadata:
    encoder         : VirtualDubModRus 1.5.10.2 (build 2542/release)
    IAS1            : Islenska
  Duration: 01:27:37.00, start: 0.000000, bitrate: 1313 kb/s
    Stream #0:0: Video: mpeg4 (Advanced Simple Profile) (XVID / 0x44495658), yuv420p, 720x400 [SAR 1:1 DAR 9:5], 979 kb/s, 25 fps, 25 tbr, 25 tbn, 25 tbc
    Stream #0:1: Audio: mp3 (U[0][0][0] / 0x0055), 48000 Hz, stereo, fltp, 192 kb/s
    Stream #0:2: Audio: mp3 (U[0][0][0] / 0x0055), 48000 Hz, stereo, fltp, 128 kb/s
Output #0, avi, to 'b.avi':
  Metadata:
    IAS1            : Islenska
    ISFT            : Lavf58.29.100
    Stream #0:0: Video: mpeg4 (Advanced Simple Profile) (XVID / 0x44495658), yuv420p, 720x400 [SAR 1:1 DAR 9:5], q=2-31, 979 kb/s, 25 fps, 25 tbr, 25 tbn, 25 tbc
    Stream #0:1: Audio: mp3 (U[0][0][0] / 0x0055), 48000 Hz, stereo, fltp, 128 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:2 -> #0:1 (copy)
Press [q] to stop, [?] for help
[avi @ 0000000002bf00c0] Timestamps are unset in a packet for stream 0. This is deprecated and will stop working in the future. Fix your code to set the timestamps properly
frame=131425 fps=7616 q=-1.0 Lsize=  718952kB time=01:27:37.00 bitrate=1120.3kbits/s speed= 305x
video:628523kB audio:82141kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 1.166227%


  



  And also for the second, for comparison :

  



  ffmpeg version 4.2 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 9.1.1 (GCC) 20190807
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-amf --enable-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt
  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
Input #0, avi, from 'Benjam├¡n d├║fa.avi':
  Metadata:
    encoder         : VirtualDubModRus 1.5.10.2 (build 2542/release)
    IAS1            : Islenska
  Duration: 01:27:37.00, start: 0.000000, bitrate: 1313 kb/s
    Stream #0:0: Video: mpeg4 (Advanced Simple Profile) (XVID / 0x44495658), yuv420p, 720x400 [SAR 1:1 DAR 9:5], 979 kb/s, 25 fps, 25 tbr, 25 tbn, 25 tbc
    Stream #0:1: Audio: mp3 (U[0][0][0] / 0x0055), 48000 Hz, stereo, fltp, 192 kb/s
    Stream #0:2: Audio: mp3 (U[0][0][0] / 0x0055), 48000 Hz, stereo, fltp, 128 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:2 -> #0:1 (mp3 (mp3float) -> mp3 (libmp3lame))
Press [q] to stop, [?] for help
Output #0, avi, to 'b2.avi':
  Metadata:
    IAS1            : Islenska
    ISFT            : Lavf58.29.100
    Stream #0:0: Video: mpeg4 (Advanced Simple Profile) (XVID / 0x44495658), yuv420p, 720x400 [SAR 1:1 DAR 9:5], q=2-31, 979 kb/s, 25 fps, 25 tbr, 25 tbn, 25 tbc
    Stream #0:1: Audio: mp3 (libmp3lame) (U[0][0][0] / 0x0055), 48000 Hz, stereo, fltp
    Metadata:
      encoder         : Lavc58.54.100 libmp3lame
[avi @ 00000000004b7440] Timestamps are unset in a packet for stream 0. This is deprecated and will stop working in the future. Fix your code to set the timestamps properly
frame=131425 fps=1090 q=-1.0 Lsize=  718952kB time=01:27:37.00 bitrate=1120.3kbits/s speed=43.6x
video:628523kB audio:82141kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 1.166233%


  


• ffmpeg - stream_loop mp3 + looping video (per track)

  5 mars 2023, par cYberSport91

  I'm using ffmpeg to create a livestream video playlist of a folder of mp3s and a folder of videos.

  



  I'd like everytime a new song comes on a new video loops until the next song.

  



  Initially I was using live-stream-radio which is perfect except how it's handled is after every track a new ffmpeg stream loop is initialized. And in a lot of clients this issues a stop command, and there's "dead space" between.

  



  My attempt was when creating the gif playlist text file (they were gifs but I converted to mp4), I set the duration for the duration of the corresponding track. The problem is the video plays once, and then freezes on the final frame until the next track.

  



  rm music.txt
rm gifs.txt
printf "ffconcat version 1.0\n" >> gifs.txt
printf "ffconcat version 1.0\n" >> music.txt
for i in {1..9}; do
  printf "file 'mp3/00%s.mp3'\n" $i >> music.txt
done

for i in {1..9}; do
  DURATION=$(ffmpeg -i mp3/00$i.mp3 2>&1 | awk '/Duration/ { print substr($2,0,length($2)-1) }')
  printf "file 'gif/00%s.mp4'\nduration %s\n" $i $DURATION >> gifs.txt
done

ffmpeg \
    -stream_loop -1 \
    -i gifs.txt \
    -i music.txt \
    -vcodec libx264 \
    -f flv "$URL"


  



  Any ideas here would be great.