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• MKV video playback shows a black picture and audio plays good

  24 mars 2023, par gbriones.gdl

  I have an MKV video file that has something wrong, every time I start my player, the video shows full black picture and the audio starts playing good, if I use the seek bar to position the playback anywhere in the time, then the video shows correct picture but audio stops playing, eventually (it takes several seconds) audio starts playing again in sync with video.

  


  The player I am using is the one in Kodi 20.1.0, I have tried enabling/disabling HW acceleration without success.

  


  I also tried VLC 3.0.16, which has a simmilar behavior with the exception that video starts showing from the very begining when opening the file, just when seeking the audio stops for several seconds.

  


  I also tried using ffmpeg to reencode the video with different codecs without success, I have tried multiple video and audio codec combinations, and also tried changing the pixel format.

  


  Then eventually I managed to fix the video by extracting streams into separate files, then merge them again, without reencoding, I thought that maybe something could be wrong with the metadata of the video, so I copied the same metadata and final output file still works fine. My question is how can I fix my video without having to split and merge streams ?

  


  Here is the info about my input file :

  


  $ ffmpeg -i S01E08.mkv 
ffmpeg version 4.4.2-0ubuntu0.22.04.1 Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 11 (Ubuntu 11.2.0-19ubuntu1)
  configuration: --prefix=/usr --extra-version=0ubuntu0.22.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librabbitmq --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-pocketsphinx --enable-librsvg --enable-libmfx --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  libavutil      56. 70.100 / 56. 70.100
  libavcodec     58.134.100 / 58.134.100
  libavformat    58. 76.100 / 58. 76.100
  libavdevice    58. 13.100 / 58. 13.100
  libavfilter     7.110.100 /  7.110.100
  libswscale      5.  9.100 /  5.  9.100
  libswresample   3.  9.100 /  3.  9.100
  libpostproc    55.  9.100 / 55.  9.100
Input #0, matroska,webm, from 'S01E08.mkv':
  Metadata:
    ENCODER         : Lavf59.27.100
  Duration: 00:25:02.21, start: 0.000000, bitrate: 1382 kb/s
  Stream #0:0: Video: hevc (Main 10), yuv420p10le(tv, bt470bg/unknown/unknown, progressive), 1280x960, 59.94 fps, 59.94 tbr, 1k tbn, 59.94 tbc
    Metadata:
      ENCODER         : Lavc59.37.100 libx265
      DURATION        : 00:25:00.032000000
  Stream #0:1(spa): Audio: aac (HE-AAC), 48000 Hz, stereo, fltp (default)
    Metadata:
      title           : Stereo
      DURATION        : 00:25:02.207000000
  Stream #0:2(jpn): Audio: aac (HE-AAC), 48000 Hz, stereo, fltp
    Metadata:
      title           : Stereo
      DURATION        : 00:25:00.116000000
  Stream #0:3(spa): Subtitle: ass
    Metadata:
      ENCODER         : Lavc59.37.100 ssa
      DURATION        : 00:24:56.585000000
At least one output file must be specified


  


  Here are the steps I followed to fix the video, I had to use mkv format for the outputs because other formats were no good at writing metadata :

  


  ffmpeg -i S01E08.mkv -map 0:v:0 -c:v copy -map_metadata 0 video.mkv
ffmpeg -i S01E08.mkv -map 0:a:0 -c:a copy -map_metadata 0 audio1.mkv
ffmpeg -i S01E08.mkv -map 0:a:1 -c:a copy -map_metadata 0 audio2.mkv
ffmpeg -i S01E08.mkv -map 0:s -c:s copy -map_metadata 0 subs.mkv
ffmpeg -i video.mkv -i audio1.mkv -i audio2.mkv -i subs.mkv -map 0:v -map 1:a -map 2:a -map 3:s -c:v copy -c:a copy -c:s copy -map_metadata 0 -map_metadata 1 -map_metadata 2 -map_metadata 3 -disposition:s:0 0 -default_mode infer_no_subs video_audio.mkv


  


  I had to compare both input and output files :

  


  $ ffmpeg -i video_audio.mkv
ffmpeg version 4.4.2-0ubuntu0.22.04.1 Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 11 (Ubuntu 11.2.0-19ubuntu1)
  configuration: --prefix=/usr --extra-version=0ubuntu0.22.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librabbitmq --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-pocketsphinx --enable-librsvg --enable-libmfx --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  libavutil      56. 70.100 / 56. 70.100
  libavcodec     58.134.100 / 58.134.100
  libavformat    58. 76.100 / 58. 76.100
  libavdevice    58. 13.100 / 58. 13.100
  libavfilter     7.110.100 /  7.110.100
  libswscale      5.  9.100 /  5.  9.100
  libswresample   3.  9.100 /  3.  9.100
  libpostproc    55.  9.100 / 55.  9.100
Input #0, matroska,webm, from 'video_audio.mkv':
  Metadata:
    ENCODER         : Lavf58.76.100
  Duration: 00:25:02.21, start: 0.000000, bitrate: 1382 kb/s
  Stream #0:0: Video: hevc (Main 10), yuv420p10le(tv, bt470bg/unknown/unknown, progressive), 1280x960, 59.94 fps, 59.94 tbr, 1k tbn, 59.94 tbc (default)
    Metadata:
      ENCODER         : Lavc59.37.100 libx265
      DURATION        : 00:25:00.031000000
  Stream #0:1(spa): Audio: aac (HE-AAC), 48000 Hz, stereo, fltp (default)
    Metadata:
      title           : Stereo
      DURATION        : 00:25:02.207000000
  Stream #0:2(jpn): Audio: aac (HE-AAC), 48000 Hz, stereo, fltp
    Metadata:
      title           : Stereo
      DURATION        : 00:25:00.116000000
  Stream #0:3(spa): Subtitle: ass
    Metadata:
      ENCODER         : Lavc59.37.100 ssa
      DURATION        : 00:24:56.585000000
At least one output file must be specified

$ ffprobe -show_streams S01E08.mkv > probe_bad.txt
$ ffprobe -show_streams video_audio.mkv > probe_good.txt
$ diff probe_bad.txt probe_good.txt 
32,33c32,33
< duration_ts=1502207
< duration=1502.207000
---
> duration_ts=N/A
> duration=N/A
40c40
< DISPOSITION:default=0
---
> DISPOSITION:default=1
53c53
< TAG:DURATION=00:25:00.032000000
---
> TAG:DURATION=00:25:00.031000000


  


  Then I thought that maybe the disposition flag in the video stream was causing the error, so I ran ffmpeg to copy all streams from my input video S01E08.mkv and added the disposition flag with the following command :

  


  ffmpeg -i S01E08.mkv -map 0:v -map 0:a:0 -map 0:a:1 -map 0:s -c:v copy -c:a copy -c:s copy -map_metadata 0 -disposition:v:0 default -disposition:s:0 0 -default_mode infer_no_subs test.mkv


  


  Still no luck, test.mkv shows no video when opening the file, I had to double check that disposition flag was changed :

  


  $ ffprobe -show_streams test.mkv > probe_bad2.txt
$ diff probe_bad.txt probe_bad2.txt 
40c40
< DISPOSITION:default=0
---
> DISPOSITION:default=1
53c53
< TAG:DURATION=00:25:00.032000000
---
> TAG:DURATION=00:25:00.031000000


  


  In other words I have to focibly split and merge to make the file work correctly. May be I need to set the duration and duration_ts of the video stream to N/A but I don't know how to do this.

  


• Black overlay appears when merging a transparent video to another video

  13 juin 2012, par RakeshS

  This is what I have done so far :

  Command to create a transparent PNG image :

  convert -size 640x480 -background transparent -fill blue \
  
  -gravity South label:ROCK image1-0.png

  Command to create a transparent video :

  ffmpeg -loop 1 -f image2 -i image1-0.png -r 20 -vframes 100 \
  
  -vcodec png -pix_fmt bgra mov-1.mov

  (as per this post) - I expect this video to be a transparent video.

  Command to overlay a video with another :

  ffmpeg -i final-video.mov -sameq -ar 44100 \
  
  -vf "movie=mov-1.mov [logo];[in][logo] overlay=0:0 [out]" \
  
  -strict experimental final-video.mov

  Above commands works perfect and I have not faced any problem, but I don't get what I expect which is kinda watermarking effect, I want mov-1.mov to be transparent with final-video.mov.

  Questions :

  1. Is there any way to verify if the generated video is transparent ? other than merging ?
  2. Not sure why the above mov-1.mov is not transparent when it is merged with final-video.mov, any info to solve this problem would be great.

  Please help.

• how can i stop ffmpeg when no new frame come to /dev/video0

  17 mai 2022, par itirou tarou

  I am now modifying stream from camera with our program(programA) and output as .ts files like below.

  


  camera => programA => /dev/video0 => ffmpeg => .ts files

  


  When camera stopped, programA stop automatically and no new frame arrive to /dev/video0.
I want ffmpeg stop automatically in such situation.
What ffmpeg option should I use ?
Currently I'm using option below, but ffmpeg doesn't stop.

  


  ffmpeg -f video4linux2 -i /dev/video0 -vsync vfr -f hls -c:v h264_nvenc out.m3u8


  


  Edited :
  
I tried to invalidate /dev/video0 but it failed like below.

  


  # modprobe -r v4l2loopback
modprobe: FATAL: Module v4l2loopback is in use.


  


  After I stopped programA and ffmpeg, the command success.
  
ProgramA is kicked by systemd service and restart automatically when it stopped.
  
ffmpeg is kicked by programB, but programB doesn't control programA.
  
But it sounds like good idea to inform B so B can kill ffmpeg.
  
I'll try that way. Thank you.