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• ffmpeg : Combining two A/V streams results in out of sync audio in VLC play but not QuickTime [closed]

  24 juillet 2022, par Alex

  I have two files (one audio, one video, both mp4) I want to combine into a single mp4 without re-encoding the streams. They both have the same duration (well, technically one is 0.05s longer than the other, but it's close enough for my application). The command I am using to combine them is :

  


  ffmpeg -i audio.mp4 -i video.mp4 -c:v copy -c:a copy test.mp4

  


  When I play test.mp4 in VLC player, the audio is way out of sync. The video duration is correct, but the sound is all happening too soon and it gets more out of sync as it continues. However, if I play back the same file using QuickTime, it's perfect !

  


  What is going on here ? Is there a way for me to ensure correct playback regardless of video player, without re-encoding the streams ?

  


  Here's the full output of the command :

  


  % ffmpeg -i audio.mp4 -i video.mp4 -c:v copy -c:a copy test.mp4
ffmpeg version 5.0.1 Copyright (c) 2000-2022 the FFmpeg developers
  built with Apple clang version 13.1.6 (clang-1316.0.21.2.5)
  configuration: --prefix=/opt/homebrew/Cellar/ffmpeg/5.0.1_2 --enable-shared --enable-pthreads --enable-version3 --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librist --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox --enable-neon
  libavutil      57. 17.100 / 57. 17.100
  libavcodec     59. 18.100 / 59. 18.100
  libavformat    59. 16.100 / 59. 16.100
  libavdevice    59.  4.100 / 59.  4.100
  libavfilter     8. 24.100 /  8. 24.100
  libswscale      6.  4.100 /  6.  4.100
  libswresample   4.  3.100 /  4.  3.100
  libpostproc    56.  3.100 / 56.  3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'audio.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: mp42mp41isomiso2
    creation_time   : 2022-07-24T22:23:15.000000Z
  Duration: 00:00:27.17, start: 0.000000, bitrate: 129 kb/s
  Stream #0:0[0x1](und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 127 kb/s (default)
    Metadata:
      creation_time   : 2022-07-24T22:23:15.000000Z
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]
Input #1, mov,mp4,m4a,3gp,3g2,mj2, from 'video.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: mp42mp41isomiso2
    creation_time   : 2022-07-24T22:23:15.000000Z
  Duration: 00:00:27.12, start: 0.000000, bitrate: 7662 kb/s
  Stream #1:0[0x1](und): Video: hevc (Main) (hvc1 / 0x31637668), yuv420p(tv), 1280x720, 7653 kb/s, SAR 1:1 DAR 16:9, 103.75 fps, 120 tbr, 12k tbn (default)
    Metadata:
      creation_time   : 2022-07-24T22:23:15.000000Z
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
Output #0, mp4, to 'test.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: mp42mp41isomiso2
    encoder         : Lavf59.16.100
  Stream #0:0(und): Video: hevc (Main) (hvc1 / 0x31637668), yuv420p(tv), 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 7653 kb/s, 103.75 fps, 120 tbr, 12k tbn (default)
    Metadata:
      creation_time   : 2022-07-24T22:23:15.000000Z
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
  Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 127 kb/s (default)
    Metadata:
      creation_time   : 2022-07-24T22:23:15.000000Z
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]
Stream mapping:
  Stream #1:0 -> #0:0 (copy)
  Stream #0:0 -> #0:1 (copy)
Press [q] to stop, [?] for help
[mp4 @ 0x148708150] Non-monotonous DTS in output stream 0:0; previous: 29308, current: 29308; changing to 29309. This may result in incorrect timestamps in the output file.
[mp4 @ 0x148708150] Non-monotonous DTS in output stream 0:0; previous: 111505, current: 111505; changing to 111506. This may result in incorrect timestamps in the output file.
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x148704fe0] Invalid timestamps stream=0, pts=128503, dts=128504, size=6321
[mp4 @ 0x148708150] Invalid DTS: 128504 PTS: 128503 in output stream 0:0, replacing by guess
[mp4 @ 0x148708150] Non-monotonous DTS in output stream 0:0; previous: 128504, current: 128504; changing to 128505. This may result in incorrect timestamps in the output file.
frame= 2814 fps=0.0 q=-1.0 Lsize=   25817kB time=00:00:27.16 bitrate=7784.7kbits/s speed=1.5e+03x    
video:25340kB audio:424kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.201361%


  


• Cannot encode vp9 video with alpha to ivf container

  28 juillet 2022, par Jakob Košir

  I'm trying to convert a vp8/webm video with transparency to vp9 and ivf container. I can encode the video to vp9 into webm container with the following command which correctly produces a vp9 video with transparency :

  


  ffmpeg -c:v libvpx -i dancer1.webm -c:v libvpx-vp9 dancer_vp9.webm


  


  So basically forcing libvpx encoders instead of ffmpeg native ones to support alpha.

  


  However if I try to use ivf container instead of webm the resulting video does not have transparency :

  


  ffmpeg -c:v libvpx -i dancer1.webm -c:v libvpx-vp9 dancer_vp9.ivf


  


  Does not have transparency when played with VLC, when converting frames to PNG using ffmpeg (ffmpeg -c:v libvpx-vp9 -i dancer_vp9.ivf -vf "select=eq(n\,0)" frame.png) and when played in Chrome (using webcodecs API). Does ivf not support alpha channel somehow or am I doing something wrong ?

  


  I also tried copying the stream with alpha from webm container to ivf (ffmpeg -i dancer1_vp9.webm -c copy dancer1_vp9_copy.ivf) which produces the same result, no transparency.

  


  Curiously if I force or don't force libvpx decoder (which is required to support transparency, ffmpeg native one seems to just discard the alpha channel) when reading vp8/vp9 webm video it produces the same result when outputting to ivf container, while when outputting to webm container the resulting video has alpha when using libvpx decoder and not when using native ffmepg decoder.

  


  ffprobe output of created ivf file :

  


  ffprobe version 5.0.1 Copyright (c) 2007-2022 the FFmpeg developers
  built with Apple clang version 13.1.6 (clang-1316.0.21.2.5)
  configuration: --prefix=/opt/homebrew/Cellar/ffmpeg/5.0.1_3 --enable-shared --enable-pthreads --enable-version3 --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librist --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox --enable-neon
  libavutil      57. 17.100 / 57. 17.100
  libavcodec     59. 18.100 / 59. 18.100
  libavformat    59. 16.100 / 59. 16.100
  libavdevice    59.  4.100 / 59.  4.100
  libavfilter     8. 24.100 /  8. 24.100
  libswscale      6.  4.100 /  6.  4.100
  libswresample   4.  3.100 /  4.  3.100
  libpostproc    56.  3.100 / 56.  3.100
Input #0, ivf, from 'dancer_vp9.ivf':
  Duration: 00:01:02.87, start: 0.000000, bitrate: 249 kb/s
  Stream #0:0: Video: vp9 (Profile 0) (VP90 / 0x30395056), yuv420p(tv), 640x360, 30 tbr, 30 tbn


  


• FFMPEG - Get timestamp from hls stream while downloading

  31 juillet 2022, par Oytoch

  I need to download a stream, take 1 frames per seconds for image analyse.

  


  I use FFmpeg to take the frames with a pipe to my script.

  


  ffmpeg -i XX.m3u8 -vcodec mjpeg -f image2pipe -r 1 -s 1280*720 pipe:1


  


  For my analyse, I need the timestamp and in the HLS we have this data in the m3u8 file :

  


  #EXT-X-PROGRAM-DATE-TIME:2022-07-31T19:10:12.745Z
#EXTINF:2.000,live
XXXXX.ts
#EXT-X-PROGRAM-DATE-TIME:2022-07-31T19:10:14.745Z


  


  ffmpeg output also something like this

  


  frame=    1 fps=0.0 q=7.5 size=      59kB time=00:00:01.00 bitrate= 480.3kbits/s speed=  36x


  


  the problem is that we don't know which second we are downloading

  


  is there a solution to get this timestamp ?
Thanks