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• Remove black frames and sync audio with ffmpeg

  24 janvier 2020, par rahim123

  I’m trying to figure out a way to automatically process .mp4 or .mkv videos that have been manually edited to remove a bunch of segments, leaving many blank spaces (black frames with no audio). I want to remove all but one black frame (although I would settle for removing all of them if it’s much simpler) and then also sync the audio after the video timings change.

  I found this question and tried the three main suggestions :

  1. ffmpeg -i in.mkv -vf mpdecimate,setpts=N/FRAME_RATE/TB out.mkv
  2. ffmpeg -i in.mkv -vf [mpdecimate][] out.mkv
  3. ffmpeg -i in.mkv -vf [decimate][]=cycle=6,[setpts][]=N/25/TB out.mkv

  The first one does eliminate the black segments, but it doesn’t sync the audio. The other two commands don’t work :

  > ffmpeg -i in.mp4 -vf [decimate][]=cycle=6,[setpts][]=N/25/TB out.mp4
  
  ffmpeg version 4.2.1 Copyright (c) 2000-2019 the FFmpeg developers
  
    built with gcc 9 (SUSE Linux)
  
    configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64 --incdir=/usr/include/ffmpeg --extra-cflags='-O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables -fstack-clash-protection -Werror=return-type -flto=auto -g' --optflags='-O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables -fstack-clash-protection -Werror=return-type -flto=auto -g' --disable-htmlpages --enable-pic --disable-stripping --enable-shared --disable-static --enable-gpl --disable-openssl --enable-avresample --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcelt --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libdc1394 --enable-libdrm --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libssh --enable-libsrt --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libv4l2 --enable-libvpx --enable-libwebp --enable-libxml2 --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lto --enable-lv2 --enable-libmfx --enable-vaapi --enable-vdpau --enable-libfdk-aac-dlopen --enable-nonfree --enable-libvo-amrwbenc --enable-version3 --enable-libx264 --enable-libx265 --enable-librtmp --enable-libxvid
  
    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
  
    libavresample   4.  0.  0 /  4.  0.  0
  
    libswscale      5.  5.100 /  5.  5.100
  
    libswresample   3.  5.100 /  3.  5.100
  
    libpostproc    55.  5.100 / 55.  5.100
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'in.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf58.20.100
  
    Duration: 00:34:23.62, start: 0.000000, bitrate: 506 kb/s
  
      Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, smpte170m/unknown/smpte170m), 640x480 [SAR 1:1 DAR 4:3], 412 kb/s, 29.97 fps, 29.97 tbr, 1867500000.00 tbn, 59.94 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 86 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
  
    Stream #0:1 -> #0:1 (aac (native) -> aac (native))
  
  Press [q] to stop, [?] for help
  
  [AVFilterGraph @ 0x55ece8def080] Bad (empty?) label found in the following: "[]=cycle=6,[setpts][]=N/25/TB".
  
  Error reinitializing filters!
  
  Failed to inject frame into filter network: Invalid argument
  
  Error while processing the decoded data for stream #0:0
  
  [aac @ 0x55ece8c5be80] Qavg: 222.643
  
  [aac @ 0x55ece8c5be80] 2 frames left in the queue on closing
  
  Conversion failed!

  > ffmpeg -i in.mp4 -vf [decimate][]=cycle=6,[setpts][]=N/25/TB out.mp4
  
  ffmpeg version 4.2.1 Copyright (c) 2000-2019 the FFmpeg developers
  
    built with gcc 9 (SUSE Linux)
  
    configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64 --incdir=/usr/include/ffmpeg --extra-cflags='-O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables -fstack-clash-protection -Werror=return-type -flto=auto -g' --optflags='-O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables -fstack-clash-protection -Werror=return-type -flto=auto -g' --disable-htmlpages --enable-pic --disable-stripping --enable-shared --disable-static --enable-gpl --disable-openssl --enable-avresample --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcelt --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libdc1394 --enable-libdrm --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libssh --enable-libsrt --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libv4l2 --enable-libvpx --enable-libwebp --enable-libxml2 --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lto --enable-lv2 --enable-libmfx --enable-vaapi --enable-vdpau --enable-libfdk-aac-dlopen --enable-nonfree --enable-libvo-amrwbenc --enable-version3 --enable-libx264 --enable-libx265 --enable-librtmp --enable-libxvid
  
    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
  
    libavresample   4.  0.  0 /  4.  0.  0
  
    libswscale      5.  5.100 /  5.  5.100
  
    libswresample   3.  5.100 /  3.  5.100
  
    libpostproc    55.  5.100 / 55.  5.100
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'in.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf58.20.100
  
    Duration: 00:34:23.62, start: 0.000000, bitrate: 506 kb/s
  
      Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, smpte170m/unknown/smpte170m), 640x480 [SAR 1:1 DAR 4:3], 412 kb/s, 29.97 fps, 29.97 tbr, 1867500000.00 tbn, 59.94 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 86 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
  
    Stream #0:1 -> #0:1 (aac (native) -> aac (native))
  
  Press [q] to stop, [?] for help
  
  [AVFilterGraph @ 0x558b0d48af80] Bad (empty?) label found in the following: "[]=cycle=6,[setpts][]=N/25/TB".
  
  Error reinitializing filters!
  
  Failed to inject frame into filter network: Invalid argument
  
  Error while processing the decoded data for stream #0:0
  
  [aac @ 0x558b0d2f7e80] Qavg: 222.643
  
  [aac @ 0x558b0d2f7e80] 2 frames left in the queue on closing
  
  Conversion failed!

  I also tried this script, but it also fails to sync the audio. I tried with both .mp4 and .mkv source files. Thanks for the help.

• ffmpeg implicitly shifts video and audio

  2 mars 2020, par ynn

  I separated a .mkv file with audio and video into two files by the following command.

  ffmpeg -i input.mkv -vn -codec copy out.wav #extract audio
  
  ffmpeg -i input.mkv -an -codec copy out.mkv #extract video

  And I just merge them into one .mkv file :

  ffmpeg -i out.mkv -i out.wav -codec copy final.mkv #this behaves quite strangely

  I thought the initial input input.mkv and the final output final.mkv should be exactly the same, but, in final.mkv, the video and the audio was shifted by about five seconds. Using ffprobe, I found the cause was the video part (out.mkv) was trimmed off by the length (i.e. five seconds) for no reason.

  What’s happening here ? How can I avoid this strange shift ?

  ---

  Detailed Explanation :

  Hereafter I use this sample input called input.mkv. First, extract video and audio from it.

  $ ffmpeg -i input.mkv -vn -codec copy out.wav
  
  $ ffmpeg -i input.mkv -an -codec copy out.mkv

  Next, check the duration of them.

  $ ffprobe -i out.wav 2>&1 | grep Duration
  
    Duration: 00:00:18.88, bitrate: 1536 kb/s
  
  $ ffprobe -i out.mkv 2>&1 | grep Duration
  
    Duration: 00:00:18.87, start: 0.000000, bitrate: 1877 kb/s

  Then combine them.

  $ ffmpeg -i out.mkv -i out.wav -codec copy final.mkv

  Finally, check the duration of streams.

  $ ffprobe -i final.mkv 
  
  Input #0, matroska,webm, from 'final.mkv':
  
    Metadata:
  
      ENCODER         : Lavf58.29.100
  
    Duration: 00:00:18.88, start: 0.000000, bitrate: 3414 kb/s
  
      Stream #0:0: Video: h264 (High), yuv420p(tv, bt709, progressive), 900x586 [SAR 1:1 DAR 450:293], 30.30 fps, 30.30 tbr, 1k tbn, 60 tbc (default)
  
      Metadata:
  
        DURATION        : 00:00:18.866000000
  
      Stream #0:1: Audio: pcm_s16le, 48000 Hz, 2 channels, s16, 1536 kb/s
  
      Metadata:
  
        DURATION        : 00:00:18.880000000

  Strangely, duration of the video stream has been trimmed off from 18.8700 to 18.8660, though the length of the audio stream is not touched at all.

  It seems the longer the video is, the bigger part is trimmed. (In my case of a one hour video, no less than five seconds were trimmed off.)

  ---

  Version Information :

  ~ $ ffmpeg -version
  
  ffmpeg version n4.2.2 Copyright (c) 2000-2019 the FFmpeg developers
  
  built with gcc 9.2.1 (Arch Linux 9.2.1+20200130-2) 20200130
  
  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

• ffmpeg error : Too large number of skipped frames xxxxx > 60000

  16 septembre 2019, par Fulkron

  I try to record on RasperryPI from usb Cam (/dev/video0) using segments to obtain sliced video.
  The command I’m using is :

  ffmpeg -input_format mjpeg -video_size 640x480 -i /dev/video0 -y -y -f v4l2 -an -pix_fmt yuv420p -codec copy -f segment -segment_time 60 -segment_wrap 10 -t 180 stream/looper%02d.avi

  I got an error after 2 minutes about skipped frames (see later for detail).
  Is I run the same command without segmentation is working.

  I tested on different HW, with different segment parameters, with different usb cam but the situation still the same.

  Here there is the output :

     ffmpeg version 4.1.4-1+rpt1~deb10u1 Copyright (c) 2000-2019 the FFmpeg developers
  
    built with gcc 8 (Raspbian 8.3.0-6+rpi1)
  
    configuration: --prefix=/usr --extra-version='1+rpt1~deb10u1' --toolchain=hardened --libdir=/usr/lib/arm-linux-gnueabihf --incdir=/usr/include/arm-linux-gnueabihf --arch=arm --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --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-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-omx-rpi --enable-mmal --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  
    libavutil      56. 22.100 / 56. 22.100
  
    libavcodec     58. 35.100 / 58. 35.100
  
    libavformat    58. 20.100 / 58. 20.100
  
    libavdevice    58.  5.100 / 58.  5.100
  
    libavfilter     7. 40.101 /  7. 40.101
  
    libavresample   4.  0.  0 /  4.  0.  0
  
    libswscale      5.  3.100 /  5.  3.100
  
    libswresample   3.  3.100 /  3.  3.100
  
    libpostproc    55.  3.100 / 55.  3.100
  
  Input #0, video4linux2,v4l2, from '/dev/video0':
  
    Duration: N/A, start: 40185.241073, bitrate: N/A
  
      Stream #0:0: Video: mjpeg, yuvj422p(pc, bt470bg/unknown/unknown), 640x480, 25 fps, 25 tbr, 1000k tbn, 1000k tbc
  
  [segment @ 0x9800b0] Opening 'stream/looper00.avi' for writing
  
  Output #0, segment, to 'stream/looper%02d.avi':
  
    Metadata:
  
      encoder         : Lavf58.20.100
  
      Stream #0:0: Video: mjpeg, yuvj422p(pc, bt470bg/unknown/unknown), 640x480, q=2-31, 25 fps, 25 tbr, 600 tbn, 1000k tbc
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (copy)
  
  Press [q] to stop, [?] for help
  
  [segment @ 0x9800b0] Opening 'stream/looper01.avi' for writing/A speed=1.01x    
  
  [segment @ 0x9800b0] Opening 'stream/looper02.avi' for writing/A speed=1.01x    
  
  [avi @ 0x9822a0] Too large number of skipped frames 72034 > 60000speed=1.01x    
  
  av_interleaved_write_frame(): Invalid argument
  
  [avi @ 0x9822a0] Too large number of skipped frames 72034 > 60000
  
  frame= 3011 fps= 25 q=-1.0 Lsize=N/A time=00:02:00.06 bitrate=N/A speed=1.01x 

  I did not find any suggestion to solve it.
  Could you help me ?

  Thanks
  Dario