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• Dividing, processing and merging files with ffmpeg

  9 novembre 2015, par João Carlos Santos

  I am trying to build an application that will divide an input video file (usually mp4) into chunks so that I can apply some processing to them concurrently and then merge them back into a single file.

  To do this, I have outlined 4 steps :

  1. Forcing keyframes at specific intervals so to make sure that each
     chunk can be played on its own. For this I am using the following
     command :

     ffmpeg -i input.mp4 -force_key_frames
"expr:gte(t,n_forced*chunk_length)" keyframed.mp4

     where chunk_length is the duration of each chunk.

  2. Dividing keyframed.mp4 into multiple chunks.
     Here is where I have my problem. I am using the following command :

     `ffmpeg -i keyframed.mp4 -ss 00:00:00 -t chunk_length -vcodec copy -acodec copy test1.mp4`

     to get the first chunk from my keyframed file but it isn’t capturing
     the output correctly, since it appears to miss the first keyframe.

     On other chunks, the duration of the output is also sometimes
     slightly less than chunk_length, even though I am always using the
     same -t chunk_length option

  3. Processing each chunk For this task, I am using the following
     commands :

     ffmpeg -y -i INPUT_FILE -threads 1 -pass 1 -s 1280x720 -preset
medium -vprofile baseline -c:v libx264 -level 3.0 -vf
"format=yuv420p" -b:v 2000k -maxrate:v 2688k -bufsize:v 2688k -r 25
-g 25 -keyint_min 50 -x264opts "keyint=50:min-keyint=50:no-scenecut" -an -f mp4 -movflags faststart /dev/null
     ffmpeg -y -i INPUT_FILE -threads 1 -pass 2 -s 1280x720 -preset
medium -vprofile baseline -c:v libx264 -level 3.0 -vf
"format=yuv420p" -b:v 2000k -maxrate:v 2688k -bufsize:v 2688k -r 25
-g 25 -keyint_min 50 -x264opts "keyint=50:min-keyint=50:no-scenecut" -acodec libfaac -ac 2 -ar 48000 -ab 128k -f mp4 -movflags faststart OUTPUT_FILE.mp4

     This commands are not allowed to be modified, since my goal here is
     to parallelize this process.

  4. Finally, to merge the files I am using concat and a list of the
     outputs of the 2nd step, as follows :

     ffmpeg -f concat -i mylist.txt -c copy final.mp4

  In conclusion, I am trying to find out a way to solve the problem with step 2 and also get some opinions if there is a better way to do this.

• Audio out of sync, direct capture device stream (Windows 10)

  3 mai 2020, par user3459555

  Using ffplay, the video stays in sync using this command :

  



  ffplay -f dshow -rtbufsize 702000k video="Cam Link"
ffplay version git-2020-05-01-39fb1e9 Copyright (c) 2003-2020 the FFmpeg developers
  built with gcc 9.3.1 (GCC) 20200328
  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-libsrt --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-libvmaf --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --disable-w32threads --enable-libmfx --enable-ffnvcodec --enable-cuda-llvm --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt --enable-amf
  libavutil      56. 43.100 / 56. 43.100
  libavcodec     58. 82.100 / 58. 82.100
  libavformat    58. 42.101 / 58. 42.101
  libavdevice    58.  9.103 / 58.  9.103
  libavfilter     7. 80.100 /  7. 80.100
  libswscale      5.  6.101 /  5.  6.101
  libswresample   3.  6.100 /  3.  6.100
  libpostproc    55.  6.100 / 55.  6.100
Input #0, dshow, from 'video=Cam Link':vq=    0KB sq=    0B f=0/0
  Duration: N/A, start: 141954.961000, bitrate: N/A
    Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 1920x1080, 59.94 fps, 59.94 tbr, 10000k tbn, 10000k tbc
142992.53 M-V: -0.001 fd=   3 aq=    0KB vq=    0KB sq=    0B f=0/0


  



  Every controller button press stays in sync.

  



  The audio however :

  



  ffplay -f dshow audio="Digital Audio Interface (Cam Link)" -tune zerolatency
ffplay version git-2020-05-01-39fb1e9 Copyright (c) 2003-2020 the FFmpeg developers
  built with gcc 9.3.1 (GCC) 20200328
  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-libsrt --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-libvmaf --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --disable-w32threads --enable-libmfx --enable-ffnvcodec --enable-cuda-llvm --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt --enable-amf
  libavutil      56. 43.100 / 56. 43.100
  libavcodec     58. 82.100 / 58. 82.100
  libavformat    58. 42.101 / 58. 42.101
  libavdevice    58.  9.103 / 58.  9.103
  libavfilter     7. 80.100 /  7. 80.100
  libswscale      5.  6.101 /  5.  6.101
  libswresample   3.  6.100 /  3.  6.100
  libpostproc    55.  6.100 / 55.  6.100
Input #0, dshow, from 'audio=Digital Audio Interface (Cam Link)':
  Duration: N/A, start: 143092.007000, bitrate: 1411 kb/s
    Stream #0:0: Audio: pcm_s16le, 44100 Hz, 2 channels, s16, 1411 kb/s
143103.21 M-A:  0.000 fd=   0 aq=    0KB vq=    0KB sq=    0B f=0/0


  



  Is always behined by about a full second.

  



  I'm not trying to record this, just trying to directly play from the Elgato Cam Link 1:1 output to my computer screen. When this is played in the Elgato Game Capture software, the video and audio are 1:1, no issues. So I know it's not the console or the capture device.

  


• USB webcam streaming in ARM board (i.MX6)

  5 septembre 2017, par Titus

  I want to streaming the camera via NETWORK. I have connected the USB webcam to i.MX6 board and want to stream in Ubuntu14.04/16.04 via network.

  Incidentally, I have installed the gstreamer and ffmpeg tools for this in i.MX6 board.

  Also I am able to stream USB webcam within Ubuntu14.04 PC using the following ffmpeg commands. But it’s also not working if I use ffplay in other Ubuntu16.04 and I am not sure why (both are same ffmpeg versions).

  ffmpeg -f v4l2 -i /dev/video0 -preset ultrafast -vcodec libx264 -tune zerolatency -b 900k -f mpegts udp://192.168.0.37:1234
  
  
  
  ffplay udp://192.168.0.37:1234

  Ubuntu 16.06 : (NOT WORKING)

  tus@titus-PC:~/workdir$ ffplay udp://192.168.0.105:1234
  
  ffplay version 2.8.11-0ubuntu0.16.04.1 Copyright (c) 2003-2017 the FFmpeg developers
  
    built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 20160609
  
    configuration: --prefix=/usr --extra-version=0ubuntu0.16.04.1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --cc=cc --cxx=g++ --enable-gpl --enable-shared --disable-stripping --disable-decoder=libopenjpeg --disable-decoder=libschroedinger --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzvbi --enable-openal --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzmq --enable-frei0r --enable-libx264 --enable-libopencv
  
    libavutil      54. 31.100 / 54. 31.100
  
    libavcodec     56. 60.100 / 56. 60.100
  
    libavformat    56. 40.101 / 56. 40.101
  
    libavdevice    56.  4.100 / 56.  4.100
  
    libavfilter     5. 40.101 /  5. 40.101
  
    libavresample   2.  1.  0 /  2.  1.  0
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  2.101 /  1.  2.101
  
    libpostproc    53.  3.100 / 53.  3.100
  
      nan    :  0.000 fd=   0 aq=    0KB vq=    0KB sq=    0B f=0/0  

  Ubuntu 14.04 : (WORKING)

  titus@titus-laptop:~$ 
  
  titus@titus-laptop:~$ ffplay udp://127.0.0.1:1234
  
  ffplay version 3.3.2 Copyright (c) 2003-2017 the FFmpeg developers
  
    built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.3)
  
    configuration: --extra-libs=-ldl --prefix=/opt/ffmpeg --mandir=/usr/share/man --enable-avresample --disable-debug --enable-nonfree --enable-gpl --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb --disable-decoder=amrnb --disable-decoder=amrwb --enable-libpulse --enable-libfreetype --enable-gnutls --enable-libx264 --enable-libx265 --enable-libfdk-aac --enable-libvorbis --enable-libtheora --enable-libmp3lame --enable-libopus --enable-libvpx --enable-libspeex --enable-libass --enable-avisynth --enable-libsoxr --enable-libxvid --enable-libvidstab --enable-libwavpack --enable-nvenc
  
    libavutil      55. 58.100 / 55. 58.100
  
    libavcodec     57. 89.100 / 57. 89.100
  
    libavformat    57. 71.100 / 57. 71.100
  
    libavdevice    57.  6.100 / 57.  6.100
  
    libavfilter     6. 82.100 /  6. 82.100
  
    libavresample   3.  5.  0 /  3.  5.  0
  
    libswscale      4.  6.100 /  4.  6.100
  
    libswresample   2.  7.100 /  2.  7.100
  
    libpostproc    54.  5.100 / 54.  5.100
  
  [h264 @ 0xb0621660] non-existing PPS 0 referenced sq=    0B f=0/0   
  
      Last message repeated 1 times
  
  [h264 @ 0xb0621660] decode_slice_header error
  
  [h264 @ 0xb0621660] non-existing PPS 0 referenced
  
  [h264 @ 0xb0621660] decode_slice_header error
  
  [h264 @ 0xb0621660] non-existing PPS 0 referenced
  
  [h264 @ 0xb0621660] decode_slice_header error
  
  [h264 @ 0xb0621660] non-existing PPS 0 referenced
  
  [h264 @ 0xb0621660] decode_slice_header error
  
  [h264 @ 0xb0621660] no frame!
  
  [h264 @ 0xb0621660] non-existing PPS 0 referenced sq=    0B f=0/0   
  
  1751.47 M-V: -0.021 fd=   0 aq=    0KB vq=   11KB sq=    0B f=0/0   
  
  1751.63 M-V: -0.020 fd=   0 aq=    0KB vq=   11KB sq=    0B f=0/0   
  
  1751.80 M-V: -0.020 fd=   0 aq=    0KB vq=   11KB sq=    0B f=0/0 

  Finally I want to stream with different ARM boards. Am also not able to build ffplay command. Same issue with raspberry pi too. I am doing something wrong or misunderstood something here ?