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• ffmpeg - store desired output to python variable

  15 January 2024, by Chris P

  If i run: ffmpeg -list_devices true -f dshow -i dummy i get:

  


  ffmpeg version 2023-01-30-git-2d202985b7-full_build-www.gyan.dev Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 12.2.0 (Rev10, Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-bzlib --enable-lzma --enable-libsnappy --enable-zlib --enable-librist --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libaribb24 --enable-libdav1d --enable-libdavs2 --enable-libuavs3d --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libaom --enable-libjxl --enable-libopenjpeg --enable-libvpx --enable-mediafoundation --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-liblensfun --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libvpl --enable-libshaderc --enable-vulkan --enable-libplacebo --enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
  libavutil      57. 44.100 / 57. 44.100
  libavcodec     59. 59.100 / 59. 59.100
  libavformat    59. 36.100 / 59. 36.100
  libavdevice    59.  8.101 / 59.  8.101
  libavfilter     8. 56.100 /  8. 56.100
  libswscale      6.  8.112 /  6.  8.112
  libswresample   4.  9.100 /  4.  9.100
  libpostproc    56.  7.100 / 56.  7.100
[dshow @ 00000236357d0480] "HP True Vision HD Camera" (video)
[dshow @ 00000236357d0480]   Alternative name "@device_pnp_\\?\usb#vid_04f2&pid_b6ab&mi_00#6&763f234&2&0000#{65e8773d-8f56-11d0-a3b9-00a0c9223196}\global"
[dshow @ 00000236357d0480] "Microphone Array (Intel® Smart Sound Technology for Digital Microphones)" (audio)
[dshow @ 00000236357d0480]   Alternative name "@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\wave_{E8824DE9-F848-47F1-BB2A-EB24E11050FC}"
dummy: Immediate exit requested


  


  From this output i want to store: "HP True Vision HD Camera" (first video output) in a python variable.

  


  Is this possible?

  


  I am trying

  


  import subprocess
ffmpeg_command = ["ffmpeg", "-list_devices", "true","-f", "dshow", "-i", "dummy"]
pipe = subprocess.run(ffmpeg_command,stdout=subprocess.PIPE,stderr=subprocess.PIPE,bufsize=10**8)
output = pipe.stdout
lines = output.splitlines()
for line in lines:
    if line.startswith("[dshow @"):
        if "(video)" in line:
            camera_info = line.split("\"")[1]
            print(camera_info)


  


• Video - ffmpeg wrong frame number when merging mkv files

  9 June 2014, by communications

  im trying to join several mkv files together with ffmpeg.

  they all have the same encoding settings.

  i think ffmpeg joins the files, because the filesize of the resulting file has the size of all others combined

  BUT when i open the file, only the number of frames of the last part are shown, so i guess its a problem in the header, where is says how long the video is...

  How can i fix that?

  Heres the command i use:

  ffmpeg -i "concat:100frames_part0.mkv|100frames_part1.mkv|100frames_part3.mkv" -c copy 100frames.mkv

• x264/avcodec: Deduce frame sequence number from NAL unit

  4 April 2014, by Dan Tumaykin

  I’m using avcodec H264 decoder in my project. I receive NAL units from network, stick together NALs from same frame (additional header is added on network layer) and than pass to the decoder. I was wondering if frame sequence number is encoded into NAL unit - it would be logical, as we need the reference to IDR frames.

  If this information is present - how can I extract it?

  Right now I looking into ITU-T H.264 specification, which is quite complex I can admit. So far I have not found the answer to my question.