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• How can I use FFMPEG to extract a specific color from a video and put it over alpha ?

  28 février 2024, par Michael Macha

  I have a rendered animation which looks great, but my original file was not saved properly and has lost some of the data. I can quickly get that data back, if I can extract a specific color from the rendered video to a new file or image sequence, over either a key color or preferably transparency.

  


  Since I'm hand animating this, it's important that I automate as much as possible. I think FFMPEG could come to the rescue here and help me retrieve that data.

  


  My current line is this :

  


  ffmpeg -i ./"Light Bleeder Twirl Above.mp4" -vf "colorkey=0xe1eff9:0.1:0.1,format=rgba" -c:a copy ./out%04d.png


  


  Here, E1EFF9 is the color I'm after. It successfully extracts the handful of frames to PNG files, but it copies all of the data, not just E1EFF9.

  


  I'm not sure why colorkey isn't doing what I want it to. If someone could provide some insight, it would be much appreciated.

  


  Addendum : So, my idea worked in principle ; I did a chroma key with Kdenlive and color-to-alpha'd the black to transparency after a manual rescale. It isn't exactly the same, but it's very close and saves a lot of time. I still feel like it should most certainly have worked with FFMPEG, much faster, and would still like to know what was wrong with my script.

  


• avcodec/pngdec : read cLLi and mDVc chunks

  4 février 2024, par Leo Izen

  avcodec/pngdec : read cLLi and mDVc chunks
  These chunks contain the Content Light Level Information and the
  
  Mastering Display Color Volume information that FFmpeg already supports
  
  as AVFrameSideData. This patch adds support for the png decoder to read
  
  these chunks if present and attach the corresponding side data to the
  
  decoded frame.
  Signed-off-by : Leo Izen <leo.izen@gmail.com>
  

  • [DH] libavcodec/pngdec.c

• Extract all audio from a mov file into a aac file [closed]

  5 février 2024, par Sushrut Kaul

  I have a video which contains several streams as shown below :

  


  Stream #0:0[0x1](eng): Video: prores (XQ) (ap4x / 0x78347061), yuv444p12le(bt709/smpte432/smpte2084, progressive), 3840x2160, 1222881 kb/s, SAR 1:1 DAR 16:9, 23.98 fps, 23.98 tbr, 24k tbn (default)
    Metadata:
      creation_time   : 2022-08-26T22:20:26.000000Z
      handler_name    : Apple Video Media Handler
      vendor_id       : appl
      encoder         : Apple ProRes 4444 XQ
      timecode        : 00:59:59:00
    Side data:
      Content Light Level Metadata, MaxCLL=726, MaxFALL=93
  Stream #0:1[0x2](eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (FL), s32 (24 bit), 1152 kb/s (default)
    Metadata:
      creation_time   : 2022-08-26T22:20:26.000000Z
      handler_name    : Apple Sound Media Handler
      vendor_id       : [0][0][0][0]
  Stream #0:2[0x3](eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (FR), s32 (24 bit), 1152 kb/s (default)
    Metadata:
      creation_time   : 2022-08-26T22:20:26.000000Z
      handler_name    : Apple Sound Media Handler
      vendor_id       : [0][0][0][0]
  Stream #0:3[0x4](eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, mono, s32 (24 bit), 1152 kb/s (default)
    Metadata:
      creation_time   : 2022-08-26T22:20:26.000000Z
      handler_name    : Apple Sound Media Handler
      vendor_id       : [0][0][0][0]
  Stream #0:4[0x5](eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (LFE), s32 (24 bit), 1152 kb/s (default)
    Metadata:
      creation_time   : 2022-08-26T22:20:26.000000Z
      handler_name    : Apple Sound Media Handler
      vendor_id       : [0][0][0][0]
  Stream #0:5[0x6](eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (BL), s32 (24 bit), 1152 kb/s (default)
    Metadata:
      creation_time   : 2022-08-26T22:20:26.000000Z
      handler_name    : Apple Sound Media Handler
      vendor_id       : [0][0][0][0]
  Stream #0:6[0x7](eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (BR), s32 (24 bit), 1152 kb/s (default)
    Metadata:
      creation_time   : 2022-08-26T22:20:26.000000Z
      handler_name    : Apple Sound Media Handler
      vendor_id       : [0][0][0][0]
  Stream #0:7[0x8](eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (DL), s32 (24 bit), 1152 kb/s (default)
    Metadata:
      creation_time   : 2022-08-26T22:20:26.000000Z
      handler_name    : Apple Sound Media Handler
      vendor_id       : [0][0][0][0]
  Stream #0:8[0x9](eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, 1 channels (DR), s32 (24 bit), 1152 kb/s (default)
    Metadata:
      creation_time   : 2022-08-26T22:20:26.000000Z
      handler_name    : Apple Sound Media Handler
      vendor_id       : [0][0][0][0]


  


  As you can see, these audio streams are single channel as each stream is mapping to a unique channel.

  


  I want to combine these audio streams into a aac file such that the output has the channel information retained.

  


  I use the following command to do this :

  


  ffmpeg -i -filter _complex "[0:a:0][0:a:1][0:a:2][0:a:3][0:a:4][0:a:5][0:a:6][0:a:7]join=inputs=8:channel_layout=7.1[aout]" -map "[aout]" -c:a aac output_audio_join.aac

  


  The individual audio streams were having a duration of duration=103.728625 seconds.

  


  The output however is 862.207660 seconds. Why ?