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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.

  


• Error when Decode h264 file by using FFMPEG with multithreading ?

  12 septembre 2013, par TTGroup

  I write the code for decoding many .flv video files. Each video file is decoded by a separate thread.
  When I try on 1 thread, everything is ok. But when I try on more than 2 threads, it always occurs the error "insufficient thread locking around avcodec_open/close()".

  I have searched and I know the functions avcodec_open() and avcodec_close() is not thread safe.
  And after that, I putted the mutex locking at anywhere that two that functions are called.

  lockObj.Lock();
  
  avcodec_open/close();
  
  lockObj.UnLock();

  But the error "insufficient thread locking around avcodec_open/close()" is still happen.

  Someone can tell me the solution ?

  Many thanks,

  T&TGroup

• Red5 and FFmpeg in streaming [closed]

  22 mai 2013, par user2408040

  I have installed Red5 and ffmpeg in Ubuntu.

  My idea is use the example http://localhost:5080/demos/ofla_demo.html for a simple streaming with ffmpeg.

  I use ffmpeg as follow :

  ffmpeg -i out.flv -f flv "rtmp://localhost:5080/oflaDemo"

  I hope is to see in http://localhost:5080/demos/ofla_demo.html my streaming but this not happen.

  Someone can tell me I'm doing wrong ?

  Sorry my English :)

  Regards