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• ffmpeg unique frames only

  5 novembre 2013, par William

  I have a video sequence (MPEG1) of 30 fps that is decoded in two ways :

  • opencv_ffmpeg returns 30 images per second, but only 5 of them are unique, while all others are clones of the unique ones.

  • proprietary players (MediaPlayer) returns only the 5 unique frames and "holds" them for (1/5) sec each.

  Is there a way to grab only the unique frames that the coder knows and not the total amount the ffmpeg decoder produces to fulfill the fps rate ?

  I'm developing a tracker and my tracker is forced to run 6 times slower and do many mistakes due to these "cloned frames".

  Does anyone know any technical term to the problem ? Unfortunately, ffmpeg is a black box for an opencv user and the documentation is sparse.

• Insert still frames into H.264 video stream

  7 juillet 2021, par Bassinator

  I'm building an application that receives video packets which are encoded as H.264 from Microsoft Teams - I get one packet for each frame of video. Specifications of the packet contents are given here. For every packet I receive, I write the byte contents of the data[] buffer to a file. This resulting file is a playable H.264 encoded video.

  


  I'm trying to handle the scenario of syncing the audio and video streams from a Teams meeting, and inserting a still frame PNG as a "filler" when nobody has their camera on.

  


  I used the following FFMPEG command to generate n number of seconds of H.264 video from the filler frame :

  


  ffmpeg -loop 1 -i video_filler_frame.png -framerate 30 -c:v libx264 -t 2 -vf scale=1920:1080 C:\Code\temp\out.mp4


  


  This generates an MP4 file (H.264 encoded) - as a test in my code, I tried to read the contents of that generated file as a byte array and append them to the video file.

  


  However, this doesn't appear to work. I'm guessing this is because there is some kind of header or other metadata that prevents us from doing the simple solution of just appending the bytes of the next frame.

  


  My question is, how can I achieve what I am trying to do ? I'd like to splice in n number of frames as I am writing the individual packet contents to the file. In other words, for example, consider the following sequence :

  


  

  • Write packets of video to the file

  


  • My code determines that filler frames are needed at some point in this process

    

    • Insert needed number of filler frames to the file

    


    


  


  • Continue writing packets of video as they come in

  


  


• Anomalie #3750 : Itérateur JSON, erreur de compilation lorsque la source contient &

  8 octobre 2018, par placido .

  J’avais fait le ticket au départ, notamment parce que le message de debug de compilation partait complètement en vrille, ce qui semble trahir un cas de remontée d’erreur pas bien géré.
  Pour le reste on a qu’à dire que cette page fera office de précis de documentation pour les urls de ressources JSON avec ’&’.

  Donc oui, on peut sans doute fermer.