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• I ues FFMPEG to convert bitmap to yuv,and try to save it,but failed

  20 avril 2013, par liaoyuandeyehuo

  I use this way to convert bitmap to yuv
  Save bitmap to video (libavcodec ffmpeg)
  and then save the buffer like this :

  FILE* fp=fopen("aha.yuv","w");
  
  if(!fp) return NULL;
  
  fwrite(outPic->data[0],nbytes,1,fp);
  
  fwrite(outBuffer,nbytes,1,fp);
  
  fclose(fp);

  but it has only several lines. All most all of the .yuv file is gray.
  I am sure the inbuffer points to the input BGR32 data. So where is wrong ?
  Is The way to save the outBuffer right ?

• Extracting thumbnails with FFMPEG is super slow on large video files ? [duplicate]

  5 octobre 2015, par vaid

  This question already has an answer here :

  • Fastest way to extract a specific frame from a video (PHP/ffmpeg/anything)
    
    1 answer
    

  I extract thumbnails from a .MOV file using FFMPEG on Linus (Debian 64bit).

  The file I extract the thumbnail from is about 430 Megabytes large.

  I use the following command to do so :

  ffmpeg -i 'largeVideoFile.mov' -ss 00:14:37 -vframes 1 'thumbnail.jpg'

  It takes well over 3 minutes for a single frame to be extracted.

  How can I speed it up ?

• How to make cropping when doing motion-tracking look super smooth ? (using cv2 and yolo v8)

  4 décembre 2024, par Thomas Lancer

  I'm using yolo to track a face in a video on a frame by frame basis, and then I'm using cv2 to crop the video (with some padding) around the speakers face so it creates a motion tracking type effect. (short example here : https://www.instagram.com/reel/DCIFkFEObkE/?hl=en)

  


  The problem I'm running into is my final crop looks "shaky". Like it's flickering a bit. I think this is because every frame yolo is updating the coordinates, and so there's a slight change in x, y and because of that it creates this shakiness/flickering effect. Here's what mine looks like compared to the example : https://drive.google.com/file/d/1MKHWK-5EH5abSq6i32r71GWld76tN1GP/view?usp=sharing

  


  You can see there's this "shakiness" type look to it. it's especially apparent when the speaker is relatively still.

  


  I've tried doing an exponential moving average and a few other averaging techniques but none have fixed it.

  


  Is my fundamental approach of doing a frame by frame crop wrong ? or is there just some smoothing algorithm or some dumb mistake that you think I may be making ? Any advice is mega appreciated !