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• ffmpeg vertically center align multiple lines of text using drawtext and subtitle both filters independent of font size

  22 janvier 2020, par Rehan

  I want to vertically center align the text on video no matter what the font size is. And possibly if it could be done using drawtext filter and subtitles filter as well for subtitles filter if anyone can guide how to move the lines few columns up.

  I tried multiple [in]drawtext=...,drawtext=...[out] filter but when change the font size alignment goes wrong curious to know if there is some calculated formula to do this accurately.

• 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 !