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• Change gray pixel to black pixels in video

  12 janvier 2023, par yabru

  I want to change every gray pixel in my video with the (r,g,b) 158,158,158 to black 0,0,0

  


  I've tried the solution of THIS post, but backwards. I just do not understand the syntax.

  


  ffmpeg -y -I my_video.mp4 -c copy -c:v libx264 -preset ultrafast -vf "yadif,format=rgb24, lutrgb=r='if(eq(val,158),0,val)':g='if(eq(val,158),0,val)':b='if(eq(val,158),0,val)'" my_video_fixed.mp4

  


  ^ doesn't change anything

  


  could anyone help me modify my command (with an explanation of the solution) :)

  


  version : ffmpeg version 5.1.2

  


• Overlaying one video on another one, and making black pixels transparent

  25 janvier 2023, par Michael A

  I'm trying to use FFMPEG to create a video with one video overlayed on top another.

  



  I have 2 MP4s. I need to make all BLACK pixels in the overlay video transparent so that I can see the main video underneath it.

  



  I found two ways to overlay one video on another :

  



  First, the following positions the overlay in the center, and therefore, hides that portion of the main video beneath it :

  



      ffmpeg -i 1.mp4 -vf "movie=2.mp4 [a]; [in][a] overlay=352:0 [b]" combined.mp4 -y


  



  And, this one, places the overlay video on the left, but it's opacity is set to 50% so at least other one beneath it is visible :

  



  ffmpeg -i 1.mp4 -i 2.mp4 -filter_complex "[0:v]setpts=PTS-STARTPTS[top]; [1:v]setpts=PTS-STARTPTS, format=yuva420p,colorchannelmixer=aa=0.5[bottom]; [top][bottom]overlay=shortest=0" -acodec libvo_aacenc -vcodec libx264 out.mp4 -y


  



  My goal is simply to make all black pixels in the overlay (2.mp4) completely transparent. How can this be done.

  


• Black detect ffmpeg and use in a javascript

  6 février 2023, par sol

  I had an ffmpeg script that allow me to detect black frames from a video file sample from the bottom.

  


  and i want to create a javascript code that will allow me to do the same function sample from the bottom but its not working.

  


  original code from ffmpeg script :

  


  `ffmpeg -i LKE-BLACK.mp4 -vf "blackdetect=d=0.5:pix_th=0.10" -an -f null - 2>&1 | findstr blackdetect > output.txt

  


  node script :

  


  var fs = require('fs');
const ffmpeg = require("ffmpeg.js");

var createStream = fs.createWriteStream("data.txt");
createStream.end();

const transcode = async ({ target: { files }  }) => {
    message.innerHTML = 'Loading ffmpeg-core.js';
    await ffmpeg.load();
    message.innerHTML = 'Start transcoding';
    
    await ffmpeg.transcode('-i', 'LKE-BLACK.mp4', "-vf", "blackdetect=d=0.5:pix_th=0.10", '-an', '-f', 'null - 2>&1', );
    message.innerHTML = 'Complete transcoding';

    fs.writeFile("data.txt", function (err) {
        if (err) throw err;
        console.log('File is created successfully.');
      });
}