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• Pipe video frames from ffmpeg to canvas without loading the entire video into memory

  1er janvier 2024, par Aviato

  I am working on a project that involves frame manipulation and I decided to choose node canvas API for that. I used to work with OpenCV Python and there was a cv2.VideoCapture class that takes a video as input and prepares to read the frames of the video and we can loop through the frames one at a time without having to load all the frames at once in memory.
Now I tried a lot of ways to replicate the same using ffmpeg, i.e. trying to load frames from a video in an ordered, but "on-demand," fashion.

  


  I tried using ffmpeg as a child process to process frames and standout the frames.

  


  const spawnProcess = require('child_process').spawn,
    ffmpeg = spawnProcess('ffmpeg', [
        '-i', 'test.mp4',
        '-vcodec', 'png',
        '-f', 'rawvideo',
        '-s', '1920*1080', // size of one frame
        'pipe:1'
    ]);
ffmpeg.stdout.on('data', (data) => {
    try {
        // console.log(tf.node.decodeImage(data).shape)
        console.log(`${++i} frames read`)
        //context.drawImage(data, 0, 0, width, height)
        
        
    } catch(e) {
        console.log(e)
    } 
})


  


  The value in the console shows something around 4000 + console logs, but the video only had 150 frames, after much investigating and console logging the data, I found that was buffer data, and it's not processing it for each frame. The on-data function returns the buffer data in an unstructured way
I want to read frames from a video and process each one at a time in memory, I don't want to hold all the frames at once in memory or in the filesystem.

  


  

  


  I also want to pipe the frames in a format that could be rendered on top of a canvas using drawImage

  


• Overlay video with other video in ffmpeg

  15 août 2018, par user2212461

  I have a short and a long mp4 video. In the long video, I would like to replace the visual with a part of the visual of the short video. Additionally, I would like to keep the audio of the long video throughout.

  The following set of commands work. However the concat and audio replacing seems to add a slight delay to the video, which makes the audio slightly out of sync from the video.

  ffmpeg -ss 0 -i short.mp4 -t 2.0 -vcodec copy -an v1_short.mp4
  
  ffmpeg -ss 0 -i long.mp4 -t 6.0 -vcodec copy -an v1_before.mp4
  
  ffmpeg -ss 8.0 -i v_before.mp4 -vcodec copy -an v1_after.mp4.mp4
  
  ffmpeg -i v1_before.mp4 -i v1_short.mp4 -i v1_after.mp4 -filter_complex "[0:v] [1:v] [2:v] concat=n=3:v=1 [v]" -map "[v]" out_temp.mp4
  
  ffmpeg -i long.mp4 -i out_temp.mp4 -c copy -map 0:v -map 1:a out_final.mp4

  How can I do this without the audio getting out of sync ?

  I am using ffmpeg version 4.0.2.

• Remove video noise from video with ffmpeg without producing blur / scale down effect

  17 avril 2024, par Sucahyo Aji

  My videos are 1920x1080 recorded with high ISO (3200) using smartphone (to get bright view, backlight scene mode). It produce a lot of noise. I try many video filter but all of them produce blur similar to when we reduce the resolution in half then increase it back again.

  


  Is there a good video noise filter that only remove noise without producing blur ?

  


  Because if it produce blur, I would prefer to not do any filtering at all.

  


  I have tried video filter :

  


  


  • nlmeans=s=30:r=3:p=1

    


  


  • vaguedenoiser=threshold=22:percent=100:nsteps=4

    


  


  • owdenoise=8:6:6

    


  


  • hqdn3d=100:0:50:0

    


  


  • bm3d=sigma=30:block=4:bstep=8:group=1:range=8:mstep=64:thmse=0:hdthr=5:estim=basic:planes=1

    


  


  • dctdnoiz=sigma=30:n=4

    


  


  • fftdnoiz=30:1:6:0.8

    


  


  


  All produce blur, some even worse. I have to use strong setting to make the noise moderately removed. I end up halving the resolution and use remove grain then scale it up again. This is much better for me than all the above method (pp filter is used to reduce size without reducing image detail) :

  


  

  • scale=960:540,removegrain=3:0:0:0,pp=dr/fq|8,scale=1920:1080

  


  


  code example

  


  FOR %%G IN (*.jpg) DO "ffmpeg.exe" -y -i "%%G"  -vf "nlmeans=s=30:r=3:p=1" -qmin 1 -qmax 1 -q:v 1   "%%G.jpg"

  


  Part of the image
  
The image: