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• How to generate a GIF thumbnail from a video without saving individual frames to disk ?

  12 mars 2023, par Rabie Daddi

  I have a Node.js script that uses fluent-FFmpeg to generate a GIF thumbnail from a video for the first 4 seconds. Currently, the script saves individual frames as PNG images to disk, and then reads them back in to generate the GIF. However, this creates a lot of unnecessary I/O.

  


  Is there a way to modify the script to generate the GIF directly from the video frames, without saving them to disk first ? Ideally, I would like to do this while still using FFmpeg for the processing.

  


  Here's the current code for generating the frames and the GIF :

  


  function generateFrames(videoUrl) {
  return new Promise((resolve, reject) => {
    ffmpeg(videoUrl)
      .setStartTime(0) // start at 0 seconds
      .setDuration(4) // cut 4 seconds
      .videoFilters('scale=if(gte(iw\\,ih)\\,min(600\\,iw)\\,-2):if(lt(iw\\,ih)\\,min(600\\,ih)\\,-2)')
      .fps(4)
      .output('output/img%04d.png') // output file pattern with %04d indicating a sequence number with four digits
      .on('end', () => {
        console.log('GIF generated successfully!');
        resolve()
      })
      .on('error', (err) => {
        console.log('Error generating GIF: ' + err.message);
        reject()
      })
      .run();
  });
}

function generateGif() {
  const inputPattern = 'output/img%04d.png';
  const outputFilename = 'output/output2.gif';

  ffmpeg(inputPattern)
    .inputFPS(9)
    .output(outputFilename)
    .on('error', (err) => {
      console.log('Error generating GIF: ' + err.message);
    })
    .run();
}


execute = async () => {
  await generateFrames('video.mp4')
  generateGif()
}

execute()


  


  Any help or suggestions would be greatly appreciated. Thank you !

  


• Add support for building fuzzer tools for an individual demuxer

  10 octobre 2020, par Michael Niedermayer

  Add support for building fuzzer tools for an individual demuxer
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] Makefile
  • [DH] tools/Makefile
  • [DH] tools/target_dem_fuzzer.c

• Significantly different scores when calculating VMAF for the whole video vs individual frames [closed]

  24 octobre 2024, par YG1992

  Suppose i have a raw video 'encoded_raw.yuv' and 'original_raw.yuv' on YUV420p. I am getting significantly different results when im calculating VMAF using both methods

  


  Method 1

  


  $ ffmpeg -s widthxheight -pix_fmt yuv420p -i .\encoded_raw.yuv -s widthxheight -pix_fmt yuv420p -i .\original_raw.yuv -lavfi libvmaf=log_path=vmaf_logfile.json:log_fmt=json -f null -


  


  versus Method 2 : extracting the png out of a single frame and computing the VMAF score for the individual frame

  


  $ ffmpeg -video_size widthxheight -i ./encoded_raw.yuv -vf select=eq(n\,1) -vframes 1 -pix_fmt yuv420p encoded_raw_1.png
$ ffmpeg -video_size widthxheight -i ./original_raw.yuv -vf select=eq(n\,1) -vframes 1 -pix_fmt yuv420p original_raw.png
$ ffmpeg -s widthxheight -pix_fmt yuv420p -i .\encoded_raw_1.png -s widthxheight -pix_fmt yuv420p -i .\original_raw.png -lavfi libvmaf=log_path=vmaf_logfile.json:log_fmt=json -f null -`


  


  method 1 vmaf at frame 1 from json = 80

  


  method 2 vmaf = 70

  


  any reason why this is so ?

  


  Note : for moduse this is on topic as this covers
-> software tools commonly used by programmers (ie ffmpeg)