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• Trying to extract frames to memory using fluent-ffmpeg

  4 juin 2020, par anyname

  I am trying to extract frames directly to memory with FFmpeg to save time writing the frames on disk since I don't need it

  



  I tried running with this code in the first place but it didn't work

  



  const ffmpeg = require('fluent-ffmpeg')
const tf = require('@tensorflow/tfjs-node')
const RVF = (path,HW)=>{
     //HW is hxw string of each frame 

    const command = ffmpeg(path,{stdoutLines:0}).size(HW)
    .addOutputOption(['-f image2'])
    .on('error',(err)=>{
        console.log(err)
    })

    const ffstream = command.pipe()
    let numOfFrames = 0

    ffstream.on('data',(chunck)=>{
          // to check if the data is right frame of no 
          // first frame passes this correctly
        console.log(tf.node.decodeImage(chunck).shape)
        console.log(chunck.length)
        console.log(`frames ${++numOfFrames}`)
    })
}


  



  first frames is extracted correctly but I am getting this error on the second one

  



  Error: ffmpeg exited with code 1: av_interleaved_write_frame(): Invalid argument
frame=    2 fps=0.0 q=3.9 Lsize=N/A time=00:00:00.08 bitrate=N/A speed=1.71x
video:101kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Conversion failed!


  


• How to extract these files when using ffmpeg.wasm to output in picture group ?

  24 mai 2023, par Jveshi

  How to extract these files when using ffmpeg.wasm to output in picture group ?

  


  I am working on the video upload function, in which ffmpeg.wasm is used for video encode. The function of video encode has been realized. There is also a function to generate video thumbnails, which needs to be completed.

  


  The video player uses the DPlayer. The player's requirement for thumbnails is to capture sprite images of 100 pictures. So I want to output a picture group, but I can't extract these files, How to solve it ? the relevant code is below.

  


  ---

  


  //The length of the test video is 160 seconds
ffmpeg -i ../../test.mp4 -vf fps=1/(160/100) ../../thumbnail/thumbnail%d.png


  


  var in_name = "upload.mp4";
var out_name = "thumbnail%d.png";

(async () => {
    await ffmpeg.load();
    ffmpeg.FS('writeFile', in_name, await fetchFile(original_video_file));
    await ffmpeg.run('-i', in_name, '-vf' , 'fps=1/(160/100)' , out_name);
    var new_file = ffmpeg.FS('readFile', out_name);
    var thumbnail = new Blob([new_file.buffer], { type: 'image/png' });
    console.log(thumbnail);
})();


  


  The error reported by the above code is

  


  Uncaught (in promise) Error : ffmpeg.FS('readFile', 'thumbnail%d.png') error. Check if the path exists

  


  enter image description here

  


  ---

  


  If you can understand Chinese, here are some of my previous attempts.

  


  https://segmentfault.com/q/1010000043821339

  


• How can I extract PGS/SUP subtitles from mkv container via libav

  24 août 2024, par Elia

  Trying to write a C code that does the equivalent of the following ffmpeg command :

  


  ffmpeg -i video.mkv -map 0:"$STREAM_INDEX" -c:s copy subtitles.sup


  


  I have managed to read the media container, locate the subtitle streams, and filter the relevant one based on stream metadata. However I only succeeded in getting the bitmap data, without the full PGS header and sections.

  


  Tried dumping packet->data to a file hoping it includes full sections, but the data doesn't start with the expected PGS magic header 0x5047.
  
Also using avcodec_decode_subtitle2 doesn't seem to be useful as it only gives bitmap data without the full PGS header and sections.

  


  What steps are supposed to happen after finding the relevant subtitle stream that allows extracting it as raw data that exactly matches the output of the ffmpeg command above ?

  


  Some sample code :

  


      while(av_read_frame(container_ctx, packet) == 0) {
      if(packet->stream_index != i) {
        continue;
      }

      // Try 1 - dump packet data to file
      fwrite(packet->data, 1, packet->size, fout);

      // Try 2 - decode subtitles
      int bytes_read = 0, success = 0;
      AVSubtitle sub;

      if ((bytes_read = avcodec_decode_subtitle2(codec_context, &sub, &success, packet)) < 0) {
        fprintf(stderr, "Failed to decode subtitles %s", av_err2str(bytes_read));
        goto end;
      }
      fprintf(stdout, "Success! Status:%d - BytesRead:%d NumRects:%d\n", success, bytes_read, sub.num_rects);

      if (success) {
        // Only managed to extract bitmap data here via sub.rects
      }

      av_packet_unref(packet);
    }