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• images->video->web canvas : RGB/YUV issues

  5 février 2016, par nrob

  We’ve written an web app which :

  1. takes 3D, time dependent weather data
  2. tiles each 3D time point to make a 2D frame (written out as a png image)
  3. stitches these frames together into a video (using ffmpeg/avconv)
  4. streams this video into a web app
  5. polls the canvas for frames
  6. sends the frames to the GPU where they are converted back to 3D and ray traced

  You can see the app here, code here and you can see the data video here

  Currently the pngs are written as RGB images, the video codec is in YUV and getting frames from the canvas returns RGB. As such there is a significant loss of information due to the conversion between image spaces.

  Does anyone have suggestions what is the best way round this ?

  I’ve tried a bunch of RGB video codecs, but I can’t get any to work, and I don’t know if the web browser will support it anyway. Can anyone suggest a good RGB codec (both lossy and lossless would be great)

  Also, is it possible to write to YUV images/read them from a video canvas in HTML5 ?

  Ultimately, I don’t even want anything to do with images/videos, I’m just hacking the codecs to stream/compress large animated 3D data volumes

• Building A livestreaming server like youtube from scratch

  9 décembre 2022, par Dipo Ahmed

  I am trying to build a live streaming server like youtube where I can watch the video live or if I want to I can play the video from any duration I want.

  


  What I have tried so far.
I have built a node js WebSocket server where I push the video blob that I receive from the browser via MediaRecorder API every 2 seconds. This blob is then getting converted to hls by a ffmpeg process which generates 2 seconds *.ts files and a .m3u8 file which I am playing with video.js in browser.

  


  This is my ffmpeg command

  


   spawn('ffmpeg', [
        '-i', '-',
        // '-re',
        '-fflags', '+igndts',

        '-vcodec', 'h264',
        '-acodec', 'aac',

        '-preset', 'slow',
        '-crf', '22',
        // You can also use QP value to adjust output stream quality, e.g.: 
        // '-qp', '0',
        // You can also specify output target bitrate directly, e.g.:
        '-b:v', '1500K',
        '-b:a', '128K', // Audio bitrate

        '-f', 'hls',
        '-hls_time', '1',
        // '-hls_playlist_type', 'vod',
        '-hls_list_size', '2',
        '-hls_flags', 'independent_segments',
        '-hls_segment_type', 'mpegts',
        '-hls_segment_filename', `${path}/stream%02d.ts`, `${path}/stream.m3u8`,
    ]);


  


  The problem is that the video js player duration is not updating like in youtube where the video duration increases every second.

  


  Any direction will be appreciated. Please tell me if my approach is wrong and what needs to be learned for me to build this system.

  


• FFMPEG HLS streaming and transcoding on the fly to HTML player - video duration changes while transcoding

  20 août 2019, par Thomas Tho

  I am trying to make a video streaming server and watch videos directly from web browser. The idea is to make the server to stream video from remote server, transcode with different audio format in local server, and then instantly stream to the client (this is specific way I need it to function).
  This is the FFMPEG code im currently using :

  ffmpeg -i "url" -c:v copy -c:a aac -ac 2 -f hls -hls_time 60 -hls_playlist_type event -hls_flags independent_segments out.m3u8

  The HLS stream is attached to the HTML player with hls.js and it works. However, the video duration is constantly changing while video is being transcoded. I have tried to change video duration with JS like $('video').duration = 120;with no luck.

  How do i make the player to display the video file duration instead of stream current transcoded time ?

  I am also planning to implement video seeking but i am clueless. The current idea is to send seeking time to the server, terminate ffmpeg, and start from specific time. However, i think the player might get stuck on loading and will not start playing without reloading.