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• What's the most performant way to encode an mp4 video of frames from a webgl canvas using Javascript in a web browser ?

  17 janvier 2024, par Keith Carter

  I can capture the frames from the canvas using readPixels (https://developer.mozilla.org/en-US/docs/Web/API/WebGLRenderingContext/readPixels) but then what ?

  


  I think there are a few wasm versions of ffmpeg but they're slow.

  


  I found this web assembly mp4 encoder but it's no longer supported and doesn't work in Chrome on my phone (Android 13).

  


  Any other suggestions ?

  


• Encoding MJPEG from webcam in UWP development with C#

  24 avril 2018, par Federico Parra

  this is my first question in StackOverflow.

  How can I encode video being captured from webcam as a MJPEG using C# in UWP enviroment (Visual Studio 2017) ?
  Perhaps using FFMPEG or DirectShow ? Any particular bindings required to use them in UWP ?

  I’ve been through these walk-throughs trying to go the official way using MediaCapture :

  https://docs.microsoft.com/en-us/windows/uwp/audio-video-camera/basic-photo-video-and-audio-capture-with-mediacapture
  https://docs.microsoft.com/en-us/uwp/api/windows.media.capture.mediacapture

  According to Microsoft though, there is no MJPEG encoder included in MediaEncoder (only decoder) : https://docs.microsoft.com/en-us/windows/uwp/audio-video-camera/supported-codecs

  About FFMPEG UWP integration, I found this :
  https://github.com/Microsoft/FFmpegInterop
  https://blogs.windows.com/buildingapps/2015/06/05/using-ffmpeg-in-windows-applications/#HHYbWAVcM7LhkvYZ.97

  But it’s geared towards decoding, and I want to encode.

  Just in case someone is wondering, I want to use MJPEG for Two reasons :
  1) less CPU intensive (much less) because it doesn’t do inter-frame compression, means my Surface Pro (and other similar computers) will keep quiet without fans running like crazy
  2) I need all frames (i.e. not one every 30) to be crystal clear because of an algorithm I need to run on each of them after

  Any pointers would be greatly appreciated.

  Thank you,
  Federico

• FFmpeg av_read_frame not reading frames properly ?

  16 juin 2019, par Sir DrinksCoffeeALot

  Alright, so I’ve downloaded some raw UHD sequences in .yuv format and encoded them with ffmpeg in .mp4 container (h264 4:4:4, 100% quality, 25fps). When i use ffprobe to find out how many frames are encoded i get 600, so that’s 24 secs of video.

  BUT, when i run those encoded video sequences through av_read_frame i only get like 40-50% of frames processed before av_read_frame returns error code -12. So I’m wild guessing that there are some data packages in middle of the streams which get read by av_read_frame and forces a function to return -12.

  What my questions are, how should i deal with this problem so i can encode full number of frames (600) ? When av_read_frame returns value different from 0 should i av_free_packet and proceed to read next frame ? Since av_read_frame returns values < 0 for error codes, which error code is used for EOF so i can insulate end of file code ?