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• Change the default audio and video codec loaded by avformat_alloc_output_context2

  8 juin 2021, par mythili3093

  I'm using ffmpeg library for live streaming via RTMP. I want to know how to give my choice of audio and video codec for the particular format in avformat_alloc_output_context2.

  


  In Detail :

  


  The following command works perfectly for me.

  


  ffmpeg -re -stream_loop -1 -i ~/Downloads/Microsoft_Surface.mp4 -vcodec copy -c:a aac -b:a 160k -ar 44100 -strict -2 -f flv -flvflags no_duration_filesize rtmp://192.168.1.7/live/surface


  


  In the output, I have set my audio codec to be aac and copied the video codec from input, which is H264.
I want to emulate this in the library, but don't know how to.

  


  avformat_alloc_output_context2(&_ctx, NULL, "flv", NULL);


  


  Above code sets oformat audio codec to ADPCM_SWF and video codec to FLV1. How to change that to AAC and H264 ?

  


  So far, used av_guess_format to construct AVOutputFormat. It accepts only format as input. And I don't know where to mention audio and video codec.

  


  AVOutputFormat* output_format = av_guess_format("flv", NULL, NULL);


  


  Also tried giving filename to avformat_alloc_output_context2 with the rest of the parameters NULL.

  


  AVOutputFormat* output_format = av_guess_format(NULL, "flv_acc_sample.flv", NULL);


  


  This file has AAC audio and H264 video. But still ffmpeg loads oformat with ADPCM_SWF audio and FLV1 video codecs.

  


  Searched stackoverflow for similar questions, but could not find the solution I was looking for.
Any hint/guidance is hugely appreciated. Thank you.

  


• How to incorporate screencasting into a rails project

  13 mars 2015, par ruby_newbie

  I am working on a personal project and I want to incorporate screencasting with it. I want the screencast to be able to record the entire screen not just the page in a web browser so I think JS is out as a solution. I have searched and found a few clues but nothing concrete as to how i can make it happen short of learning Java. Here is what I have tried :

  Rmov :https://rubygems.org/gems/rmov I cant get bundler to run bundle with this gem but this has the exact functionality I want. I think it has to do with quicktime being 32 bit but I am not sure. I opened an issue on Github in hopes to resolve it.

  I saw this post : http://devblog.avdi.org/2013/01/21/my-screencasting-process/ which links to this script : https://github.com/avdi/Xcast/blob/master/Xcast
  but I am failing on the require ’highline/system_extensions’ line (require cannot load such file).

  I found this : http://rvideo.rubyforge.org/ but I am still confused as to how to implement it. FFMPEG seems promising though and like it may be the tool I am looking for.

  Does anyone know of a tool that would allow me to do this or a good tutorial that explains this process in detail ? Any help is appreciated and let me know if you need any more info that I can provide.

• Getting error "WebAssembly.Memory() : could not allocate memory" when running ffmpeg.wasm on android chrome browser

  27 juin 2022, par Ravi Kundu

  Error in detail :

  


  WebAssembly.Memory(): could not allocate memory
at https://*******/ffmpeg-core.js:22:82
at https://*******/ffmpeg.min.js:1:6506
at f (https://*******/ffmpeg.min.js:1:11322)
at Generator._invoke (https://*******/ffmpeg.min.js:1:11110)
at Generator.next (https://*******/ffmpeg.min.js:1:11747)
at i (https://*******/ffmpeg.min.js:1:4295)
at c (https://*******/ffmpeg.min.js:1:4498)


  


  Code for ffmpeg :

  


  const downloadWithFFMPEG = async () =>{
  const sourceBuffer = await fetch(recordingURL).then(r => r.arrayBuffer());
  await ffmpeg.load();
  await ffmpeg.FS(
    "writeFile",
    "input.webm",
    new Uint8Array(sourceBuffer, 0, sourceBuffer.byteLength)
  );
  await ffmpeg.run("-i", "input.webm", "-c", "copy", "output.mp4")
  const output = ffmpeg.FS("readFile", "output.mp4");
  var link = document.createElement('a')
  link.href = URL.createObjectURL(new Blob([output.buffer], { type: 'video/mp4;codecs=H264' }));
  link.download = this.data;
  link.click();
  recording = false;
}


  


  Brief about problem :
The error only comes for android chrome browser. The same code works fine on pc/laptop chrome.
Have also enabled Webassembly-thread on chrome ://flags for android browser as someone suggested me to do it but still same error. Can someone help me ?