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• avfilter: simplify processing child context options

  10 March 2022, by Anton Khirnov

  avfilter: simplify processing child context options
  THe call to av_opt_set() is redundant, since the option is written in
  
  the options dict, which is later passed to avfilter_init_dict().
  

  • [DH] libavfilter/avfilter.c

• Writing data to a Node.js child process's stdin fails due to ECONNRESET

  8 July 2015, by Swoth

  Problem
  Passing data to a child process’s stdin seems to fail. It fails due to an ECONNRESET after writing the data.

  Context
  I am developing a small programm that is supposed to render a video, as fast as possible, based on frames captured from a canvas. The animation is rendered to a headless canvas implementation using Rekapi (JavaScript animation framework). The headless canvas is a Node.js module called node-canvas by Automattic. The animation frames are rendered one after another, after each rendering the frame is retrieved using canvas.getImageData().data (Uint8ClampedArray - rgba, faster than canvas.toDataUrl) and put into an array. Every frame is supposed to be send to ffmpeg to create a video.

  Rekapi -> canvas -> getImageData -> array -> ffmpeg

  What I do
  I already tried various possibilities to pipe that data to ffmpeg. In general I created a child process in Node.js executing ffmpeg:

  var spawn = require('child_process').spawn;    
  
  var child = spawn('ffmpeg', [
  
          '-pix_fmt', 'rgba',
  
          '-s','1280x720',
  
          '-r', 25,
  
          '-f', 'rawvideo',
  
          '-vcodec', 'rawvideo',
  
          '-i', '-', // read frames from stdin
  
          '-threads', 0, // use all cores
  
          'test.mpg']);

  Now I write my array data to the child’s stdin:

  for(var i = 0; i < dataArray.length; ++i){
  
      var buffer = new Buffer(dataArray[i]);
  
      child.stdin.write(buffer);
  
      console.log('wrote: ' + i);
  
  }

  I wrote 25 frames this way. The console displays the following:

  wrote: 24
  
  wrote: 25
  
  events.js:85
  
        throw er; // Unhandled 'error' event
  
              ^
  
  Error: read ECONNRESET
  
      at exports._errnoException (util.js:746:11)
  
      at Pipe.onread (net.js:559:26)

  ffmpeg generated a 0 byte test.mpg.
  I am very new to Node.js, thus I might not understand the big picture of it’s child processes.

• avcodec/jpeg2000: Move L band scaling from the 9/7f wavelet to quantization stage

  22 June 2015, by Michael Niedermayer

  avcodec/jpeg2000: Move L band scaling from the 9/7f wavelet to quantization stage
  This reduces the number of operations
  
  Its not done for 9/7i as that would overflow thanks to JPEG2000 allowing
  
  32 decomposition levels
  Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavcodec/jpeg2000.c
  • [DH] libavcodec/jpeg2000dwt.c