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• using ffmpeg/ffprobe to create a waveform json using php

  7 mars 2015, par edwardsmarkf

  I have many ogg & opus files on my server and need to generate json-waveform numeric arrays on an as-needed basis (example below).

  recently i discovered the node based waveform-util which uses ffmpeg/ffprobe for rendering a JSON waveform and it works perfectly. i am undecided if having a node process constantly running is the optimum solution to my issue.

  since ffmpeg seems to be able to handle anything i can throw at it, i wish to stick with an ffmpeg solution.

  i have three questions :

  1) is there a php equivalent ? i have found a couple that generate PNG images but not one that generates JSON-waveform numeric arrays

  2) are there any significant advantages of going with the node-based solution rather than a php based solution (assuming there is a php based solution) ?

  3) is there a way using CLI ffmpeg/ffprobe to generate a json-waveform ? i saw all the -show_ options (-show_data, -show_streams, -show_frames) but nothing looked like it produced what i am looking for.

  the json-waveform needs to be in this format :

  [ 0.0002, 0.001, 0.15, 0.14, 0.356 .... ]

  thank you all.

• Error using javacv library for live streaming camera to server

  22 juin 2015, par Prathyush Kumar

  I am new to live-streaming i’m following this link
  here for implementing camera streaming to server with ffserver listening on port 8090.But my code breaks at this line

  public void startRecording() {
  
      try {
  
          recorder.start();    //breaks here
  
          startTime = System.currentTimeMillis();
  
          recording = true;
  
          audioThread.start();
  
      } catch (FFmpegFrameRecorder.Exception e) {
  
          e.printStackTrace();
  
      }
  
  }

  I debugged a little bit to find out what is happening and i found out in this line in FFmpegFrameRecorder.class

  if((this.oformat.flags() & 1) == 0) {
  
      AVIOContext pb1 = new AVIOContext((Pointer)null);
  
      if((ret = avformat.avio_open(pb1, this.filename, 2)) < 0) {//throwing exception here
  
          this.release();
  
          throw new Exception("avio_open error() error " + ret + ": Could not open \'" + this.filename + "\'");
  
      }
  
  
  
      this.oc.pb(pb1);
  
  }

  ret is -5 which is less than 0 and so it cannot open the file(rtmp ://live:live@192.168.0.115:8090/live/test.flv).

  I am not able to understand whats happening in avformat.class Please help

  Is this any configuration problem for ffserver or is it anything else ?I’m not able to figure this out please any help would be greatly appreciated.

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

  8 juillet 2015, par 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.