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• I have an audio data stream from ffmpeg, how can I play it in a browser ?

  9 novembre 2013, par Conor Patrick

  I've been able to successfully stream live audio from my mic to my node server. I would now like to stream that to all connected clients. I have been trying to do it with web sockets.

  I'm streaming the audio with this command

  ffmpeg -f alsa -i hw:0 -acodec mp2 -f mp3 -r 30 http://localhost:8086

  Node gets the buffer array and I write it to all connected clients like so with the 'ws' package

  // HTTP Server to accept incomming MP3 Stream (audio)
  
  var audioServer = require('http').createServer( function(request, response) {
  
  
  
         audioSocket.broadcast(data, {binary:true});
  
  
  
  }).listen(8086);
  
  
  
  var audioSocket = new (require('ws').Server)({port: 8088});
  
  audioSocket.broadcast = function(data, opts) {
  
  
  
      for( var i in this.clients ) {
  
          this.clients[i].send(data);
  
      }
  
  };

  Any idea of how I can play this data on a browser ? I tried following this topic but the decodeAudioData() method fails.

  My client side code

  node={};
  
  var audio = new WebSocket('ws://localhost:8088/');
  
  audio.binaryType = "arraybuffer";
  
  var context = new webkitAudioContext();
  
  
  
  audio.onmessage = function(data){
  
      node.buf=data.data;
  
      node.sync=0;
  
      node.retry=0;
  
      decode(node);
  
  }
  
  
  
  function syncStream(node){ // should be done by api itself. and hopefully will.
  
      var buf8 = new Uint8Array(node.buf); 
  
      buf8.indexOf = Array.prototype.indexOf;
  
      var i=node.sync, b=buf8;
  
      while(1) {
  
          node.retry++;
  
          i=b.indexOf(0xFF,i); if(i==-1 || (b[i+1] & 0xE0 == 0xE0 )) break;
  
          i++;
  
      }
  
      if(i!=-1) {
  
          var tmp=node.buf.slice(i); //carefull there it returns copy
  
          delete(node.buf); node.buf=null;
  
          node.buf=tmp;
  
          node.sync=i;
  
          return true;
  
      }
  
      return false;
  
  }
  
  
  
  function decode(node) {
  
      context.decodeAudioData(node.buf,
  
      function(decoded){
  
          node.source  = context.createBufferSource();
  
          node.source.connect(context.destination);
  
          node.source.buffer=decoded; 
  
          node.source.noteOn(context.currentTime);
  
          console.log('IT WORKED!  DECODED', decoded);
  
      },
  
      function(){ // only on error attempt to sync on frame boundary
  
          //console.log('error');
  
          if(syncStream(node)) decode(node);
  
      });
  
  }

• FFMPEG : Explain parameters of any codecs fuction pointers

  3 décembre 2013, par Zax

  I'm going through the article, How to integrate a codec in FFMPEG multimedia framework.
  According to it, every codec needs to have 3 basic functions to be defined and these functions are assigned to function pointers of the structure AVCodec.

  The 3 function pointers specified in the above article are :

  .init -> takes care of allocations and other initializations
  
  
  
  .close -> freeing the allocated memory and de-initializations
  
  
  
  .decode -> frame by frame decoding.

  For the function pointer .decode, the funtion assigned is :

  static int cook_decode_frame(AVCodecContext *avctx,
  
              void *data, int *data_size,
  
              uint8_t *buf, int buf_size) {
  
  ...

  The details of these parameters are specified in the above article. However, in the latest code, when the same function is taken as an example, its declaration is as shown below :

  static int cook_decode_frame(AVCodecContext *avctx, void *data,
  
                               int *got_frame_ptr, AVPacket *avpkt)

  I need to perform some mapping operations on the memory. So, i request if anyone could kindly explain the above parameters in the function declarations. Also, which parameter has the input buffer for decoding the frame ? And after decoding a frame, to which parameter is the decoded frame mapped ?

  Thanks in advance.

  -Regards.

• FFMPEG : Explain parameters of any codecs function pointers

  7 juillet 2014, par Zax

  I’m going through the article, How to integrate a codec in FFMPEG multimedia framework.
  According to it, every codec needs to have 3 basic functions to be defined and these functions are assigned to function pointers of the structure AVCodec.

  The 3 function pointers specified in the above article are :

  .init -> takes care of allocations and other initializations
  
  
  
  .close -> freeing the allocated memory and de-initializations
  
  
  
  .decode -> frame by frame decoding.

  For the function pointer .decode, the function assigned is :

  static int cook_decode_frame(AVCodecContext *avctx,
  
              void *data, int *data_size,
  
              uint8_t *buf, int buf_size) {
  
  ...

  The details of these parameters are specified in the above article. However, in the latest code, when the same function is taken as an example, its declaration is as shown below :

  static int cook_decode_frame(AVCodecContext *avctx, void *data,
  
                               int *got_frame_ptr, AVPacket *avpkt)

  I need to perform some mapping operations on the memory. So, i request if anyone could kindly explain the above parameters in the function declarations. Also, which parameter has the input buffer for decoding the frame ? And after decoding a frame, to which parameter is the decoded frame mapped ?