source: gs3-extensions/web-audio/trunk/js-mad/script/main-jsmad.js@ 28388

var JsMadProcessing = function(audio_id,active_workflow) {

    this.audio_id = audio_id;
    this.active_workflow = active_workflow || null;
  
    var url = $('#'+audio_id).attr("href");
    console.info("JsMadProcessing::JsMadProcessing() retrieving over AJAX: " + url);

    var stream = new Mad.AjaxStream(url);

    var that = this;

    var channels = 2; // stereo
    var rate = 44100; // 44.1 Khz
    //var rate = 48000; // 44.1 Khz
    //var bufsize = 65536 * 4096; 
    //var bufsize = 65536 * 1024; 
    //var bufsize = 2048;
    var bufsize = 1024 * 8;

    //this.dev = Sink(function(buffer) {that.refill(buffer)}, channels, bufsize, rate);
    //console.log("*** got sample rate of: " + this.dev.sampleRate);


    this.playBufferStore = new Array();

    stream.requestAbsolute(1 * 1024, function() { that.streamCallback(stream) });

}




JsMadProcessing.prototype.streamCallback = function(stream) {


    var mp3 = new Mad.MP3File(stream);
    var mpeg = mp3.getMpegStream();
        
    //var howmuch = 10000; 
    var ss1 = Date.now();

    var synth = new Mad.Synth();
    var frame = new Mad.Frame();
    
    frame = Mad.Frame.decode(frame, mpeg); // decode first frame to establish num channels and samplerate
    var num_channels = frame.header.nchannels();
    var sampleRate = frame.header.samplerate;

    console.info("JsMadProcessing::streamCallback() decoding URL retrieved MP3 with " + num_channels + " channels, samplerate = " + sampleRate);


    var that = this;

    var numSamples = 0;

    synth.frame(frame);    
    var prev_synth_frame_len = synth.pcm.samples[0].length; 
    console.info("JsMadProcesing.streamCallback(): synth frame length (initial frame) = " + prev_synth_frame_len);

    var i=1; // already processed one frame

    var overflowBuffer = null;

    console.log("*** main-jsmad.js::stream_callback(): hardwiring workflow buffer size to 2048");

    var speedup_batch_limit;
    var speedup_pause;
    
    if (BrowserDetect.browser == "Firefox") {
    speedup_batch_limit = 100;
    speedup_pause = 0;
    }
    else {
    // e.g. Chrome 
    // => the following values played more nicely with letting DSP playback operate straightaway 
    //    i.e. when jsmad is still working its way through the frames
    
    speedup_batch_limit = 10;
    speedup_pause = 2;

    //speedup_batch_limit = 100;
    //speedup_pause = 0;

    console.log("*** Running JsMadProcessing with: batch limit = " + speedup_batch_limit 
            + ", pause = " + speedup_pause + " msecs");
    }


    (function() {

    var more_frames = 1;
    try {

        var speedup_i = 0;

        while (speedup_i < speedup_batch_limit) { // Decode 100 frames at a time, before setTimeout break

        frame = Mad.Frame.decode(frame, mpeg);
        synth.frame(frame);
        
        var synth_frame_len = synth.pcm.samples[0].length; 

        var playBuffer = null;
        var pbp = 0; // pbp = play buffer pos

        if (overflowBuffer != null) {
            playBuffer = new Float32Array(overflowBuffer.length+(synth_frame_len*num_channels));
            playBuffer.set(overflowBuffer);
            pbp = overflowBuffer.length;
            overflowBuffer = null;
        }
        else {
            playBuffer = new Float32Array(synth_frame_len*num_channels);
            pbp = 0;
        }

                
        for (var sfp=0; sfp<synth_frame_len; sfp++) {
            for (var c=0; c<num_channels; c++) {
            playBuffer[pbp] = synth.pcm.samples[c][sfp];
            pbp++;
            }
        }
        
        numSamples += synth_frame_len;

        // uncomment the following line if you want to hear speeded-up playback as it works through the audio file
        //var written = pannedPlayback.mozWriteAudio(playBuffer);


        if (synth_frame_len != prev_synth_frame_len) {
            console.log("*** new synth frame len (frame num = " + i + "): len = " + synth_frame_len);
            prev_synth_frame_len = synth_frame_len;
        }

        if (that.active_workflow != null) {
            // Send the data into the Javascript DSP workflow

            // Note: workflow geared to 2048 samples at a time

            var wi = 0;

            var playBufferLen = playBuffer.length;
            while (wi<playBuffer.length) {

            if (wi+2048<=playBufferLen) {               
                var workflowBuffer = playBuffer.subarray(wi,wi+2048);
                that.active_workflow.pumpDataHead("rawInput",workflowBuffer);
                that.playBufferStore.push(workflowBuffer);
            }
            else {
                // tail end => set up in overflow buffer
                var workflowBufferTail = playBuffer.subarray(wi);

                overflowBuffer = new Float32Array(playBufferLen-wi);
                overflowBuffer.set(workflowBufferTail);

            }
            wi += 2048;
            }


            // Old approach: pump data in, in frames that are set by webAudioContext
            //that.active_workflow.pumpDataHead("rawInput",playBuffer);
        }

        speedup_i++;
        i++;
        }
        
    }
    catch(err) {
        if (err == "Header decoding failed") {
        console.info("JsMadProcessing::streamCallack() decoded " + i + " frames");
        }
        else {
        console.error(err);
        }
        more_frames = 0;
    }

    if (more_frames) {
        setTimeout(arguments.callee,speedup_pause); // even a delay of '0' gives the browser thread a break
    }
    else {
        var ss2 = Date.now();

        var song_duration = numSamples / sampleRate;
        var speedup_duration = (ss2 - ss1)/1000;

        var speedup_factor = song_duration / speedup_duration;
        //console.log("Computed song duration: " + song_duration + " secs");
        console.info("JsMad processing done in " + speedup_duration + " secs (a speed factor of " + speedup_factor + ")");
    }
        
    })();
    
}


JsMadProcessing.prototype.refill = function(buffer) 
{
    console.log("refill called, asking for size = " + buffer.length);

    var buffer_len = buffer.length;
    var buffer_pos = 0;

    while ((this.playBufferStore.length>0) && (buffer_pos<buffer_len)) {

    var playBuffer = this.playBufferStore.shift();
    buffer.set(playBuffer,buffer_pos);

    buffer_pos += playBuffer.length;
    }


}