I'm trying to build some code to process the audio found in other pages by injecting some JavaScript into the page. I was under the impression that I could create an AudioContext and then create an onaudioprocess function, and it would be called with all outgoing audio. 

```
var AudioContext = window.AudioContext || window.webkitAudioContext;
var context = new AudioContext();
var proc = context.createScriptProcessor(16384, 0, 2);

proc.onaudioprocess = function (event) {
    var buffer= event.outputBuffer.getChannelData(0);
    for( var iSample in buffer )
        if( buffer[iSample] > 0.0 )
            alert( "SDRFSDF" );
};

proc.connect(context.destination);

```

I set this up, and I never get any nonzero samples, even if I'm playing a video or some other audio source. Did I forget to hook something up? Is this even possible?