HTML 5 Audio - AnalyserNode.getByteFrequencyData() Returns Undefined

Question

This appears to be a common question - Javascript Web Audio API AnalyserNode Not Working - But I can't be sure if I've found an edge case with my implementation.

I create an audio source using createMediaElementSource(), but instead of using an audio tag from the page markup, the element is created dynamically using Buzz.js.

Here's my test setup:

window.addEventListener('load', function(e) {
    audioContext = new webkitAudioContext();
    audioAnalyser = audioContext.createAnalyser();

    sound = new buzz.sound("sound.mp3");
    sound.load().bind("canplaythrough", function(e) {
        source = audioContext.createMediaElementSource(this.sound);
        source.connect(audioAnalyser);

        audioAnalyser.connect(audioContext.destination);

        this.play().loop(); 
    });
}, false);

window.setInterval(function(){
    array = new Uint8Array(audioAnalyser.frequencyBinCount);
    console.log(audioAnalyser.getByteFrequencyData(array));                                           
})

With the code above, the sound plays. I can also attach others nodes (biquad filters, gain etc) which work, but the audioAnalyser.getByteFrequencyData returns undefined values on every frame...

Might it have anything to do with using Buzz.js?

score 9 · Answer 1 · answered Nov 17 '13 at 01:20

It was a failure of comprehension...

Basically, I was expecting the console to log some kind of output from the following:

window.setInterval(
    array = new Uint8Array(audioAnalyser.frequencyBinCount);
    console.log(audioAnalyser.getByteFrequencyData(array));                                           
)

What I should have done was this:

window.setInterval(function(){
    array = new Uint8Array(audioAnalyser.frequencyBinCount);
    audioAnalyser.getByteFrequencyData(array); 
    console.log(array);                                 
})

A bit silly, but I hope that helps anyone coming here who might have expected getByteFrequencyData to return a value of somekind.

HTML 5 Audio - AnalyserNode.getByteFrequencyData() Returns Undefined

1 Answers1