Audio API: Fail to resume music and also visualize it. Is there bug in html5-audio? - html

Question

I have a button. Every time it is clicked, a music is played. When it's clicked the second time, the music resumes. I also want to visualize the music.
So i begin with html5 audio (complete code in http://jsfiddle.net/karenpeng/PAW7r/):
$("#1").click(function(){
audio1.src = '1.mp3';
audio1.controls = true;
audio1.autoplay = true;
audio1.loop = true;
source = context.createMediaElementSource(audio1);
source.connect(analyser);
analyser.connect(context.destination);
});
But when it's clicked more than once, it console.log error:
Uncaught Error: INVALID_STATE_ERR: DOM Exception 11
Then i change to use web audio API, and change the source to:
source = context.createBufferSource();
The error is gone.
And then, i need to visualize it.
But ironicly, it only works in html5 audio!
(complete code in http://jsfiddle.net/karenpeng/FvgQF/, it does not work in jsfiddle cuz i dont know how to write processing.js script properly, but it does run on my pc)
var audio = new Audio();
audio.src = '2.mp3';
audio.controls = true;
audio.autoplay = true;
audio.loop=true;
var context = new webkitAudioContext();
var analyser = context.createAnalyser();
var source = context.createMediaElementSource(audio);
source.connect(analyser);
analyser.connect(context.destination);
var freqData = new Uint8Array(analyser.frequencyBinCount);
analyser.getByteFrequencyData(freqData);
//visualization using freqData
when i change the source to :
source = context.createBufferSource();
it does not show anything.
So is there way to visualize it and yet without error and enable it to resume again and again?

Answer 1

Actually, I believe the problem is that you're trying to create a SECOND web audio node for the same media element. (Your code, when clicked, re-sets the SRC, controls, etc., but it's not creating a new Audio().) You should either hang on to the MediaElementAudioSourceNode you created, or create new Audio elements.
E.g.:
var context = new webkitAudioContext();
var analyser = context.createAnalyser();
var source = null;
var audio0 = new Audio();
$("#0").click(function(){
audio0.src = 'http://www.bornemark.se/bb/mp3_demos/PoA_Sorlin_-_Stay_Up.mp3';
audio0.controls = true;
audio0.autoplay = true;
audio0.loop = true;
if (source==null) {
source = context.createMediaElementSource(audio0);
source.connect(analyser);
analyser.connect(context.destination);
}
});​
Hope that helps!
-Chris Wilson

Answer 2

From what I can tell, this is likely because the MediaElementSourceNode may only be able to take in an Audio that isn't already playing. The Audio object is declared outside of the click handler, so you're trying to analyze audio that's in the middle of playing the second time you click.
Note that the API doesn't seem to specify this, so I'm not 100% sure, but this makes intuitive sense.