Bug 89017 – JavaScriptAudioNode does not fire onaudioprocess with 0 input channels

• Component: Web Audio
• Status: NEW

[Chris Rogers]

JavaScriptAudioNode (part of the Web Audio API) does not fire the onaudioprocess event as it should if it is configured to have 0 input channels.  Changing it to 1 or 2 makes it work.

Steps to Reproduce:
Here is a simple sine wave demo:
<script>
var context = new webkitAudioContext();
var node = context.createJavaScriptNode(1024, 0, 1);
var freq = context.sampleRate / (440 * 2 * Math.PI);
var x = 0;

node.onaudioprocess = function(e) {
   var data = e.outputBuffer.getChannelData(0);
   for (var i = 0; i < data.length; ++i) {
       data[i] = Math.sin(x++ / freq);
   }
}
</script>
<button onclick="node.connect(context.destination)">Play</button>
<button onclick="node.disconnect()">Pause</button>

1 - Clicking play makes no sound and in fact onaudioprocess is never fired.
2 - Change the JavaScriptAudioNode to take 1 input channel, eg. context.createJavaScriptNode(1024, 1, 1);
3 - Notice that it works now.

[Xingnan Wang]

(In reply to comment #0)
> JavaScriptAudioNode (part of the Web Audio API) does not fire the onaudioprocess event as it should if it is configured to have 0 input channels.  Changing it to 1 or 2 makes it work.
> 
> Steps to Reproduce:
> Here is a simple sine wave demo:
> <script>
> var context = new webkitAudioContext();
> var node = context.createJavaScriptNode(1024, 0, 1);
> var freq = context.sampleRate / (440 * 2 * Math.PI);
> var x = 0;
> 
> node.onaudioprocess = function(e) {
>    var data = e.outputBuffer.getChannelData(0);
>    for (var i = 0; i < data.length; ++i) {
>        data[i] = Math.sin(x++ / freq);
>    }
> }
> </script>
> <button onclick="node.connect(context.destination)">Play</button>
> <button onclick="node.disconnect()">Pause</button>
> 
> 1 - Clicking play makes no sound and in fact onaudioprocess is never fired.
> 2 - Change the JavaScriptAudioNode to take 1 input channel, eg. context.createJavaScriptNode(1024, 1, 1);
> 3 - Notice that it works now.

Hi Chris,

I cannot reproduce the bug (with zero input). 
I`ve tested on both the latest chromium and chrome in my ubuntu and mac, the onaudioprocess events could be caught and the sound was played well.

[Chris Rogers]

Jer, just wanted to note that there have been some recent-ish changes to JavaScriptAudioNode channel handling...