Audio Workers: number of input/output channels and inputs/outputs

[olivierthereaux]

Originally reported on W3C Bugzilla ISSUE-17534 Mon, 18 Jun 2012 11:27:42 GMT
Reported by Marcus Geelnard (Opera)
Assigned to

The JavaScriptAudioNode does not have the ability to dynamically change its number of input/ouptut channels after creation.

This makes it impossible to re-implement nodes such as AudioGainNode (depends on number of input channels) and ConvolverNode (depends on number of AudioContext output channels - according to [1]).

[1] https://dvcs.w3.org/hg/audio/raw-file/tip/webaudio/specification.html#Convolution-reverb-effect

[olivierthereaux]

Original comment by Olivier Thereaux on W3C Bugzilla. Fri, 26 Jul 2013 15:02:50 GMT

Updating issue title to reflect the change of name from JavaScriptAudioNode to
ScriptProcessorNode

[agoode]

What is the next step here? Is it as simple as just proposing some changes to the specification?

[olivierthereaux]

@agoode this issue has not been a high priority as there has been a number of other issues to be fixed first to make ScriptProcessorNode actually usable, but yes - a PR against the spec would be a good way to get this one forward.

[cwilso]

Would be good to discuss whether we need this feature for Audio Workers. We probably do. Sigh.

[joeberkovitz]

Does this go beyond simply stating that the AudioProcessEvent can bear a different number of channels over the lifetime of the AudioWorkerGlobalScope?

[cwilso]

Yes. The AudioWorker needs to be able to CONTROL the number of output channels (in order to replicate channelMerger).

[joeberkovitz]

Idea: Could there be a function in AudioWorkerGlobalScope that can be used to update the number of output channels in future AudioProcessEvents, and returns that many usable output buffers for use in the current event?

[cwilso]

For the number of channels, I think we can simply update an attribute and state that the hosting code will use that as a way to determine how many output buffers to provide (input buffers will be determined by the channelcount and channelmode).

Input and output connections are going to be harder.