Whether process() is called for an AudioWorkletNode should depend on whether the active source flag is true and whether the AudioNodes connected to inputs are actively processing

[karlt]

The "rendering a render quantum" steps steps appear to keep calling process() for all AudioWorkletNodes that are "still alive" and have [[callable process]] true.

The only place that I see the active source flag read is in the definition of actively processing.

"still alive" is not defined, but I don't think it is necessary either.

It's tempting to simply replace "still alive" with "actively processing", but this would be problematic due to the dependency of "actively processing" state on the "in a cycle" state, which has not yet been determined at this point in the algorithm.

Perhaps a more carefully placed check on "actively processing" in the "rendering a render quantum" steps would be sufficient to address this.

[hoch]

This change is an editorial one with no behavior change.

1. Remove "still alive" from the step 4.2.2 of the rendering loop algorithm.
2. Add a check for "actively processing" 4.2.8.1 - "If node is marked or not actively processing, abort these steps."

@karlt Probably I am missing some corner cases, but this can be a starting point of the discussion. Does this makes sense to you?

[karlt]

Thanks for taking a look. I think your proposed change makes sense and correctly skips processing. It also correctly implements "Note that once a unhandled exception is thrown, the processor will output silence throughout its lifetime."

The thing I'm not sure is clearly specified is the silent output for nodes that are not actively processing. Would it be worthwhile explicitly "muting" nodes that are not actively processing, to clarify that their last buffer made available for reading is not used? i.e. instead of changing step 1 of "Visiting a node", replace step 5 "Add node to the beginning of ordered node list" with

5. If node is not actively processing, then mute node.
6. Else, add node to the beginning of ordered node list.

[karlt]

While checking the [[callable process]] behavior, I noticed that 4.4.11 "Set [[callable process]] to true" seems out of place. [[callable process]] is initialized true in the constructor, and we don't want it set to true again after "processorerror" has been triggered. Looks like 4.4.11 can be removed?

[padenot]

AudioWG call 2024-05-14:

Let's fix this by doing what @hoch suggests, followed-up by what @karlt says. We can also do what @karlt says in his last comment in the same PR.