Pluck Synth Issues without Standardized Audio Context

[gerardsmyth]

For performance reasons we are using Tone without the Standardized Audio Context library. This is generally working great in Chrome, but unfortunately, we are getting some audio issues with the Pluck Synth.

From investigating, it appears as if the process() method in the worklet for the FeedbackCombFilter is only receiving one channel of input data when there is silence, (ie after the pluck noise has gone through), which leads to old data being left in the second channel of the DelayLine.

If the standardized audio context is being used then the worklet seems to always get two channels of input data, even if all the values are 0, which seems to prevent theissue.

Do you know what the standardized audio context is doing to change this behaviour, or have any suggestions on how we might be able to resolve this without using the whole library?

Many thanks for your help.
Gerard

[chrisguttandin]

Hi @gerardsmyth,

I believe this is because Tone.js is using a version of standardized-audio-context which still has a polyfill for the AudioWorklet. That polyfill had the limitation that it needed a fixed number of inputs. I guess that's the reason for the inconsistency you are experiencing.

In general standardized-audio-context tries to only fix what's broken. It means it should not cause any performance problems in a browser with full support. But of course a browser with full support of the API does not exist and standardized-audio-context is not perfect either. I'm curious what exactly was the performance problem that made you remove standardized-audio-context?

[gerardsmyth]

Hi @chrisguttandin

Many thanks for your reply.

Are you able to point me in the direction of the code for that polyfill? Potentially we could try and implement just that part to resolve this Pluck Synth issue.

The main performance issue we had was related to the detectCycles process. We often have quite a large audio graph, and this process was taking a lot of time. (see chrisguttandin/standardized-audio-context#996)
Thanks again for all your work on this.

Gerard

[chrisguttandin]

Okay, I see. Unfortunately there is no simple solution for chrisguttandin/standardized-audio-context#996.

I believe it boils down to these two lines: https://github.com/chrisguttandin/standardized-audio-context/blob/cb2eddc19a8a9cbebc1af7fa5581377205cc5c89/src/factories/audio-worklet-node-constructor.ts#L26-L27. Maybe setting the channelCountMode to 'explicit' is all that needs to be done. I'm not 100% sure though.