Bug 215965 – getUserMedia causes stall in audio output / unexpected audio ducking

• Component: WebRTC
• Status: NEW

[Boris Smus]

My application has a button that opens audio input and simultaneously plays a UI sound to indicate that the mic is hot.

Here's a really basic test page that lets you play audio and then open the audio input via `getUserMedia`: https://codepen.io/borismus/pen/PoNjbPa 

Try this and notice the pause in music.

- On Mac it seems to fade out as if its deliberately ducking Or maybe this is just what happens when the main thread playing audio stalls. 
- On iOS it seems to pause abruptly as if it's some kind of blockage. 

The expected behavior is found in Chrome, where no pausing or ducking happens, and audio can play.

[Radar WebKit Bug Importer]

<rdar://problem/68138897>

[youenn fablet]

(In reply to Boris Smus from comment #0)
> My application has a button that opens audio input and simultaneously plays
> a UI sound to indicate that the mic is hot.
> 
> Here's a really basic test page that lets you play audio and then open the
> audio input via `getUserMedia`: https://codepen.io/borismus/pen/PoNjbPa 
> 
> Try this and notice the pause in music.
> 
> - On Mac it seems to fade out as if its deliberately ducking Or maybe this
> is just what happens when the main thread playing audio stalls.

I do not hear that on my Mac.
I can hear a slight pause.

This seems to be a system wide pause: the same happens if I open https://codepen.io/borismus/pen/PoNjbPa on Chrome and asks Chrome to play Music and then asks Safari to open audio input using the same fiddle. 

If I close Safari, the same temporary pause happens.
It might be that this happens when starting and stopping our core audio shared unit.

> - On iOS it seems to pause abruptly as if it's some kind of blockage. 

When you say pause, it is a temporary pause right?
This might be the same issue as MacOS.

[Boris Smus]

Let's focus on iOS as that's where the problems is substantially worse.

I do mean a temporary pause, thanks for clarifying. It resumes in about one second on my iPhone X.

[youenn fablet]

(In reply to Boris Smus from comment #3)
> Let's focus on iOS as that's where the problems is substantially worse.
> 
> I do mean a temporary pause, thanks for clarifying. It resumes in about one
> second on my iPhone X.

One second seems longer than what I can repro.
Would you be able to send me a sysdiagnose ([e-mail])?

[Boris Smus]

Quick update to nudge this along: I sent you the log part of that bundle on 9/2.