Ok, I have been performing further tests and I can confirm the problem. Audio is in fact coming out OK through both outputs: the earpiece and the main speaker. But the total audio level is reduced, I’d say about 1/2 to 2/3. And clicking on the “Stop camera” option on the Safari’s navigation bar does in fact increase the audio output level.
And the unfortunate news is that this is an Apple bug. It does not affect OpenVidu in particular, it is problem with iOS WebkitView. Here at the Apple’s developer forum there are some entries talking about it: iOS 15 Safari WebRTC Issue | Apple Developer Forums
Other WebRTC services are also reporting the problem. You can even see an engineer from Twilio complaining about it:
The actual bug is being tracked by Apple here: 230902 – REGRESSION(Safari 15 - iOS15): [WebRTC] MediaStreamTack audio volume too low. Other duplicated issues have appeared lately: 231421 – Audio output is directed to earpiece while audio user media being fetched.
I think the bug is currently assigned to an Apple engineer, and as it has some intense activity, with some luck it will be fixed soon in a new patch release for iOS. I have added a new entry to the bug tracker in name of OpenVidu team, to add some more pressure and follow its development (230902 – REGRESSION(Safari 15 - iOS15): [WebRTC] MediaStreamTack audio volume too low).
PD: I see someone who apparently succeeded fixing the issue using AudioContext (230902 – REGRESSION(Safari 15 - iOS15): [WebRTC] MediaStreamTack audio volume too low) Maybe that is worth a try in your app?
Best regards.