Bluetooth mic input creates garbled sound on the iOS client

[retravision]

Hello forum!

I'm looking for advice on how to resolve this issue arising from bluetooth earbuds/earphones connected to iPhone. When I speak into the bluetooth mic, the output at any receiving phone is garbled (digital artefacts).

iOS: 12.1.4

Mumble: 1.3.1

By borrowing, I have found that some bluetooth devices don't cause this problem (they work fine on Mumble), but these are too expensive for me to own permanently. These are:

- Bose

- Jabra Stealth

All other cheap/generic bt earbuds/earphones cause the problem.

Also, I've found that replaying the recorded messages directly off the Mumble server is fine (no garble/artefacts)! This implies that the corruption seems to be happening on the receiving parts of the end-to-end transmission.

Questions:

- Has anyone found a root cause to this pattern, e.g. the cost of chipset in the bt device, or hard-coded bluetooth parameter in the device?

- Is there any workaround that preserves full-duplex messaging?

Thanks!

P.s. Here is a similar old post, on the same topic.

https://forums.mumble.info/viewtopic.php?f=15&t=3384