Bluetooth headphones show up as audio out device but not microphone

[RattlesnakeJake]

I have a pair of Sony wf-1000xm2. They show up and work fine as Bluetooth headphones but don't show up as a microphone.

[MrDrMcCoy]

I finally got a response from a support ticket about this:

引用自 Steam Support：

I wanted to clarify that currently the Steam Deck does not support microphone usage with devices connected to it via Bluetooth. Support does not have any information regarding the status of when/if this functionality will be available in the future.

I run a similar config with Arch Linux on my main system. There is no technical reason why Bluetooth headset profiles should be missing from the Steam Deck, and I indeed am able to get my Bluetooth mics to work properly with the same devices. The only reason I can think of that Valve may be refusing to support headset profiles is user experience. Allow me to explain:

Bluetooth is a pretty bandwidth-limited protocol, with janky audio codecs, and bi-directional communication (sending and receiving at the same time) was an afterthought. Headset profiles have a pretty limited ability to use decent codecs, so the best official one (mSBC) sounds pretty bad. Because of this limitation, Valve likely decided that it would be better to simply omit headset profiles entirely. I disagree of course, but that's my best guess as to what's going on.

If you want the technical background, the developer discussion from the underlying audio stack can be found here[gitlab.freedesktop.org].

If you're wondering how Android and others are able to pull off high-quality Bluetooth headset communication, I'm pretty sure they have to break the Bluetooth spec by doing a non-standard probing of what the hardware supports and set up a special communication channel for the audio. Because there's no spec to follow for this, the Pipewire developers have little to go on for developing similar functionality. It may be some time before we see anything like this, unfortunately.