After updating the firmware on my Sony Noise Cancelling Headset, and upgrading to Fedora 40 , my A2DP ) profiles stopped working.

I did a quick search and found someone with the same issue and it would be fixed in a Kernel upgrade. Common enough on a bleeding edge that is Fedora, however as the months moved on and the kernel upgraded, the problem remained.

I tried to implement workarounds several times but eventually came across this passage from hank aka hankuoffroad on the Fedora Forums

This is a known behavior when using Bluetooth audio on Linux on hands-free mode: you cannot use A2DP for high-quality audio output while simultaneously using the Bluetooth microphone via HSP/HFP, due to profile limitations in the Bluetooth specification and current Linux audio stack.

I knew this of course, but my Sony WH-CH700N Wireless Noise Cancelling Headphones don't have a microphone. ... Hold on how does Noise Cancelling work exactly again ?

Active noise control (ANC), also known as noise cancellation (NC), or active noise reduction (ANR), is a method for reducing unwanted sound by the addition of a second sound specifically designed to cancel the first

Wikipedia

If the first is the background noise, it needs a microphone to capture it so it can be inverted.

Ah ha...I had recently also disabled my Zoom H2v2 as it was now sometimes acting as a speaker.

So presumably pipewire tries to find any microphone on the system, when it cant find the best one it will resort to the one used for noise canceling in the headset.

Once the headset is been used for audio in as well, then there isn't enough bandwidth to do high definition audio, so you end up with the low quality two way profiles.

Would the solution be as easy as enabling a proper microphone . . . .