Sorry for bringing this up again. But I haven't given up hope that I might find the right person who might fix this problem: The Bluetooth Hands Free Profile produces useless audio during phone calls on "my side", i.e. the other party can hear me perfectly. This has been true for all SFOS versions on the Nexus 5.

Symptoms: Audio sounds heavily distorted. Similar effects have been described with VoIP telephony due to an endian problem. No idea if that's related.

However, A2DP audio works flawlessly.

When the Nexus 5 was first released, the same problem was reported with the stock Android. This was resolved along with the first upgrade. Unfortunately, I have not been able to find the corresponding entry in the release notes, which, I hope, would provide us with a clue.

The only hint I found was to add an autodetect_mtu to /etc/pulse/default.pa:
That did exactly nothing. :-(

What else could I try? And where can I find info on how Google fixed the initial HFP problem with their first upgrade?