Cannot connect Sennheiser Momentum True Wireless 2 over Bluetooth
Summary
Connecting Sennheiser Momentum True Wireless 2 headphones over Bluetooth does not work. The headphones say "Connected" and then reboot immediately after.
Environment
Kubuntu 20.04, also reproducible on Kubuntu 19.10.
PulseAudio 13.0 from Kubuntu 19.10, or 13.99 from Kubuntu 20.04, or revision 36a4923f from git master.
Steps to reproduce
- Connect Sennheiser Momentum True Wireless 2 to the PC over Bluetooth.
(Note: You need to pair the headphones with the PC first. If, while pairing, PulseAudio is running, the headphones will automatically connect as part of the pairing process, and will fail as described in this bug. If you want to just reproduce the connection part, you need to first shut down PulseAudio, then pair the headphones, then start PulseAudio and the headphones will connect and fail.)
What is the current bug behavior?
The headphones say "Connected" and then disconnect and reboot. After a few seconds they will say "Power on" and try to connect again, and fail again the same way.
What is the expected correct behavior?
The headphones should connect and work.
Additional info
I have captured PulseAudio log and Bluetooth packets while the headphones are trying to connect.
pulseaudio.log mtw2_linux.pcapng
In the packet dump, I can see that the problem seems to appear when the host (the PC) sends ListPlayerApplicationSettingAttributes message (packet 593 in the dump) and the headphones respond with Not Implemented code (packet 599). There are encoding errors in both messages, so something is not clean on both sides wrt. this message. I don't know what this message does or what part of the PulseAudio code makes it being sent.
I have also captured the packets on Windows when connecting these headphones.
(This dump was captured from USBCap; use Decode As -> Bluetooth in Wireshark). In this dump there is no ListPlayerApplicationSettingAttributes message exchange, the connection completes successfully with the SetConfiguration message response. The headphones work on Windows.