A2DP loopback fails to produce audio on alsa-plugins' a52 sink
Summary
When attempting to stream audio from a bluetooth device, no audio is produced.
pavucontrol shows levels on the input, but not for the output.
I've posted an issue with alsa-plugins as well, please look at the pulseaudio log snippets I have posted there.
It seems like the a2dp loopback sets up a crazy amount of latency, years of it, with with both tsched=0 and tsched=1.
I am not sure if that is the problem or not, nor am I able to ascertain if this should be fixed on their end or yours.
environment
Note in attached pa_info.txt that I have an overide "pcm.!a52" alsa configuration. This was done to increase the bitrate (default 448) to 640. Doing so enables audio from the a2dp loopback to be produced on the surround sound sink once per boot and only with my Android phone (no attempt to stream audio from an iPhone to the surround sound sink has been successful).
The entire system has to be rebooted for it to work again: neither restarting pulseaudio, reloading alsa, or logging out and in again nor any combination thereof are sufficient. If the audio stream stops for any reason, that's it; no further audio will be produced until the next reboot.
Steps to reproduce
Connect a device via bluetooth as an a2dp source, attempt to stream audio to a sink using the a52 plugin (digital surround profile).
What is the current bug behavior?
No audio from the a2dp source is output, although pulseaudio is clearly receiving the audio stream.
What is the expected correct behavior?
Audio should be produced from the a2dp loopback regardless of what profile is enabled on the card it streams to.
I note that this has been problematic in the past, see 178 and 290.pa_info.txt.