While this isn't a Windows problem, I was hoping someone on the list could
offer advice, or knows someone who can.
I'm part of a team that has developed an open source USB audio device. It
supports both UAC1 and UAC2. It works flawlessly on almost every host I
connect it to. It is very easy to insert debug code in the device.
Lately I have found at least one version of Android which handles other
devices but not mine. This is disturbing, and I wish to determine what
could be wrong. I'm not ruling out an Android bug here, but at the same
time I don't want to cause confustion with any end users.
So the question is: Who do you know with experience from descriptor
investigation and/or Android USB audio debug?
I have an Ellisys 200 here which decodes the USB audio class and generates
dump files. I have grabbed enumeration sequences of my device on both good
and bad host combinations. And I will grab sequences of the "bad" host
working with other devices. I also have test computers with USB3HWVerifier
and USB20CV installed.
The "bad" host is an old Sony Xperia which served my device flawlessly on
both UAC1 and UAC2 while on Android 5.0.1. On Android 5.1.1 it seems to
enumerate fine on UAC2 but doesn't request the volume control information
other OSes do. It also can't start playback. The Ellisys logs don't show
any obvious smoking guns.