Hi! I'm attempting to get the "Clock Selector" mixer control to work with the PreSonus AudioBox 1818VSL (a UAC2 device).
The control shows up in amixer as an enumerated value, but I don't seem to be able to set it (I've tried amixer, alsactl, and setting it programmatically). The possible values are correct (listing Internal Clock, S/PDIF Clock, and ADAT Clock as possible options); It just doesn't appear to take my setting, by which I mean amixer doesn't update the settings, I still have the occasional click when the sampling rates match over S/PDIF and I attempt to use external sync. No error is returned.
After digging around USB specs and ALSA's usb/mixer.c and being unfamiliar with both the USB audio spec and the inner workings of ALSA, I thought it'd be best to ask the list about this: How would I check to see if ALSA is asking the device to change clock source at all?
-Louis