SGI audio observations

Audio interface for the high-quality digital audio subsystems on IRIS 4D/30, 4D/35, and Indigo systems, and future IRIS audio subsystems. Note that the obsolete IRIS 4D/20 has a different (/dev/audio) interface.

The device can only switch input ports, not output ports.

DC offset can be significant (1300 or more).

Recording/playback gain: 0..255