terminology for sound thingamajigs.

[peasthope@shaw.ca]

Folk,

man speaker-test has 
"... --channels ... --device ... --speaker ...".

man alsamixergui has
"... -c <card number or identification> ... -D <device identification> ...".

The distinction between channel and device isn't obvious.  Why does 
a simple USB audio adapter with mono input and stereo output 
provide four devices?  http://wiki.debian.org/ALSA uses terminology 
without explanation.  Neither http://en.wikipedia.org/wiki/Sound_card 
nor http://www.alsa-project.org/ helps much.

Does anyone know of a decent overview of sound hardware and terminology?  
Yes, I've googled.

Thanks,                 ... Peter E.

-- 
Telephone 1 360 450 2132.
Shop pages http://carnot.yi.org/ accessible as long as the old drives survive.
Personal pages http://members.shaw.ca/peasthope/ .