On 6/3/08, Erik Slagter erik@slagter.name wrote:
Hi there,
Today I bought this sound device, I was hoping it had the C-Media CM650? USB chip which is already supported by alsa (according to the list).
Instead it has a CM6207 inside.
The good news is that it supports USB audio "class" and it's more or less usable, some mixer outputs are available (although they're all called "speaker") and with some trickery the various outputs can be used.
The other good news is that Sweex supplies the "official" datasheet from C-media which I think is quite interesting and may very well be useful to resolve the last few issues.
Write this up for the Free Linux Driver project.
http://lwn.net/Articles/276973/ http://www.linuxdriverproject.org/twiki/bin/view/Main/DriversNeeded
These are the actual issues (so far, I didn't yet test it exhaustively):
- using 2 channel output the sound is garbled; it looks like the "wrong" 2
channel alt setting is used (output of /proc/asound/card?/stream0 on request), 4/6 channel output is OK though.
- some high squeeking noise although C-Media claims the IC to be high-end
(or maybe their definition of high-end differs from mine ;-))
- all outputs are labelled "speaker 1"
- only two outputs have a mute knob, the others cannot be silenced in any
way, only turned down
- one of the two outputs with the mute knob doesn't appear to do anything
(or maybe it's the sp/dif output?)
- the other (with mute) controls the front output
- the others (without mute) don't seem to do anything at all
Is this a typical case of (a) bug(s) in the usb audio class driver or should I think of "vendor extensions" here?
Would any of the developers have some interest in the datasheet of the chip and or any data of this thing? Of course I'd like it very much if the device would be fully supported but I can only ask nicely ;-)
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