Comment 161 for bug 178442

Ok, I have now read up a little on this issue, looked a little in kernel, alsa-lib, and pulseaudio code.

It seems to me the basic limitation in the hw or kernel driver, is that the number of channels is fixed to 10 out and 12 in, and the s32le format.

For the channels, I think it's reasonable to expect someone opening front:x to be able to send a 2 channel stream in. Which points us to a modified version of comment #30 as the preferred fix. I'd be positive to commit such a fix into Ubuntu, at least until upstream has agreed on something else. I don't think that will hurt professional audio applications (e g JACK), because they seldom use anything but the hw: interface, which is not affected by changes made in the front: interface.

However, for the s32le restriction, I think pulseaudio already tries all possible formats, so it should be unwise to have that conversion in alsa-lib - better let pulseaudio do the conversions.

An additional problem is that for recording, I've seen both channel 8,9 [1] and 0,1 [2] being used for input. Is the main input channel different between the different ICE1712 cards? I'd be glad if we could sort this out before the commit is made - could you help?

[1] http://article.gmane.org/gmane.linux.alsa.devel/59480

[2] Comment #7 in this thread.