On Tue, 2012-05-08 at 06:02 -0700, David Henningsson wrote: > 2012-05-07 20:06, Arun Raghavan skrev: > > The separate mics may eventually be useful for beamforming and > > associated processing. Would your approach require changes to alsa-lib > > again if we wanted to do that? If yes, it might be better to let > > PulseAudio take care of this. > The attached patch (untested!) would just add the possibility to do a > four-to-two channel mixdown when you open front:%f (for the cards > explicitly selected in the patch), so for four-channel beamforming you > could still open hw:%f in four channel mode. That would still require special profiles in Pulseaudio... So, we have three options on the table: 1) Have a generic 4-channel input mapping in default.conf. - Provides access to all four channels on all known and most unknown devices. - Causes some unnecessary delay in startup on most systems. - May expose bugs in the remapping code. - Patch exists. 2) Have udev-triggered device-specific mappings. - Provides access to all four channels on the devices for which a udev-rule is written. - Requires patching for each individual device. - Depending on the configuration file content, may expose bugs in the remapping code. - No patches exist. I know how to make them. 3) Downmix to stereo in alsa. - Provides access only to downmixed audio. - Requires patching for each individual device. - No worries about remapping bugs. - An untested patch exists for one device. I don't know how to make these patches. The downmixing option doesn't sound very nice with iO4. Owners of that device probably want to access all channels individually. I don't really see much benefit in option 3 over option 2. The worry about the remapping bugs is not very relevant, in my opinion. I still vote for option 1, but I accept any of the options. I probably won't write the patches, though, if we go with option 2 or 3. -- Tanu
