At CCRMA we have several studios with linux computers in them (in addition to computers sprinkled throughout the building). Some of the studios have digiface interfaces, some multiface. All of them are connected to the sound system or mixer digitally through adat lightpipes. Workstations have Delta 66 or Gina3G soundcards.
It would be nice for a user to be able to play, say, a stereo Ardour session in any of them without any changes to the session or routing.
The digifaces send channels 1-24 out the adat ports. The multifaces on the other hand send 9-16 on the adat port. Deltas and Ginas send out stuff on channels 1-4 or 1-6.
You can see the multiface interfaces are a problem. To get sound out of them you have to send on channels 9-16 which is different from _all_ others!
I tried several workarounds without much success:
a) fix this at the alsa level. Should be the way to go, right? Create an /etc/asound.conf that uses ttable to translate channels for the multifaces so that the digital out is actually sent through channels 1-8 (and create the same name plug interface in all other computers that does nothing so that the user can set that name as the default in qjackctl and will get the same behavior in all computers).
Works, but not quite. When I try to use that "fake" plug interface with jack2 I get a warning that I'm using a plug interface (sort of fair) and jack only opens it with _2_ i/o channels (even though the ttable is 18 channels wide!). If I _force_ input and output channels in jack to 18 it does work fine. But now it will _not_ work on other computers that have less (or more) than 18 channels. Argh.
b) fix it in hdspmixer. Well, it turns out that hdspmixer does not read the default matrix gains from a file so I can't really override the default. AFAICT the gains are calculated algorithmically in the code and there is no command line option to load presets from a file.
Or I could write a small script that will set the right gains for 1-8 to go out through 9-16 but if a user starts hdspmixer that gets undone with no warning.
And, of course:
c) give up and connect an 8 channel analog snake to the analog outputs of the multifaces and do away with a digital connection to the mixer...
Anyone has any other suggestions?? This should be easy to fix, right? :-) -- Fernando