On Tue, 5 Jun 2018, Mac wrote:
The piece I don't see is, assuming there is a device with 5 outputs, how do you
get jack to create playback_3, _4 etc.
(I get aplay doesn't show jack, but, for example aplay -L lists (this is a
shortened list):
front:CARD=PCH,DEV=0
HDA Intel PCH, ALC892 Analog
Front speakers
surround71:CARD=PCH,DEV=0
HDA Intel PCH, ALC892 Analog
7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
hw:CARD=PCH,DEV=0
HDA Intel PCH, ALC892 Analog
Direct hardware device without any conversions
hw:CARD=PCH,DEV=1
HDA Intel PCH, ALC892 Digital
Direct hardware device without any conversions
How does jack decide to only do 2 playback_1,_2?
I take it there is something else in alsa startup that says provide for example
surround71
I do not know if jack will accept surround71:PCH,0 for device. I do not know the mechanism by which it switches either. You are getting beyond my knowledge. It would not hurt to try. The other thing to look at may be hdajackretask. This shows what the audio jacks are currently being used for. I do not know if changing "blue Line In" to "Rear Side" will change hw:HDA from 2.0 to 4.0 for example. but it may be worth a try. Setting physical jacks to do surround operation may be all it takes.
In my case the real answer is I don't know. I tend to disable any internal audio device to clear up one more thing that may interfere with "real audio".