[LAD] Merging alsa subdevices into multichannel

[Eliot Blennerhassett]

On Tuesday 18 November 2008 11:45:51 Jens M Andreasen wrote:
> When I connect to hw:0,0 the first application will grab  hw:0,0,0 the
> next application will grab hw:0,0,1 and the third application will grab
> hw:0,0,2 ("mic", "front mic" and "line in" assuming this is the order
> they are selected in the mixer app)

My mental model of this is that each subdevice represents a separate (stereo) 
ADC.  (BTW The ordering of hw0,0,[0,1,2] may be independent of the order of 
those controls in the mixer app)

> How do I do to make jackd understand that it should open all three of
> them instead of only one?

As long as they all run from the same clock, you can create a 6 
channel 'device' in your .asoundrc

Two examples follow. 
The first is parameterised on card/dev/subdev
Eg  ttable4:1,2,3  will use card1, device2, link subdevices 3 and 4 into a 4 
channel stream.

The second is 16 channel with only card as a parameter. Always uses device0, 
subdevices 0..7 (You can cut this one down to make your 6 channel device)

use it like:  jackd -d alsa -C ttable16

Sorry I don't know how to make it less verbose, or how to make the number of 
channels parameterisable.

regards

--
Eliot Blennerhassett
http://www.audioscience.com


# This creates a 4 channel interleaved pcm stream based on
# the multi device. JACK will work with this one.

pcm.ttable4 {
	@args [ CARD DEV SUBDEV ]
	@args.CARD {
		type string
		default {
			@func getenv
			vars [
				ALSA_PCM_CARD
				ALSA_CARD
			]
			default {
				@func refer
				name defaults.pcm.card
			}
		}
	}
	@args.DEV {
		type integer
		default {
			@func igetenv
			vars [
				ALSA_PCM_DEVICE
			]
			default {
				@func refer
				name defaults.pcm.device
			}
		}
	}
	@args.SUBDEV {
		type integer
		default 0
	}
	type route;
	hint {
		show {
			@func refer
			name defaults.namehint.basic
		}
		description "4 channel multi route"
	}
	slave.pcm {
		type multi;
		slaves.a.pcm {
			type hw
			card $CARD
			device $DEV
			subdevice $SUBDEV
			#mmap_emulation true
		}
		slaves.a.channels 2;
		slaves.b.pcm {
			type hw
			card $CARD
			device $DEV
			subdevice { @func iadd integers [ $SUBDEV 1 ] }
			#mmap_emulation true
		}
		slaves.b.channels 2;
		bindings.0.slave a;
		bindings.0.channel 0;
		bindings.1.slave a;
		bindings.1.channel 1;
		bindings.2.slave b;
		bindings.2.channel 0;
		bindings.3.slave b;
		bindings.3.channel 1;
	}
	ttable.0.0 1;
	ttable.1.1 1;
	ttable.2.2 1;
	ttable.3.3 1;
}
# see above.
ctl.ttable4 {
	@args [ CARD DEV SUBDEV ]
	@args.CARD {
		type string
		default {
			@func getenv
			vars [
				ALSA_PCM_CARD
				ALSA_CARD
			]
			default {
				@func refer
				name defaults.pcm.card
			}
		}
	}
	@args.DEV {
		type integer
		default {
			@func igetenv
			vars [
				ALSA_PCM_DEVICE
			]
			default {
				@func refer
				name defaults.pcm.device
			}
		}
	}
	@args.SUBDEV {
		type integer
		default 0
	}
	type hw;
	card $CARD;
}


# This creates a 16 channel interleaved pcm stream based on
# the multi device. JACK will work with this one.
pcm.ttable16 {
        @args [ CARD ]
	@args.CARD {
		type string
		default {
			@func getenv
			vars [
				ALSA_PCM_CARD
				ALSA_CARD
			]
			default {
				@func refer
				name defaults.pcm.card
			}
		}
	}
       hint {
                show {
                        @func refer
                        name defaults.namehint.basic
                }
                description "16 channel multi route"
        }

	type route;
	slave.pcm {
		type multi;
		slaves.a.pcm {
			type hw
			card $CARD
			device 0
			subdevice 0
		}
		slaves.a.channels 2;
		slaves.b.pcm {
			type hw
			card $CARD
			device 0
			subdevice 1
		}
		slaves.b.channels 2;
		slaves.c.pcm {
			type hw
			card $CARD
			device 0
			subdevice 2
		}
		slaves.c.channels 2;
		slaves.d.pcm {
			type hw
			card $CARD
			device 0
			subdevice 3
		}
		slaves.d.channels 2;
		slaves.e.pcm {
			type hw
			card $CARD
			device 0
			subdevice 4
		}
		slaves.e.channels 2;
		slaves.f.pcm {
			type hw
			card $CARD
			device 0
			subdevice 5
		}
		slaves.f.channels 2;
		slaves.g.pcm {
			type hw
			card $CARD
			device 0
			subdevice 6
		}
		slaves.g.channels 2;
		slaves.h.pcm {
			type hw
			card $CARD
			device 0
			subdevice 7
		}
		slaves.h.channels 2;
		bindings.0.slave a;
		bindings.0.channel 0;
		bindings.1.slave a;
		bindings.1.channel 1;
		bindings.2.slave b;
		bindings.2.channel 0;
		bindings.3.slave b;
		bindings.3.channel 1;
		bindings.4.slave c;
		bindings.4.channel 0;
		bindings.5.slave c;
		bindings.5.channel 1;
		bindings.6.slave d;
		bindings.6.channel 0;
		bindings.7.slave d;
		bindings.7.channel 1;
		bindings.8.slave e;
		bindings.8.channel 0;
		bindings.9.slave e;
		bindings.9.channel 1;
		bindings.10.slave f;
		bindings.10.channel 0;
		bindings.11.slave f;
		bindings.11.channel 1;
		bindings.12.slave g;
		bindings.12.channel 0;
		bindings.13.slave g;
		bindings.13.channel 1;
		bindings.14.slave h;
		bindings.14.channel 0;
		bindings.15.slave h;
		bindings.15.channel 1;
	}
	ttable.0.0 1;
	ttable.1.1 1;
	ttable.2.2 1;
	ttable.3.3 1;
	ttable.4.4 1;
	ttable.5.5 1;
	ttable.6.6 1;
	ttable.7.7 1;
	ttable.8.8 1;
	ttable.9.9 1;
	ttable.10.10 1;
	ttable.11.11 1;
	ttable.12.12 1;
	ttable.13.13 1;
	ttable.14.14 1;
	ttable.15.15 1;
}
# see above.
ctl.ttable16 {
        @args [ CARD ]
	@args.CARD {
		type string
		default {
			@func getenv
			vars [
				ALSA_PCM_CARD
				ALSA_CARD
			]
			default {
				@func refer
				name defaults.pcm.card
			}
		}
	}
	type hw;
	card $CARD;
}