[LAU] Jack & pulse...knickers in a twist.

[Mac]

On Tue, Jun 5, 2018 at 12:55 PM, Len Ovens <len at ovenwerks.net> wrote:

> On Tue, 5 Jun 2018, Mac wrote:
>
> Ok, so I modified my script to:
>>
>
> ...
>
> This produces exactly what I'd expect and, so far, appears well behaved and
>> reproducable.
>>
>
> Good.
>
> But, some questions:
>>
>> 1.) The pulse in/out are labelled front-left, front-right.
>> The script does not mention these labels, so where did they come from.
>>
>
>
You are, of course, correct, for some reason I missed front-left and read
front_left.


> The script does use these labels:
>
>> jack_connect system:capture_1 PulseIn:front-left
>> jack_connect system:capture_2 PulseIn:front-right
>> jack_connect PulseOut:front-left system:playback_1
>> jack_connect PulseOut:front-right system:playback_2
>>
>
> We told pulse to create two jack clients: PulseIn and PulseOut. Pulse
> named the ports front-left and front-right. You can see these ports by
> looking at qjackctl's Connections window or by typing jack_lsp in a
> terminal.
>
> (There nothing in the output of aplay -l or -L with these either.)
>> (And, where does playback_1/_2 come from?)
>>
>
> playback-1/-2 are again jack ports, but in this case they are created by
> the jack backend or master device rather than a client. So they are called
> "system:*" However, aside from that, they can be treated like the ports
> from any other client.
>
> aplay is an alsa utility and so does not show jack ports, jack_lsp will
> show jack ports (both audio and midi).
>
> 2.) Aplay -l or -L lists a bunch of devices. For example PCH is actually
>> capable
>> of surround sound and there are 2 hdmi devices, and there is spdif as
>> well.
>> How do I get system:xxxx to show more of the on board outputs?
>>
>
> system will show only one device. If you are sure they are all in sync, it
> may be possible to create an alsa multi virtual card... see:
> https://alsa.opensrc.org/TwoCardsAsOne
> http://www.jrigg.co.uk/linuxaudio/ice1712multi.html
> and others.
>
> I will need to digest those a bit.


> The second link above gives some of the troubles that may be encountered
> with this method. However, this is the only way to get them all to be
> "system:" ports.
>
> There is another way to do the same thing that seems to be (in my
> experience) more robust. I use zita-ajbridge in the form of zita-a2j for
> inputs and zita-j2a for outputs. Zita-ajbridge does not care if the devices
> are synced or not. However, in this case the port client will have a
> different name besides system. I normally choose the name of the device:
> zita-j2a -j PCH,1-out -d hw:PCH,1 -r 44100 -p 128 -n 2 &
>
> this gives me a port like:
> PCH,1-out:playback_1
>
> Now, when you mention using suround, I also realize you would want your
> pulse-jack bridge to have more than 2 ports. So you would change the
> channels=value to 4,5 or 6 depending on how many channels you need in the:
> pactl load-module module-jack-sink client_name=PulseOut channels=2
> connect=no
> line. Pulse will conveniently label them in suround like terms. (jack and
> zita will assume a multi channel audio card meant for mutitrack recording
> where channels are used as a number of mono sources)
>
>
I added  channels=3 and it did as expected, created PulseOut:front-left
front_right aux0.

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


zita-j2a will also allow more than two channels with the -c parameter. It
> is ok to use a large number here as zita-j2a will only use as many ports as
> there are actual DACs.
>
> I've used zita-lrx, but that was with a firewire device.


> The whole thing is really very much like connecting a group of stereo
> componants together. each program or utility is like a box. Jack shows the
> plugs on each box and you use a (virtual) wire to connect the boxes as you
> wish. The maker of each box decides what to label their plugs and the owner
> is expected to figure out what they want to do with them.
>
>
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