Re: [Jackit-devel] Multiple cards.

Re: [Jackit-devel] Multiple cards.

[Patrick Shirkey]

Joern Nettingsmeier wrote:
> Patrick Shirkey wrote:
> 
>>
>>In your example you don't say whether your cards have are stereo or mono
>>  channels.
>>
>>I get this ouput when starting jack
>>
>>----
>># jackd -R -v -d alsa -d ttable
>>jackd 0.33.0
>>Copyright 2001-2002 Paul Davis and others.
>>jackd comes with ABSOLUTELY NO WARRANTY
>>This is free software, and you are welcome to redistribute it
>>under certain conditions; see the file COPYING for details
>>
>>3475 waiting for signals
>>creating alsa driver ... ttable|1024|2|48000|swmon
>>ALSA: no playback configurations available
>>ALSA: cannot configure capture channel
>>cannot load driver module alsa
>>jack main caught signal 15
>>-----
>>
>>Using the following in my .asoundrc file. I'm not sure if it is correct
>>as card0 has two stereo pcm devices. I'm not sure whether they are being
>>defined in the following or not.
>>
>>Does
>>
>>         slaves.a.channels 2
>>
>>refer to the pcm devices
>>
>>         eg. hw:0,0 and hw:0,1
>>
>>or the first two mono channels available on card0?
>>
>>         eg. left and right channels on hw:0,0
> 
> 
> don't know.
> just try slaves.a.pcm "hw:0,0"; slaves.a.channels 4;
> or alternatively channels 2 and slave.b.pcm "hw:0,1"; slave.b.channels
> 2;
> and see what happens.
> 

nope it is for the pcm devices based on that test.

> also try arecord|aplay to see if the multi device is doing what you
> think it does.
> 
> i must confess i have no clear idea what devices and subdevices (the
> second and optionally third digit after the card number) really are on a
> hardware level. perhaps you should take this thread over to alsa-dev ?
> 

It seems they represent the place which the binding points to for each 
channel.

So     "ttable     0.0     1"     means

"make    binding 0 from fake card "multi".point to channel 0    on this 
fake pcm device"

After exploring this through the afternoon I have come to think that it 
is not exactly what I would like.

IIUC using this in .asoundrc will allow me to make a fake multichannel 
card that uses multiple devices from different cards. Fooling JACK into 
thinking that it is accessing one card instead of many.

This allows me to have multiple outputs available inside the ardour 
connections gui for example.

It seems unecessary to have to set this up though because the devices 
are already available to be accessed as hw:0,0 hw:0,1 hw:1,0 ...

Shouldn't JACK find all available inputs and outputs by default instead 
of relying on the user to define the device to be used?

If not it seems that JACK is missing an extremely lucrative feature 
which would contribute greatly to Linux audio and would no doubt peak 
the interest of anyone who is not already interested.

I can hear Paul now saying you have no desire to make this happen 
because you do not work with consumer devices. Unless someone paid you 
to do it.

I have two questions.

If it is possible to do and the code was written would it be included in 
JACK?

If it is possible to do how much would it cost to have it implemented?


-- 
Patrick Shirkey - Boost Hardware Ltd.
For the discerning hardware connoisseur
Http://www.boosthardware.com
Http://www.boosthardware.com/LAU/guide/
========================================


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Re: [Jackit-devel] Multiple cards.

[Paul Davis]

>IIUC using this in .asoundrc will allow me to make a fake multichannel 
>card that uses multiple devices from different cards. Fooling JACK into 
>thinking that it is accessing one card instead of many.

This was always the idea of how this should work.

>It seems unecessary to have to set this up though because the devices 
>are already available to be accessed as hw:0,0 hw:0,1 hw:1,0 ...
>
>Shouldn't JACK find all available inputs and outputs by default instead 
>of relying on the user to define the device to be used?
>
>If not it seems that JACK is missing an extremely lucrative feature 
>which would contribute greatly to Linux audio and would no doubt peak 
>the interest of anyone who is not already interested.

This isn't a question of JACK's policy, rather its more JACK following
ALSA's design. Because ALSA allows the user to define PCM devices,
ALSA doesn't currently offer any convenient way of enumerating all the
possible PCM devices. If you sit down and think hard about the many
situations a user might find themselves in, I think you'll see that
the approach of "find all "hw" devices, gang them up, and go" really
isn't very helpful. And for those people who try it, they will face
the sync problem in nearly every case.

>I can hear Paul now saying you have no desire to make this happen 
>because you do not work with consumer devices. Unless someone paid you 
>to do it.

That's correct. Consumer devices are just that. People trying to do
multichannel work by ganging such devices are engaged in a strategy I
don't want to support with my own time.

>If it is possible to do and the code was written would it be included in 
>JACK?

Its possible, and if it was reasonably written, it would be included
in JACK.

>If it is possible to do how much would it cost to have it implemented?

I don't know. Somebody else would have to do it.

--p

_______________________________________________________________

Sponsored by:
ThinkGeek at http://www.ThinkGeek.com/

Re: [Jackit-devel] Multiple cards.

[Patrick Shirkey]

Paul Davis wrote:

>>I can hear Paul now saying you have no desire to make this happen 
>>because you do not work with consumer devices. Unless someone paid you 
>>to do it.
> 
> 
> That's correct. Consumer devices are just that. People trying to do
> multichannel work by ganging such devices are engaged in a strategy I
> don't want to support with my own time.
> 

Not even if the reason is to allow cueing of a track. I think it may 
even be possible to allow this to work in sample sync if alsaplayer is 
the app used to play the file.

Eg1. I could cue the file using my headphones channel on a consumer card 
and then click a switch in alsaplayer to allow the file to stream 
through my pro card. As long as the file was paused between switching 
channels it should retain sample sync because alsaplayer is sample accurate.

Eg2. I could set up three channels in ardour mixer for each alsaplayer 
gui and then I just fade them in/out depending on what channel I want to 
hear the file through. This would definitely loose sample sync but could 
allow for some interesting time effects. Do you fancy the idea of 
"ardour dub sessions"?

> 
>>If it is possible to do and the code was written would it be included in 
>>JACK?
> 
> 
> Its possible, and if it was reasonably written, it would be included
> in JACK.
> 

That's good to know.


> 
>>If it is possible to do how much would it cost to have it implemented?
> 
> 
> I don't know. Somebody else would have to do it.
> 

Is there anything that would entice you into whipping it out?

I can send you a sticker if it helps :)



-- 
Patrick Shirkey - Boost Hardware Ltd.
For the discerning hardware connoisseur
Http://www.boosthardware.com
Http://www.boosthardware.com/LAU/guide/
========================================


_______________________________________________________________

Sponsored by:
ThinkGeek at http://www.ThinkGeek.com/

Re: [Jackit-devel] Multiple cards.

[Paul Davis]

>Not even if the reason is to allow cueing of a track. I think it may 
>even be possible to allow this to work in sample sync if alsaplayer is 
>the app used to play the file.
>
>Eg1. I could cue the file using my headphones channel on a consumer card 
>and then click a switch in alsaplayer to allow the file to stream 
>through my pro card. As long as the file was paused between switching 
>channels it should retain sample sync because alsaplayer is sample accurate.

this will work already, but not if the 2 cards have different
interleave configurations. you just define a "multi" device, and use
it. either gang a bunch of similar consumer devices (e.g. 16 bit
stereo, interleaved) or use a big enough multichannel card. but not
both, until someone fixes the code (and it will hard to do, because it
messes with some core assumptions that JACK's alsa_driver uses to make
itself efficient).

>Eg2. I could set up three channels in ardour mixer for each alsaplayer 
>gui and then I just fade them in/out depending on what channel I want to 
>hear the file through. This would definitely loose sample sync but could 
>allow for some interesting time effects. Do you fancy the idea of 
>"ardour dub sessions"?

ditto.

--p

_______________________________________________________________

Sponsored by:
ThinkGeek at http://www.ThinkGeek.com/