Re: [LAD] zita-ajbridge and aloop

On Thu, Jul 11, 2013 at 03:59:09PM +0200, IOhannes m zmoelnig wrote:
 
> i'm having serious troubles using zita-ajbridge with alsa loopback
> devices.
>
> my basic requirement is, to allow *any* ALSA-only application to be
> "jackified".

The normal way to do that would be the ALSA's pcm.jack device.

In your $HOME/.asoundrc:

pcm.!default {
    type plug
    slave { pcm "jack" }
}

pcm.jack {
    type jack
    playback_ports {
        0 zita-mu1:in_4.L
        1 zita-mu1:in_4.R
    }
    capture_ports {
        0 system:capture_1
        1 system:capture_2
    }
}

There are two problems with this:

* The .asoundrc specifies the Jack ports it will connect to
  instead of those it creates.
* Not all apps will find the device because
  - they don't use the 'default' device, and
  - they expect a hw: device, and pcm.jack isn't one.

But it works well with mplayer, firefox, chromium and maybe others.

> $ zita-a2j -v -d hw:Loopback,0 -L
> ...
 
> ok, so i stop mplayer, and start some other application e.g. Pd (what
> else). hooking it up to the loopback device, i start my testpatch:
> silence :-(

Did you use

  hw:Loopback,1
                        
(i.e. the 'other side' of hw:Loopback,0') for Pd ? Works here, but you
need

   -alsaadd hw:Loopback,1

in order to find it in Pd's list of devices (which is utterly broken).
 
> ok, so mabye Pd is broken, i try some zita app, e.g. zita_delay (from
> libzita-alsa-pcmi)
> ...
> $ alsa_delay hw:Loopback,0 hw:Loopback,0 48000 1024 2
> ...
> not very surprisingly, it doesn't detect any input signal (zita-j2a is
> not running), but i also don't hear any output signal.

See above.

To run alsa_delay you could try:

zita-a2j -d hw:Loopback,0,0
zita-j2a -d hw:Loopback,0,1
alsa_delay hw:Loopback,1,0 hw:Loopback,1,1 48000 256 2

which works nicely here (after connecting the Jack ports).

> currently the *only* application that i can convince to use
> zita-ajbridge seems to be mplayer, and only in S16_LE mode.
>
> what are the requirements for an application to use zita-ajbridge?

Wrong question.

zita-a2j and zita-j2a are *not* ALSA devices to be used by an
application - rather the inverse: they are applications that
use an ALSA device (which should be a hw: one). It's aloop which
presents itselfs as a device, tries to masquerade as a real hw:
device but doesn't exactly behave as one.

Ciao,

-- 
FA
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It's also a pipe-dream, founded on self-delusion, nerd hubris
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