[LAU] Jack and Virtual Loopback device as permanent Alsa-to-Jack bridge

[James Warden]

--- On Tue, 5/4/10, Peter Nelson <peter at fuzzle.org> wrote:

> From: Peter Nelson <peter at fuzzle.org>
> Subject: Re: [LAU] Jack and Virtual Loopback device as permanent Alsa-to-Jack bridge
> To: linux-audio-user at lists.linuxaudio.org
> Date: Tuesday, May 4, 2010, 10:41 AM
> On Tue, 2010-05-04 at 06:19 -0700,
> James Warden wrote:
> > 
> > --- On Tue, 5/4/10, Peter Nelson <peter at fuzzle.org>
> wrote:
> > 
> > > From: Peter Nelson <peter at fuzzle.org>
> > > Subject: Re: [LAU] Jack and Virtual Loopback
> device as permanent Alsa-to-Jack bridge
> > > To: linux-audio-user at lists.linuxaudio.org
> > > Date: Tuesday, May 4, 2010, 8:38 AM
> > > On Mon, 2010-05-03 at 06:01 -0700,
> > > James Warden wrote:
> > > > Hello,
> > > > 
> > > > I wrote a WIKI page on how to bridge ALSA
> apps that do
> > > not "talk jack" at all (like skype) or poorly
> (like lmms) by
> > > using the ALSA virtual loopback sound card. There
> are a few
> > > reasons why I chose to use this trick, which I
> explain along
> > > the WIKI page. Just read it if you are bored and
> send back
> > > comments if you like :)
> > > > 
> > > > http://alsa.opensrc.org/index.php/Jack_and_Loopback_device_as_Alsa-to-Jack_bridge
> > > > 
> > > > Cheers!
> > > > J.
> > > 
> > > Sadly this is not infallible either. After a
> while I
> > > sometimes end up
> > > with just static and need to restart either the
> ALSA user
> > > or alsa_in...
> > > 
> > >
> > Hi Peter, it does not sound too good :/ I have not
> experienced 'static' on my system. What are your system
> specs ?
> > 
> > J.
> 
> I'm using a Debian Lenny system, but with ALSA 1.0.21
> drivers, on an AMD
> Athlon 64 X2 5600+
> 
> Seems to be some kind of timing issues with snd-aloop.
> Rhythmbox, for
> instance, will sometimes also get stuck and continue
> playing the same
> sample buffer over and over, and also sometimes gets stuck
> at the end of
> a track.
> 


Peter,
I let my laptop play music the whole evening with rhythmbox, fired mythtv at the same time and checked some youtube video, all through the jack-loop setup. I have not heard a single glitch. Don't know what is going on with your system.
I was running jack at p=1024, n=3, r=48k (21ms). My DAW PC usually runs at p=256, n=2, r=96k (2.7ms)

My asoundrc uses the default dmix and dsnoop buffering, so you may want to fiddle a little with explicit options w.r.t buffering. As I mentioned in the howto, there is some latency, that's unavoidable but you can compensate for it if you ever record anything from the loop device inside say ardour.

J.


> -- 
> Peter
> 
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