[linux-audio-user] Setup Jack with two different cards ?

[Arnold Krille]

On Saturday 14 May 2005 15:14, NiXO Beee wrote:
> I'v been googlin' a bit but to no avail.
> In the machine I'm preparing there is an onboard nforce2 audio chipset wich
> I'd like to use to output some secondary signals (the first card is an OK
> emu10k1, with every in and out working properly.)
> Is there a tutorial somewhere that explains how to do that ?
> Do I have to launch another Jack daemon or can the first one handle two
> sound cards ?

The reasons why this can work or can not work where discussed various time on 
this and other lists. The main reason is: The two cards are running with 
different quartzes and therefor with (slightly) different sampling rates. So 
basicly one of the cards is requesting the data earlyer than the other => you 
get glitches and the software will produce error. A solution would be to 
create an alsa-plugin which adds a jitter-buffer but this introduces 
latencies.
Another approach is described in the el-cheapo-howto 
[http://www.djcj.org/LAU/quicktoots/toots/el-cheapo/], another one is in the 
alsa-docs 
[http://www.alsa-project.org/alsa-doc/doc-php/asoundrc.php?company=Generic&card=Generic&chip=Generic&module=Generic#virmulti].

While I think the first approach works (haven't tested due to the lack of two 
cards of the same type) I can confirm the second one doesn't work with alsa 
and jack. But since both my emu10k1 and my onboard-sound have a 5+1 output (3 
stereo-outs each) I didn't invest more as I have only one pair of 
speakers. ;-)

Arnold

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