[LAU] pros and cons for audio backends of 2nd sound card

Len Ovens len at ovenwerks.net
Tue Feb 9 00:58:44 CET 2021


On Mon, 8 Feb 2021, Athanasios Silis wrote:

> Which audio adapter do you use to use a 2ndary sound card in jack?
> 1.jacl_load audioadapter
> 2. alsa_[in | out] ?
> 3. zita_[a2j | j2a] ?

zita-ajbridge

> why do you use the one you use? What are its advantages ? Have you
> identified or do you know of any disadvantages for each of the above ?

alsa_in/out must run at the same parameters as jack, takes more cpu.

I stay away from internals because the internal can bring jack down. I 
don't know if you can run more than one internal at a time.

So I use zita-ajbridge because it uses less cpu, sounds good, allows the 
second card to run at whatever SR it supports, Allows hard sync if the 
cards are synced (there will be an offset), allows setup of more than one 
extra device. I can handle USB device (un)plug on the fly with other code.

All of these things are important because I deploy the setup where I do 
not know what the user will try (some users have 3 or 4 of those horrible 
USB mics).

> Do you have preferred options to minimize xruns ?

It seems that if the jack master is stable that makes a lot of difference. 
Other than that... the same as for any jack master. prioritize irq 
handler(s) (jack master should probably be highest), don't share the irq 
with other stuff, don't share the USB bus with other stuff, raise buffer 
size as required.

--
Len Ovens
www.ovenwerks.net


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