pros and cons for audio backends of 2nd sound card

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pros and cons for audio backends of 2nd sound card

Athanasios Silis
Hi all,
I am asking here because over the years I have not found convincing/detailed information in google about:

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] ?

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 ?

Do you have preferred options to minimize xruns ?

Thank you in advance for your help
Athanasios

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Re: pros and cons for audio backends of 2nd sound card

Len Ovens
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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Re: pros and cons for audio backends of 2nd sound card

David W. Jones
On 2/8/21 1:58 PM, Len Ovens wrote:

> 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.

My main laptop setup is to have everything going through JACK to use the
external USB soundcard, with PulseAudio set to use JACK as its back end.
I have the built-in audio disabled. I found that much simpler. The
external card feeds an external mixer and amp, the card has hardware
monitoring and a headphone jack. And a lovely volume control wheel. :)

The old Intel Atom-based netbook is for playing music/videos, so it just
uses PulseAudio with the built-in audio hardware.

The desktop system has no audio - the motherboard audio has never worked
and the few times I tried the USB sound card on it, I couldn't get that
working, either. So I removed all the pro audio stuff from it, it just
has Debian's default PulseAudio setup on it.

--
David W. Jones
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authenticity, honesty, community
http://dancingtreefrog.com
"My password is the last 8 digits of π."
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Re: pros and cons for audio backends of 2nd sound card

Chris Caudle-2
In reply to this post by Athanasios Silis
On 2021-02-08 15:58, 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] ?

I am not sure the state of audioadapter in jackd v2.  When I need I use
zita_a2j, it is superior to alsa_in/out.  Jackd v1 incorporated the
equivalent of the zita adapters into an internal client.  Doing the same
for jackd v2 was on the list of development tasks a couple of years ago,
but I do not know the current status.

> 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 ?

The problems in alsa_in/out and the solution in zita_a2j/j2a are
described in the paper authored by Fons:

https://kokkinizita.linuxaudio.org/papers/adapt-resamp.pdf

--
Chris Caudle
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