[LAD] 9 soundcards ?

Len Ovens len at ovenwerks.net
Mon Feb 24 19:14:01 CET 2020

On Mon, 24 Feb 2020, Manuel Haible wrote:

> Now i am proceeding with project that we talked some time ago:
> Now I am planning to use several RME Madi HDSPe cards and Madi/Adat converters. 
> Running one at 96k (for audio) as master and two at 48k (for control voltages and
> some basic audio) resampled with zita.
> 3 Madi cards = 32 i/o @ 96k + 128 i/o @ 48k
> Can this amount of audio streams be handled by modern multicore systems?
> Plus DAW, plugins, ect ?
> With a pleasant latency?
> I guess yes, as there exists the RME MadiFX, too - which provides ~196 i/o @ 48k.

Multicore? yes. Multithread per core? Not so much in my experience. I have 
not exerimented with any of this since I bought the i5 (4 cores, 4 
threads) a few years ago. However, in my my experimentation leading up to 
that purchase, I found that 64/2 was about as low as I could go with multi 
thread cores, but turning the multithread(hyperthreading?) feature off in 
bios allowed very stable operation even down to 16/2. (using a ice1712 
based PCI audio card). Be aware that the sound card itself will end up all 
on one thread/core. You can see this by looking at /proc/interrupts where 
almost all of the interrupts for the audio card wioll be on one core. So 
probably each of your cards will be on a different core. As you are using 
zita-ajbridge that is probably not a concern.

> >> So low latency is important but sample accuracy not so much.
>   The time-shift of sample-streams would be different on each start up, right?

Yes, It depends on how long it takes the bridge to start up and when it 
gets started. If the setup is started by a script, it depends on system 
load pretty much.

> Even if a jack-client is "hanging" or x-runs occure, after re-syncing the
> time-shift changes, right?
> How much of a time-shift is about to be expected?

within one buffer size worth of samples.

>  >> there is no need for sample accuracy or other sonic artifacts introduced
>  >> by SRC
> What kind of sonic artefacts in the resampled audio are expected?

The Zita SRC code is very good and so it is not so much anything you would 
hear if listening just to the resampled output. However, I would not set 
up a stereo pair with one resampled and the other not. Anything using 
close mics should be fine as is.

> Would it be a good idea to apply an aliasing-filter before feeding the
> zita-resampler?


Len Ovens

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