[Jack-Devel] How does --hwmon work?

[David Kastrup]

Ralf Mardorf <ralf.mardorf at alice-dsl.net> writes:

> There is a cause for {under,over}runs ;). You already mentioned the
> right term, the so called "bottleneck" :D.
>
> Unfortunately the "bottleneck" doesn't show up by a blinking LED or
> something else.
>
> I didn't compare the current lowlatency Ubuntu kernels with my
> rt-patched kernels.
>
> An rt-patched kernel could improve latency a little bit. It's my first
> finished week I worked full-time, after being "free", independent of
> uncool time management :D. However, assumed you shouldn't know or be
> able how to find out, how to build a Debian/Ubuntu package for an
> rt-patched kernel, I'm willing to help you next weekend. I've build the
> kernel-rt a thousand times, before I migrated to Arch Linux.
>
> Sometimes > 48 KHz is used to reduce latency, but regarding best audio
> quality, you only need 48 KHz.

Downsampling from 48kHz to 44.1kHz is a lot uglier than from 96kHz.
Equalizers are a lot more similar to their analog counterparts when you
stay in good distance from the Nyquist frequency (you get frequency
warps otherwise).  Downsampling to consumer frequencies can use a lot
better filtering without realtime constraints.  Nonlinear processing
(like tube amp simulations and other distortions or pitch changes) may
bring inaudible frequencies into the audible domain.

And the analog circuitry for cutting out aliasing is a lot more relaxed
when working between 32kHz and 96kHz rather than 20.7kHz and 22.05kHz
(numbers pulled from the frequency ranges of the Hammerfall's specs).

When using a handheld recorder with electret capsules, I use
16bit/48kHz.  I can set it to 24bit/96kHz, but the additional storage is
just spent on noise and fantasy.

> If I would be you, I first would try to use an rt-patched kernel at 96
> KHz, as well as 48 KHZ.

Well, I thought that Ubuntu Studio (though I don't know whether the
actual distribution from scratch differs from apt-get install
ubuntu-studio) should more or less know what it's doing.  But I haven't
investigated.

But there _are_ also some instructions on the net regarding how to set
up control groups best for audio, and I haven't looked at that either
yet.

-- 
David Kastrup