Quoting Callum Lerwick <seg@xxxxxxxxxx>:
On Sat, 2006-05-20 at 20:56 -0700, thewade wrote:
As far as I know the realtime kernel module, sometimes called the LSM
module, is not a part of the mainline Fedora Core kernel(s). Is it now?
It used to require a PAM patch and I think a rebuild of the kernel.
From what I remember reading in Kernel Traffic, upstream didn't like the
LSM approach. They came up with the rlimit approach instead, which has
been merged upstream and is supported in FC5. That's what we're using in
jack's README.Fedora.
No no, I am wrong and you are right. I remember this, that rlimits was
preffered over the LSM module. Great!
If I wasn't doing realtime stuff then I would probably agree with you.
How low do you need to go?
On my Athlon 64 3000+ system, I can run jack reliably at a period size
of 256, on the motherboard's cheezy onboard sound. Any lower and it
overruns like mad. Which makes sense, according to qjackcontrol that's a
latency of 10.7ms at 48khz. Given the stock kernel has a 250hz timer,
that gives you a nyquist scheduling frequency of 125hz, which is a
period of 8ms. With a stock kernel I don't think we can go any lower
than 8ms.
I am using and Athalon 64 3400+ in i386 mode because PD doesn't handle
64 bit tables well yet, and a Hammerfall HDSP card. I would be
satisified with less then 10ms (I think I am between 5ms and 8ms now)
because that still allows me to do a large amount of processing without
too much lag for live performances. Any lower and the numper of
computations I can do without generating XRUNS decreases. Any higher
and there starts to be an echo or slapback effect when I play live
(which sadly doesnt happen much these days).
I think that's probably good enough for most users. Maybe CCRMA can
continue to supply kernels for those who demand more. Now if only I
could get Rosegarden to stop complaining...
I haven't used rosegarden. Its primarily MIDI stuff, right?
I use PD, Audacity, and I am learning Ardour. PD rocks but the other
two still need a few UI improvements to be the Soundforge and Sonar I
am used too in Winblows land. Also I need to put linux on my iPod so I
can play flac files...
Packaging alternative kernels in Extras is a can of worms I don't think
anyone is in a rush to open. But as far as I know its not yet totally
out of the question...
I have no problem adding the CCRMA repo to my yum.repos.d directory, as
I do now with FC4. What is the advantage of including CCRMA in Fedora
Extras? Just default install inclusion I imagine.
-wade
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