Subject: Re: Re[2]: [linux-audio-dev] Reverse-engineering files
From: David Olofson (david_AT_gardena.net)
Date: Tue Dec 05 2000 - 01:26:10 EET
On Monday 04 December 2000 18:48, Paul Barton-Davis wrote:
> >My impression is that these mixers do the actual signal processing
> > in lots of "small" DSPs, while the part of MackieOS that runs on
> > the "computer" part of the design is little more than a base for
> > the UI. Thus, it's not certain that MackieOS is playing in the
> > sub 3 ms range hard RT league at all.
>
> MackieOS doesn't have to operate in the RT league for DSP, because
> as you point out, thats all done on slave DSPs. But the "pentium
> class (133MHz)" host/master processor *is* responsible for
> automation data, motor control for the faders, MIDI time code
> handling and variety of other tasks that all call for pretty good
> (say, 5ms or better) latency.
Ok, as i suspected... That is, it probably *is* a hard RTOS, but
doesn't need to be in the µs latency class, which makes things quite
a bit simpler. Actually, an OS of that size doesn't even need to have
preemptive multitasking - the RT work can be done in ISRs, just as
you do in embedded DOS software.
If you write an OS from scratch for a single hardware configuration,
and for a single task, it really isn't that complicated. (I've been
programming various machines directly on the hardware, including disk
access, and it's really not as complicated as it sounds. A great deal
of the Amiga games were written that way, for example...)
Anyway, why this interest in MackieOS? I mean, what's so interesting
about it?
We could grab some drivers, turn a simple DOS extender into something
that lilo could fire up, and hack a simple RT kernel on top of that.
(IRQ level for hard RT, cooperative multitasking for the rest, or
borrow a real scheduler from RTL or RTAI.) It's not much more work
than it was writing a demo or small game back in the Amiga days. Or
one of those 100% asm demo coding style trackers for that matter...
But what's the point in comparing that to Linux/lowlatency?
The *hard* part is to extend such a foundation into a real OS, with
all kinds of services, drivers etc. That's when an OS turns from an
embedded application into a System, and that's where most OSes have
failed. If you're looking for systems you can build *real*
worksations around, how many are there really? GNU with a few
different kernels, some proprietary Unices, Winblows (Ok, I'm being
nice! ;-), BeOS, MacOS, OS/2... But even some of these are
questionable considering the lack of drivers, config tools etc.
In short, I'd say MackieOS looks more like a modular embedded
application than an OS to me. Not to be compared with a Real OS,
which has tons of more issues to deal with.
//David
.- M A I A -------------------------------------------------.
| Multimedia Application Integration Architecture |
| A Free/Open Source Plugin API for Professional Multimedia |
`----------------------> http://www.linuxaudiodev.com/maia -'
.- David Olofson -------------------------------------------.
| Audio Hacker - Open Source Advocate - Singer - Songwriter |
`--------------------------------------> david_AT_linuxdj.com -'
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