Subject: Re: [linux-audio-dev] introduction & ideas
From: Paul Davis (pbd_AT_Op.Net)
Date: Sun Mar 10 2002 - 04:01:51 EET
>I think accurate MIDI timing eventually comes down on how well the
>operating system performes. If Linux had a better performing nanosleep()
>, i.e. if it would reprogram the clock chip to generate one shot interrupts
>at the exact time the first ready thread will need to be woken up, then
>the MIDI timing would be close to what the hardware is able to obtain.
Just want to say that I agree with this entirely. I'm a little
pessimistic about Linus accepting KURT-like patches, given what he
said last time. But he has changed his mind about other things, so you
never know.
>I don't think a new clock would make much sense. You could just run
>the kernel with a higher clock resolution I think.
Well, the overhead of the system timer interrupt is ever-present. If
you use a different h/w clock for MIDI scheduling, its not there all
the time. This can be useful for some systems/setups.
>I disagree. Just use POSIX realtime clocks on a good kernel. You just
>happen to need a realtime kernel for MIDI. And then there will still
>be jitter in a dense MIDI stream, since a message takes about 1ms to
>transmit.
whats a good kernel? do you mean with HZ=1000 ?
>That's a problem with the kernel then. BeOS could do this. Linux could
>probably too without too much modification. The scheduling latency is
>good enough with the latency/preemptive kernel patches. It is just the
>clock resolution that is a little low.
I agree (though from what Andrew Morton has said, the preemptive
patches aren't really a big contribution to bounded latency).
--p
This archive was generated by hypermail 2b28 : Sun Mar 10 2002 - 03:54:20 EET