In message <[EMAIL PROTECTED]>you write:
>> > The only thing I can think of is that the sound card clock is drifting
>> > too.
>>
>> Do you mean the drift as the difference between the "real" wall-clock
>> time and sequencer ticks? Or between the sequencer time and ticks?
>
>The sequencer clock generates ticks on the pcm clock interrupt. But the
>number of ticks it generates is a constant (x/y from your previous
>email). Ie, each interrupt generates the same amount of ticks, even
>though the interrupts might not be evenly spaced or maybe the interrupts
>are two short, etc.
this doesn't even require a poor clock on the audio interface. the
arrival of interrupts at the CPU and the invocation of the ISR does
not happen instantaneously. the APIC used to handle and route IRQ's to
the CPUs can do various things to delay the arrival (mostly when the
kernel asks it to). these delays are certainly on the same order as
the kinds of times you're talking about.
does the timer code really assume that when it gets "ticked", the
number of ticks is constant? thats a really bad assumption ...
BTW, this all seems like more and more of reason to do all this in
user-space, where the jitter might be very slightly greater, but the
drift would be non-existent, i think.
--p
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