Re: [Linuxsampler-devel] Re: Gigasampler curve types

[David O. <da...@ol...>]

On Monday 03 November 2003 18.57, Mark Knecht wrote:
[...]
> If the conversion is not part of LS, then what's the additional
> latency incurred when playing a keyboard live? How long are MIDI
> event's delayed going through a completely separate app? Is it
> deterministic, or will it vary from event to event?

If you have an additional process that must be scheduled to process=20
every event, there is a significant risk of increased worst case=20
latency. I'm not sure how likely it is that an event is hit by two=20
"slow" reschedules (one in the MIDI processor and one in LS), but=20
it's most probably possible.

RT-Dave, the control engineer, would assume this *will* happen=20
occasionally, effectively doubling the worst case latency, until=20
proven wrong. ;-)

There most certainly will be an increase in minimum and average=20
latency, but as long as event processing is done "instantly" (by=20
blocking on input and sending the resulting events instantly; no=20
timers and stuff in the MIDI processor), that effect should be=20
insignificant. (Microseconds...)


[...]
> On the other hand, since almost all of my MIDI goes through the
> Alsa stack somehow, and I view connections with kaconnect, could
> that be a place to put these velocity modifiers?

Well, that was my first though when I started following this thread -=20
but unfortunately, ALSA runs only on Linux. (And QNX, though I have=20
no idea what state that stuff is in nowadays.)

It would be nicer IMHO, if things like the "MIDI corrector" could use=20
some portable plugin API - but OTOH, it can't be all that hard to=20
port it to various APIs. No big deal. What's important is that it=20
runs at the right place in the chain, and that it doesn't add=20
significant latency.


[...]
> Anyway, the best thought that I have right now is that these curves
> Cristian asked me to look at are, at least partially, in existence
> to handle stuff like this. I might be wrong, but that's all I've
> got right now.

Yeah, it sure looks like something like that...


//David Olofson - Programmer, Composer, Open Source Advocate

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