[linux-audio-dev] Plugin APIs (again)

Steve Harris S.W.Harris at ecs.soton.ac.uk
Mon Dec 9 09:34:00 UTC 2002


On Mon, Dec 09, 2002 at 02:31:24PM +0100, David Olofson wrote:
[audio rate controls]
> Well, ok. You can have those *too*. (I'm Santa! :-)

Well, you can obviously "have" them, but I dont think you want to have
sophisticated support for both. That would make the API bloaty, and only
nuts like me actually use audio rate control in 2002.

Converting between continuous control and event control is not reliable,
and kinda removes the point of cont. control.
 
> > I look forward to a few years where all DSP code can run blockless
> > and with audio rate (or near audio rate) control.
> 
> Have you considered that timestamped events may actually have 
> *better* than sample accurate timing...? ;-) (Well, I actually 
> suspect that subsample accurate timing will show up sooner or later - 
> as a buzword or because it actually matters. Maybe we should allocate 
> some bits for it while we're at it?)

I dont think its meaningful. At least not efficiently. I't be a better use
of cycles (and devloper time) to just run the whole thing at 96k IMNSHO.
 
> And more seriously, how efficient is audio rate controls when you 
> have tens of them for every channel...? Should you keep recalculating 
> all of you filer coefficients, reprogramming all of your LFOs and 
> envelope generators for *every sample* all the time? Or first test 
> for change in every control for every sample?

Yes. The point is that you have that choice. Anyway its not really
practical on general pupose processors, yet...
 
> I don't think that DSPs or generic CPUs will *ever* be fast enough 
> that you can completely stop worrying about performance. You think 
> convolution is heavy stuff? Wait until you see what the cutting edge 

Hey, I've never though that you can forget about performance, its just
that the cost of things like blockless processing and contonuous control
get lost in the noise when you start throwing RT convolvers around.

And aynway statments like "CPUs will *ever* be fast enough"... are 
usually proven false later ;)

There are some hardware synths in existence today that use cont. control
and blockless processing. The improvement in sound quality is noticable.

- Steve



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