Subject: Re: [linux-audio-dev] PTAF link and comments
From: Laurent de Soras [Ohm Force] (laurent@ohmforce.com)
Date: Tue Feb 04 2003 - 19:06:52 EET
David Olofson wrote:
>
> As long as you connect ins and outs of the same type, they'll
> generally have compatible ranges. If not (say, your filter can't
> handle more than Nyqvist/4, but the PITCH output that controls it has
> no absolute limits), you most probably want *clamping* rather than
> scaling, so just making everything [0, 1] won't be of any help.
The normalized values are for user tweaking, and natural
values for data exchange. But there is still a use to
connect two normalized parameters, especially when they
are not of the same unit. Variations of one cause natural
variations on the other one. Of course you may want to
apply some kind of mapping between both to adjust
sensitivity or whatever. This is just basic modulation
requirements.
> > > Yeah.
> > Ugh!
But why do you want absolutely to put the metadata in factory ?
I've been confronted to this problem and I can say it's way
simpler to make data available from plug-in rather than to add
another interface to get the data from the factory. Metadata
caching could be handled by another SDK on the top of this
API.
> These will always waste CPU cycles stalling on
> memory access, and will do more of it as memory bandwidth
> keeps lagging behind.
For simple audio processors, this generally doesn't make
that much difference. Real performance gain is done by
parallelizing the processing, ie 4 biquads running
simultaneously to process 4 channels in the EQ of a mixing
console. Here, using SIMD requires custom interleaving or
deinterleaving, moving memory again. But this memory is
often already in the L1 cache, so penalty is small and
final result is really worth the price. Actually these
memory considerations matter when there are high risks
of cache miss. Processing small audio blocks with a smart
scheduler avoids these problems.
-- Laurent
PS: funny, I just noticed there is two things called MAS.
The one I quoted in my first mail was the MOTU Audio Suite,
a plug-in standard for Digital Performer on Macintosh.
==================================+========================
Laurent de Soras | Ohm Force
DSP developer & Software designer | Digital Audio Software
mailto:laurent@ohmforce.com | http://www.ohmforce.com
==================================+========================
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