Subject: Re: [linux-audio-dev] changing control port values with LADSPA: a serious issue?
From: David Olofson (david_AT_gardena.net)
Date: Sat Mar 16 2002 - 23:56:53 EET
On Saturday 16 March 2002 20.19, Jake Donham wrote:
> Hi,
>
> Seems like you want another kind of control port, one which returns
> buffers of control values, just like audio ports return buffers of
> samples, so you can control a parameter arbitrarily.
>
> I see a bunch of discussion around this issue in the list archives,
> and it seems like this solution was rejected for performance
> reasons. Not sure I understand the performance impact though.
1) Simple operations are memory bound on modern machines.
2) Using more buffers increases cache footprint, and thus
increases the number of cache misses.
3) If there is heavy work going on in the background,
there's a big chance the audio and control buffers
will be thrown out - which results in increased
use of memory having a *much* harder impact on
performance.
> It doesn't seem like a good idea to hard-code particular kinds of
> parameter interpolation, linear or otherwise.
You have to consider the cost of any conditional code in plugins and
hosts - and not only the complexity, but also the cost of pipeline
flushes when branches are mispredicted...
//David
.- M A I A -------------------------------------------------.
| Multimedia Application Integration Architecture |
| A Free/Open Source Plugin API for Professional Multimedia |
`----------------------> http://www.linuxaudiodev.com/maia -'
.- David Olofson -------------------------------------------.
| Audio Hacker - Open Source Advocate - Singer - Songwriter |
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