Re: [linux-audio-dev] more on plugins/LADSPA

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Subject: Re: [linux-audio-dev] more on plugins/LADSPA
From: James McCartney (asynth_AT_io.com)
Date: Sat Mar 18 2000 - 01:09:30 EST


on 3/17/00 7:18 PM, David Olofson at david_AT_gardena.net wrote:

>
>> dual rates on any input (arate & krate),
>
> How does this work?

Any input can be audio rate, control rate or scalar. The plugin must deal
with all rates at any input. When an input changes rate by being replugged,
the ugen may want to change its runtime function. The ugen can choose how to
deal with an input. It can supply a different function for each rate. If it
only wants to support scalar or control rate it can just subsample it. If it
requires audio rate then it can upsample it if necessary. But it must
support them all.

---
Some other issues: I'm still not fully aware on LADSPA.

SC requires that all memory allocation be done from its own real time pool, because SC ugens are allocated as part of garbage collected virtual machine objects.

Unit generators must keep track of an end time stamp and be able to calculate its end time stamp from the end time stamps of its inputs. If it is a finite duration function like an envelope, then it can cause an end time calculation to flow through the graph. If two ugens are added together the end time is the greater of the two, if they are multiplied, then it is the lesser of the two. SC supports sample accurate stop times in this way. This is hard to explain briefly, see Roger Dannenberg's papers on Nyquist. SC is doing nearly the same thing.

As a convention SC requires that all control rate signals are linearly interpolated when consumed by other ugens. Thus there is not zipper noise in any SC ugen. This is just a quality of implementation issue, but I think it is very important.

--- james mccartney james_AT_audiosynth.com <http://www.audiosynth.com> SuperCollider - a real time synthesis programming language for the PowerMac. <ftp://www.audiosynth.com/pub/updates/SC2.2.7.sea.hqx>


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