Subject: Re: [linux-audio-dev] LADSPA Specs ?
From: Paul Davis (pbd_AT_op.net)
Date: Mon May 13 2002 - 01:06:32 EEST
>> I certainly agree that envelope control can be implemented by the host
>> passing dynamically changing parameters to the plugin. I have already
>> given a lot of thought on that. Consider the situation of a volume
>> adjustment plugin with host-controlled parameter as the envelope.
>> Suppose each buffer size is 128 samples, which is reasonably small for
>> dynamic parameter. When we want to do a fade-out, the host sends the
>> buffer to the volume adjustment plugin, specifying a decreasing,
>> negative gain each time. The problem is, for every 128 samples, there is
>> a leap of the control parameter, resulting in audiable steps of the
>> volume. Depending on the amount of parameter changes, this can be quite
[ ...]
>The easiest solution to this kind of problem (parameter change faster than
>nr. of run() calls) is to make the parameter (here: the envelope) another
>audio input stream - this way you get 1:1 parameter:sample mapping.
We discussed this about 2 months ago (or less). The consensus appeared
to me to be that its the responsibility of a *plugin* to interpolate
in the most appropriate fashion whenever the value of a control port
changes. The host *cannot* know the best way to do this without a
ridiculous amount of information being supplied by the the plugin, and
the code is the same in either case. So, the host can choose its own
level of resolution for automated parameters - for example, it can
choose to subdivide its own "natural" blocksize into smaller chunks
for calling process() with - and then the plugin finishes off by some
parameter-specific interpolation.
Does this need to be discussed again? Does anyone disagree with this
"annotation" to the API?
>host can be used to feed generated waves to such a port quite easily [for
>GLAME we of course use another plugin for this wave generation, but that
>again is not possible with LADSPA].
Why not?
--p
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