Re: [alsa-devel] Re: [linux-audio-dev] laaga, round 2

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Subject: Re: [alsa-devel] Re: [linux-audio-dev] laaga, round 2
From: Paul Davis (pbd_AT_Op.Net)
Date: Fri May 11 2001 - 18:49:48 EEST


[ ... lots of good stuff elided ... ]

>I could keep going here, but I will wait for your objections. I hope this
>is clear.

very clear. for this and for other reasons connected with jim's
comments on mixing in h/w sample format, i've already sketched out a
new design for the internals of AES that is closer to a signal graph
approach. but i'm still working on my thoughts about it.

>> >1) Use LADSPA (potentially make run_adding the default a la RTCmix)
>>
>> as Jim noted, it would also have to modified to accomodate plugins
>> whose input and output port count changes dynamically. this is
>> not a small modification, since i think it requires a *server*
>> callback to be provided to the plugin. i don't think this is
>> a bad idea, but it would impact the "S" in LADSPA rather a lot!
>>
>
>This is true, though I am not certain whether it is a big change in
>complexity.

Well, I will just note that it moves LADSPA one step closer to VST,
which I see very little point in doing. VST has a fairly involved
"host" API that is made available to the plugin (though it also does
not involve dynamic input/output announcements, IIRC).

>> Yes, but my point was that you'd have to find a way to deliver a
>> message with the semantics of "CC #22, value 123" via a float control
>> port. That doesn't seem very easy to do. Control data changes only
>> once per cycle, and its single float value.
>>
>
>It is interesting that you say semantics - I would argue that for many of
>the standard midi messages floating point represents the same meaning with
>more precision. Obvious exceptions being channel and program numbers.

oh no, its not the precision thats the issue. Its how you combine a
MIDI message with a CC identifier and a value into a single control
float value. Actually, for CC's its easier, because we could just have
a LADSPA plugin with 127 control ports that were all outputs, each one
representing the current CC value (well, something like that anyway).

But for other kinds of MIDI/SKINI messages, you'd have to condense a
"structured message" down a single float value, and I'm not sure how
you could do that.

--p


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