Re: [linux-audio-dev] XAP spec & PTAF comments [merge]

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Subject: Re: [linux-audio-dev] XAP spec & PTAF comments [merge]
From: Steve Harris (S.W.Harris@ecs.soton.ac.uk)
Date: Fri Feb 07 2003 - 12:07:50 EET


On Thu, Feb 06, 2003 at 08:38:10 +0100, David Olofson wrote:
> > It sounds like the wrong thing, the general case is that the host
> > generates values its knows to be in range, then the plugin checks
> > it again to check its in range...
>
> Not the host; the *sender*. That is the sequencer (which can be part
> of the host), or more interestingly, any plugin that has control
> outputs.

OK, but it seems like a bad requirement to place on the plugin. If we
allow it, it really should be to be the host that enforces it.
 
> > If we allow hard ranges (not really neccesary, as LADSPA shows)
> > then the host should enforce them.
>
> Which would mean the host has to break in whenever you connect two
> controls, *only* to do this.

Yes, thats (one of the reasons) why its bad.
 
> On Thursday 06 February 2003 11.38, Steve Harris wrote:
> [...audio data...]
> > "Normalised floating point" is a well know term, but normalised
> > between -1.0 and 1.0 is wrong.
>
> Why? Is +/- 42.0 P-P or something a better 0 dB reference? :-)

Ah, I meant "not the right phrase", not "not the right thing".
 
> [...points about silence in RT systems...]
> > You cant use the "free" cycles, because youre never sure when the
> > plugin is going to wake up and start chewing CPU again, and in any
> > case you dont know how much it was really using.
>
> It's useful in Audiality, but only really when you're dealing with
> multiple songs, "rooms" or whatever in the same application. Might be
> that it's not a feature that should be in XAP.

I would say so.
 
> > "Silence" is relative. A reverb will onyl decay to mathematic
> > silence after a really long time, but that isnt the intention of
> > this hint IMNSHO.
>
> Good point, though it doesn't make silence useless in Audiality, at
> least. If the reverb *does* go "silent" within any reasonably amount
> of time, the information is useful. Synths generally go silent as
> soon as the release phase of the last note is done (which is
> generally well defined), so it's *definitely* useful there.

Useful for post-roll yes, but not really useful saving a few cycles.

> The reason I have it is that games and other multimedia stuff should
> be able to just set up all FX processing needed for the whole thing
> and then not worry about it. You can have the full FX net for every
> song in the game "running" at all times virtually without cost. The
> plugins won't start burning CPU until you actually send some sound
> their way, and they'll stop burning CPU as soon as their tails are
> out.
>
> Whether or not this is useful in your average studio is another
> matter, but it does *work*.

Right, I suspect it isn;t the reuirements and aims are different.

- Steve


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