[linux-audio-dev] XAP: a polemic

[David Olofson]

On Wednesday 18 December 2002 19.19, Tim Hockin wrote:
> > Two standard float controls would work fine. Better, in fact, as
> > you can handle defaults and presets without any special-casing at
> > all.
>
> That could work, too.  I want to be careful how much we expect the
> plugin coder to do, though.

Yes... Well, first of all, this is all totally optional. It's only 
needed by tempo and beat sync plugins. (Through that doesn't mean it 
needs a hairy API. ;-)


[...]
> > BTW, how about making integer controls 64 bit? (*41* extra bits!
> > :-)
>
> Is there a justification?

I can't think of any example. It's just more bits, basically. 
Frankly, that's the only strong motivation I see for ints at all, 
since if you just need an integer *value*, float should do. (Just 
disable rounding.)

It might be nice to know that you'll never get 1.5 on a port 
hinted/typed as integer, but I'm not sure that's a good motivation. 
If you really need an integer, you'll round or truncate first thing 
anyway, so such illegal values never get into the machinery.


> 32 bit CPUs are bad at 64 bit math. 
> Maybe a hint that says INT64, otherwise assume int32 ?

Yes... Might be interesting if you want compact protocols for sending 
events over networks or something.


> Do we
> assume signed or unsigned? having it be 64 bits means we need to
> deal with sign extension.

Well, fp is signed, and AFAIK, there are a bunch of programming 
languages that don't have unsigned ints at all, so I would suggest 
assuming they're signed. (Unless they're strictly meant for flags or 
something, but that seems like a nasty thing to do...)


> > It's no big deal in any way, because they can't be ramped (no
> > event
>
> They can be, it's just not so accurate.  If you want to swing
> between 0 and 1000 in one block, set a ramp event.

Well, yeah... You'd have to implement ramping for integers in 
plugins, and that's not quite as trivial as ramping floats. (I do it 
all the time in Audiality - but that's 16:16 fixed point, so no one 
relies on much accuracy in the lowest bits.)


//David Olofson - Programmer, Composer, Open Source Advocate

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