num/denom v's double (was: Re: [LAD] [ANN] LV2 beta3)

Steve Harris steve at
Wed May 30 09:30:30 UTC 2007

On 26 May 2007, at 18:05, Dave Robillard wrote:

> On Fri, 2007-05-11 at 18:24 +0100, Steve Harris wrote:
>> On 11 May 2007, at 15:07, Fons Adriaensen wrote:
>>> On Fri, May 11, 2007 at 03:33:04PM +0200, Lars Luthman wrote:
>>>> That sounds like a good argument for two ints to me. Although
>>>> you'd have
>>>> to do a lot better than double if you wanted to represent  
>>>> irrational
>>>> numbers in binary form. =)
>>> Two 32-bit ints can represent (the non-integer part of) most (not  
>>> all)
>>> irrational values to better precision than a double. The algo to  
>>> find
>>> them is a bit mysterious but very simple. Simple example: 355/113 is
>>> equal to pi with a relative error of less than 1e-7, not bad for two
>>> 3-digit numbers. It's not difficult to find two 32-bit ints that  
>>> would
>>> be better than a double.
> So, what's the verdict on this?
> Don't want to fall into the perpetual beta with known issue trap, I'd
> like to fix the sample rate issue and crank out another beta ASAP..
> I'm skeptical we'd ever actually see a plugin that would use rational
> sample rate, so I vote double unless:
> - rational is required for perfect video sync over long time frames
> - someone can provide a concrete example of a realistic plugin that
> would require/benefit from rational

Agreed. And no-one has to my knowledge.

Multirate processing would require an extension, so that extension  
may as well add the num/denom format for the sample rates as and when  
it's needed.

- Steve

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