[PD] [PD-dev] Rewriting a unified phasor / metro object for reading tables

[Roman Haefeli]

On Wed, 2013-05-08 at 22:00 +0100, Ed Kelly wrote:
> Hi Lists(s),
> 
> 
> I'm rewriting phasor~ and unifying it with metro so that a pulse is
> generated from the boundaries of each ramp - so that bars of music can
> be read using tabread~ objects with a sample-accurate metro.
> 
> 
> I'm sure someone will say this can already be done,

Yes!

>  but it has to be dropped into the Ninja Jamm patch, so there isn't
> really time to rewrite the rest of the patch.

Frankly, I am pretty sure, just using what Pd provides is too easy to
use and likely less time consuming than writing your custom external.
(Or I am totally missing the point of this adventure).
 

> I don't fully understand the way phasor~ wraps, but I have the object
> firing out bar numbers correctly. I'm putting clocks in for 16ths and
> 24ths of the beat, initiated on each wrap. I need to minimise CPU, so
> what I want to know is this:
> 
> 
> Does phasor~ always start from 0 and go to 1, i.e. is there always a
> signal value of 0 at the start of the ramp and a signal value of 1 at
> the end? As I write this, my common sense tells me it should be "yes"
> but I want to make sure. I suppose I should just try it really...

No, it's not the case. A [phasor~] ramp virtually starts always at 0 and
ends at 1 - true, but most of the time the wrapping point doesn't lie
exactly on sample boundaries. This means the sample values around the
wrapping point are almost never 1 or 0, respectively. 

Trying to derive precise timing from the audio domain is a moot exercise
anyway, in my opinion. The best you can get from this approach is sample
precision and analyzing all samples of a signal is relatively
expensive. 

If you truly care about CPU consumption and a proper design from the
start, use [metro] - which is as precise as 32-bit floats can be - and
[vline~] - which actually uses the  precise timing from [metro] (as
opposed to [line~] that doesn't).

With this combo [metro]/[vline~] you can rebuild [phasor~] with the
additional benefit of giving you more-than-sample-exact bangs at the
wrapping points. The only drawback compared to [phasor~] is that the
latter allows to control the frequency with a signal and the
[metro]/[vline~] based phasor obviously doesn't. 

I'll be glad to help you build the [phasor~] replacement that has an
additional bang outlet, if you need it.

Roman