[PD] Re : connecting a samphold and a phasor together

[Frank Barknecht]

On Wed, Apr 28, 2010 at 09:10:53AM -0700, Benoît Fortier wrote:
> Thank you, I didn't knew about the one block delay. Problem solved very elegantly indeed!

However the problem is not really solved, only "delayed". :) Your phasor~'s
frequency will not change when it is at zero, but at least 1 sample or in Pd
even one block later (so usually 64 samples)  when the phasor~ is already at a
value different from 0. 

This affects certain algorithms more than others, but you have to be aware of
it. Here's Miller's notes from
http://crca.ucsd.edu/~msp/techniques/latest/book-html/node96.html about the
issue:

  Having the oscillator's phase control the updating of its own frequency is an
  example of feedback, which in general means using any process's output as one
  of its inputs. When processing digital audio signals at a fixed sample rate (as
  we're doing), it is never possible to have the process's current output as an
  input, since at the time we would need it we haven't yet calculated it. The
  best we can hope for is to use the previous sample of output--in effect, adding
  one sample of delay. In block environments (such as Max, Pd, and Csound) the
  situation becomes more complicated, but we will delay discussing that until the
  next chapter (and simply wish away the problem in the examples at the end of
  this one). 

A [phasor~] with a builtin [samphold~] on its own output could be a nice
external.

Ciao
-- 
 Frank Barknecht            Do You RjDj.me?          _ ______footils.org__