[PD] question about 09.pvoc.pd

[Miller Puckette]

Hi Chris,

I don't fully understand the semantics of sample rates in block~ed subpatches
myself...  anyway, I think in the case of overlap, sample rate isn't the number
of samples per second, but rather, one over the time difference between
successive samples, which then shouldn't change when you change overlap
factor.  It's a question of definition only, and really should ultimately
be chosen for greatest convenience...  but I don't yet think I know what 
ultimately will prove most convenient and I would hate to change it now...

cheers
Miller

On Tue, May 21, 2002 at 09:59:40PM -0400, cb wrote:
> Hi,
> I've been studying DSP theory, FFT-based techniques in particular.
> I've found the FFT tutorials in PureData to be a great place to see those techniques applied to sound.
> 
> However, one little implementation detail still has me confused: 
> In the engine of the phase vocoder patch (the FFT-ANALYSIS subpatch), there is a Float object which is used to calculate the next read location in milliseconds.  This value is then converted to a sample position & passed through a Line~ to specify the start location of the first Tabread4~.
> 
> What I don't understand is why the conversion of the Float from milliseconds to samples doesn't take into account the overlap of the subpatch-in other words, why isn't the local sample rate used, instead of the sample rate of the parent window?
> 
> Thanks in advance for any insight anyone might have to share.
> 
> Chris Campbell
> cb at inner-ear.net