[PD] block~: overlap not a power of 2

Matthias Blau blau_m at web.de
Sun Sep 4 14:36:07 CEST 2005

Thanks Johannes,

> now what has this to do with the overlap factor ?
> well, the overlapping blocks need a) also fit into the dsp-tick-scheme
> and b) overlapping should be done reasonably fast.
> no with block-sizes being 2^n and overlap-factors being 2^m, the offset
> between 2 blocks will always be integer 2^(n-m) [n>m].
> if you would want an overlap-factor of 3, the offset between to blocks
> would be 64/3 which would involve some interpolation in order to get the
> samples "in-between".
perfectly clear, provided someone would, at the appropriate point in the 
pd manuals/documentation (in Miller's book, in the help file for 
block~/switch~), state that offset=blocksize/overlap (I asked about the 
definition of overlap in vain because I couldn't find exactly that 
information a while ago). This would be particularly useful as overlap 
is usually defined either as absolute value or percentage of overlapping 
samples (as the name would suggest) or as offset between subsequent 
blocks (again either as absolute or relative value).

> it's because pd will first cast the input to an integer (1.5 will become
> 1) and afterwards it will check whether the value is 2^n. and 1=2^0
that would be a valuable information in the help file for block~/switch~ 
as well.

> i agree that it should also bail out when getting non-integer values, in
> order to not confuse people too much.
So do I.

Regards, Matthias

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