[PD] accuracy of signal/message-objects

Roman Haefeli reduzierer at yahoo.de
Mon May 7 14:14:31 CEST 2007

On Mon, 2007-05-07 at 12:58 +0200, IOhannes m zmoelnig wrote:

> when you send a message to [vline~] it is scheduled to the next
> dsp-block (sample accurateley); the last one is already done
> when you send a message to [vsnapshot~] it operates on the last
> dsp-block; the next one does not yet exist
> this is somehow logical: when you query [vsnapshot~] you do want the
> result immediately (because that's the way how messages are handled in
> pd); the only result it can give you, is that of already known samples.

thanks, it seems logical for me now...

> the only way to overcome this, is by delaying the sampling bang by one
> dsp-block.
> the other thing with the "irregularities" is simpler:
> even when messages have "sub-sample" accuracy, the signal-vectors are
> only sample-accurate.
> so when you read the sample-values of a sawtooth immediately after the
> jump, you will always get different values unless the frequency of your
> ugen is "in sync" with your samplerate.
> see also: shannon's sampling theorem

ah, i see. from what i expected from [vsnapshot~] before, it should have used
some kind of interpolation, that it obviously does not have. now it is
also clear for me, why the discontinuousities grew with higher
frequencies/smaller periods.  

> attached is a modified patch

what/where is that [vmetro] object from? it is not included in my
version of pd 0.40.2. anyway, if i am not mistaken, your patch works
also with [metro].


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