[PD] Using PD in a non real-time mode?

Roman Haefeli reduzierer at yahoo.de
Tue Aug 5 12:57:27 CEST 2008

On Tue, 2008-08-05 at 12:24 +0200, Derek Holzer wrote:
> Wow. OK, I guess I never tried it the "wrong" way.... ;-)  just to 
> satisfy curiosity... would downsample/upsample cause aliasing errors or not?
> best,
> d.

let's say:
 - you record at 24k, aiming for a result at 48k
 - all time  variables (metro, delay, etc) are doubled
 - all frequencies are halved, respectively 12 is subtracted
   from all pitches.
then you wouldn't even have to resample the result, but it would be
sufficient to simply change the samplerate field in the header from
24'000 to 48'000. you wouldn't have any artifacts at all in this case. 

if you simply record at 24k without all the modifications in your patch
as described above and if you resample the rendered result to 48k, you
probably would have a bit artefacts, but what is much worse: you cannot
increase the quality of your recording by upsampling it. it will still
sound the same (as with the lower samplerate) and it would be lacking
all frequencies above 12k. so: yeah, it is definitely recommended,
whenever possible, to do offline rendering in pd, even if it uses more
than 100% cpu.


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