[PD] big soundfiles [interpolation]

Derek Holzer derek at umatic.nl
Wed Nov 24 11:28:52 CET 2010


Hi Ronni,

like I said, it has to do with interpolation. I'm working on a chapter 
for the Pd FLOSS Manual about soundfiles now, but here is the short 
version... math gurus on the list please correct me if I am wrong since 
this will likely end up in that chapter!

When you play back the samples in the array at the same rate that they 
were recorded, then Pd doesn't have a lot of work to do since it just 
reads back the values. However, when you play them back at a different 
rate, for example by reading a 44.1K sample at 48K, then Pd often has to 
interpolate (i.e. guess the "missing" values in between the samples) in 
order to create the audio. That is what the "4" in [tabread4~] means: 4 
point interpolation which uses the 4 nearest values to calculate any 
value which might fall in between two samples.

Super-geek explanation by Miller here: 
http://www-crca.ucsd.edu/~msp/techniques/v0.11/book-html/node31.html

Here is the part where I know the answer but not the explanation, 
however... but the larger the soundfile you load into an array, the 
lower the quality of the interpolation. Can someone fill *me* in on this 
so I can write intelligently about it in the FLOSS Manual?

Best,
Derek

On 11/24/10 2:57 AM, ronni montoya wrote:
> hi derek , can you explain me why does sound qualit goes own as file
> size goes up? Is that something particular in pd?
-- 
::: derek holzer ::: http://macumbista.net :::
---Oblique Strategy # 117:
"Make it more sensual"



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