View Single Post
Old 04-25-2008, 02:23 PM   #20
Human being with feelings
Join Date: May 2006
Posts: 2,373

Originally Posted by Staccato View Post
Is this some basic resampling theory or something? Would you mind giving a brief overview of why resampling from 48 to 44.1 causes level anomalies? Thanks in advance.
Well let's have a look at interpolation then. Pictures are taken straight from

Interpolation tries to "guess" (well it actually calculates) the values that are in between samples. So algorithms for this would be linear: (red dots are the discrete sample values, blue = continous interpolation)

Which is bad for audio since it causes lots of distortion.

Or polynomial:

Which is alot better, see the nice round edges? But then you'll also notice that this rounded edges occasionally go OVER the individual sample values we had before (these are also called intersample peaks).

So when the audio signal gets resampled it gets interpolated and this interpolated values then get resampled, thus it can happen that the new sample points are placed at a spot where the interpolated wavefrom is ABOVE the sample values of the previous sampled signal, therefore you get overs.
LOSER is offline   Reply With Quote