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From: hanke@nessie.cs.id.ethz.ch (Norbert Hanke)
Newsgroups: comp.dsp
Subject: Re: 48k to 44.1k sample rate conversion
Message-ID: <1991May13.173129.18295@bernina.ethz.ch>
Date: 13 May 91 17:31:29 GMT
References: <5826@media-lab.media.mit.edu.MEDIA.MIT.EDU>
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In article <5826@media-lab.media.mit.edu.MEDIA.MIT.EDU> joe@media-lab.media.mit.edu (Joe Chung) writes:
( some stuff deleted )

>rate. The only problem is that the LCM of 44.1k and 48k is 21.168 Meg!

It is 7.056 MHz

>Obviously, sample rate converters don't store the entire intermediate,
>upsampled version, but I was wondering if anyone has a good idea of 
>what sorts of schemes they do use. Do they do some sort of overlap-
>save method akin to block convolution? Does anyone have any code
>to do this?

Sample rate conversion is not that difficult: when done by a FIR filter
the filter coefficients have to be calculated for the 7.056 MHz sampling
frequency. But fortunately, 146 out of 147 input samples (at 7.056 MHz) are
0 for 48 kHz input, and 159 out of 160 output samples don't have to be
calculated. These two facts together make the computing power requirements
reasonable for sampling rate converters. More difficult, however, is the
calculation of about 10000 filter coefficients for a high quality sampling
rate converter.

Norbert Hanke
ETH Zurich, Switzerland