Chapter 3Sampling Rate Conversion

U. Zölzer

Several different sampling rates are established for digital audio applications. For broadcasting, professional, and consumer audio, sampling rates of 32, 48, and 44.1 kHz are used, respectively. Moreover, other sampling rates are derived from different frame rates for film and video. In connecting systems with different uncoupled sampling rates, there is a need for sampling rate conversion. In this chapter, synchronous sampling rate conversion with rational factor upper L slash upper M for coupled clock rates and asynchronous sampling rate conversion will be discussed where the different sampling rates are not synchronized with each other.

3.1 Basics

Sampling rate conversion consists of upsampling and downsampling and anti‐imaging and antialiasing filtering [Cro83, Vai93, Fli00, Opp99]. The discrete‐time Fourier transform of the sampled signal x left-parenthesis n right-parenthesis with sampling frequency f Subscript upper S Baseline equals 1 slash upper T (omega Subscript upper S Baseline equals 2 pi f Subscript upper S) is given by

(3.1)upper X left-parenthesis e Superscript j normal upper Omega Baseline right-parenthesis equals StartFraction 1 Over upper T EndFraction sigma-summation Underscript k equals negative infinity Overscript infinity Endscripts upper X Subscript a Baseline left-parenthesis j omega plus j k ModifyingBelow StartFraction 2 pi Over upper T EndFraction With presentation form for vertical right-brace Underscript omega Subscript upper S Baseline Endscripts right-parenthesis with normal upper Omega equals omega upper T

with the Fourier transform of the continuous‐time signal . For ideal ...

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