Databases Reference
In-Depth Information
18
Analysis/Synthesis and Analysis by
Synthesis Schemes
18.1 Overview
Analysis/synthesis schemes rely on the availability of a parametric model of the
source output generation. When such a model exists, the transmitter analyzes
the source output and extracts the model parameters, which are transmitted to
the receiver. The receiver uses the model along with the transmitted parameters
to synthesize an approximation to the source output. The difference between
this approach and the techniques we have looked at in previous chapters is that what is trans-
mitted is not a direct representation of the samples of the source output; instead, the transmitter
informs the receiver how to go about regenerating those outputs. For this approach to work,
a good model for the source has to be available. Since good models for speech production
exist, this approach has been widely used for the low-rate coding of speech. We describe
several different analysis/synthesis techniques for speech compression. In recent years the
fractal approach to image compression has been gaining in popularity. Because this approach
is also one in which the receiver regenerates the source output using “instructions” from the
transmitter, we describe it in this chapter.
18.2 Introduction
In previous chapters we presented a number of lossy compression schemes that provide an
estimate of each source output value to the receiver. Historically, an earlier approach towards
