Digital Signal Processing Reference
In-Depth Information
Chapter 2
Motivation, Aims, and Solutions
It is not knowledge, but the act of learning, not possession but
the act of getting there, which grants the greatest enjoyment.
—
Carl Friedrich Gauss
2.1 Motivation of Intelligent Audio Analysis
There are numerous scenarios and fields for potential application of Intelligent Audio
Analysis that are commercially interesting and may help us in our daily lives. These
are detailed out in the application part of this topic (Part III) that aims to give some
practical examples, but a more general perspective on use-cases of the whole field
is given for a motivational introduction at this point. Intelligent Audio Analysis is
currently used and holds future promises in particular for
Audio Encoding
: Obviously, in an acoustic representation, highest bitrates are
required, which can be eased step-wise by going to partly or fully parametric rep-
resentation [
1
], and partly or fully symbolic representation (cf. Fig.
2.1
). As for
speech, 'symbolic' could thereby be phones as acoustic realisations of phonemes,
which are “the smallest segmental unit of sound employed to form meaningful con-
trasts between utterances” [
2
]. In the case of music, 'symbolic' could refer to note
events or chords, etc. However, highest bit rate reduction is only reached by semantic
encoding—though obviously at the highest loss factor as, rather than preserving the
original audio, only its semantics are kept for storage or transmission via highly band
limited channels. This then requires to synthesise audio at the moment of decoding
based on these semantics. In music, an example would be note events and instrumen-
tation saved in symbolic representation for storage and later synthesis for play-back.
However, compromises can be made also at this level by combination with (few)
parameters or even highly compressed acoustics—the semantics can then touch cer-
tain aspects of the audio signal for good reproduction at the moment of decoding and
regeneration.
