Audio analysis bands can follow perceptual scales while processing stays on full-resolution QMF bands.

Evidence

Different configurations exist for such cascading and summing, and the implementation presented in the figure involves feeding the lowest three bands to filter banks having 8, 4, and 4 bands, respectively, without further downsampling. The resulting bandwidths are then narrower at low frequencies and wider at high frequencies, although the transition is not smooth. In some perceptually motivated applications, the signal analysis is performed with frequency-band signals in which the higher QMF bands are also combined to form a perceptually motivated frequency resolution. The resulting bandwidths of one configuration in such processing are shown in Figure 15.13. The bandwidths follow somewhat the Bark frequency bands. Note that although the perceptual analysis is performed in such combined bands at the higher frequencies, the processing and inverse QMF transforms are applied at the original QMF bands because they contain the full information of the signal content. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 2139

Categorization

• XREF: Connects to the Bark scale and perceptual audio coding literature the reader knows from psychoacoustics.