[speex-dev] Psycho Acoustic models i Speech Coding

[Christian Buchner]

> Does anyone have an idea about the possibility to apply psychoacoustic
> models as the ones in mp3 or AAC to a CELP coder? Thanks!

> /Pontus

This is (sort of) done in the decoder with the optional perceptual
filtering. Speex tries to shape the noise so that it sounds more
pleasant, I believe.

To really use perceptual coding, one would require fine granular
control over quantization noise in various spectral bands. Speex
is not a subband coder and has no such control. But it already does
a better job than MP3 and other codecs at these bitrates without
using a PSY model.

Besides those PSY models are mostly FFT based which would greatly
increase the encoder complity. We don't really want that. Do we ;)

Christian

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