Low bit rate audio coder and decoder operating in a transform domain using vector quantization

TLDR: In this paper, a pre-emphasis step is performed to perform gross decorrelation, followed by an adaptive linear prediction to perform further decorrelation and a transform is performed on the residual of the linear prediction, to obtain transform coefficients representing the residual in the frequency domain.

Abstract: Audio source data is subjected to a pre-emphasis step (302) to perform gross decorrelation, followed by an adaptive linear prediction (306) to perform further decorrelation. A transform is performed on the residual of the linear prediction, to obtain transform coefficients representing the residual in the frequency domain. A number of tonal components are identified (310), subtracted from the transform coefficients and encoded by vector quantization. The transform coefficients are then grouped into sub-bands, and each sub-band encoded in the frequency domain by vector quantization. The sub-bands are of uniform width on an auditory scale, so that each vector may comprise a different number of transform coefficients.