Transform coding of speech and audio signals

摘要

In a method of perceptual transform coding of audio signals in a telecommunication system, performing the steps of determining transform coefficients representative of a time to frequency transformation of a time segmented input audio signal; determining a spectrum of perceptual sub-bands for said input audio signal based on said determined transform coefficients; determining masking thresholds for each said sub-band based on said determined spectrum; computing scale factors for each said sub-band based on said determined masking thresholds, and finally adapting said computed scale factors for each said sub-band to prevent energy loss for perceptually relevant sub-bands.

主权项

1. A method for use in transform coding, comprising:
obtaining an audio signal; obtaining a spectrum (Spe(p)) corresponding to at least a portion of said audio signal; mapping Spe(p) to a spectrum of perceptual sub-bands according to the following linearBSpe⁡(b)=1Hb⁢∑p∈Jb⁢⁢Spe⁡(p)+Tb,b=0,…⁢,BMAX-1,operation: where Bmax is an integer value not greater than 20 and the values of Hb, Tb and Jb are defined in table 1 as:TABLE 1Spectrum mapping constantbJbHbTb00131113221333134413551366137713881399131010, 11241112, 13241214, 15241316, 17251418,19251520, 21, 22, 23461624, 25, 26361727, 28, 29361830, 31, 32, 33, 34571935, 36, 37, 38, 39, 40, 41, 42, 4398; forward smoothing BSpe(b) according to: BSpe(b) =max (BSpe(b), BSpe(b-1)-4), b=1, . . . , Bmax; backward smoothing BSpe(b); after forward and backward smoothing, thresholding and renormalizing BSpe(b); and after thresholding and renormalizing BSpe(b), encoding at least a portion of the audio signal using BSpe(b).