Time domain aliasing cancellation type transform coding method for e.g. audio signal of speech, involves determining frequency masking threshold to apply to sub band, and normalizing threshold to permit spectral continuity between sub bands

摘要

#CMT# #/CMT# The method involves determining a frequency masking threshold from a masking curve calculation block (606) for applying to a sub band in order to apply a perceptual weighting to the sub band in the transformed field. The masking threshold is normalized for permitting spectral continuity between the two sub bands. The number of bits to be allocated to each sub band is determined from a spectral envelope based on the normalized masking curve calculation applied to the sub-band. #CMT# : #/CMT# Independent claims are also included for the following: (1) a method for decoding a signal (2) a computer program comprising a set of instructions to perform a method for coding a signal (3) a computer program comprising a set of instructions to perform a method for decoding a signal (4) a decoder comprising a memory. #CMT#USE : #/CMT# Method for time domain aliasing cancellation (TDAC) type transform coding of a digital signal e.g. audio signal of speech and music, in different high frequency sub bands using a coder (claimed) e.g. hierarchical coder, according to a G.729.1 standard. #CMT#ADVANTAGE : #/CMT# The method permits calculation of the perceptual weighting using the masking threshold on only a part of the frequency band and ensures the spectral continuity with other frequency bands in an improved manner by normalizing the masking threshold on the spectrum covering the frequency bands. #CMT#DESCRIPTION OF DRAWINGS : #/CMT# The drawing shows a schematic block diagram of a time domain aliasing cancellation coding structure using a masking curve calculation for allocation of bits. 600 : Weighting block 601, 602 : Modified discrete cosine transform blocks 604 : Spectral envelope calculation block 606 : Masking curve calculation block 607 : Bit allocating block.