Patent ID: 6754618
Filing Date: 2004-06-22
Classification: G10L

Abstract:
A communication system comprising:an encoder circuit responsive to an audio signal for performing compression on the audio signal and adaptive to generate an audio output signal based upon the compressed audio signal, the encoder circuit for sampling the audio signal to generated sampled signals, each sampled signals having a real and an imaginary component associated therewith, each sampled signal having an energy and a phase defined within a current block and each sampled signal having being transformed to have a real and an imaginary component, a previous block preceding the current block and a block preceding the previous block, the encoder circuit for calculating the phase of the samples of the current block using the real and the imaginary components of the samples of the previous block and the block preceding the previous block, wherein calculations for determining the unpredictability measure is reduced by avoiding trigonometric calculations of the samples signals of the current block thereby improving system performance wherein the encoder circuit for calculating the unpredictability measure, cw, using the following equations: cw=[temp5âˆ’2.0 &rgr;w(temp4)]1/2/(temp3), wherein temp5 is calculated as follows: temp5=rw2+&rgr;w2 and temp4 is calculated as follows: temp4=(temp1)xr(w)+(temp2)xj(w) and temp3 is calculated as: temp3=rw+abs(&rgr;w) and wherein temp2 is calculated as: temp2=(sin 2fw[t-1])(cos fw[t-2])âˆ’(cos 2fw[t-1])(sin fw[t-2]) and wherein temp1 is calculated as: temp1=(cos 2fw[t-1])(cos fw[t-2])+(sin 2fw[t-1])(sin fw[t-2]) wherein rw is the square root of the energy of the sampled signal at the current block, fw[t-1] and fw[t-2] are the phase of the sampled signal at the previous block preceding the unsent block and the block preceding the previous block, respectively, xr(w) and xj(w) are the real and imaginary components of the sampled signals, respectively, and &rgr;w is the predictability value of the square root of the energy at the current block.