Patent ID: 7272555

Claim:
A method for speech processing in a code excitation linear prediction (CELP) based speech system having a plurality of modes including at least a first mode and a second mode consecutive with the first mode, comprising: providing an input speech signal; dividing the speech signal into a plurality of frames; dividing at least one of the plurality of frames into sub-frames including a plurality of pulses; selecting a first number of pulses for the first mode, with a second number of remaining pulses in the frame plus the first number of pulses in the first mode for the second mode; providing a plurality of sub-modes between the first mode and the second mode, wherein each sub-mode contains a third number of pulses including at least all the pulses in the first mode, and wherein the third number of pulses in the sub-mode are selected by dropping a portion of the pulses in the second mode; forming a base layer including the first number of pulses; forming an enhancement layer including the second number of the remaining pulses; generating a bit stream including a basic bit stream and an enhancement bit stream, including generating linear prediction coding (LPC) coefficients, generating pitch-related information, generating pulse-related information, forming the basic bit stream including the LPC coefficients, the pitch-related information, and the pulse-related information of the pulses in the base layer, and forming the enhancement bit stream including the pulse-related information of the pulses in the enhancement layer, wherein the basic bit stream is used to update memory states of the speech system.