Patent ID: 8620647

Claim:
A method of coding a speech signal using a multi-rate speech coder having an adaptive codebook, a fixed codebook, and a coding rate selected from a plurality of coding rates including a first coding rate and a second coding rate, the method comprising: obtaining an adaptive codebook gain; obtaining a fixed codebook gain; scalar quantizing the adaptive codebook gain and the fixed codebook gain for coding the speech signal, if the coding rate is the first coding rate, to generate a first quantized adaptive codebook gain and a first quantized fixed codebook gain; vector quantizing the adaptive codebook gain and the fixed codebook gain for coding the speech signal, if the Coding rate is the second coding rate, to generate a second quantized adaptive codebook gain and a second quantized fixed codebook gain; converting the speech signal into a first encoded speech using the first quantized adaptive codebook gain and the first quantized fixed codebook gain if the coding rate is the first coding rate; and converting the speech signal into a second encoded speech using the second quantized adaptive codebook gain and the second quantized fixed codebook gain if the coding rate is the second coding rate.