Patent ID: 8392179

Claim:
A method for code excited linear prediction (CELP) audio encoding employing an LPC synthesis filter controlled by LPC parameters, a plurality of codebooks each having codevectors, at least one codebook providing an excitation more appropriate for speech-like signals than for non-speech-like signals and at least one other codebook providing an excitation more appropriate for non-speech-like signals than for speech like signals, and a plurality of gain factors, each associated with a codebook, wherein a speech-like signal means a signal that comprises either a) a single, strong periodical component (a “voiced” speech-like signal), b) random noise with no periodicity (an “unvoiced” speech-like signal), or c) the transition between such signal types, and a non-speech-like signal means a signal that does not have the characteristics of a speech-like signal, the method comprising applying linear predictive coding (LPC) analysis to an audio signal to produce LPC parameters, selecting, from at least two codebooks, codevectors and/or associated gain factors by minimizing a measure of the difference between said audio signal and a reconstruction of said audio signal derived from the codebook excitations, said at least two codebooks including said at least one codebook providing an excitation more appropriate for speech like signals and said at least one other codebook providing an excitation more appropriate for non-speech-like signals, and generating an output usable by a CELP audio decoder to reconstruct the audio signal, said output including LPC parameters, codevector indices, and gain factors, wherein the at least one codebook providing an excitation output more appropriate for speech-like signals than for non-speech-like signals includes a codebook that produces a noise-like excitation and a codebook that produces a periodic excitation and said at least one other codebook includes a codebook that produces a sinusoidal excitation useful for emulating a perceptual audio encoder.