System and method for mixed codebook excitation for speech coding

Patent metadata

Field	Value
Publication number	US-9972325-B2
Application number	US-201313768814-A
Country	US
Kind code	B2
Filing date	Feb 15, 2013
Priority date	Feb 17, 2012
Publication date	May 15, 2018
Grant date	May 15, 2018

Abstract

In accordance with an embodiment, a method of encoding an audio/speech signal includes determining a mixed codebook vector based on an incoming audio/speech signal, where the mixed codebook vector includes a sum of a first codebook entry from a first codebook and a second codebook entry from a second codebook. The method further includes generating an encoded audio signal based on the determined mixed codebook vector, and transmitting a coded excitation index of the determined mixed codebook vector.

First claim

What is claimed is:

1. A method of encoding an audio/speech signal, the method comprising:
for each frame in an incoming audio/speech signal having a low bit rate, determining a mixed excitation and an adaptive codebook excitation based on the incoming audio/speech signal, the mixed excitation comprising a sum of a first excitation entry from a first codebook and a second excitation entry from a second codebook, wherein the first and second codebooks are both fixed but different codebooks, wherein the adaptive excitation comprises an entry from an adaptive codebook, wherein the first codebook comprises pulse-like entries, wherein the pulse-like entries comprise non-periodic, signed, and unit magnitude pulses specially designed for an Algebraic Code-Excited Linear Prediction (ACELP) speech coding algorithm, and the second codebook comprises noise-like entries, wherein determining the mixed excitation is performed in time domain;
applying a first filter to the first excitation entry from the first codebook;
applying a second filter to the second excitation entry from the second codebook, the second filter being different from the first filter;
for each subframe in each frame in the incoming audio/speech signal, searching pulse-like entries in the first codebook, by using an Analysis-By-Synthesis searching approach, to find an entry that minimizes a weighted error between a synthesized speech and the incoming audio/speech signal, and coding an index of the entry to obtain at least one coded excitation index;
generating an encoded audio signal based on the determined mixed excitation and the adaptive codebook excitation; and
transmitting the at least one coded excitation index of the determined mixed excitation, wherein the determining and generating are performed using a hardware-based audio encoder.

2. The method of claim 1 , wherein determining the mixed excitation comprises:
computing first correlations between a filtered target vector and filtered entries in the first codebook, wherein the filtered target vector is based on the incoming audio signal;
determining a first group of highest first correlations;
computing second correlations between a filtered target vector and filtered entries in the second codebook;
determining a second group of highest second correlations; and
computing a first criterion function of combinations of the first and second groups, wherein the first criterion function comprises a function of one of the first group of highest first correlations, one of the second group of highest second correlations and an energy of corresponding entries from the first codebook and the second codebook.

3. The method of claim 2 , further comprising:
determining a third group of candidate correlations based on a highest computed first criterion functions; and
selecting the mixed excitation based on applying a second criterion function to the third group, wherein the mixed excitation corresponds to codebook entries from the first codebook and the second codebook associated with a highest value of the second criterion function.

4. The method of claim 3 , wherein:
the first criterion function is

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Assignees

• Huawei Tech Co Ltd

Inventors

• Gao Yang

Classifications

• G10L19/005

  Correction of errors induced by the transmission channel, if related to the coding algorithm · CPC title

• H03M7/30

  Compression (speech analysis-synthesis for redundancy reduction G10L19/00; for image communication H04N); Expansion; Suppression of unnecessary data, e.g. redundancy reduction · CPC title

• G10L19/09

  Long term prediction, i.e. removing periodical redundancies, e.g. by using adaptive codebook or pitch predictor · CPC title

• G10L19/12 Primary

  the excitation function being a code excitation, e.g. in code excited linear prediction [CELP] vocoders · CPC title

• G10L19/26

  Pre-filtering or post-filtering · CPC title