METHOD AND APPARATUS FOR PROCESSING AN AUDIO SIGNAL

• US 20130103407A1
• Filed: 04/08/2011
• Published: 04/25/2013
• Est. Priority Date: 04/08/2010
• Status: Active Grant

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Jeong, Gyu Hyeok, Jeon, Hye Jeong, Lee, Byung Suk, Lee, Chang Heon
• Granted Patent: US 9,153,238 B2
• Time in Patent Office: Days
• US Class Current: 704/500
• CPC Class Codes: G10L 19/008 Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
• CPC Class Codes: G10L 19/038 Vector quantisation, e.g. TwinVQ audio
• CPC Class Codes: G10L 19/04 using predictive techniques
• CPC Class Codes: G10L 19/06 Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
• CPC Class Codes: G10L 19/07 Line spectrum pair [LSP] vocoders
• CPC Class Codes: G10L 2019/0005 Multi-stage vector quantisation

Abstract

The present invention relates to a method for processing an audio signal, comprising the following steps: performing a linear predictive analysis on the current frame of an audio signal so as to generate a first target vector, which is a target vector of a first stage, on the basis of a plurality of linear prediction transform coefficients; performing vector quantization on the first target vector so as to acquire a predetermined number of first temporary candidate code vectors of the first stage; calculating first temporary candidate errors, which are errors between the first temporary candidate code vectors and the first target vector; and determining a first number, which is the number of the first candidate code vectors, on the basis of the first temporary candidate errors, and acquiring first final candidate code vectors in the same amount as the first number.

Claims

1. An audio signal processing method comprising:

generating a first target vector which is a target vector of a first stage based on a plurality of linear predictive conversion coefficients by performing linear predictive analysis on a current frame of an audio signal;

acquiring a temporarily determined number of first temporary candidate code vectors of the first stage by vector-quantizing the first target vector;

calculating first temporary candidate errors which are errors between the first temporary candidate code vectors and the first target vector; and

determining a first number which is the number of first candidate code vectors based on the first temporary candidate errors and acquiring the same number of first final candidate code vectors as the first number.

2. The audio signal processing method according to claim 1, further comprising:

generating first final candidate errors as target vectors of a second stage based on the first final candidate code vectors;

acquiring a temporarily determined number of second temporary candidate code vectors of the second stage by vector-quantizing the second target vectors;

calculating second temporary candidate errors which are errors between the second temporary candidate code vectors and the second target vectors of the second stage; and

determining a second number which is the number of second candidate code vectors based on the second candidate errors and acquiring the same number of second final candidate code vectors as the second number.

3. The audio signal processing method according to claim 2, wherein acquiring the second temporary candidate code vectors includes:

acquiring the same number of temporary candidate code vectors as a which is an arbitrary natural number for each of the second target vectors; and

acquiring the temporarily determined number of second temporary candidate code vectors by removing part of the temporary code vectors.

4. The audio signal processing method according to claim 2, wherein the temporarily determined number is calculated based on a predetermined table value or the first number.

5. The audio signal processing method according to claim 1, wherein the first number is determined based on the first temporary candidate errors and a threshold.

6. The audio signal processing method according to claim 5, wherein the first number is determined to be a small number if an increment of the first temporary candidate errors gradually decreases after the first temporary candidate errors are arranged in ascending order.

7. An audio signal processing method comprising:

generating a first target vector which is a target vector of a first stage based on a plurality of linear predictive conversion coefficients by performing linear predictive analysis on a current frame of an audio signal;

acquiring a temporarily determined number of first final candidate code vectors of the first stage by vector-quantizing the first target vector;

calculating first final candidate errors which are errors between the first final candidate code vectors and the first target vector; and

determining a second number which is the number of second candidate code vectors of a second stage based on the first final candidate errors.

8. The audio signal processing method according to claim 7, further comprising:

generating first final candidate errors as target vectors of the second stage based on the first candidate code vectors;

acquiring the same number of second temporary candidate code vectors of the second stage as the second number by vector-quantizing the second target vectors;

calculating second temporary candidate errors which are errors between the second temporary candidate code vectors and the second target vectors; and

determining a third number which is the number of third candidate code vectors of a third stage based on the second temporary candidate errors.

9. An audio signal processing apparatus comprising:

a linear predictor for generating a first target vector which is a target vector of a first stage based on a plurality of linear predictive conversion coefficients by performing linear predictive analysis on a current frame of an audio signal;

a temporary candidate vector generator for acquiring a temporarily determined number of first temporary candidate code vectors of the first stage by vector-quantizing the first target vector;

an error generator for calculating first temporary candidate errors which are errors between the first temporary candidate code vectors and the first target vector; and

a current number determinator for determining a first number which is the number of first candidate code vectors based on the first temporary candidate errors and acquiring the same number of first final candidate code vectors as the first number.

10. An audio signal processing apparatus comprising:

a linear predictor for generating a first target vector which is a target vector of a first stage based on a plurality of linear predictive conversion coefficients by performing linear predictive analysis on a current frame of an audio signal;

a candidate vector generator for acquiring a temporarily determined number of first final candidate code vectors of the first stage by vector-quantizing the first target vector;

an error generator for calculating first final candidate errors which are errors between the first final candidate code vectors and the first target vector; and

a next number determinator for determining a second number which is the number of second candidate code vectors of a second stage based on the first final candidate errors.

11. An audio signal processing method comprising:

generating a first target signal based on a plurality of linear predictive conversion coefficients by performing linear predictive analysis on a current frame of an audio signal;

performing vector quantization on a first stage based on the first target signal, the vector quantization including generating first candidate code vectors including a first initial best code vector having a smallest error based on the first target signal and outputting a first initial best error corresponding to the first initial best code vector as a second target signal which is a target signal of a second stage;

repeatedly performing the vector quantization from the second stage to an Nth stage;

determining a Kth stage (K=1, . . . , N) in which index update is to be performed among the first to Nth stages;

correcting the Kth target signal using the first target signal and an Kth-excluded sum signal;

determining a Kth optimal best code vector among Kth candidate code vectors based on the corrected Kth target signal; and

selecting one of a Kth initial best code vector and the Kth optimal best code vector as a Kth final best code vector,

wherein the Kth-excluded sum signal is a sum of first to Nth initial best code vectors excluding the Kth initial best code vector.

12. The audio signal processing method according to claim 11, wherein the selection is performed based on a total error of the Kth initial best code vector and a total error of the Kth optimal best code vector,

the total error of the Kth initial best code vector is a difference between a vector obtained by summing the Kth-excluded sum signal and the Kth initial best code vector and the first target signal, and

the total error of the Kth initial best code vector is a difference between a vector obtained by summing the Kth-excluded sum signal and the Kth initial best code vector and the first target signal.

13. The audio signal processing method according to claim 11, further comprising:

determining a K+ath stage (a;

integer) in which index update is to be performed among the first to Nth stages; and

repeating the update, the determination, and the selection for the K+ath stage.

14. The audio signal processing method according to claim 13, wherein the determination of the K+ath stage and the repetition are performed when the Kth optimal best code vector is determined to be the Kth final best code vector.

15. An audio signal processing apparatus comprising:

a linear predictor for performing linear predictive analysis on a current frame of an audio signal and generating a first target signal based on a plurality of linear predictive conversion coefficients;

initial quantizers for performing vector quantization on a total of N stages based on the first target signal, the initial quantizers including a first initial quantizer that performs vector quantization on the first stage by generating first candidate code vectors including a first initial best code vector having a smallest error based on the first target signal and outputting a first initial best error corresponding to the first initial best code vector as a second target signal which is a target signal of a second stage and ith initial quantizer for performing the vector quantization based on ith target signal (i=2, . . . , N);

an update controller for determining a Kth stage (K=1, . . . , N) in which index update is to be performed from among the first to Nth stages;

a Kth stage target signal corrector for correcting the Kth target signal using the first target signal and an Kth-excluded sum signal;

a re-searcher for determining a Kth optimal best code vector from among Kth candidate code vectors based on the corrected Kth target signal; and

an update determinator for selecting one of a Kth initial best code vector and the Kth optimal best code vector as a Kth final best code vector,

wherein the Kth-excluded sum signal is a sum of first to Nth initial best code vectors excluding the Kth initial best code vector.