Bandwidth extension audio decoding method and device for predicting spectral envelope

Patent metadata

Field	Value
Publication number	US-9892739-B2
Application number	US-201514952902-A
Country	US
Kind code	B2
Filing date	Nov 25, 2015
Priority date	May 31, 2013
Publication date	Feb 13, 2018
Grant date	Feb 13, 2018

Abstract

Embodiments of the present invention provide a signal decoding method and device. The method includes decoding a bit stream of a voice signal or an audio signal to acquire a decoded signal; predicting an excitation signal of an extension band according to the decoded signal, where the extension band is adjacent to a band of the decoded signal, and the band of the decoded signal is lower than the extension band; selecting a first band and a second band from the decoded signal, and predicting a spectral envelope of the extension band according to a spectral coefficient of the first band and a spectral coefficient of the second band; and determining a frequency-domain signal of the extension band according to the spectral envelope of the extension band and the excitation signal of the extension band.

First claim

What is claimed is:

1. A signal decoding method, comprising:
decoding a bit stream of a voice signal or an audio signal to acquire a decoded signal, wherein a coding mode of the voice signal or the audio signal is a time-frequency joint coding mode or a frequency-domain coding mode;
selecting a fourth band from the decoded signal, wherein a quantity of bits allocated to the fourth band is greater than a preset bit quantity threshold;
predicting an excitation signal of an extension band according to a spectral coefficient of the fourth band, wherein the extension band is adjacent to a band of the decoded signal, and wherein the band of the decoded signal is lower than the extension band;
selecting a first band and a second band from the decoded signal;
predicting a spectral envelope of the extension band according to a spectral coefficient of the first band and a spectral coefficient of the second band, wherein a distance from a highest frequency bin of the first band to a lowest frequency bin of the extension band is less than or equal to a first value, and a distance from a highest frequency bin of the second band to a lowest frequency bin of the first band is less than or equal to a second value; and
determining a frequency-domain signal of the extension band according to the spectral envelope of the extension band and the excitation signal of the extension band.

2. The method according to claim 1 , wherein selecting the first band and the second band comprises selecting the first band and the second band from the band of the decoded signal according to a direction from a start point of the extension band to a low frequency, wherein the distance from the highest frequency bin of the first band to the lowest frequency bin of the extension band is equal to 0 and the distance from the highest frequency bin of the second band to the lowest frequency bin of the first band is equal to 0.

3. The method according to claim 1 , wherein predicting the spectral envelope of the extension band comprises:
dividing the first band into M subbands, wherein M is a positive integer;
determining a mean value of an energy or amplitude of each subband according to the spectral coefficient of the first band;
determining an adjusted value of the energy or amplitude of each subband according to the mean value of the energy or amplitude of each subband;
predicting a first spectral envelope of the extension band according to the adjusted value of the energy or amplitude of each subband;
determining a mean value of energy or amplitude of the second band according to the spectral coefficient of the second band; and
predicting the spectral envelope of the extension band according to the first spectral envelope of the extension band and the mean value of the energy or amplitude of the second band.

4. The method according to claim 3 , wherein determining the adjusted value of the energy or amplitude of each subband comprises:
determining whether a variance of mean values of energy or amplitude of the M subbands is within a preset threshold range;
when the variance of mean values of energy or amplitude of the M subbands is within the preset threshold range, using the mean value of the energy or amplitude of each subband as the adjusted value of the energy or amplitude of each subband; and
when the variance of mean values of energy or amplitude of the M subbands is not within the preset threshold range, adjusting a mean value of energy or amplitude of each subband in a subbands to determine an adjusted value of the energy or amplitude of each subband in the a subbands, and using a mean value of energy or amplitude of each subband in b subbands as an adjusted value of the energy or amplitude of each subband in the b subbands, wherein the mean value of the energy or amplitude of each subband in the a subbands is greater than or equal to a mean value threshold, the mean value of the energy or amplitude of each subband in the b subbands is less than the mean value threshold, a and b are positive integers, and a+b=M.

5. The method according to claim 3 , wherein, for an i th subband and an (i+1) th subband in the M subbands, determining the adjusted value of the energy or amplitude of each subband comprises:
determining whether a ratio between a mean value of energy or amplitude of the i th subband and a mean value of energy or amplitude of the (i+1) th subband is not within a preset threshold range;
determining whether the mean value of the energy or amplitude of the i th subband is greater than the mean value of the energy or amplitude of the (i+1) th subband;
when the ratio between a mean value of energy or amplitude of the i th subband and the mean value of energy or amplitude of the (i+1) th subband is not within a preset threshold range and when the mean value of the energy or amplitude of the i th subband is greater than the mean value of the energy or amplitude of the (i+1) th subband, adjusting the mean value of the energy or amplitude of the i th subband to determine an adjusted value of the energy or amplitude of the i th subband, and using the mean value of the energy or amplitude of the (i+1) th subband as an adjusted value of the energy or amplitude of the (i+1) th subband;
when the ratio between a mean value of energy or amplitude of the i th subband and the mean value of energy or amplitude of the (i+1) th subband is not within a preset threshold range and when the mean value of the energy or amplitude of the i th subband is less than the mean value of the energy or amplitude of the (i+1) th subband, adjusting the mean value of the energy or amplitude of the (i+1) th subband to determine an adjusted value of the energy or amplitude of the (i+1) th subband, and using the mean value of the energy or amplitude of the i th subband as an adjusted value of the energy or amplitude of the i th subband; and
when the ratio between the mean value of energy or amplitude of the i th subband and the mean value of energy or amplitude of the (i+1) th subband is within the preset threshold range, using the mean value of the energy or amplitude of the i th subband as an adjusted value of the energy or amplitude of the i th subband, and using the mean value of the energy or amplitude of the (i+1) th subband as an adjusted value of the (i+1) th subband, wherein i is a positive integer, and 1≦i≦M−1.

6. The method according to claim 3 , wherein predicting the spectral envelope of the extension band according to the first spectral envelope of the extension band and the mean value of the energy or amplitude of the second band comprises:
determining a second spectral envelope of an extension band of a current frame according to a first spectral envelope of the extension band of the current frame and a mean value of energy or amplitude of a second band of the current frame;
determining whether or not a preset condition is satisfied;
when the preset condition is satisfied, weighting the second spectral envelope of the extension band of the current frame and a spectral envelope of an extension band of a previous frame to determine a spectral envelope of the extension band of the current frame; and
when the preset condition is not satisfied, using the second spectral envelope of the extension band of the current frame as a spectral envelope of the extension band of the current frame.

7. The method according to claim 6 , wherein the preset condition is one of:
a coding mode of a voice signal or an audio signal of the current frame being different from a coding mode of a voice signal or an audio signal of the previous frame;
a decoded signal of the previous frame being non-fricative, and a ratio between a mean value of energy or amplitude of an m th band in a decoded signal of the

Assignees

• Huawei Tech Co Ltd

Inventors

• Liu Zexin
• Miao Lei

Classifications

• G10L19/08

  Determination or coding of the excitation function; Determination or coding of the long-term prediction parameters · CPC title

• G10L19/107

  Sparse pulse excitation, e.g. by using algebraic codebook · CPC title

• G10L19/002

  Dynamic bit allocation (for perceptual audio coders G10L19/032) · CPC title

• G10L19/24

  Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding · CPC title

• G10L21/038

  using band spreading techniques · CPC title