Frequency envelope vector quantization method and apparatus

• US 9,805,732 B2
• Filed: 12/29/2015
• Issued: 10/31/2017
• Est. Priority Date: 07/04/2013
• Status: Active Grant

• Current Assignee: Crystal Clear Codec, LLC
• Original Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Inventors: Hu, Chen, Miao, Lei, Liu, Zexin
• Primary Examiner(s): Roberts, Shaun
• Application Number:
  US14/981,923
• Publication Number:
  US 20160111105A1
• Time in Patent Office: 672 Days
• Field of Search: 704206
• CPC Class Codes: G10L 19/038 Vector quantisation, e.g. TwinVQ audio
• 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 2019/0005 Multi-stage vector quantisation
• CPC Class Codes: H03M 7/3082 Vector coding for television signals, see H04N19/94

Abstract

Embodiments of the present application proposes a frequency envelope vector quantization method and apparatus, where the method includes: dividing N frequency envelopes in one frame into N1 vectors; quantizing a first vector in the N1 vectors by using a first codebook, to obtain a code word corresponding to the quantized first vector, where the first codebook is divided into 2^B1 portions; determining, according to the code word corresponding to the quantized first vector; determining a second codebook according to the codebook of the i^th portion; and quantizing a second vector in the N1 vectors based on the second codebook. In the embodiments of the present application, vector quantization can be performed on frequency envelope vectors by using a codebook with a smaller quantity of bits. Therefore, complexity of vector quantization can be reduced, and an effect of vector quantization can also be ensured.

Claims

1. A method of quantizing frequency envelops of an audio signal, for use by an audio signal encoder, comprising:

obtaining N frequency envelopes of a frame of the audio signal, wherein N is a positive integer;

organizing the N frequency envelopes into N1 groups, wherein each group comprises M frequency envelopes, and wherein N1 and M are positive integers, M is greater than or equal to 2, and N is greater than N1;

quantizing a first group of frequency envelopes to obtain a first vector by using a first codebook wherein the first codebook has 2^B code words and each code word corresponds to a vector, wherein the first codebook is divided into 2^B1 portions, and wherein B is a positive integer greater than or equal to 2, and B1 is a positive integer greater than or equal to 1;

determining that a code word corresponding to the first vector is in the i^th portion of the first codebook, wherein i is a positive integer greater than or equal to 1 and less than or equal to 2^B1;

determining a second codebook according to the i^th portion of the first codebook; and

quantizing a second group of frequency envelopes by using the second codebook.

2. The method according to claim 1, wherein determining the second codebook according to the i^th portion of the first codebook comprises:

taking the i^th portion of the first codebook as the second codebook, wherein a quantity of code words in the i^th portion of the first codebook is 2^(B-B1).

3. The method according to claim 1, wherein determining the second codebook according to the i^th portion of the first codebook comprises:

taking a pre-trained codebook as the second codebook, wherein a quantity of code words in the pre-trained codebook and a quantity of code words in the i^th portion of the first codebook are the same, and are both 2^(B-B1).

4. The method according to claim 1, wherein when B1 is 1, the determining that a code word corresponding to the first vector is in the i^th portion of the first codebook comprises:

determining whether the code word corresponding to the first vector is in the first half of the first codebook or in the second half of the first codebook.

5. The method according to claim 1, wherein when M is 2 and B1 is 1, the determining that the code word corresponding to the first vector is in the i^th portion of the first codebook comprises:

determining whether a ratio of a first value of the first vector to a second value of the first vector is within a preset range;

wherein

when the ratio is within the preset range, the code word corresponding to the first vector is in the first half of the first codebook;

or

when the ratio is not within the preset range, the code word corresponding to the first vector is in the second half of the first codebook.

6. The method according to claim 1, wherein organizing the N frequency envelopes into N1 groups comprises:

when the frame of the audio signal comprises M subframes, and each subframe comprises N1 frequency envelopes of N1 different frequency ranges, combining a frequency envelope of a frequency range in each subframe into one group, to obtain N1 groups, wherein each group comprises M frequency envelopes.

7. An audio signal encoding apparatus, comprising a processor and a memory storing program codes, wherein the program codes, when executed by the processor, cause the apparatus to perform a process that comprises:

obtaining N frequency envelopes of a frame of an audio signal, wherein N is a positive integer;

organizing the N frequency envelopes into N1 groups, wherein each group comprises M frequency envelopes, and wherein N1 and M are positive integers, M is greater than or equal to 2, and N is greater than N1;

quantizing a first group of frequency envelops to obtain a first vector by using a first codebook, wherein the first codebook has 2^B code words and each code word corresponds to a vector, wherein the first codebook is divided into 2^B1 portions, and wherein B is a positive integer greater than or equal to 2, and B1 is a positive integer greater than or equal to 1;

determining, that a code word corresponding to the first vector is in the i^th portion of the first codebook, wherein i is a positive integer greater than or equal to 1 and less than or equal to 2^B1;

determining a second codebook according to the i^th portion; and

quantizing a second group of frequency envelopes by using the second codebook.

8. The apparatus according to claim 7, wherein determining the second codebook according to the i^th portion of the first codebook comprises:

taking the i^th portion of the first codebook as the second codebook, wherein a quantity of code words in the i^th portion of the first codebook is 2^(B-B1).

9. The apparatus according to claim 7, wherein determining the second codebook according to the i^th portion of the first codebook comprises:

taking a pre-trained codebook as the second codebook, wherein a quantity of code words in the pre-trained codebook and a quantity of code words in the i^th portion of the first codebook are the same, and are both 2^(B-B1).

10. The apparatus according to claim 7, wherein when B1 is 1, the determining that a code word corresponding to the first vector is in the i^th portion of the first codebook comprises:

determining whether the code word corresponding to the first vector is in the first half of the first codebook or in the second half of the first codebook.

11. The apparatus according to claim 7, wherein when M is 2 and B1 is 1, the determining that the code word corresponding to the first vector is in the i^th portion of the first codebook comprises:

determining whether a ratio of a first value of the first vector to a second value of the first vector is within a preset range;

wherein

when the ratio is within the preset range, the code word corresponding to the first vector is in the first half of the first codebook;

or

when the ratio is not within the preset range, the code word corresponding to the first vector is in the second half of the first codebook.

12. The apparatus according to claim 7, wherein organizing the N frequency envelopes into N1 groups comprises:

when the frame of the audio signal comprises M subframes, and each subframe comprises N1 frequency envelopes of N1 different frequency ranges, combining a frequency envelope of a frequency range in to each subframe into one group, to obtain N1 groups, wherein each group comprises M frequency envelopes.