Speech post-processing using MDCT coefficients

• US 7,590,523 B2
• Filed: 03/20/2006
• Issued: 09/15/2009
• Est. Priority Date: 03/20/2006
• Status: Active Grant

• Current Assignee: Nytell Software LLC (Intellectual Ventures LLC)
• Original Assignee: Mindspeed Technologies Inc. (MACOM Technology Solutions Holdings, Inc.)
• Inventors: Gao, Yang
• Primary Examiner(s): Smits, Talivaldis Ivars
• Assistant Examiner(s): Borsetti, Greg A
• Application Number:
  US11/385,428
• Publication Number:
  US 20070219785A1
• Time in Patent Office: 1,275 Days
• Field of Search: 704/200, 704/203, 704/228, 704/E21.002, 704/200.1, 704/205, 708/400, 708/402
• US Class Current: 704/200.1
• CPC Class Codes: G10L 19/0212 using orthogonal transformation
• CPC Class Codes: G10L 19/26 Pre-filtering or post-filtering
• CPC Class Codes: G10L 25/27 characterised by the analysis technique

Abstract

There is provided a speech post-processor for enhancing a speech signal divided into a plurality of sub-bands in frequency domain. The speech post-processor comprises an envelope modification factor generator configured to use frequency domain coefficients representative of an envelope derived from the plurality of sub-bands to generate an envelope modification factor for the envelope derived from the plurality of sub-bands, where the envelope modification factor is generated using FAC=αENV/Max+(1−α), where FAC is the envelope modification factor, ENV is the envelope, Max is the maximum envelope, and α is a value between 0 and 1, where α is a different constant value for each speech coding rate. The speech post-processor further comprises an envelope modifier configured to modify the envelope derived from the plurality of sub-bands by the envelope modification factor corresponding to each of the plurality of sub-bands.

Claims

1. A speech post-processing method for use by a speech post-processor to generate a post-processed speech signal, the speech post-processing method comprising:

decoding an encoded speech signal to obtain frequency domain coefficients representative of a speech signal divided into a plurality of sub-bands;

generating an envelope modification factor using the frequency domain coefficients;

generating a fine structure modification factor using the frequency domain coefficients;

determining a gain based on the envelope modification factor and an envelope;

modifying the frequency domain coefficients as a result of multiplying the frequency domain coefficients by the gain, the envelope modification factor and the fine structure modification factor to provide post-processed frequency domain coefficients; and

generating the post-processed speech signal using the post-processed frequency domain coefficients;

wherein the determining the gain is based on;

2. A speech post-processing method for use by a speech post-processor to generate a post-processed speech signal, the speech post-processing method comprising:

decoding an encoded speech signal to obtain frequency domain coefficients representative of a speech signal divided into a plurality of sub-bands;

generating an envelope modification factor using the frequency domain coefficients;

generating a fine structure modification factor using the frequency domain coefficients;

determining a gain based on the envelope modification factor and an envelope;

modifying the frequency domain coefficients as a result of multiplying the frequency domain coefficients by the gain, the envelope modification factor and the fine structure modification factor to provide post-processed frequency domain coefficients; and

generating the post-processed speech signal using the post-processed frequency domain coefficients;

wherein the generating the envelope modification factor uses;

FAC1=α

ENV/Max+(1−

α

),

where FAC1 is the envelope modification factor, ENV is the envelope, Max is the maximum envelope, and α

is a value between 0 and 1.

3. The speech post-processing method of claim 2, wherein α

is a first constant value for a first speech coding rate (α

1), and α

is a second constant value for a second speech coding rate (α

2), where the second speech coding rate is higher than the first speech coding rate, and α

1>

α

2.

4. A speech post-processing method for use by a speech post-processor to generate a post-processed speech signal, the speech post-processing method comprising:

decoding an encoded speech signal to obtain frequency domain coefficients representative of a speech signal divided into a plurality of sub-bands;

generating an envelope modification factor using the frequency domain coefficients;

generating a fine structure modification factor using the frequency domain coefficients;

determining a gain based on the envelope modification factor and an envelope;

modifying the frequency domain coefficients as a result of multiplying the frequency domain coefficients by the gain, the envelope modification factor and the fine structure modification factor to provide post-processed frequency domain coefficients; and

generating the post-processed speech signal using the post-processed frequency domain coefficients;

wherein the generating the fine structure modification factor uses;

FAC2=β

MAG/Max+(1−

β

),

where FAC2 is the fine structure modification factor, MAG is a magnitude, Max is the maximum magnitude, and β

is a value between 0 and 1.

5. The speech post-processing method of claim 4, wherein β

is a first constant value for a first speech coding rate (β

1), and β

is a second constant value for a second speech coding rate (β

2), where the second speech coding rate is higher than the first speech coding rate, and β

1>

β

2.

6. A speech post-processor for generating a post-processed speech signal, the speech post-processor comprising:

software and circuitry for providing;

a decoder configured to decode an encoded speech signal to obtain frequency domain coefficients representative of a speech signal divided into a plurality of sub-bands;

an envelope modification factor generator configured to use the frequency domain coefficients for generating an envelope modification factor;

a fine structure modification factor generator configured to use the frequency domain coefficients for generating a fine structure modification factor;

wherein speech post-processor is configured to determine a gain based on the envelope modification factor and an envelope, and further configured to modify the frequency domain coefficients as a result of multiplying the frequency domain coefficients by the gain, the envelope modification factor and the fine structure modification factor to provide post-processed frequency domain coefficients, and further configured to generate the post-processed speech signal using the post-processed frequency domain coefficients;

wherein the speech post-processor determines the gain according to;

7. A speech post-processor for generating a post-processed speech signal, the speech post-processor comprising:

software and circuitry for providing;

a decoder configured to decode an encoded speech signal to obtain frequency domain coefficients representative of a speech signal divided into a plurality of sub-bands;

an envelope modification factor generator configured to use the frequency domain coefficients for generating an envelope modification factor;

a fine structure modification factor generator configured to use the frequency domain coefficients for generating a fine structure modification factor;

wherein speech post-processor is configured to determine a gain based on the envelope modification factor and an envelope, and further configured to modify the frequency domain coefficients as a result of multiplying the frequency domain coefficients by the gain, the envelope modification factor and the fine structure modification factor to provide post-processed frequency domain coefficients, and further configured to generate the post-processed speech signal using the post-processed frequency domain coefficients;

wherein the envelope modification factor generator generates the envelope modification factor using;

FAC1=α

ENV/Max+(1−

α

),

where FAC1 is the envelope modification factor, ENV is the envelope, Max is the maximum envelope, and α

is a value between 0 and 1.

8. The speech post-processor of claim 7, wherein α

is a first constant value for a first speech coding rate (α

1), and α

is a second constant value for a second speech coding rate (α

2), where the second speech coding rate is higher than the first speech coding rate, and α

1>

α

2.

9. A speech post-processor for generating a post-processed speech signal, the speech post-processor comprising:

software and circuitry for providing;

a decoder configured to decode an encoded speech signal to obtain frequency domain coefficients representative of a speech signal divided into a plurality of sub-bands;

an envelope modification factor generator configured to use the frequency domain coefficients for generating an envelope modification factor;

a fine structure modification factor generator configured to use the frequency domain coefficients for generating a fine structure modification factor;

wherein speech post-processor is configured to determine a gain based on the envelope modification factor and an envelope, and further configured to modify the frequency domain coefficients as a result of multiplying the frequency domain coefficients by the gain, the envelope modification factor and the fine structure modification factor to provide post-processed frequency domain coefficients, and further configured to generate the post-processed speech signal using the post-processed frequency domain coefficients;

wherein the fine structure modification factor generator generates the fine structure modification factor using;

FAC2=β

MAG/Max+(1−

β

),

where FAC2 is the fine structure modification factor, MAG is a magnitude, Max is the maximum magnitude, and β

is a value between 0 and 1.

10. The speech post-processor of claim 9, wherein β

is a first constant value for a first speech coding rate (β

1), and β

is a second constant value for a second speech coding rate (β

2), where the second speech coding rate is higher than the first speech coding rate, and β

1>

β

2.