Speech post-processing using MDCT coefficients
View Patent ↗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.
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:
g
1
=
∑
k
=
0
9
ENV
(
k
)
∑
k
=
0
9
FAC
1
(
k
)
*
ENV
(
k
)
where g1 is the gain, FAC1 is the envelope modification factor and ENV is the envelope.
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=αENV/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=βMAG/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:
g
1
=
∑
k
=
0
9
ENV
(
k
)
∑
k
=
0
9
FAC
1
(
k
)
*
ENV
(
k
)
where g1 is the gain, FAC1 is the envelope modification factor and ENV is the envelope.
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=αENV/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=βMAG/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 .