Scalable speech coding/decoding apparatus, method, and medium having mixed structure

• US 20070033023A1
• Filed: 07/21/2006
• Published: 02/08/2007
• Est. Priority Date: 07/22/2005
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Taori, Rakesh, Lee, Kangeun, Sung, Hosang, Kim, Sangwook
• Granted Patent: US 8,271,267 B2
• Time in Patent Office: Days
• US Class Current: 704/229
• CPC Class Codes: G10L 19/0212 using orthogonal transformation
• CPC Class Codes: G10L 19/24 Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding
• CPC Class Codes: G10L 25/18 the extracted parameters being spectral information of each sub-band

Abstract

Provided are a scalable wide-band speech coding/decoding apparatus, method, and medium. An input wide-band speech input signal is first divided into a low-band signal and a high-band signal. The divided low-band signal is then coded using a code excited linear prediction (CELP) method. The divided high-band signal is coded using a harmonic method. A signal representing a difference between a synthetic signal obtained from the low-band and the high band, and a signal input to the low-band and the high-band is then coded using a modified discrete cosine transform (MDCT) method. The coded signal is then multiplexed. The multiplexed signal is then output. Accordingly, high quality speech can be achieved for all layers.

Claims

1. A scalable speech coding apparatus having a mixed structure, the apparatus comprising:

a band divider dividing a speech input signal into a low-band signal and a high-band signal according to a specific frequency, and outputting the low-band signal and the high-band signal;

a low-band coder outputting a low-band first index by coding the low-band signal, transmitting information required for coding the high-band signal to a high-band coder, and transmitting an uncoded first error signal to a wide-band coder;

a high-band coder outputting a high-band second index obtained when the high-band signal is coded by using information received from the low-band coder, and transmitting an uncoded second error signal to the wide-band coder;

a wide-band coder quantizing coefficients of the first and second error signals using a modified discrete cosine transform (MDCT) method through time-frequency mapping, and outputting a wide-band third index; and

a bit-stream generator outputting a scalable bit-stream composed of the low-band first index received from the low-band coder, the high-band second index received from the high-band coder, and the wide-band third index received from the wide-band coder.

2. The apparatus of claim 1, wherein the bit-stream is combined with narrow-band information composed of one or more layers obtained by using the low-band first index, and wide-band information composed of one or more layers obtained by using the high-band second index and the low-band third index.

3. The apparatus of claim 1, wherein:

the first error signal is an expression error signal which represents a difference between a low-band signal input to the low-band coder and a first synthetic signal synthesized using an excited signal generated from the low-band coder; and

the second error signal is an expression error signal which represents a difference between a high-band signal input to the high-band coder and a second synthetic signal synthesized using an excited signal generated by the high-band coder using harmonic synthesis.

4. The apparatus of claim 1, wherein the low-band coder generates the low-band first index which is obtained by multiplexing a low-band signal input to the low-band coder using a code excited linear prediction (CELP) method.

5. The apparatus of claim 1, wherein the low-band coder has a CELP structure in which a high-band signal received using the CELP method is filtered, and an excited signal of the filtered high-band signal is generated by searching for a fixed codebook and an adaptive codebook.

6. The apparatus of claim 1, wherein:

the information required for coding the high-band signal comprises information on low-band pitch delay and information on a low-band excited signal energy; and

the high-band coder uses a harmonic coding method so as to generate the high-band second index obtained by multiplexing a first parameter obtained by quantizing a linear prediction coding coefficient, a second parameter which determines a harmonic component to be coded by using the information on pitch delay received from the low-band coder and which is obtained by quantizing a harmonic phase based on the determined result, and a third parameter obtained by quantizing a high-band effective power by using the information on low-band excited signal energy received from the low-band coder.

7. A scalable speech coding method having a mixed structure, the method comprising:

(a) dividing a speech input signal into a low-band signal and a high-band signal according to a specific frequency, and outputting the low-band signal and the high-band signal;

(b) generating and outputting a low-band first index by coding the output low-band signal, and outputting specific information required for coding the high-band signal and an uncoded first error signal;

(c) coding the output high-band signal by using the specific information, and outputting a high-band second index and an uncoded second error signal;

(d) quantizing coefficients of the first and second error signals using a modified discrete cosine transform (MDCT) through time-frequency mapping, and outputting a low-band third index; and

(e) outputting a scalable bit-stream composed of the low-band first index, the high-band second index, and the wide-band third index.

8. The method of claim 7, wherein the bit-stream is combined with narrow-band information composed of one or more layers obtained by using the low-band first index, and wide-band information composed of one or more layers obtained by using the high-band second index and the low-band third index.

9. The method of claim 7, wherein:

the first error signal is an expression error signal which represents a difference between a low-band signal input to the low-band coder generating the first index, and a first synthetic signal synthesized by using an excited signal generated from the low-band coder; and

the second error signal is an expression error signal which represents a difference between a high-band signal input to the high-band coder generating the second index, and a second synthetic signal synthesized by using an excited signal generated by the high-band coder using harmonic synthesis.

10. The method of claim 7, wherein, in (b), the first index is generated by multiplexing a low-band signal input to the low-band coder using a code excited linear prediction (CELP) method.

11. The method of claim 7, wherein:

the specific information comprises information on low-band pitch delay and information on a low-band excited signal energy; and

the low-band coder uses a harmonic coding method so as to generate the high-band second index obtained by multiplexing a first parameter obtained by quantizing a linear prediction coding coefficient, a second parameter obtained by quantizing a harmonic phase based on the determined result, and a third parameter obtained by quantizing a high-band effective power using the information on low-band excited signal energy received from the low-band coder.

12. A computer-readable medium comprising computer readable instructions implementing the method of claim 7.

25. A computer readable medium comprising computer readable instructions implementing the method of claim 8.

26. A computer readable medium comprising computer readable instructions implementing the method of claim 9.

27. A computer readable medium comprising computer readable instructions implementing the method of claim 10.

28. A computer readable medium comprising computer readable instructions implementing the method of claim 11.

13. A scalable speech decoding apparatus having a mixed structure, the apparatus comprising:

a bit-stream divider receiving a scalable bit-stream transmitted at a specific transmission rate according to a network condition, and transmitting the scalable bit-stream to each decoder of a corresponding frequency band by dividing the scalable bit-stream according to a frequency band used in reproduction;

a low-band decoder receiving a low-band signal into which the scalable bitstream is divided by the bit-stream divider, decoding and outputting the received low-band signal, and transmitting specific information required for decoding a high-band signal among coefficients decoded in a low-band;

a high-band decoder decoding and outputting a high-band signal into which the scalable bit-stream is divided by the bitstream divider, using the specific information;

a wide-band decoder decoding a wide-band signal into which the scalable bitstream is divided by the bit-stream divider, and dividing and outputting the decoded wide-band signal into a low-band signal and a high-band signal according to a specific frequency; and

a band combiner outputting a wide-band synthetic signal of a combined band by receiving a first synthetic signal, which is generated when a signal output from the low-band decoder is combined with the low-band signal output from the wide-band decoder, and a second synthetic signal which is generated when a signal output from the high-band decoder is combined with the high-band signal output from the wide-band decoder.

14. The apparatus of claim 13, wherein the wide-band synthetic signal comprises a low-band output having one or more layers of low-band signal, and a wide-band output having one or more layers of high-band signal and wide-band signal.

15. The apparatus of claim 13, wherein the low-band decoder decodes an input bit-stream using a code excited linear prediction (CELP) method.

16. The apparatus of claim 13, wherein:

the specific information comprises a low-band pitch signal; and

the high-band decoder obtains a harmonic position by using the low-band pitch signal, and decodes the received bit-stream by using harmonic information associated with the obtained harmonic position.

17. A scalable speech decoding method having a mixed structure, the method comprising:

(a) receiving a scalable bit-stream transmitted at a specific transmission rate according to a network condition, and dividing and outputting the scalable bit-stream into a low-band signal, a high-band signal, and a wide-band signal according to a frequency band used for reproduction;

(b) receiving the low-band signal of the scalable bitstream, decoding and outputting the received low-band signal, and outputting information on a pitch signal among coefficients decoded in a low-band;

(c) receiving the high-band signal of the scalable bitstream and the pitch signal information, and decoding and outputting the high-band signal by using the pitch signal information;

(d) receiving and decoding the wide-band signal of the scalable bitstream, and dividing and outputting the decoded wide-band signal into a low-band signal and a high-band signal according to a specific frequency; and

(e) outputting a wide-band synthetic signal of a combined band by receiving a first synthetic signal, which is generated when a signal output in (b) is combined with a low-band signal output in (d), and a second synthetic signal which is generated when a signal output in (c) is combined with a high-band signal output in (d).

18. The method of claim 17, wherein the wide-band synthetic signal comprises a low-band output having one or more layers of low-band signal, and a wide-band output having one or more layers of high-band signal and wide-band signal.

19. The method of claim 17, wherein, in (b), an input bit-stream is decoded by using a code excited linear prediction (CELP) method.

20. The method of claim 17, wherein, in (c), a harmonic position is obtained by using the low-band pitch signal, and the received bit-stream is decoded by using harmonic information associated with the obtained harmonic position.

21. A computer-readable medium comprising computer readable instructions implementing the method of claim 17.

22. A computer readable medium comprising computer readable instructions implementing the method of claim 18.

23. A computer readable medium comprising computer readable instructions implementing the method of claim 19.

24. A computer readable medium comprising computer readable instructions implementing the method of claim 20.

29. A scalable speech coding apparatus having a mixed structure, the apparatus comprising:

a band divider dividing a speech input signal into a low-band signal and a high-band signal according to a specific frequency, and outputting the low-band signal and the high-band signal;

a low-band coder outputting a low-band first index by coding a low-band signal, outputting information required for coding a high-band signal, and transmitting an uncoded first error signal to a wide-band coder;

a high-band coder outputting a high-band second index obtained when the high-band signal is coded by using outputted information received from the low-band coder, and transmitting an uncoded second error signal to the wide-band coder;

a wide-band coder quantizing coefficients of the first and second error signals using a modified discrete cosine transform (MDCT) method through time-frequency mapping, and outputting a wide-band third index; and

a bit-stream generator outputting a scalable bit-stream composed of the low-band first index received from the low-band coder, the high-band second index received from the high-band coder, and the wide-band third index received from the wide-band coder.

30. A computer readable medium comprising computer readable instructions implementing the method of claim 29.

31. A scalable speech decoding method having a mixed structure for decoding a scalable bit-stream, the method comprising:

(a) receiving a low-band signal of the scalable bitstream, decoding and outputting the received low-band signal, and outputting information on a pitch signal among coefficients decoded in a low-band;

(b) receiving a high-band signal of the scalable bitstream and the pitch signal information, and decoding and outputting the high-band signal by using the pitch signal information;

(c) receiving and decoding a wide-band signal of the scalable bitstream, and dividing and outputting the decoded wide-band signal into a low-band signal and a high-band signal according to a specific frequency; and

(d) outputting a wide-band synthetic signal of a combined band by receiving a first synthetic signal, which is generated when a signal output in (a) is combined with a low-band signal output in (c), and a second synthetic signal which is generated when a signal output in (b) is combined with a high-band signal output in (c).

32. A computer readable medium comprising computer readable instructions implementing the method of claim 31.