Method, apparatus and system for encoding and decoding broadband voice signal

• US 8,271,270 B2
• Filed: 08/14/2007
• Issued: 09/18/2012
• Est. Priority Date: 11/28/2006
• Status: Expired due to Fees

• Current Assignee: Chungbuk National University Industry Academic Cooperation Foundation (Chungbuk National University), Samsung Electronics Co. Ltd.
• Original Assignee: Chungbuk National University Industry Academic Cooperation Foundation (Chungbuk National University), Samsung Electronics Co. Ltd.
• Inventors: Kim, Jong-hark, Jeong, Gyu-hyeok, Seo, Sang-won, Lee, In-sung
• Primary Examiner(s): Yen, Eric
• Application Number:
  US11/838,268
• Publication Number:
  US 20080126084A1
• Time in Patent Office: 1,862 Days
• Field of Search: 704/203, 704/219, 704/500
• US Class Current: 704/203
• CPC Class Codes: G10L 19/09 Long term prediction, i.e. removing periodical redundancies, e.g. by using adaptive codebook or pitch predictor

Abstract

A method, apparatus, and system for encoding or decoding a broadband voice signal are provided. The method includes extracting a linear prediction coefficient (LPC) from the broadband voice signal; outputting a linear prediction (LP) residual signal; pitch-searching a spectrum of the LP residual signal; extracting spectral magnitudes and phases of the LP residual signal, which correspond to a damping factor; obtaining, from among the extracted spectral magnitudes and phases, a first spectral magnitude and a first phase at which a power value of the LP residual signal is minimized; quantizing the first spectral magnitude and the first phase; and decoding the broadband voice signal. The apparatus includes a linear prediction coefficient (LPC) analyzer; an LPC inverse filter; a pitch searching unit; a sinusoidal analyzer; and a phase and spectral magnitude quantizer. The system includes a broadband voice encoding apparatus and a broadband voice decoding apparatus.

Claims

1. A method performed on a coding apparatus, the method comprising:

extracting a linear prediction coefficient (LPC) from a broadband voice signal;

removing, using a processor of the coding apparatus, an envelope from the broadband voice signal using the LPC to obtain a linear prediction (LP) residual signal;

pitch-searching a spectrum of the LP residual signal;

extracting a plurality of spectral magnitudes and phases of the LP residual signal, which correspond to a damping factor, by adding the damping factor to a matching pursuit algorithm;

obtaining, from among the extracted plurality of spectral magnitudes and phases, a first spectral magnitude and a first phase at which a power value of the LP residual signal is minimized; and

quantizing the first spectral magnitude and the first phase,

wherein the damping factor is determined according to a ratio of a parameter of a current frame to a parameter of a previous frame, and

wherein the extracting the plurality of spectral magnitudes and phases of the LP residual signal comprises;

setting a plurality of candidate frequencies derived from the frequencies obtained by pitch-searching the LP residual signal using the frequency damping factor;

calculating a sinusoidal dictionary value by obtaining, from among the plurality of candidate frequencies, a frequency and a phase at which an error value is minimized, with respect to each frequency obtained by pitch-searching, and accumulating the sinusoidal dictionary value calculated with respect to each frequency obtained by pitch-searching;

generating a final residual signal by subtracting the accumulated sinusoidal dictionary value from a target signal, which is the LP residual signal; and

detecting a frequency damping factor which corresponds to the first spectral magnitude and the first phase at which a power value of the final residual signal is minimized with respect to each frequency obtained by pitch-searching.

2. The method of claim 1, further comprising decoding the broadband voice signal.

3. The method of claim 1, wherein the setting of the plurality of candidate frequencies comprises setting the plurality of candidate frequencies between a frequency corresponding to (n−

1) times a fundamental frequency and a frequency corresponding to (n+1) times the fundamental frequency using the frequency damping factor with respect to a frequency corresponding to n times the fundamental frequency in the LP residual signal.

4. The method of claim 3, wherein a number of the accumulated sinusoidal dictionaries is equal to a number of spectra of the broadband voice signal.

5. The method of claim 1, wherein the spectral magnitude damping factor is obtained and quantized using the first spectral magnitude and the first phase.

6. The method of claim 5, wherein the first spectral magnitude is quantized using Discrete Cosine Transformation (DCT).

7. The method of claim 6, wherein quantizing the first phase comprises:

obtaining a first plurality of distances by obtaining a first plurality of differences between the first phase and first codebook phases generated from the first phase, multiplying the first plurality of differences by an envelope value corresponding to the first phase to generate a plurality of multiplication results, and adding each of the first plurality of differences to a respective one of the first plurality of multiplication results;

detecting and outputting a first codebook phase allowing a distance among the first plurality of distances to be minimized;

generating a second phase by adjusting a phase error vector generated from a difference between the first codebook phase and the first phase, and obtaining a second plurality of distances by obtaining a second plurality of differences between the second phase and second codebook phases generated from the second phase, multiplying the second plurality of differences by an envelope value corresponding to the second phase to generate a second plurality of multiplication results, and adding each of the second plurality of differences to a respective one of the second plurality of multiplication results; and

detecting and outputting a second codebook phase allowing a distance among the second plurality of distances to be minimized.

8. The method of claim 7, wherein the damping factor, the spectral magnitude, the phase, and a pitch are quantized by determining bit assignment based on mode information according to various transmission rates.

9. The method of claim 5, wherein the decoding of the broadband voice signal comprises:

decoding the quantized first spectral magnitude and the quantized first phase;

decoding the quantized damping factor;

synthesizing the LP residual signal using at least one of the first spectral magnitude, the first phase, the damping factor, and a pitch value; and

decoding the broadband voice signal from the LP residual signal.

10. The method according to claim 1, wherein the damping factor comprises a spectral magnitude damping factor which comprises a ratio of a spectral magnitude parameter of a current frame to a spectral magnitude parameter of a previous frame, and a frequency damping factor which comprises a ratio of a frequency parameter of a current frame to a frequency parameter of a previous frame.

11. The method of claim 1, wherein the step of pitch-searching comprising;

integer pitch-searching a spectrum of the LP residual signal; and

fractional pitch-searching a spectrum of the LP residual signal.

12. The method of claim 1, wherein the pitch-searching uses an open-loop pitch search.

13. An encoder for encoding a broadband voice signal in a broadband voice encoding system, the encoder including at least one central processing unit (CPU), the encoder comprising:

a linear prediction coefficient (LPC) analyzer which extracts, using the at least one CPU, an LPC from the broadband voice signal;

an LPC inverse filter which outputs a linear prediction (LP) residual signal obtained by removing an envelope from the broadband voice signal using the LPC;

a pitch searching unit which pitch-searches a spectrum of the LP residual signal;

a sinusoidal analyzer which extracts a plurality of spectral magnitudes and phases of the LP residual signal, which correspond to a damping factor, by adding the damping factor to a matching pursuit algorithm, and obtains a first spectral magnitude and a first phase, at which a power value of the LP residual signal is minimized, from among the extracted plurality of spectral magnitudes and phases; and

a phase and spectral magnitude quantizer which quantizes the first spectral magnitude and the first phase,

wherein the damping factor is determined according to a ratio of a parameter of a current frame to a parameter of a previous frame, and

wherein the sinusoidal analyzer comprises;

a frequency damping factor application unit which sets a plurality of candidate frequencies derived from the frequencies obtained by pitch-searching the LP residual signal using the frequency damping factor;

an error minimization unit which obtains a frequency and a phase, at which an error value is minimized, from among the plurality of candidate frequencies with respect to each frequency obtained by pitch-searching;

a dictionary component generator which obtains a sinusoidal dictionary value based on the frequency and the phase output from the error minimization unit;

an accumulator which receives the sinusoidal dictionary value generated with respect to each frequency obtained by pitch-searching the dictionary component generator and accumulates the sinusoidal dictionary value;

a calculator which generates a final residual signal by subtracting the accumulated sinusoidal dictionary value from the LP residual signal; and

a damping factor selector which detects a frequency damping factor which corresponds to the first spectral magnitude and the first phase at which a power value of the final residual signal is minimized with respect to each frequency obtained by pitch-searching.

14. The encoder of claim 13, wherein the frequency damping factor application unit sets the plurality of candidate frequencies between a frequency corresponding to (n−

1) times a fundamental frequency and a frequency corresponding to (n+1) times the fundamental frequency using the frequency damping factor with respect to a frequency corresponding to n times the fundamental frequency in the LP residual signal.

15. The encoder of claim 14, wherein a number of the accumulated sinusoidal dictionaries is equal to a number of spectra of the broadband voice signal.

16. The encoder of claim 13, further comprising a damping factor synthesizer which obtains the spectral magnitude damping factor using the first spectral magnitude and the first phase.

17. The encoder of claim 16, wherein the phase and spectral magnitude quantizer quantizes the first spectral magnitude using a Discrete Cosine Transformation (DCT).

18. The encoder of claim 17, wherein the phase and spectral magnitude quantizer comprises:

a distance calculation block which obtains a distance by obtaining a plurality of differences between the first phase and a plurality of first codebook phases generated from the first phase, multiplying the plurality of differences by an envelope value corresponding to the first phase to generate a plurality of multiplication results, and adding each of the plurality of differences to a respective one of the plurality of multiplication results;

a minimization block which detects a first codebook phase allowing the distance to be minimized and outputs a second phase by applying a weight function to a phase error vector generated from a difference between the first codebook phase and the first phase that corresponds to the minimized distance; and

a weight function block which outputs the weight function of the spectral magnitude and a pitch to the minimization block.

19. The encoder of claim 18, wherein a plurality of phase and spectral magnitude quantizers coupled together in parallel quantize the first phase.

20. The encoder of claim 18, wherein the apparatus quantizes the damping factor, the spectral magnitude, the phase, and a pitch by determining a bit assignment based on mode information according to various transmission rates.

21. The encoder according to claim 13, wherein the damping factor comprises a spectral magnitude damping factor which comprises a ratio of a spectral magnitude parameter of a current frame to a spectral magnitude parameter of a previous frame, and a frequency damping factor which comprises a ratio of a frequency parameter of a current frame to a frequency parameter of a previous frame.

22. A broadband voice encoding and decoding system comprising:

a broadband voice encoder which includes at least one central processing unit (CPU) and obtains a linear prediction (LP) residual signal by removing an envelope from a broadband voice signal using a linear prediction coefficient (LPC) extracted from the broadband voice signal, extracts a plurality of spectral magnitudes and phases of the LP residual signal, which correspond to a damping factor, by adding the damping factor to a matching pursuit algorithm, obtains a first spectral magnitude and a first phase, at which a power value of the LP residual signal is minimized, from among the extracted plurality of spectral magnitudes and phases, and quantizes the first spectral magnitude and the first phase, wherein the damping factor is determined according to a ratio of a parameter of a current frame to a parameter of a previous frame; and

a broadband voice decoder which decodes the broadband voice signal by decoding the quantized first spectral magnitude, the quantized first phase, and the quantized damping factor and synthesizing the LP residual signal, and

wherein the extracting the plurality of spectral magnitudes and phases of the LP residual signal of the broadband voice encoder comprises;

setting a plurality of candidate frequencies derived from the frequencies obtained by pitch-searching the LP residual signal using the frequency damping factor;

calculating a sinusoidal dictionary value by obtaining, from among the plurality of candidate frequencies, a frequency and a phase at which an error value is minimized, with respect to each frequency obtained by pitch-searching, and accumulating the sinusoidal dictionary value calculated with respect to each frequency obtained by pitch-searching;

generating a final residual signal by subtracting the accumulated sinusoidal dictionary value from a target signal, which is the LP residual signal; and

detecting a frequency damping factor which corresponds to the first spectral magnitude and the first phase at which a power value of the final residual signal is minimized with respect to each frequency obtained by pitch-searching.

23. A non-transitory computer readable storage medium storing a computer readable program for executing a method comprising:

extracting a linear prediction coefficient (LPC) from the broadband voice signal;

removing an envelope from the broadband voice signal using the LPC to obtain a linear prediction (LP) residual signal;

pitch-searching a spectrum of the LP residual signal;

extracting a plurality of spectral magnitudes and phases of the LP residual signal, which correspond to a damping factor, by adding the damping factor to a matching pursuit algorithm;

obtaining, from among the extracted plurality of spectral magnitudes and phases, a first spectral magnitude and a first phase at which a power value of the LP residual signal is minimized; and

quantizing the first spectral magnitude and the first phase,

wherein the damping factor is determined according to a ratio of a parameter of a current frame to a parameter of a previous frame, and

wherein the extracting the plurality of spectral magnitudes and phases of the LP residual signal comprises;

setting a plurality of candidate frequencies derived from the frequencies obtained by pitch-searching the LP residual signal using the frequency damping factor;

calculating a sinusoidal dictionary value by obtaining, from among the plurality of candidate frequencies, a frequency and a phase at which an error value is minimized, with respect to each frequency obtained by pitch-searching, and accumulating the sinusoidal dictionary value calculated with respect to each frequency obtained by pitch-searching;

generating a final residual signal by subtracting the accumulated sinusoidal dictionary value from a target signal, which is the LP residual signal; and

detecting a frequency damping factor which corresponds to the first spectral magnitude and the first phase at which a power value of the final residual signal is minimized with respect to each frequency obtained by pitch-searching.

24. The non-transitory computer readable recording medium according to claim 23, wherein the method further comprises decoding the broadband voice signal.