APPARATUS AND METHOD FOR PROCESSING FREQUENCY SPECTRUM USING SOURCE FILTER

• US 20140244244A1
• Filed: 02/27/2014
• Published: 08/28/2014
• Est. Priority Date: 02/27/2013
• Status: Abandoned Application

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: SUNG, Jong Mo, BEACK, Seung Kwon, LEE, Tae Jin, KANG, Kyeong Ok
• Application Number:
  US14/191,929
• Publication Number:
  US 20140244244A1
• Time in Patent Office: Days
• US Class Current: 704/203
• CPC Class Codes: G10L 19/0212 using orthogonal transformation
• CPC Class Codes: G10L 19/04 using predictive techniques
• CPC Class Codes: G10L 19/12 the excitation function being a code excitation, e.g. in code excited linear prediction [CELP] vocoders

Abstract

A frequency spectrum processing apparatus and method using a source filter are disclosed. The frequency spectrum processing apparatus may include a first excitation spectrum generation unit to generate a first excitation spectrum using a tonal excitation spectrum according to an input signal and a gain of the tonal excitation spectrum, a second excitation spectrum generation unit to generate a second excitation spectrum using a non-tonal excitation spectrum according to the input signal and a gain of the non-tonal excitation spectrum, and an output spectrum generation unit to generate an output spectrum using the first excitation spectrum and the second excitation spectrum.

Claims

1. A frequency spectrum processing apparatus comprising:

a first excitation spectrum generation unit to generate a first excitation spectrum using a tonal excitation spectrum according to an input signal and a gain of the tonal excitation spectrum;

a second excitation spectrum generation unit to generate a second excitation spectrum using a non-tonal excitation spectrum according to the input signal and a gain of the non-tonal excitation spectrum; and

an output spectrum generation unit to generate an output spectrum using the first excitation spectrum and the second excitation spectrum.

2. The frequency spectrum processing apparatus of claim 1, wherein

the tonal excitation spectrum includes a periodic component of the input signal, and

the non-tonal excitation spectrum includes an aperiodic component of the input signal.

3. A frequency spectrum processing apparatus comprising:

a first spectrum transform unit to transform an input signal of a time domain into a first spectrum of a frequency domain;

a linear prediction (LP) unit to determine an LP coefficient by LP analyzing the first spectrum;

a tonal codebook search unit to search a tonal codebook that minimizes a difference between a second spectrum, the second spectrum which is LP synthesized by a tonal component including a periodic component of the input signal and the LP coefficient, and the first spectrum;

a non-tonal codebook search unit to search a non-tonal codebook that minimizes a difference between a third spectrum, the third spectrum which is LP synthesized by a non-tonal component including an aperiodic component of the input signal and the LP coefficient, and a fourth spectrum generated by removing a contribution of the tonal codebook from the first spectrum; and

a signal output unit to output an encoded signal using the LP coefficient, the tonal codebook, and the non-tonal codebook.

4. The frequency spectrum processing apparatus of claim 3, wherein the first spectrum transform unit comprises:

a gain output unit to output a quantized gain of a fifth spectrum generated using a high band spectrum formed by transforming a high band signal that includes an upper band of the input signal and a low band spectrum formed by transforming a low band signal that includes a lower band of the input signal; and

a normalization unit to output the first spectrum by normalizing the fifth spectrum by the quantized gain.

5. The frequency spectrum processing apparatus of claim 3, further comprising:

a filtering unit to output a sixth spectrum including residual information according to the LP coefficient by filtering the first spectrum by the LP coefficient.

6. The frequency spectrum processing apparatus of claim 5, wherein the tonal codebook search unit comprises:

a rearrangement unit to rearrange the sixth spectrum according to a track structure for searching for the tonal codebook;

an open-loop tonal codebook output unit to output an open-loop tonal codebook based on a size component with respect to the rearranged sixth spectrum; and

a closed-loop tonal codebook search unit to search for a closed-loop tonal codebook using the open-loop tonal codebook, the LP coefficient, and the first spectrum.

7. The frequency spectrum processing apparatus of claim 6, wherein the open-loop tonal codebook output unit comprises:

a pulse search unit to search for a pulse having a largest absolute value corresponding to the size component with respect to a coefficient of the sixth spectrum rearranged according to the track structure; and

a codebook output unit to generate and output the open-loop tonal codebook using found pulses.

8. The frequency spectrum processing apparatus of claim 6, wherein the closed-loop tonal codebook search unit comprises:

an optimal tonal codebook setting unit to set the open-loop tonal codebook as an optimal tonal codebook;

a minimum error setting unit to set an error value of the first spectrum and the second spectrum as a minimum error value;

a candidate tonal codebook generation unit to generate a candidate tonal codebook by substituting a pulse corresponding to a current track in the optimal tonal codebook with a pulse corresponding to a current position of a same track;

an error update unit to update the optimal tonal codebook using the candidate tonal codebook when the minimum error value is updated; and

a codebook output unit to output the updated optimal tonal codebook to the closed-loop tonal codebook.

9. The frequency spectrum processing apparatus of claim 6, further comprising:

a quantization unit to divide each pulse of tracks constituting the tonal codebook into components including a position, a code, and a size and quantize each of the components.

10. The frequency spectrum processing apparatus of claim 5, further comprising:

a low band encoding unit to output a low band signal bitstream by encoding a low band signal including a lower band of the input signal; and

a third spectrum transform unit to output a third spectrum by transforming a layer signal obtained by decoding the low band signal transform.

11. The frequency spectrum processing apparatus of claim 10, wherein the third spectrum transform unit comprises:

a decoding unit to output the quantized layer signal by decoding the low band signal bitstream;

a modified discrete cosine transform (MDCT) unit to MDCT and output the layer signal; and

a normalization unit to output the third spectrum by normalizing the layer signal.

12. The frequency spectrum processing apparatus of claim 3, wherein the non-tonal codebook search unit comprises:

a contribution to remove a contribution of the tonal codebook from the first spectrum and the sixth spectrum;

an open-loop delay search unit to search for an open-loop non-tonal codebook delay using the third spectrum and the contribution-removed sixth spectrum; and

a closed-loop delay and gain search unit to search for the closed-loop non-tonal codebook delay and a gain using the third spectrum and the contribution-removed first spectrum.

13. The frequency spectrum processing apparatus of claim 12, wherein the open-loop delay search unit comprises:

a spectrum division unit to divide the contribution-removed sixth spectrum according to a sub-band structure set for searching for the open-loop non-tonal codebook delay; and

a delay search unit to search for a delay having a largest normalized correlation between the third spectrum and the contribution-removed sixth spectrum in an open-loop search period corresponding to a current sub-band.

14. The frequency spectrum processing apparatus of claim 12, wherein the closed-loop delay and gain search unit comprises:

a spectrum division unit to divide the contribution-removed first spectrum, according to a sub-band structure set for searching for the closed-loop non-tonal codebook;

a search period determination unit to determine a closed-loop search period according to the open-loop non-tonal codebook delay;

an MDCT coefficient determination unit to set the third spectrum as an excitation signal in the closed-loop search period of the current sub-band, and determine an MDCT coefficient using the LP coefficient;

a delay search unit to search for a delay that minimizes an error between the MDCT coefficient and a quantized band coefficient in which the contribution of the tonal codebook is removed; and

a gain determination unit to determine a gain in the delay.

15. A frequency spectrum processing method comprising:

generating a first excitation spectrum using a tonal excitation spectrum according to an input signal and a gain of the tonal excitation spectrum;

generating a second excitation spectrum using a non-tonal excitation spectrum according to the input signal and a gain of the non-tonal excitation spectrum; and

generating an output spectrum using the first excitation spectrum and the second excitation spectrum.

16. A frequency spectrum processing method comprising:

transforming an input signal of a time domain into a first spectrum of a frequency domain;

determining a linear prediction (LP) coefficient by LP analyzing the first spectrum;

searching a tonal codebook that minimizes a difference between a second spectrum, the second spectrum which is LP synthesized by a tonal component including a periodic component of the input signal and the LP coefficient, and the first spectrum;

searching a non-tonal codebook that minimizes a difference between a third spectrum, the third spectrum which is LP synthesized by a non-tonal component including an aperiodic component of the input signal and the LP coefficient, and a fourth spectrum generated by removing a contribution of the tonal codebook from the first spectrum; and

a signal output unit to output an encoded signal using the LP coefficient, the tonal codebook, and the non-tonal codebook.

17. The frequency spectrum processing method of claim 16, wherein the searching of the tonal codebook comprises:

rearranging a sixth spectrum including residual information with respect to an LP coefficient according to a track structure for searching for the tonal codebook;

outputting an open-loop tonal codebook based on a size component with respect to the rearranged sixth spectrum; and

searching for a closed-loop tonal codebook using the open-loop tonal codebook, the LP coefficient, and the first spectrum.

18. The frequency spectrum processing method of claim 17, wherein the searching of the closed-loop tonal codebook comprises:

setting the open-loop tonal codebook as an optimal tonal codebook;

setting an error value of the first spectrum and the second spectrum as a minimum error value;

generating a candidate tonal codebook by substituting a pulse corresponding to a current track in the optimal tonal codebook with a pulse corresponding to a current position of a same track;

updating the minimum error value and the optimal tonal codebook by comparing a candidate error value of a seventh spectrum generated using the first spectrum and the candidate tonal codebook with the minimum error value; and

outputting the updated optimal tonal codebook to the closed-loop tonal codebook.

19. The frequency spectrum processing method of claim 16, further comprising:

outputting a low band signal bitstream by encoding a low band signal including a lower band of the input signal; and

outputting a third spectrum by transforming a layer signal obtained by decoding the low band signal transform.

20. The frequency spectrum processing method of claim 16, wherein the searching of the non-tonal codebook comprises:

removing a contribution of the first spectrum and the sixth spectrum;

searching for an open-loop non-tonal codebook delay using the third spectrum and the contribution-removed sixth spectrum; and

searching for the closed-loop non-tonal codebook delay and a gain using the third spectrum and the contribution-removed first spectrum.