APPARATUS AND METHOD FOR CODING AND DECODING RESIDUAL SIGNAL

• US 20090210219A1
• Filed: 04/08/2009
• Published: 08/20/2009
• Est. Priority Date: 05/30/2005
• Status: Abandoned Application

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: KIM, Do-Young, KIM, Hyun-Woo, SUNG, Jong-Mo, LEE, Mi-Suk
• Application Number:
  US12/420,215
• Publication Number:
  US 20090210219A1
• Time in Patent Office: Days
• US Class Current: 704/203
• CPC Class Codes: G10L 19/0212 using orthogonal transformation
• CPC Class Codes: G10L 19/035 Scalar quantisation
• CPC Class Codes: G10L 19/06 Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
• 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 21/038 using band spreading techniques

Abstract

Provided is a residual signal coding/decoding apparatus and method. The residual signal coding apparatus includes a transformer, a band splitter, a pulse searcher, and a pulse quantizer. The transformer transforms time-domain residual signals into a frequency domain to output transform coefficients. The band splitter splits the transform coefficients into bands to output the transform coefficients. The pulse searcher searches the transform coefficients for the respective bands to select optimal pulses and output parameters of the optimal pulses. The pulse quantizer quantizes the parameters of the optimal pulses.

Claims

1. A residual signal coding apparatus, comprising:

a transformer for transforming time-domain residual signals into a frequency domain to output transform coefficients;

a band splitter for splitting the transform coefficients into a predetermined number of bands to output the transform coefficients on a per-band basis;

a pulse searcher for searching the transform coefficients for the respective bands to select an optimal pulse and output parameters of the optimal pulse; and

a pulse quantizer for quantizing the parameters of the optimal pulse.

2. The residual signal coding apparatus as recited in claim 1, wherein the transformer outputs the transform coefficients by performing Modified Discrete Cosine Transform (MDCT) on the time-domain residual signals.

3. The residual signal coding apparatus as recited in claim 1, wherein the transformer outputs MDCT coefficients by performing the MDCT on the time-domain residual signals based on an equation expressed as:

$X<br><br>\left(k\right)=\underset{n=0}{\overset{N-1}{\sum <br><br>}}<br><br><br><br>x<br><br>\left(n\right)<br><br>h<br><br>\left(n\right)<br><br>\cos <br><br>\left\{\frac{2<br><br><br><br>\mathrm{\pi <br><br>}}{N}<br><br>\left(k+\frac{1}{2}\right)<br><br>\left(n+\frac{N}{4}+\frac{1}{2}\right)\right\}$ $k=0,1,\mathrm{\dots <br><br>}<br><br>,\frac{N}{2}-1,n=0,1,\mathrm{\dots <br><br>}<br><br>,N-1$

where X(k) represents the MDCT coefficients;

x(n) represents the time-domain residual signals;

h(n) represents a window function;

n represents time-domain sample indices;

k represents MDCT-domain frequency indices; and

N represents the size of an MDCT block.

4. The residual signal coding apparatus as recited in claim 1, wherein the pulse searcher divides the transform coefficients for the respective bands into a predetermined number of tracks and searches the transform coefficients on a per-track basis to select a predetermined number of optimal pulses.

5. The residual signal coding apparatus as recited in claim 4, wherein the pulse searcher performs:

a first step of selecting one from a predetermined number of the tracks;

a second step of obtaining magnitude information on all pulses of the selected track;

a third step of selecting the optimal pulses in a descending order of the magnitudes of the obtained magnitude information according to the number of pulses to be searched from the selected track; and

a fourth step of repeating the first to third steps with respect to the remaining tracks.

6. The residual signal coding apparatus as recited in claim 4, wherein the pulse searcher performs:

a first step of initializing a predetermined minimum error value;

a second step of selecting one of per-track pulse combinations depending on the number of pulses to be searched in each track;

a third step of generating per-band pulse combinations by setting a pulse value to a given value only at the selected per-band pulse combination but to 0 at the remaining positions;

a fourth step of outputting per-band transform coefficients that is based on the per-band pulse combinations;

a fifth step of calculating an error value that is a difference between the per-band transform coefficients outputted in the fourth step and the original transform coefficients outputted from the transformer;

a sixth step of selecting the pulse in the per-track pulse combinations constituting the per-band pulse combination as the optimal pulse, when the calculated error value is smaller than the minimum error value stored in the first step; and

a seventh step of repeating the second to sixth steps with respect to the remaining per-track pulse combinations.

7. The residual signal coding apparatus as recited in claim 5, wherein the number of pulses to be searched from each track is 1.

8. The residual signal coding apparatus as recited in claim 1, wherein the pulse quantizer comprises:

a magnitude quantizer for quantizing pulse magnitude information out of the parameters of the optimal pulse with a predetermined number of bits using a predetermined codebook;

a sign quantizer for quantizing pulse sign information out of the parameters of the optimal pulse with a predetermined number of bits using a track structure of the pulse searcher; and

a position quantizer for quantizing pulse position information out of the parameters of the optimal pulse with predetermined number of bits using the track structure of the pulse searcher.

9. A residual signal coding method, comprising the steps of:

a) transforming time-domain residual signals into a frequency domain to output transform coefficients;

b) splitting the transform coefficients into a predetermined number of bands to output the transform coefficients on a per-band basis;

c) searching the transform coefficients for the respective bands to select an optimal pulse and output parameters of the optimal pulse; and

d) quantizing the parameters of the optimal pulse.

10. The residual signal coding method as recited in claim 9, wherein the transform coefficients are outputted in the step a) by performing Modified Discrete Cosine Transform (MDCT) on the time-domain residual signals.

11. The residual signal coding method as recited in claim 10, wherein MDCT coefficients are outputted in the step a) by performing the MDCT on the time-domain residual signals according to the following equation

$X$

( k ) = ∑

n = 0 N - 1 



x 

( n ) 

h 

( n ) 

cos 

{ 2 



π

N 

( k + 1 2 ) 

( n + N 4 + 1 2 ) } $k=0,1,\mathrm{\dots <br><br>}<br><br>,\frac{N}{2}-1,n=0,1,\mathrm{\dots <br><br>}<br><br>,N-1$

where X(k) represents the MDCT coefficients;

x(n) represents the time-domain residual signals;

h(n) represents a window function;

n represents time-domain sample indices;

k represents MDCT-domain frequency indices; and

N represents the size of an MDCT block.

12. The residual signal coding method as recited in claim 9, wherein the transform coefficients for the respective bands are split into a predetermined number of tracks and the transform coefficients of each track are searched to select a predetermined number of optimal pulses in the step c).

13. The residual signal coding method as recited in claim 12, wherein the step c) includes the steps of:

c1) selecting one from a predetermined number of the tracks;

c2) obtaining magnitude information on all pulses of the selected track;

c3) selecting the optimal pulses in descending order of the magnitudes of the obtained magnitude information according to the number of pulses to be searched from the selected track; and

c4) repeating the first to third steps with respect to the remaining tracks.

14. The residual signal coding method as recited in claim 12, wherein the step c) includes the steps of:

c5) initializing a predetermined minimum error value;

c6) selecting one of per-track pulse combinations depending on the number of pulses to be searched in each track;

c7) generating per-band pulse combinations by setting a pulse value to a given value only at the selected per-band pulse combination but to 0 at the remaining positions;

c8) outputting per-band transform coefficients that are based on the per-band pulse combinations;

c9) calculating an error value that is a difference between the per-band transform coefficients outputted in the fourth step and the original transform coefficients outputted from the transformer;

c10) selecting the pulse in the per-track pulse p combinations constituting the per-band pulse combination as the optimal pulse, when the calculated error value is smaller than the minimum error value stored in the first step; and

c11) repeating the second to sixth steps with respect to the remaining per-track pulse combinations.

15. The residual signal coding method as recited in claim 13, wherein the number of pulses to be searched from each track is 1.

16. A residual signal decoding apparatus comprising:

a pulse de-quantizer for de-quantizing quantized pulse parameters to output restored pulse parameters;

a pulse generator for generating pulses from the restored pulse parameters to output restored transform coefficients for respective bands;

a band combiner for concatenating the restored transform coefficients for the respective bands with respect to all the bands to output restored transform coefficients; and

an inverse-transformer for inversely transforming the restored frequency-domain transform coefficients into a time domain to decode residual signals.

17. The residual signal decoding apparatus as recited in claim 16, wherein the pulse de-quantizer includes:

a magnitude de-quantizer for de-quantizing magnitude information with a predetermined number of bits among quantized pulse parameters to restore a pulse magnitude;

a sign de-quantizer for de-quantizing sign information with a predetermined number of bits among the quantized pulse parameters to restore a pulse sign; and

a position de-quantizer for de-quantizing position information with a predetermined number of bits among the quantized pulse parameters to restore a pulse position.

18. A residual signal decoding method, comprising the steps of:

a) de-quantizing quantized pulse parameters to output restored pulse parameters;

b) generating pulses from the restored pulse parameters to output restored transform coefficients for respective bands;

c) concatenating the restored transform coefficients for the respective bands with respect to all the bands to output restored transform coefficients; and

d) inversely transforming the restored frequency-domain transform coefficients into a time domain to decode residual signals.