ENCODING METHOD AND APPARATUS, AND DECODING METHOD AND APPARATUS

• US 20130030795A1
• Filed: 03/31/2011
• Published: 01/31/2013
• Est. Priority Date: 03/31/2010
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Sung, Jongmo, Bae, Hyun Joo, Kim, Hyun Woo
• Granted Patent: US 9,424,857 B2
• Time in Patent Office: Days
• US Class Current: 704/203
• CPC Class Codes: G10L 19/0017 Lossless audio signal coding; Perfect reconstruction of coded audio signal by transmission of coding error G10L19/24 takes precedence
• CPC Class Codes: G10L 19/0212 using orthogonal transformation
• CPC Class Codes: G10L 19/032 Quantisation or dequantisation of spectral components
• 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

Abstract

An encoding method of an encoder is provided. The encoder generates first MDCT coefficients by transforming an input signal, and generates MDCT indices by quantizing the first MDCT coefficients. The encoder generates second MDCT coefficients by dequantizing the MDCT indices, and calculates MDCT residual coefficients using differences between the first MDCT coefficients and the second MDCT coefficients. The encoder generates a residual index by encoding the MDCT residual coefficients, and generates gain indices corresponding to gains from the first MDCT coefficients and the second MDCT coefficients.

Claims

1. An encoding method of an encoder, the method comprising:

transforming an input signal to generate first modified discrete cosine transform (MDCT) coefficients;

quantizing the first MDCT coefficients to generate MDCT indices;

dequantizing the MDCT indices to generate second MDCT coefficients;

computing MDCT residual coefficients using differences between the first MDCT coefficients and the second MDCT coefficients;

encoding the MDCT residual coefficients to generate a residual index; and

generating gain indices corresponding to gains from the first MDCT coefficients and the second MDCT coefficients.

2. The method of claim 1, further comprising multiplexing the MDCT indices, the residual index, and the gain indices to generate a bit stream.

3. The method of claim 1, wherein generating the residual index comprises:

selecting an index of a sub-band with a largest energy of MDCT residual coefficients among a plurality of sub-bands; and

generating a sub-band index by encoding the selected index,

wherein the residual index includes the sub-band index.

4. The method of claim 3, wherein the energy of the MDCT residual coefficient of a j-th sub-band is computed as,

wherein uj and lj are a lower boundary index and an upper boundary index of the j-th sub-band, respectively, and

E(k) is a k-th MDCT residual coefficient.

5. The method of claim 3, wherein generating the residual index further comprises encoding MDCT residual coefficients of the selected sub-band.

6. The method of claim 5, wherein encoding the MDCT residual coefficients further comprises:

configuring a plurality of tracks for MDCT residual coefficients of the selected sub-band;

selecting a pulse corresponding to a predetermined number of MDCT residual coefficients having a largest absolute value, among MDCT residual coefficients corresponding to possible positions in each track; and

coding the pulse,

wherein the residual index further includes a coded value of the pulse.

7. The method of claim 6, wherein coding the pulse comprises:

coding a position of the pulse;

coding the sign of the pulse; and

coding the amplitude of the pulse,

wherein the coded value of the pulse includes a coded value of the position, a coded value of the sign, and a coded value of the amplitude.

8. The method of claim 7, wherein the position is a position that is relative to a lower boundary index of the selected sub-band.

9. The method of claim 7, wherein encoding the MDCT residual coefficients comprises:

computing a root mean square (RMS) value of the MDCT residual coefficients of the selected sub-band; and

quantizing the RMS value to generate an RMS index,

wherein the residual index further includes the RMS index.

10. The method of claim 9, wherein coding the amplitude of the pulse comprises:

dequantizing the RMS index to generate a quantized RMS value; and

coding the amplitude of the pulse using the amplitude of the pulse divided by the quantized RMS value.

11. The method of claim 6, wherein generating the gain indices comprises:

computing exponents as logarithms of magnitudes of the second MDCT coefficients at positions excluding the position of the pulse;

setting an exponent to a minimum exponent magnitude at the position of the pulse; and

allocating bits for the gain indices based on the exponents.

12. The method of claim 11, wherein generating the gain indices further comprises determining the gain indices from the allocated bits, the first MDCT coefficients, and the second MDCT coefficients.

13. The method of claim 12, wherein the gain index is determined as i for maximizing,

wherein is an i-th codeword of a codebook corresponding to m bits,

i is an integer within a range of 0 to (2m-1),

is a k-th first MDCT residual coefficient, and

is a k-th second MDCT residual coefficient.

14. A decoding method of a decoder, the method comprising:

receiving MDCT indices, a residual index, and gain indices;

dequantizing the MDCT indices to generate first MDCT coefficients;

decoding the residual index to recover MDCT residual coefficients;

recovering gains from the gain indices using a position of a pulse corresponding to the MDCT residual coefficients and the first MDCT coefficients;

compensating gains of the first MDCT coefficients with the recovered gains generating second MDCT coefficients; and

compensating residuals of the second MDCT coefficients with the MDCT residual coefficients.

15. The method of claim 14, wherein compensating the residuals comprises adding the MDCT residual coefficients to the second MDCT coefficients.

16. The method of claim 15, wherein the MDCT residual coefficients has a value of 0 at positions excluding the position of the pulse.

17. The method of claim 14, wherein the residual index includes a sub-band index, and

recovering the MDCT residual coefficients comprises determining a sub-band of the MDCT residual coefficients by decoding the sub-band index.

18. The method of claim 14, wherein the residual index includes a coded value of the position of the pulse, a coded value of the sign of the pulse, and a coded value of the amplitude of the pulse.

19. The method of claim 18, wherein recovering the MDCT residual coefficients comprises:

decoding the coded value of the amplitude of the pulse to reconstruct the amplitude of the pulse by;

decoding the coded value of the position of the pulse to reconstruct the position of the pulse;

decoding the coded value of the sign of the pulse to reconstruct the sign of the pulse; and

recovering the MDCT residual coefficients based on the position, sign, and amplitude of the pulse.

20. The method of claim 19, wherein the residual index further includes a root mean square (RMS) index,

wherein recovering the amplitude of the pulse comprises:

generating a quantized RMS value from the RMS index; and

multiplying the decoded amplitude of the pulse by the quantized RMS value to recover the amplitude of the pulse.

21. The method of claim 14, wherein recovering the gains comprises:

computing exponents as logarithms of magnitudes of the first MDCT coefficients at positions excluding the position of the pulse;

setting an exponent to a minimum exponent magnitude at the position of the pulse; and

generating a bit allocation table by allocating bits to the gain indices based on the exponents.

22. The method of claim 21, wherein recovering the gains further comprises recovering the gains from the gain indices using the bit allocation table.

23. The method of claim 14, further comprising recovering a signal by transforming MDCT coefficients, which are generated by compensating the residuals of the second MDCT coefficients, by an inverse MDCT.

24. An encoding apparatus, comprising:

an MDCT configured to transform an input signal to generate first MDCT coefficients by;

an MDCT quantizer configured to quantize the first MDCT coefficients to generate MDCT indices by;

an enhancement layer encoder configured to dequantize the MDCT indices to generate second MDCT coefficients, to encode MDCT residual coefficients corresponding to differences between the first MDCT coefficients and the second MDCT coefficients to generate a residual index, and to generate gain indices corresponding to gains of the first MDCT coefficients from the first MDCT coefficients and the second MDCT coefficients; and

a multiplexer configured to multiplex the MDCT indices, the residual index, and the gain indices to generate a bit stream.

25. The apparatus of claim 24, wherein the enhancement layer encoder comprises a residual compensation encoder configured to select an index of a sub-band having a largest energy of MDCT residual coefficients among a plurality of sub-bands, and generate a sub-band index by encoding the selected index,

wherein the residual index includes the sub-band index.

26. The apparatus of claim 25, wherein the residual compensation encoder configures a plurality of tracks for MDCT residual coefficients of the selected sub-band, and codes the position, the sign, and the amplitude of a pulse corresponding to a predetermined number of MDCT residual coefficients having the largest absolute value among MDCT residual coefficients corresponding to possible positions in each track,

wherein the residual index further includes a coded value of the position, a coded value of the sign, and a coded value of the amplitude.

27. The apparatus of claim 26, wherein the residual compensation encoder quantize a root mean square (RMS) value of the MDCT residual coefficients of the selected sub-band to generate an RMS index by,

wherein the residual index further includes the RMS index.

28. The apparatus of claim 26, wherein the enhancement layer encoder computes exponents as logarithms of magnitudes of the second MDCT coefficients at positions excluding the position of the pulse, sets an exponent to a minimum exponent magnitude at the position of the pulse, and allocates bits for the gain indices based on the exponents.

29. The apparatus of claim 28, wherein the gain compensation encoder determines the gain index as i for maximizing,

wherein is the i-th codeword of a codebook corresponding to m bits,

i is an integer within a range of 0 to (2m-1),

is the k-th first MDCT residual coefficient, and

is the k-th second MDCT residual coefficient.

30. A decoding apparatus, comprising:

a demultiplexer configured to demultiplex a received bit stream to output MDCT indices, a residual index, and gain indices;

an MDCT dequantizer configured to dequantize the MDCT indices to generate first MDCT coefficients; and

an enhancement layer decoder configured to decode the residual index, recover gains from the gain indices using a position of a pulse corresponding to the MDCT residual coefficients and the first MDCT coefficients to recover MDCT residual coefficients, compensate gains of the first MDCT coefficients with the recovered gains to generate second MDCT coefficients, and compensate residuals of the second MDCT coefficients with the MDCT residual coefficients.

31. The apparatus of claim 30, wherein the enhancement layer decoder comprises a residual compensator configured to add the MDCT residual coefficients to the second MDCT coefficients to compensate the residuals of the second MDCT coefficients.

32. The apparatus of claim 30, wherein the residual index includes a coded value of the position of the pulse, a coded value of the sign of the pulse, and a coded value of the amplitude of the pulse,

wherein the enhancement layer decoder comprises a residual compensation decoder configured to decode the coded values of the position, sign, and amplitude of the pulse to recover the position, sign, and amplitude of the pulse.

33. The apparatus of claim 32, wherein the residual index further includes a root mean square (RMS) index,

wherein the residual compensation decoder generates a quantized RMS value from the RMS index, and multiplies the decoded amplitude of the pulse by the quantized RMS value to recover the amplitude of the pulse.

34. The apparatus of claim 30, wherein the enhancement layer decoder comprises a gain compensation decoder configured to compute exponents as logarithms of magnitudes of the first MDCT coefficients at positions excluding the position of the pulse, set an exponent to a minimum exponent magnitude at the position of the pulse, generate a bit allocation table by allocating bits to the gain indices based on the exponents, and recover the gains using the gain indices and the bit allocation table.

37. The apparatus of claim 30, further comprising an inverse MDCT configured to recover a signal by transforming MDCT coefficients in which the residuals are compensated, by the inverse MDCT.

35. (canceled)

36. (canceled)