Scalable audio coding/decoding method and apparatus

• US 6,094,636 A
• Filed: 11/26/1997
• Issued: 07/25/2000
• Est. Priority Date: 04/02/1997
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Yeon-bae
• Primary Examiner(s): Hudspeth, David R.
• Assistant Examiner(s): Azad, Abul K.
• Application Number:
  US08/979,175
• Time in Patent Office: 972 Days
• Field of Search: 704/205, 704/206, 704/207, 704/229, 704/230, 704/500-504
• US Class Current: 704/500
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: G10L 19/035 Scalar quantisation
• 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: H04B 1/665 using psychoacoustic properties of the ear, e.g. masking effect
• CPC Class Codes: H04N 19/184 the unit being bits, e.g. of the compressed video stream
• CPC Class Codes: H04N 19/60 using transform coding

Abstract

A scalable audio coding/decoding method and apparatus are provided. The coding method includes the steps of (a) signal-processing input audio signals and quantizing the same for each predetermined coding band; (b) coding the quantized data corresponding to the base layer within a predetermined layer size; (c) coding the quantized data corresponding to the next enhancement layer of the coded base layer and the remaining quantized data uncoded and belonging to the enhancement layer, within a predetermined layer size; and (d) sequentially performing the layer coding steps for all layers, wherein the steps (b), (c) and (d) each comprise the steps of: (i) obtaining gamut bit allocation information representing the number of bits of the quantized data corresponding to the respective subbands belonging to a layer to be coded; (ii) obtaining the number of bits allocated to the respective subbands within each subband size of the layers; (iii) generating an index representing the presence of quantized data for predetermined frequency components forming the subbands for the quantized data corresponding to the number of allocated bits; and (iv) generating bitstreams by coding the quantized data corresponding to the gamut bit allocation information, quantization step size, index and number of bits allocated to the respective subbands, by a predetermined coding method.

Claims

1. A scalable audio coding method for coding audio signals into a layered datastream having a base layer and a predetermined number of enhancement layers, comprising the steps of:

(a) signal-processing input audio signals and quantizing the same for each predetermined coding band;

(b) coding the quantized data corresponding to the base layer within a predetermined layer size;

(c) coding the quantized data corresponding to the next enhancement layer of the coded base layer and the remaining quantized data uncoded and belonging to the coded layer, within a predetermined layer size; and

(d) sequentially performing the layer coding steps for all layers, wherein the steps (b), (c) and (d) each comprise the steps of;

(i) obtaining gamut bit allocation information representing the number of bits of the quantized data corresponding to the respective subbands belonging to a layer to be coded;

(ii) obtaining the number of bits allocated to the respective subbands within each subband size of the layers;

(iii) generating an index representing the presence of quantized data for predetermined frequency components forming the subbands for the quantized data corresponding to the number of allocated bits; and

(iv) generating bitstreams by coding the quantized data corresponding to the gamut bit allocation information, quantization step size, index and number of bits allocated to the respective subbands, by a predetermined coding method.

2. The scalable audio coding method according to claim 1, wherein the quantized data corresponding to the number of allocated bits is quantized from the most significant bit to the least significant bit.

3. The scalable audio coding method according to claim 2, wherein coding of the quantized data corresponding to the number of allocated bits is performed in the step (iv) by coupling the quantized data in units of bits of a predetermined number.

4. The scalable audio coding method according to claim 2, wherein the number of allocated bits in the step (ii) is one bits, and the step (iv) is to generate the gamut bit allocation information and index as bitstreams by a predetermined coding method.

5. The scalable audio coding method according to claim 1, wherein the predetermined coding method is lossless coding.

6. The scalable audio coding method according to claim 5, wherein the lossless coding is Huffman coding.

7. The scalable audio coding method according to claim 5, wherein the lossless coding is Arithmetic coding.

8. The scalable audio coding method according to claim 1, wherein the step (a) comprises the steps of:

converting the input audio signals of a temporal domain into signals of a frequency domain;

coupling the converted signals as signals of predetermined subbands by time/frequency mapping and calculating a masking threshold at each subband; and

quantizing the signals for each predetermined coding band so that quantization noise of each band is smaller than the masking threshold.

9. A scalable audio coding apparatus for coding audio signals to have layered bitrate data having bitrates of a predetermined number, comprising:

a quantizing portion for signal-processing input audio signals and quantizing the same for each coding band; and

a bit packing portion for generating bitstreams by coding gamut bit allocation information for each subband of a base layer, representing the number of bits of quantized data of the respective subbands belonging to the base layer, index representing the presence of data for predetermined frequency components of the quantized data corresponding to the number of bits allocated to the respective subbands, quantization step size and the quantized data, and coding gamut bit allocation information, index, quantization step size and quantized data of the next layer after completing coding of the base layer, to perform coding on all layers.

10. The scalable audio coding apparatus according to claim 9, wherein coding the quantized data corresponding to the number of the allocated bits for each subband is performed sequentially from the most significant bits to lower significant bits.

11. The scalable audio coding apparatus according to claim 10, wherein, when the bit packing portion collects and codes the bits according to significance, coding is performed by coupling the bits in a predetermined number unit.

12. The scalable audio coding apparatus according to claim 10, wherein the number of allocated bits of the bit packing portion is one bits, and the coding is performed on the gamut bit allocation information and index by a predetermined coding method.

13. The scalable audio coding apparatus according to claim 10, wherein the bit packing portion performs coding sequentially from low frequency components to high frequency components.

14. The scalable audio coding apparatus according to claim 9 or 10, wherein the quantizing portion comprises:

a time/frequency mapping portion for converting the input audio signals of a temporal domain into signals of a frequency domain;

a psychoacoustic portion for coupling the converted signals by signals of predetermined subbands by time/frequency mapping and calculating a masking threshold at each subband; and

a quantizing portion for quantizing the signals for each predetermined coding band so that quantization noise of each band is smaller than the masking threshold.

15. A scalable audio decoding method for decoding audio data coded to have layered bitrates, comprising the steps of:

decoding gamut bit allocation information for each subband of a base layer, representing the number of bits of quantized data of the respective subbands belonging to the base layer, index representing the presence of data for predetermined frequency components of the quantized data corresponding to the number of bits allocated to the respective subbands, quantization step size and the quantized data, in the generated order of the layers of the bitstreams, decoding being performed by obtaining the number of bits allocated to the subbands belonging to each layer and decoding the quantized data corresponding to the number of allocated bits referring to the index;

restoring the decoded quantization step size and quantized data into signals having the original magnitudes; and

converting dequantized signals of a frequency domain into signals of a temporal domain.

16. The scalable audio decoding method according to claim 15, wherein decoding the quantized data in the decoding step is performed from the most significant bit to lower significant bits.

17. The scalable audio decoding method according to claim 15, wherein decoding the quantized data in the decoding step is performed in units of vectors of bits of a predetermined number.

18. The scalable audio decoding method according to claim 15, wherein the decoding step is performed by Arithmetic decoding.

19. The scalable audio decoding method according to claim 15, wherein the decoding step is performed by Huffman decoding.

20. A scalable audio decoding apparatus for decoding audio data coded to have layered bitrates, comprising:

a bitstream analyzing portion for decoding gamut bit allocation information for each subband of a base layer, representing the number of bits of quantized data of the respective subbands belonging to the base layer, index representing the presence of data for predetermined frequency components of the quantized data corresponding to the number of bits allocated to the respective subbands, quantization step size and the quantized data, in the generated order of the layers of the bitstreams, decoding being performed by obtaining the number of bits allocated to the subbands belonging to each layer and decoding the quantized data corresponding to the number of allocated bits referring to the index;

an inverse quantizing portion for restoring the decoded quantization step size and quantized data into signals having the original magnitudes; and

a frequency/time mapping portion for converting inversely quantized signals into signals of a temporal domain.

21. The scalable audio decoding apparatus according to claim 20, wherein decoding the quantized data in the decoding step is performed from the most significant bit to lower significant bits.

22. A scalable audio coding method for coding audio signals into a layered datastream having a base layer and a predetermined number of enhancement layers, comprising the steps of:

(a) signal-processing input audio signals and quantizing the same for each predetermined coding band;

(b) coding the quantized data of a first range of frequencies corresponding to the base layer within a predetermined layer size;

(c) coding the quantized data of a second range of frequencies corresponding to the next enhancement layer within a predetermined layer size; and

(d) sequentially performing the layer coding steps for all layers, wherein the steps (b), (c) and (d) each comprise the steps of;

(i) obtaining gamut bit allocation information representing the number of bits of the quantized data corresponding to the respective subbands belonging to a layer to be coded;

(ii) obtaining the number of bits allocated to the respective subbands within each subband size of the layers;

(iii) generating an index representing the presence of quantized data for predetermined frequency components forming the subbands for the quantized data corresponding to the number of allocated bits; and

(iv) generating bitstreams by coding the quantized data corresponding to the gamut bit allocation information, quantization step size, index and number of bits allocated to the respective subbands, by a predetermined coding method.

23. The scalable audio coding method according to claim 22, said second range of frequencies includes frequencies different from said first range of frequencies wherein the most significant digits of the quantized data of said frequencies different from said first range of frequencies are coded before coding next significant digits of the quantized data belonging to the corresponding enhancement layer.

24. The scalable audio coding method according to claim 23, wherein the quantized data corresponding to the number of allocated bits is quantized from the most significant bit to the least significant bit.

25. The scalable audio coding method according to claim 24, wherein coding of the quantized data corresponding to the number of allocated bits is performed in the step (iv) by coupling the quantized data in units of bits of a predetermined number.

26. The scalable audio coding method according to claim 24, wherein the number of allocated bits in the step (ii) is one bit, and the step (iv) is to generate the gamut bit allocation information and index as bitstreams by a predetermined coding method.

27. The scalable audio coding method according to claim 23, wherein the predetermined coding method is lossless coding.

28. The scalable audio coding method according to claim 27, wherein the lossless coding is Hoffman coding.

29. The scalable audio coding method according to claim 27, wherein the lossless coding is Arithmetic coding.

30. The scalable audio coding method according to claim 23, wherein the step (a) comprises the steps of:

converting the input audio signals of a temporal domain into signals of a frequency domain;

coupling the converted signals as signals of predetermined subbands by time/frequency mapping and calculating a masking threshold at each subband; and

quantizing the signals for each predetermined coding band so that quantization noise of each band is smaller than the masking threshold.