Method and apparatus for enhancing performance of entropy coding, video coding method and apparatus using the method

1. An entropy coding method that codes a first coefficient without loss, which is included in a block of a predetermined layer among coefficients generated by coding a multilayer video, the method comprising:

(a) obtaining a distribution of a second coefficient, which is included within an area of a base layer corresponding to the block;

(b) selecting a lookup table appropriate for the distribution among a plurality of lookup tables; and

(c) transforming the first coefficient into a value mapped to the selected lookup table,

wherein the distribution is obtained by one of a total number of zeros and a number of non-zero coefficients among the second coefficients.

2. The method of claim 1 , wherein the generated coefficients are quantization coefficients generated after passing through a quantization process.

3. The method of claim 1 , wherein the block is one of a 4×4 grid of pixels and an 8×8 grid of pixels.

4. The method of claim 1 , wherein the distribution is obtained by one of a number of zeros and a number of non-zero coefficients among the second coefficients.

5. The method of claim 4 , wherein (b) is performed by selecting a lookup table, in which, if the number of zeros is large, a relatively short mapping code is allocated to a small coefficient, and if the number of zeros is small, a relatively short length mapping code is allocated to a large coefficient.

6. The method of claim 1 , wherein (b) includes:

(b1) counting a number of non-zero coefficients of the first and second coefficients;

(b2) counting a number of non-zero coefficients of a third coefficient of a neighboring block of the same layer as the block;

(b3) obtaining representative values of the counted number in (b1) and the counted number in (b2); and

(b4) selecting the appropriate lookup table according to the representative values.

7. The method of claim 6 , wherein the neighboring block is at least one of the upper neighboring block and the left neighboring block.

8. The method of claim 6 , wherein the representative value is obtained by a weighted average of the count of (b1) and the count of (b2).

9. The method of claim 1 , wherein the entropy coding method includes a context-adaptive variable length coding.

10. An entropy decoding method that restores a first coefficient on a block of a layer by decoding a first bitstream of a predetermined layer among inputted bitstreams without loss, the method comprising:

(a) restoring a second coefficient included in an area of a base layer corresponding to the block;

(b) obtaining a distribution of the restored second coefficient;

(c) selecting an appropriate lookup table for the distribution among a plurality of lookup tables; and

(d) transforming the first bitstream into the first coefficient based on the selected lookup table,

wherein the distribution is obtained by one of a total number of zeros and a number of non-zero coefficients among the second coefficients.

11. The method of claim 10 , wherein the first and second coefficients are quantization coefficients.

12. The method of claim 10 , wherein the block is one of a 4×4 grid of pixels and an 8×8 grid of pixels.

13. The method of claim 10 , wherein the distribution is obtained by one of a number of zeros and a number of non-zero coefficients among the restored second coefficients.

14. The method of claim 13 , wherein (c) is performed by selecting a lookup table, in which, if the number of zeros is large, a relatively short mapping code is allocated to a small coefficient, and if the number of zeros is small, a relatively short mapping code is allocated to a big coefficient.

15. The method of claim 10 , wherein (c) includes:

(c1) counting the number of non-zero coefficients of the first and second coefficients;

(c2) counting a number of non-zero coefficients of a third coefficient of a neighboring block of the same layer as the block;

(c3) obtaining representative values of the count of (c1) and the count of (c2); and

(c4) selecting the appropriate lookup table according the representative values.

16. The method of claim 15 , wherein the neighboring block is at least one of the upper neighboring block and the left neighboring block.

17. The method of claim 15 , wherein the representative value is obtained by a weighted average of the count of (c1) and the count of (c2).

18. The method of claim 10 , wherein the entropy coding is context-adaptive variable length coding.

19. An entropy decoding device that restores a first coefficient of a block of a layer by decoding a first bitstream of a predetermined layer among inputted bitstreams without loss, the method comprising,

means for restoring a second coefficient included in an area of a base layer corresponding to the block;

means for obtaining a distribution of the restored second coefficient;

means for selecting a lookup table appropriate for the distribution among a plurality of lookup tables; and

means for transforming the first bitstream into the first coefficient, based on the selected lookup table,

wherein the distribution is obtained by one of a total number of zeros and a number of non-zero coefficients among the second coefficients.