Method of and apparatus for lossless video encoding and decoding

1. A method of lossless video encoding, the method comprising:

generating a residual block composed of residual signals corresponding to differences between pixels of a predicted block and a current block;

calculating differences between the residual signals of the residual block in a predetermined direction and generating a differential residual block based on the calculated differences; and

performing entropy-encoding on the differential residual block;

wherein the method of lossless video encoding is carried out by a computer comprising a computer processor.

2. The method of claim 1 , wherein the predetermined direction is at least one of a horizontal direction and a vertical direction.

3. The method of claim 1 , wherein when a pixel in an x th row and a y th column of the residual block is referred to as r x,y , a pixel r′ x,y in an x th row and an y th column of the differential residual block except for pixels in the 1 st column of the differential residual block is calculated by r′ x,y =r x,y −r x,y-1 .

4. The method of claim 1 , wherein when a pixel in an x th row and a y th column of the residual block is r x,y , a pixel r′ x,y in an x th row and an y th column of the differential residual block except for pixels in the 1 st row of the differential residual block is calculated by r′ x,y =r x,y −r x-1,y .

5. The method of claim 1 , further comprising:

comparing a first cost of a first mode in which the differential residual block is entropy-encoded and a second cost of a second mode in which the residual block is transformed, quantized, and then entropy-encoded, and determining a final encoding mode based on the smaller of the first cost and the second cost.

6. The method of claim 5 , further comprising adding a predetermined bit indicating the final encoding mode to a header of a bitstream.

7. The method of claim 1 , further comprising adding a predetermined bit indicating information about the predetermined direction to a header of a bitstream.

8. The method of claim 1 , further comprising performing interprediction between a reference frame and a current frame in units of a predetermined size block to generate the predicted block of the current block to be encoded.

9. An apparatus for lossless video encoding, the apparatus comprising:

a subtraction unit which generates a residual block composed of residual signals corresponding to differences between pixels of a predicted block and a current block;

a differential residue transform unit which calculates differences between the residual signals of the residual block in a predetermined direction and generates a differential residual block based on the calculated differences; and

an entropy-encoding unit which performs entropy-encoding on the differential residual block;

wherein the apparatus for lossless video encoding comprises at least a computer processor, the computer processor performing the function of at least one of the subtraction unit, the differential residue transform unit, and the entropy-encoding unit.

10. The apparatus of claim 9 , wherein when the predetermined direction is a horizontal direction and a pixel in an x th row and an y th column of the residual block is r x,y , the differential residue transform unit calculates a pixel r′ x,y in an x th row and an y th column of the differential residual block except for pixels in the 1 st column of the differential residual block using r′ x,y =r x,y −r x,y-1 .

11. The apparatus of claim 9 , wherein when the predetermined direction is a vertical direction and a pixel in an x th row and an y th column of the residual block is r x,y , the differential residue transform unit calculates a pixel r′ x,y in an x th row and an y th column of the differential residual block except for pixels in the 1 st row of the differential residual block using r′ x,y =r x,y −r x-1,y .

12. The apparatus of claim 9 , wherein the entropy-encoding unit compares a first cost of a first mode in which the differential residual block is entropy-encoded and a second cost of a second mode in which the residual block is transformed, quantized, and then entropy-encoded, and determines a final encoding mode based on the smaller of the first cost and the second cost.

13. The apparatus of claim 12 , wherein the entropy-encoding unit adds a predetermined bit indicating the final encoding mode to a header of a bitstream.

14. The apparatus of claim 12 , wherein the entropy-encoding unit adds a predetermined bit indicating information about the predetermined direction to a header of a bitstream.

15. The apparatus of claim 9 , further comprising an interprediction unit which performs interprediction between a reference frame an a current frame in units of a predetermined size block to generate the predicted block of the current block to be encoded.

16. A method of lossless video decoding, the method comprising:

receiving a bitstream comprising an entropy-encoded differential residual block that is generated by calculating differences between pixels of a residual block composed of differences between an interpredicted block and a current block;

performing entropy-decoding on the received bitstream to decode the entropy-encoded differential residual block to create a decoded differential residual block;

performing an inverse transform on the decoded differential residual block to regenerate the residual block; and

adding the residual block and the interpredicted block using video data included in the bitstream to reconstruct an original picture;

wherein the method of lossless video decoding is carried out by a computer comprising a computer processor.

17. The method of claim 16 , wherein the inverse transform of the decoded differential residual block is performed by summing up pixels positioned in a predetermined direction with respect to a current pixel to be inversely transformed in the decoded differential residual block.

18. The method of claim 16 , wherein when the entropy-encoded differential residual block has been generated using differences between horizontally neighboring pixels and a pixel in an x th row and an y th column of the inversely transformed decoded differential residual block is r′ x,y , the inverse transform of the decoded differential residual block comprises calculating a pixel r x,y in an x th row and an y th column of the residual block using

r

x

,

y

=

∑

i

=

0

y

⁢

r

x

,

i

′

.

19. The method of claim 16 , wherein when the entropy-encoded differential residual block has been generated using differences between vertically neighboring pixels and a pixel in an x th row and an y th column of the inversely transformed decoded differential residual block is r′ x,y , the inverse transform of the decoded differential residual block comprises calculating a pixel r x,y in an x th row and an y th column of the residual block using

r

x

,

y

=

∑

i

=

0

x

⁢

r

i

,

y

′

.

20. An apparatus for lossless video decoding, the apparatus comprising:

an entropy-decoding unit which receives a bitstream that is entropy-encoded using a differential residual block that is generated by calculating differences between pixels of a residual block composed of differences between an interpredicted block and a current block and performs entropy-decoding on the received bitstream to output the differential residual block;

a differential residue inverse transform unit which performs inverse transform on the differential residual block to regenerate the residual block;

an interprediction unit which generates an interpredicted block using video data included in the bitstream; and

an addition unit which adds the residual block and the interpredicted block to reconstruct the original picture;

wherein the apparatus for lossless video decoding comprises at least a computer processor, the computer processor performing the function of at least one of the entropy-decoding unit, the differential residue inverse transform unit, and the addition unit.

21. The apparatus of claim 20 , wherein the differential residue inverse transform unit sums up pixels positioned in a predetermined direction with respect to a current pixel to be inversely transformed in the decoded differential residual block.

22. The apparatus of claim 20 , wherein when the entropy-encoded differential residual block has been generated using differences between horizontally neighboring pixels and a pixel in an x th row and an y th column of the inversely transformed decoded differential residual block is r′ x,y , the differential residue inverse transform unit calculates a pixel r x,y in an x th row and an y th column of the residual block using

r

x

,

y

=

∑

i

=

0

y

⁢

r

x

,

i

′

.

23. The apparatus of claim 20 , wherein when the entropy-encoded differential residual block has been generated using differences between vertically neighboring pixels and a pixel in an x th row and an y th column of the inversely transformed decoded differential residual block is r′ x,y , the differential residue inverse transform unit calculates a pixel r x,y in an x th row and an y th column of the residual block using

r

x

,

y

=

∑

i

=

0

x

⁢

r

i

,

y

′

.