Method and apparatus for encoding and decoding motion vectors

• US 20040013309A1
• Filed: 07/16/2003
• Published: 01/22/2004
• Est. Priority Date: 07/16/2002
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Choi, Woong-Il, Jeon, Byeung-Woo
• Granted Patent: US 7,257,263 B2
• Time in Patent Office: Days
• US Class Current: 382/238
• CPC Class Codes: H04N 19/503 involving temporal prediction adaptive coding with adaptive selection between spatial and temporal predictive coding H04N19/107; adaptive coding with adaptive selection among a plurality of temporal predictive coding modes H04N19/109
• CPC Class Codes: H04N 19/52 by predictive encoding
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

There is provided a method and apparatus for encoding and decoding motion vectors. Motion vectors are encoded through the steps of: (a) predicting motion vectors of a type identical to that of a present block and obtaining predictive motion vectors with respect to neighbor blocks having motion vectors of a type different from that of the present block among a plurality of neighbor blocks adjacent to the present block; (b) calculating a representative value of the motion vectors of the type identical to that of the present block from the motion vectors of the neighbor blocks and the predictive motion vectors; (c) calculating a difference value between the calculated representative value and the motion vector of the present block; and (d) encoding the calculated difference value. The motion vectors can be more efficiently encoded even when they refer to different reference pictures.

Claims

1. A method for encoding motion vectors comprising:

(a) predicting a motion vector of a type identical to that of a motion vector of a present block and obtaining a predictive motion vector with respect to neighbor blocks having motion vectors of a type different from that of the present block among a plurality of neighbor blocks adjacent to the present block;

(b) calculating a representative value of the motion vector of a type identical to that of the present block from the motion vectors of the neighbor blocks and the predictive motion vector;

(c) calculating a difference value between the calculated representative value and the motion vector of the present block; and

(d) encoding the calculated difference value.

2. The encoding method according to claim 1, wherein the plurality of neighbor blocks include blocks which are to the left of, above, and to the upper-right of the present block.

3. The encoding method according to claim 2, wherein the left block is a block including a pixel adjacent to and to the left of the left-most pixel in the first row of the present block, the upper block is a block including a pixel adjacent to and above the left-most pixel, and the upper-right block is a block including a pixel adjacent to and to the right of a pixel adjacent to and above the right-most pixel in the first row of the present block.

4. An apparatus for encoding motion vectors comprising:

a motion vector predictor that predicts a motion vector of a type identical to that of a motion vector of a present block and produces a predictive motion vector with respect to neighbor blocks having motion vectors of a type different from that of the present block among a plurality of neighbor blocks adjacent to the present block, and calculates a representative value of the motion vector of the type identical to that of the present block from the motion vectors of the neighbor blocks and the predictive motion vector and calculates a difference value between the calculated representative value and the motion vector of the present block; and

a motion vector encoder for encoding the calculated difference value.

5. The encoding apparatus according to claim 4, wherein said motion vector predictor calculates a predictive forward motion vector MVf(predictive) as the predictive motion vector, when the motion vector of the present block is a forward motion vector MVf and the motion vector of the neighbor block is a backward motion vector MVb, according to the following equation:

6. The encoding apparatus according to claim 4, wherein said motion vector predictor calculates a predictive backward motion vector MVb(predictive) as the predictive motion vector, when the motion vector of the present block is a backward motion vector MVb and the motion vector of a neighbor block is a forward motion vector MVf, according to the following equation:

7. The encoding apparatus according to claim 4, wherein said motion vector predictor calculates a predictive value PMV_X as the representative value according to the following equation:

PMV_—

X=median(MVf_—

A, MVf_—

B, MVf_—

C) or median(MVb_—

A, MVb_—

B, MVb_—

C)

where MVf_A, MVf_B, MVf_C, MVb_A, MVb_B, and MVb_C are components of motion vectors of neighbor blocks in which MVf_A is a forward motion vector of a left block, MVf_B is a forward motion vector of an upper block, MVf_C is a forward motion vector of an upper-right block, MVb_A is a backward motion vector of a left block, MVb_B is a backward motion vector of an upper block, and MVb_C is a backward motion vector of an upper-right block, and one of these vectors can be the predictive motion vector.

8. The encoding apparatus according to claim 7, wherein said motion vector predictor calculates a differential value between the calculated representative value and the motion vector of the present block.

9. The encoding apparatus according to claim 8, wherein said motion vector predictor encodes the differential value.

10. A method for decoding motion vectors comprising:

(a) predicting a motion vector of a type identical to that of a present block and obtaining a predictive motion vector with respect to neighbor blocks having motion vectors of a type different from that of the present block among a plurality of neighbor blocks adjacent to the present block;

(b) calculating a representative value of the motion vector of the type identical to that of the present block from the motion vectors of the neighbor blocks and the predictive motion vector; and

(c) calculating the motion vector of the present block by adding the calculated representative value and a decoded difference value.

11. The decoding method according to claim 10, wherein the plurality of neighbor blocks include blocks which are to the left of, above, and to the upper-right of the present block.

12. The decoding method according to claim 11, wherein the left block is a block including a pixel adjacent to and to the left of the left-most pixel in a first row of the present block, the upper block is a block including a pixel adjacent to and above the left-most pixel, and the upper-right block is a block including a pixel adjacent to and to the right of a pixel adjacent to and above of the right-most pixel in the first row of the present block.

13. The decoding method according to claim 10, wherein the representative value is a median value.

14. The decoding method according to claim 10, wherein a predictive forward motion vector MVf (predictive) is calculated as the predictive motion vector, when the motion vector of the present block is a forward motion vector MVf and the motion vector of the neighbor block is a backward motion vector MVb, according to the following equation:

15. The decoding method according to claim 10, wherein a predictive backward motion vector MVb(predictive) is calculated as the predictive motion vector, when the motion vector of the present block is a backward motion vector MVb and the motion vector of a neighbor block is a forward motion vector MVf, according to the following equation:

16. The decoding method according to claim 10, wherein a predictive forward motion vector MVf(predictive) is calculated as the predictive motion vector, when the motion vector of the present block is a forward motion vector MVf and the motion vector of the neighbor block is a backward motion vector MVb, according to the following equation:

17. The decoding method according to claim 10, wherein a predictive backward motion vector MVb(predictive) is calculated as the predictive motion vector, when the motion vector of the present block is a backward motion vector MVb and the motion vector of a neighbor block is a forward motion vector MVf, according to the following equation:

18. The decoding method according to claim 10, wherein step (b) includes calculating a predictive value PMV_X for decoding as the representative value according to the following equation:

PMV_—

X=median(MVf_—

A, MVf_—

B, MVf_—

C) or median(MVb_—

A, MVb_—

B, MVb_—

C)

where MVf_A, MVf_B, MVf_C, MVb_A, MVb_B, and MVb_C are components of motion vectors of neighbor blocks in which MVf_A is a forward motion vector of a left block, MVf_B is a forward motion vector of an upper block, MVf_C is a forward motion vector of an upper-right block, MVb_A is a backward motion vector of a left block, MVb_B is a backward motion vector of an upper block, and MVb_C is a backward motion vector of an upper-right block, and one of these vectors can be the predictive motion vector.

19. The decoding method according to claim 10, wherein step (c) includes adding a differential value between the representative value and the motion vector of the present block.

20. An apparatus for decoding motion vectors comprising:

a motion vector decoder for decoding a difference value; and

a motion vector prediction compensator which predicts a motion vector of a type identical to that of a motion vector of a present block and obtaining a predictive motion vector with respect to neighbor blocks having motion vectors of a type different from that of the present block among a plurality of neighbor blocks adjacent to the present block, calculates a representative value of the motion vector of the type identical to that of the present block from the motion vectors of the neighbor blocks and the predictive motion vector and calculates the motion vector of the present block by adding the calculated representative value and the decoded difference value.

21. The decoding apparatus according to claim 20, wherein the plurality of neighbor blocks include blocks which are to the left of, above, and to the upper-right of the present block.

22. The decoding apparatus according to claim 21, wherein the left block is a block including a pixel adjacent to and to the left of the left-most pixel in a first row of the present block, the upper block is a block including a pixel adjacent to and above the left-most pixel, and the upper-right block is a block including a pixel adjacent to and to the right of a pixel adjacent to and above of the right-most pixel in the first row to which the present block belongs.

23. The decoding apparatus according to claim 20, wherein the representative value is a median value.

24. The decoding apparatus according to claim 20, wherein said motion vector prediction compensator calculates a predictive forward motion vector MVf(predictive) as the predictive motion vector, when the motion vector of the present block is a forward motion vector MVf and the motion vector of the neighbor block is a backward motion vector MVb, according to the following equation:

25. The decoding apparatus according to claim 20, wherein said motion vector prediction compensator calculates a predictive backward motion vector MVb(predictive) as the predictive motion vector, when the motion vector of the present block is a backward motion vector MVb and the motion vector of a neighbor block is a forward motion vector MVf, according to the following equation:

26. The decoding apparatus according to claim 20, wherein said motion vector prediction compensator calculates a predictive forward motion vector MVf(predictive) as the predictive motion vector, when the motion vector of the present block is a forward motion vector MVf and the motion vector of the neighbor block is a backward motion vector MVb, according to the following equation:

27. The decoding apparatus according to claim 20, wherein said motion vector prediction compensator calculates a predictive backward motion vector MVb(predictive) is calculated as the predictive motion vector, when the motion vector of the present block is a backward motion vector MVb and the motion vector of a neighbor block is a forward motion vector MVf, according to the following equation:

28. The decoding apparatus according to claim 20, wherein said motion vector prediction compensator calculates a predictive value PMV_X for decoding as the representative value according to the following equation:

PMV_—

X=median(MVf_—

A, MVf_—

B, MVf_—

C) or median(MVb_—

A, MVb_—

B, MVb_—

C)

where MVf_A, MVf_B, MVf_C, MVb_A, MVb_B, and MVb_C are components of motion vectors of neighbor blocks in which MVf_A is a forward motion vector of a left block, MVf_B is a forward motion vector of an upper block, MVf_C is a forward motion vector of an upper-right block, MVb_A is a backward motion vector of a left block, MVb_B is a backward motion vector of an upper block, and MVb_C is a backward motion vector of an upper-right block, one of these vectors can be the predictive motion vector.