METHOD AND APPARATUS FOR ENCODING MOTION VECTOR, AND METHOD AND APPARATUS FOR ENCODING/DECODING IMAGE USING SAME

• US 20110211640A1
• Filed: 10/23/2009
• Published: 09/01/2011
• Est. Priority Date: 10/31/2008
• Status: Active Grant

• Current Assignee: SK Telecom Co., Ltd.
• Original Assignee: SK Telecom Co., Ltd.
• Inventors: Kim, Hayoon, Jeon, Byeungwoo, Park, Mincheol, Moon, Joohee, Kim, Haekwang, Lee, Yunglyul, Kim, Dongwon
• Granted Patent: US 8,976,863 B2
• Time in Patent Office: Days
• US Class Current: 375/240.16
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/44 Decoders specially adapted therefor, e.g. video decoders which are asymmetric with respect to the encoder
• CPC Class Codes: H04N 19/517 by encoding
• CPC Class Codes: H04N 19/52 by predictive encoding
• CPC Class Codes: H04N 19/521 for estimating the reliability of the determined motion vectors or motion vector field, e.g. for smoothing the motion vector field or for correcting motion vectors
• CPC Class Codes: H04N 19/56 Motion estimation with initialisation of the vector search, e.g. estimating a good candidate to initiate a search
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

A method and an apparatus for encoding a motion vector, and a method and an apparatus for encoding/decoding an image using the same are closed. The apparatus includes: a prediction candidate selector for selecting one or more motion vector prediction candidates; a predicted motion vector determiner for determining a PMV among the one or more motion vector prediction candidates; and a differential motion vector encoder for calculating a differential motion vector encoder for calculating a DMV by subtracting the predicted motion vector having been determined, from the current motion vector, and encoding the d having been calculated. The apparatus encodes a motion vector by using the prediction motion vector which is more accurately predicted, and reduces an amount of bits required for encoding information of the predicted motion vector, thereby improving the compression efficiency.

Claims

1. An apparatus for encoding a motion vector, comprising:

a prediction candidate selector for selecting one or more motion vector prediction candidates;

a predicted motion vector determiner for determining a predicted motion vector among the one or more motion vector prediction candidates; and

a differential motion vector encoder for calculating a differential motion vector by subtracting the predicted motion vector having been determined, from the current motion vector, and encoding the differential motion vector having been calculated.

2. The apparatus of claim 1, wherein the prediction candidate selector selects motion vectors of adjacent blocks of a current block, as the one or more motion vector prediction candidates.

3. The apparatus of claim 1, wherein the prediction candidate selector selects one or more combinations of motion vectors among a motion vector of a Col block located at a same position as the current block, in a reference frame, and motion vectors of adjacent blocks of the Col block, as the one or more motion vector prediction candidates.

4. The apparatus of claim 1, wherein the prediction candidate selector selects an indication vector indicating a particular block of the reference frame, in the current block of a current frame, as the one or more motion vector prediction candidates, and the particular block has a motion vector, which levels with the indication vector, or a motion vector, which differs by less than a preset threshold from indication vector.

5. The apparatus of claim 1, wherein the prediction candidate selector selects partial motion vector prediction candidates from the one or more motion vector prediction candidates.

6. The apparatus of claim 5, wherein the prediction candidate selector calculates a probability, by which each of the one or more motion vector prediction candidates is determined as the current motion vector, by encoding one or more areas of the current frame by using each of the one or more motion vector prediction candidates, and selects the partial motion vector prediction candidates according to the probability.

7. The apparatus of claim 5, wherein the prediction candidate selector defines one or more candidate groups by selecting motion vector prediction candidates having correlations between them from the one or more motion vector prediction candidates, and selects a representative motion vector representing each of the candidate groups having been defined, as one of the partial motion vector prediction candidates.

8. The apparatus of claim 7, wherein the representative motion vector has a median value or an average value of the motion vector prediction candidates selected in each of the one or more candidate groups having been selected.

9. The apparatus of claim 1, wherein, when distances between the one or more motion vector prediction candidates are smaller than a preset threshold, the prediction candidate selector selects one or more combinations of motion vector prediction candidates identical to each other among the motion vector prediction candidates having the distance smaller than the preset threshold, an average value of the motion vector prediction candidates having the distance smaller than the preset threshold, and a median value of the motion vector prediction candidates having the distance smaller than the preset threshold.

10. The apparatus of claim 1, further comprising a prediction candidate selection flag encoder for generating and encoding a prediction candidate selection flag for identifying the one or more motion vector prediction candidates having been selected.

11. The apparatus of claim 1, wherein the predicted motion vector determiner determines a motion vector prediction candidate having a minimum amount of bits required for encoding a differential motion vector calculated by using each of the motion vector prediction candidates among the one or more motion vector prediction candidates as the predicted motion vector.

12. The apparatus of claim 1, further comprising a prediction candidate identification flag encoder for generating and encoding a prediction candidate identification flag for identifying the motion vector prediction candidate determined as the predicted motion vector.

13. The apparatus of claim 12, wherein, when the motion vector prediction candidate determined as the predicted motion vector is a motion vector prediction candidate having the highest probability to be determined as the current motion vector among the one or more motion vector prediction candidates, the prediction candidate identification flag encoder generates and encodes the prediction candidate identification flag in such a manner that the prediction candidate identification flag has a minimum bit.

14. The apparatus of claim 13, wherein the prediction candidate identification flag encoder calculates a probability, by which each of the one or more motion vector prediction candidates is determined as the current motion vector, by encoding the one or more areas of the current frame by using the one or more motion vector prediction candidates.

15. The apparatus of claim 12, wherein the prediction candidate identification flag encoder generates and encodes the prediction candidate identification flag only when one or more motion vector prediction candidates among the one or more motion vector prediction candidates are not identical.

16. The apparatus of claim 12, wherein the prediction candidate identification flag encoder generates different prediction candidate groups according to one or more block type and condition of the current block, selects each of the different prediction candidates groups, and then generates the prediction candidate identification flag.

17. The apparatus of claim 1, wherein the predicted motion vector determiner independently determines each of an x-component and a y-component of the predicted motion vector, and an x-component of one motion vector prediction candidate among x-components of the one or more motion vector prediction candidates is determined as the x-component of the predicted motion vector and a y-component of one motion vector prediction candidate among y-components of the one or more motion vector prediction candidates is determined as the y-component of the predicted motion vector.

18. The apparatus of claim 17, further comprising a prediction candidate identification flag encoder for generating and encoding a prediction candidate identification flag for identifying the one or more motion vector prediction candidates determined from the x-component of the predicted motion vector and the y-component of the predicted motion vector, when one or more combinations of absolute values of an x-component of the differential motion vector and absolute values of a y-component of the differential motion vector are smaller than or equal to one or more combinations of among a predetermined threshold of the x-component and a predetermined threshold of the y-component.

19. The apparatus of claim 18, wherein the threshold of the x-component is a maximum value among values obtained by dividing difference values between the x-components of two motion vector prediction candidates located most adjacently to each other among the x-components of the one or more motion vector prediction candidates by a predetermined number, and the threshold of the y-component is a maximum value among values obtained by dividing difference values between the y-components of two motion vector prediction candidates located most adjacently to each other among the y-components of the one or more motion vector prediction candidates by a predetermined number.

20. The apparatus of claim 18, wherein the thresholds of the x-component are values obtained by dividing difference values between the x-components of the motion vector prediction candidates among the x-components of the one or more motion vector prediction candidates by a predetermined number, and the thresholds of the y-component are values obtained by dividing difference values between the y-components of the motion vector prediction candidates among the y-components of the one or more motion vector prediction candidates by a predetermined number.

21. The apparatus of claim 20, wherein the prediction candidate identification flag encoder divides the thresholds of the x-component and the thresholds of the y-component into sections, and generates the prediction candidate identification flag depending on different numbers of motion vector prediction candidates according to the sections having been divided.

22. A method for encoding a motion vector, comprising:

selecting one or more motion vector prediction candidates;

determining one motion vector prediction candidate among the one or more motion vector prediction candidates as a predicted motion vector; and

encoding a differential motion vector after calculating the differential motion vector by subtracting the predicted motion vector having been determined, from a current motion vector.

23. An apparatus for decoding a motion vector, comprising:

a differential motion vector decoder for reconstructing a differential motion vector by decoding an encoded differential motion; and

a motion vector reconstructor for determining one motion vector prediction candidate among one or more motion vector prediction candidates as a predicted motion vector, and reconstructing a current motion vector of a current block by adding the predicted motion vector having been determined, to the differential motion having been reconstructed.

24. The apparatus of claim 23, wherein the motion vector reconstructor selects one or more motion vectors among motion vectors of adjacent blocks of the current block, a motion vector of a Col block located at a same position as the current block, in a reference frame, motion vectors of adjacent blocks of the Col block, and an indication vector indicating a particular block of the reference frame, in the current block, as the one or more motion vector prediction candidates, and the particular block has a motion vector, which levels with the indication block or a motion vector, which differs by less than a preset threshold from the indication vector.

25. The apparatus of claim 23, further comprising a prediction candidate identification flag decoder for reconstructing a prediction candidate identification flag by decoding an encoded prediction candidate identification flag.

26. The apparatus of claim 25, wherein the motion vector reconstructor determines a motion vector prediction candidate identified by the prediction candidate identification flag having been reconstructed among the one or more motion vector prediction candidates as the predicted motion vector.

27. The apparatus of claim 25, wherein, when one or more combinations of absolute values of x-components of the differential motion vector and absolute values of y-components of the differential motion vector are smaller than or equal to one or more combinations of a predetermined threshold of the x-components and a predetermined threshold of the y-components, motion vector reconstructor determines one or more combinations of x-components and y-components of the motion vector prediction candidate identified by the prediction candidate identification flag having been reconstructed, as one or more combinations of an x-component and a y-component of the predicted motion vector.

28. The apparatus of claim 25, wherein the prediction candidate identification flag decoder decodes a part of bits included in a bit-stream by the prediction candidate identification flag, and the motion vector reconstructor determines the motion vector prediction candidate identified as the predicted motion vector when the motion vector prediction candidate having the highest probability to be determined as the current motion vector is identified, and the prediction candidate identification flag decoder decodes additional bits included in the bit-stream when the motion vector prediction candidate having the highest probability to be determined as the current motion vector is not identified.

29. The apparatus of claim 23, further comprising a prediction candidate selection flag decoder for reconstructing a prediction candidate selection flag by decoding an encoded prediction candidate selection flag.

30. The apparatus of claim 29, wherein the motion vector reconstructor determines a motion vector prediction candidate identified by the prediction candidate selection flag having been reconstructed, as the one or more motion vector prediction candidates.

31. The apparatus of claim 23, wherein, when the absolute values among the absolute values of the x-components of the differential motion vector and the absolute values of the y-components of the differential motion vector are larger than the thresholds among the predetermined threshold of the x-components and the predetermined threshold of the y-components, respectively, the motion vector reconstructor determines a motion vector prediction candidate as the predicted motion vector, wherein a current motion vector reconstructed by using the motion vector prediction candidate determined by the motion vector reconstructor has a minimum value among respective current motion vectors reconstructed by using the one or more motion vector prediction candidates.

32. A method for decoding a motion vector, comprising:

decoding an encoded differential motion vector, to reconstruct the encoded differential motion vector having been decoded; and

reconstructing a current motion vector of a current block by adding a predicted motion vector to the differential motion vector having been reconstructed after determining one motion vector prediction candidate among one or more motion vector prediction candidates as the predicted motion vector.

33. An apparatus for encoding an image, comprising:

a predictor for determining a current motion vector of a current block and generating a predicted block by using the current motion vector having been determined;

a subtractor for generating a residual block by subtracting the predicted block from the current block;

a transformer for transforming the residual block;

a quantizer for quantizing the residual block having been transformed; and

an encoder for encoding the residual block having been quantized, determining one motion vector prediction candidate among one or more motion vector prediction candidates as a predicted motion vector, encoding a differential motion vector obtained by subtracting the predicted motion vector having been determined, from the current motion vector, generating a bit-stream including the residual block having been encoded and the differential motion vector having been encoded, and outputting the bit-stream.

34. The apparatus of claim 33, wherein the encoder selects one or more combinations of motion vectors of adjacent blocks of the current block, a motion vector of a Col block located at a same position as the current block, in a reference block, motion vectors of adjacent blocks of the Col block, and an indication vector indicating a particular block of the reference frame, in the current block, as the one or more motion vector prediction candidates, and the particular block has a motion vector, which levels with the indication vector, or a motion vector, which differs by less than a preset threshold from the indication vector.

35. The apparatus of claim 33, wherein the encoder generates and encodes a prediction candidate identification flag for identifying the motion vector prediction candidate determined as the predicted motion vector, and then additionally includes the prediction candidate identification flag in the bit-stream.

36. The apparatus of claim 35, wherein the encoder independently determines each of an x-component and a y-component of the predicted motion vector, and an x-component of one motion vector prediction candidate among x-components of the one or more motion vector prediction candidates is determine as the x-component of the predicted motion vector, and a y-component of one motion vector prediction candidate among y-components of the one or more motion vector prediction candidates is determine as the y-component of the predicted motion vector.

37. The apparatus of claim 35, wherein, when one or more combinations of absolute values of x-components of the differential motion vector and absolute values of y-components of the differential motion vector are smaller than or equal to one or more combinations of the x-components and the y-components, the encoder generates and encodes a prediction candidate identification flag for identifying one or more motion vector prediction candidates having been determined, among the x-components of the predicted motion vector and the y-component of the predicted motion vector, and then additionally includes the prediction candidate identification flag in the bit-stream.

38. A method for encoding an image, comprising:

determining a current motion vector of a current block and generating a predicted block by using the current motion vector having been determined;

generating a residual block by subtracting the predicted block from the current block;

transforming the residual block;

quantizing the residual block having been transformed;

encoding the residual block having been quantized;

encoding a differential motion vector obtained by subtracting a predicted motion vector, from the current motion vector, after determining one motion vector prediction candidate among one or more motion vector prediction candidates as the predicted motion vector; and

generating a bit-stream including the residual block having been encoded and the differential motion vector having been encoded, and outputting the bit-stream.

39. An apparatus for decoding an image, comprising:

a decoder for reconstructing a residual block and a differential motion vector by extracting an encoded residual block and an encoded differential motion vector from a bit-stream and decoding the encoded residual block having been extracted and the encoded differential motion vector having been extracted, determining one motion vector prediction candidate among one or more motion vector prediction candidates as a predicted motion vector, and reconstructing a current motion vector of a current block by adding the predicted motion vector having been determined to the differential motion vector having been reconstructed;

a dequantizer for dequantizing the residual block having been reconstructed;

an inverse transformer for inversely transforming the residual block having been dequantized;

a predictor for generating a predicted block by using the current motion vector having been reconstructed; and

an adder for reconstructing the current block by adding the residual block having been inversely transformed to the predicted block having been generated.

40. The apparatus of claim 39, wherein the decoder additionally reconstructs a prediction candidate identification flag by additionally extracting an encoded prediction candidate identification flag from the bit-stream and decoding the encoded prediction candidate identification flag having been extracted, and a motion vector prediction candidate identified by the prediction candidate identification flag having been reconstructed, among the one or more motion vector prediction candidates is determined as the predicted motion vector.

41. The apparatus of claim 39, wherein the decoder additionally reconstructs a prediction candidate selection flag by additionally extracting an encoded prediction candidate selection flag from the bit-stream and decoding the encoded prediction candidate selection flag having been extracted, and a motion vector prediction candidate identified by the encoded prediction candidate selection flag is determined as the one or more motion vector prediction candidates.

42. The apparatus of claim 39, wherein the decoder additionally reconstructs a prediction candidate identification flag by additionally extracting an encoded prediction candidate identification flag from the bit-stream and decoding the encoded prediction candidate identification flag having been extracted, and the decoder determines one or more combinations of x-components and y-components of the motion vector prediction candidate identified by the prediction candidate identification flag having been reconstructed, as one or more combinations of x-components and y-components of the predicted motion vector when one or more combinations of absolute values of x-components of the differential motion vector having been reconstructed and absolute values of y-components of the differential motion vector having been reconstructed are smaller than or equal to predetermined thresholds of the x-components and the y-components.

43. A method for decoding an image, comprising:

decoding an encoded residual block after extracting the encoded residual block from a bit-stream, to reconstruct the encoded residual block having been decoded;

decoding an encoded differential motion vector after extracting the encoded differential motion vector from the bit-stream, to reconstruct the encoded differential motion vector having been decoded;

reconstructing a current motion vector of a current block by using a predicted motion vector and the differential motion having been reconstructed after selecting one motion vector prediction candidate among one or more motion vector prediction candidates as the predicted motion vector;

dequantizing the residual block having been reconstructed;

inversely transforming the residual block having been dequantized;

generating a predicted block by using the current motion vector having been reconstructed; and

adding the residual block having been inversely transformed to the predicted block having been generated, to reconstruct the current block.