Motion vector predictive encoding method, motion vector predictive decoding method, moving picture encoding apparatus, moving picture decoding apparatus, and programs thereof

• US 9,497,481 B2
• Filed: 02/08/2011
• Issued: 11/15/2016
• Est. Priority Date: 02/09/2010
• Status: Active Grant

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Kitahara, Masaki, Shimizu, Atsushi, Watanabe, Mayuko
• Primary Examiner(s): Vaughn, Jr., William C
• Assistant Examiner(s): Uhl, Lindsay
• Application Number:
  US13/576,609
• Publication Number:
  US 20120294371A1
• Time in Patent Office: 2,107 Days
• Field of Search: None
• US Class Current: 1/1
• 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 19/533 Motion estimation using multistep search, e.g. 2D-log search or one-at-a-time search [OTS]
• CPC Class Codes: H04N 19/56 Motion estimation with initialisation of the vector search, e.g. estimating a good candidate to initiate a search

Abstract

In motion vector prediction encoding, the efficiency of motion vector prediction is improved and the efficiency of moving picture encoding is improved. A motion search is performed for a block to be encoded in a picture to be encoded using an encoded reference picture to calculate a motion vector. A plurality of blocks which include at least one of encoded blocks in the picture to be encoded and encoded blocks in an encoded picture and in predetermined positions relative to the position of the block to be encoded in the picture to be encoded are set as primary candidate blocks, and N primary candidate reference motion vectors are determined from motion vectors used in encoding the primary candidate blocks. The degrees of reliability of the primary candidate reference motion vectors which quantitatively represent effectiveness in motion vector prediction of the block to be encoded is calculated using encoded picture information for each of the primary candidate reference motion vectors. Top M primary candidate reference motion vectors with higher degrees of reliability are selected from the primary candidate reference motion vectors as secondary candidate reference motion vectors. A predictive motion vector of the block to be encoded is calculated using the secondary candidate reference motion vectors, and a residual between the motion vector obtained through the motion search of the block to be encoded and the predictive motion vector is encoded as encoded information of the motion vector.

Claims

1. A motion vector predictive encoding method in a moving picture encoding scheme in which a picture to be encoded is divided into blocks and encoding is performed using motion compensation for each block, the method comprising:

a step of performing a motion search for a block to be encoded in the picture to be encoded using an encoded reference picture to calculate a motion vector;

a step of setting a plurality of blocks which include at least one of encoded blocks in the picture to be encoded and encoded blocks in an encoded picture, the encoded blocks in the picture to be encoded and the encoded blocks in the encoded picture being in predetermined positions relative to the position of the block to be encoded in the picture to be encoded, as primary candidate blocks, and determining N (N is an integer greater than or equal to

     2) primary candidate reference motion vectors from motion vectors used in encoding the primary candidate blocks;

a step of calculating degrees of reliability of the primary candidate reference motion vectors which quantitatively represent effectiveness in motion vector prediction of the block to be encoded, using only information already encoded at the time of encoding the block to be encoded for each of the primary candidate reference motion vectors;

a step of selecting top M (M is a predetermined integer greater than or equal to 1 and less than N) primary candidate reference motion vectors with higher degrees of reliability from the N primary candidate reference motion vectors as secondary candidate reference motion vectors; and

a step of setting a secondary candidate reference motion vector having a value nearest the motion vector obtained by the motion search among the secondary candidate reference motion vectors as a predictive motion vector of the block to be encoded, encoding an identifier of the set predictive motion vector, and encoding a residual between the motion vector obtained through the motion search of the block to be encoded and the predictive motion vector as encoded information of the motion vector,

wherein, in the step of determining the primary candidate reference motion vectors, the primary candidate reference motion vectors are determined from the motion vectors used in encoding the primary candidate blocks and motion vectors which designate positions within a predetermined range from a position designated by each of the motion vectors used in encoding the primary candidate blocks.

2. The motion vector predictive encoding method according to claim 1, wherein, when only M′

primary candidate reference motion vectors can be set, M′

being smaller than M, instead of N primary candidate reference motion vectors to be set, the M′

primary candidate reference motion vectors are selected as the secondary candidate reference motion vectors.

3. The motion vector predictive encoding method according to claim 1, wherein, in the step of calculating the degrees of reliability of the primary candidate reference motion vectors, a set of encoded pixels adjacent to the block to be encoded is used as a template, an area obtained by shifting an area of the template by a primary candidate reference motion vector on the reference picture is set as an area to be matched, and a degree of similarity between the set of the encoded pixels of the template and a set of pixels in the area to be matched is calculated as a degree of reliability.

4. The motion vector predictive encoding method according to claim 1, wherein, in the step of calculating the degrees of reliability of the primary candidate reference motion vectors, the degrees of reliability are calculated by using degree of smallness of a decoded prediction residual signal in motion compensation of primary candidate blocks relating to the primary candidate reference motion vectors as an index of a degree of reliability.

5. The motion vector predictive encoding method according to claim 1, wherein, in the step of selecting the secondary candidate reference motion vectors from the N primary candidate reference motion vectors, a plurality of top primary candidate reference motion vectors with higher degrees of reliability are selected as the secondary candidate reference motion vectors.

15. A non-transitory computer readable storage medium storing a motion vector prediction encoding program for allowing a computer to execute the motion vector predictive encoding method according to claim 1.

6. A motion vector predictive decoding method in a moving picture decoding scheme in which a picture to be decoded of a moving picture being divided into blocks and encoded is decoded, using motion compensation for each block, the method comprising:

a step of decoding a motion vector prediction residual of a block to be decoded;

a step of setting a plurality of blocks which include at least one of decoded blocks in the picture to be decoded and decoded blocks in a decoded picture, the decoded blocks in the picture to be decoded and the decoded blocks in the decoded picture being in predetermined positions relative to the position of the block to be decoded in the picture to be decoded, as primary candidate blocks, and determining N (N is an integer greater than or equal to

     2) primary candidate reference motion vectors from motion vectors used in decoding the primary candidate blocks;

a step of calculating degrees of reliability of the primary candidate reference motion vectors which quantitatively represent effectiveness in motion vector prediction of the block to be decoded, using only information already decoded at the time of decoding the block to be decoded for each of the primary candidate reference motion vectors;

a step of selecting top M (M is a predetermined integer greater than or equal to 1 and less than N) primary candidate reference motion vectors with higher degrees of reliability from the N primary candidate reference motion vectors as secondary candidate reference motion vectors; and

a step of extracting a motion vector corresponding to an encoded identifier among the secondary candidate reference motion vectors, setting the extracted motion vector as a predictive motion vector of the block to be decoded, and adding the predictive motion vector to the decoded motion vector prediction residual to calculate a motion vector of the block to be decoded,

wherein, in the step of determining the primary candidate reference motion vectors, the primary candidate reference motion vectors are determined from the motion vectors used in decoding the primary candidate blocks and motion vectors which designate positions within a predetermined range from a position designated by each of the motion vectors used in decoding the primary candidate blocks.

7. The motion vector predictive decoding method according to claim 6, wherein, when only M′

primary candidate reference motion vectors can be set, M′

being smaller than M, instead of N primary candidate reference motion vectors to be set, the M′

primary candidate reference motion vectors are selected as the secondary candidate reference motion vectors.

8. The motion vector predictive decoding method according to claim 6, wherein, in the step of calculating the degrees of reliability of the primary candidate reference motion vectors, a set of decoded pixels adjacent to the block to be decoded is used as a template, an area obtained by shifting an area of the template by a primary candidate reference motion vector on a decoded reference picture is set as an area to be matched, and a degree of similarity between the set of the decoded pixels of the template and a set of pixels in the area to be matched is calculated as a degrees of reliability.

9. The motion vector predictive decoding method according to claim 6, wherein, in the step of calculating the degrees of reliability of the primary candidate reference motion vectors, the degrees of reliability are calculated by using degree of smallness of a decoded prediction residual signal in motion compensation of primary candidate blocks relating to the primary candidate reference motion vectors as an index of a degree of reliability.

10. The motion vector predictive decoding method according to claim 6, wherein, in the step of selecting the secondary candidate reference motion vectors from the N primary candidate reference motion vectors, a plurality of top primary candidate reference motion vectors with higher degrees of reliability are selected as the secondary candidate reference motion vectors.

16. A non-transitory computer readable storage medium storing a motion vector prediction decoding program for allowing a computer to execute the motion vector predictive decoding method according to claim 6.

11. A moving picture encoding apparatus which divides a picture to be encoded into blocks and encodes a moving picture using motion compensation for each block, the apparatus comprising:

a motion search processor programmed to perform a motion search for a block to be encoded in the picture to be encoded using an encoded reference picture to calculate a motion vector;

a primary candidate reference motion vector determination processor programmed to set a plurality of blocks which include at least one of encoded blocks in the picture to be encoded and encoded blocks in an encoded picture, the encoded blocks in the picture to be encoded and the encoded blocks in the encoded picture being in predetermined positions relative to the position of the block to be encoded in the picture to be encoded, as primary candidate blocks, and programmed to determine N (N is an integer greater than or equal to

     2) primary candidate reference motion vectors from motion vectors used in encoding the primary candidate blocks;

a degree of reliability calculation processor programmed to calculate degrees of reliability of the primary candidate reference motion vectors which quantitatively represent effectiveness in motion vector prediction of the block to be encoded, using only information already encoded at the time of encoding the block to be encoded for each of the primary candidate reference motion vectors;

a reference motion vector determination processor programmed to select top M (M is a predetermined integer greater than or equal to 1 and less than N) primary candidate reference motion vectors with higher degrees of reliability from the N primary candidate reference motion vectors as secondary candidate reference motion vectors; and

a motion vector encoding processor programmed to set a secondary candidate reference motion vector having a value nearest the motion vector obtained by the motion search among the secondary candidate reference motion vectors as a predictive motion vector of the block to be encoded, programmed to encode an identifier of the set predictive motion vector, and programmed to encode a residual between the motion vector obtained through the motion search of the block to be encoded and the predictive motion vector as encoded information of the motion vector,

wherein, in the step of determining the primary candidate reference motion vectors, the primary candidate reference motion vectors are determined from the motion vectors used in encoding the primary candidate blocks and motion vectors which designate positions within a predetermined range from a position designated by each of the motion vectors used in encoding the primary candidate blocks.

12. The moving picture encoding apparatus according to claim 11, wherein the reference motion vector determination processor is programmed to select a plurality of top primary candidate reference motion vectors with higher degrees of reliability from the N primary candidate reference motion vectors as the secondary candidate reference motion vectors.

13. A moving picture decoding apparatus which decodes a picture to be decoded of a moving picture being divided into blocks and encoded, using motion compensation for each block, the apparatus comprising:

an information source decoding processor programmed to decode a motion vector prediction residual of a block to be decoded;

a primary candidate reference motion vector determination processor programmed to set a plurality of blocks which include at least one of decoded blocks in the picture to be decoded and decoded blocks in a decoded picture, the decoded blocks in the picture to be decoded and the decoded blocks in the decoded picture being in predetermined positions relative to the position of the block to be decoded in the picture to be decoded, as primary candidate blocks, and programmed to determine N (N is an integer greater than or equal to

     2) primary candidate reference motion vectors from motion vectors used in decoding the primary candidate blocks;

a degree of reliability calculation processor programmed to calculate degrees of reliability of the primary candidate reference motion vectors which quantitatively represent effectiveness in motion vector prediction of the block to be decoded, using only information already decoded at the time of decoding the block to be decoded for each of the primary candidate reference motion vectors;

a reference motion vector determination processor programmed to select top M (M is a predetermined integer greater than or equal to 1 and less than N) primary candidate reference motion vectors with higher degrees of reliability from the N primary candidate reference motion vectors as secondary candidate reference motion vectors; and

a motion vector calculation processor programmed to extract a motion vector corresponding to an encoded identifier among the secondary candidate reference motion vectors, programmed to set the extracted motion vector as a predictive motion vector of the block to be decoded using the secondary candidate reference motion vectors, and programmed to add the predictive motion vector to the decoded motion vector prediction residual to calculate a motion vector of the block to be decoded,

wherein, in the step of determining the primary candidate reference motion vectors, the primary candidate reference motion vectors are determined from the motion vectors used in decoding the primary candidate blocks and motion vectors which designate positions within a predetermined range from a position designated by each of the motion vectors used in decoding the primary candidate blocks.

14. The moving picture decoding apparatus according to claim 13, wherein the reference motion vector determination processor is programmed to select a plurality of top primary candidate reference motion vectors with higher degrees of reliability from the N primary candidate reference motion vectors as the secondary candidate reference motion vectors.