Video encoding and decoding

• US 10,057,592 B2
• Filed: 08/11/2014
• Issued: 08/21/2018
• Est. Priority Date: 03/09/2011
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Laroche, Guillaume, Onno, Patrice
• Primary Examiner(s): Nawaz, Talha M
• Application Number:
  US14/456,678
• Publication Number:
  US 20150131729A1
• Time in Patent Office: 1,471 Days
• Field of Search: None
• CPC Class Codes: H04N 19/105 Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction
• CPC Class Codes: H04N 19/107 between spatial and temporal predictive coding, e.g. picture refresh
• CPC Class Codes: H04N 19/139 Analysis of motion vectors, e.g. their magnitude, direction, variance or reliability
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/43 Hardware specially adapted for motion estimation or compensation
• CPC Class Codes: H04N 19/46 Embedding additional information in the video signal during the compression process H04N19/517, H04N19/68, H04N19/70 take precedence
• 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 19/513 Processing of motion vectors
• CPC Class Codes: H04N 19/52 by predictive encoding
• CPC Class Codes: H04N 19/593 involving spatial prediction techniques
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

A temporal motion vector predictor is includable, together with one or more spatial motion vector predictors, in a set of motion vector predictors for a block to encode of a current frame. A method of determining the temporal motion vector predictor comprises selecting as the temporal predictor one motion vector from among motion vectors in a reference block of a reference frame different from the current frame. The reference block is a block of the reference frame collocated with the block to encode or a block of the reference frame neighboring the collocated block. The selection is based on a diversity criterion for achieving diversity among the predictors of the set.

This can reduce the motion vector memory requirements with no or no significant additional coding efficiency penalty. Alternatively, even if the motion vector memory is not reduced in size, coding efficiency improvements can be achieved.

Claims

1. A method of encoding a sequence of digital images into a bitstream, at least one block of an image being encoded by inter prediction with respect to a reference image block, comprising generating a set of motion vector predictors for a block to encode of a current frame, the set of motion vector predictors being permitted to include at least one spatial motion vector predictor and no more than one temporal motion vector predictor, the generating comprising selecting as said temporal motion vector predictor the motion vector at a predetermined position in the vicinity of a bottom right position of an area of the reference frame collocated with said block to encode of the current frame, and in a block of the reference frame neighboring the collocated area;

selecting a motion vector predictor from the generated set as a motion vector predictor for encoding a motion vector associated with the block to encode; and

encoding in the bitstream information identifying the selected motion vector predictor.

2. A method as claimed in claim 1, wherein said block of the reference frame is diagonally below and to the right of said collocated area, and the predetermined position is a top left position in said block of the reference frame.

4. A method as claimed in claim 1, wherein at least one said spatial predictor is selected before the temporal predictor is determined, and the determination of the temporal predictor is carried out in dependence upon the selected spatial predictor(s).

5. A method as claimed in claim 1, wherein the determination of the temporal predictor is carried out in dependence of the availability of the selected spatial predictor(s).

6. A non-transitory computer readable carrier medium carrying a computer program which, when run on a computer or processor, causes the computer or processor to carry out a method according to any one of claims 1 or 3.

3. A method of decoding a bitstream comprising an encoded sequence of digital images, at least one block of an image to be decoded having been encoded by inter prediction with respect to a reference image block, comprising generating a set of motion vector predictors for a block to decode of a current frame, the set of motion vector predictors being permitted to include at least one spatial motion vector predictor and no more than one temporal motion vector predictor, the generating comprising selecting as said temporal motion vector predictor the motion vector at a predetermined position in the vicinity of a bottom right position of an area of the reference frame collocated with said block to decode of the current frame, and in a block of the reference frame neighboring the collocated area;

selecting a motion vector predictor from the generated set as a motion vector predictor for the block to decode based on information decoded from the bitstream; and

determining a motion vector for the block to decode based on the selected motion vector predictor.

7. A method as claimed in claim 3, wherein at least one said spatial predictor is selected before the temporal predictor is determined, and the determination of the temporal predictor is carried out in dependence upon the selected spatial predictor(s).

8. A method as claimed in claim 3, wherein the determination of the temporal predictor is carried out in dependence of the availability of the selected spatial predictor(s).

9. A method as claimed in claim 3, wherein said block of the reference frame is diagonally below and to the right of said collocated area, and the predetermined position is a top left position in said block of the reference frame.

10. An apparatus for encoding a sequence of digital images into a bitstream, at least one block of an image being encoded by inter prediction with respect to a reference image block comprising a generator which generates a set of motion vector predictors for a block to encode of a current frame, the set of motion vector predictors being permitted to include at least one spatial motion vector predictor and no more than one temporal motion vector predictor, the generator comprising a spatial predictor selector which selects the at least one spatial motion vector predictor and a temporal predictor selector which selects as said temporal motion vector predictor the motion vector at a predetermined position in the vicinity of a bottom right position of an area of the reference frame collocated with said block to encode of the current frame, and in a block of the reference frame neighboring the collocated area;

and further comprising a motion vector predictor selector which selects a motion vector predictor from the generated set as a motion vector predictor for the block to encode; and

a motion vector predictor encoder that encodes in the bitstream information identifying the selected motion vector predictor.

11. An apparatus as claimed in claim 10, wherein the spatial predictor selector selects at least one said spatial predictor before the temporal predictor is determined, the temporal predictor selector being operable to determine the temporal predictor in dependence upon the selected spatial predictor(s).

12. An apparatus as claimed in claim 10, wherein the temporal predictor selector is operable to determine the temporal predictor in dependence upon the availability of the selected spatial predictor(s).

13. A method as claimed in claim 10, wherein said block of the reference frame is diagonally below and to the right of said collocated area, and the predetermined position is a top left position in said block of the reference frame.

14. An apparatus for decoding a bitstream comprising an encoded sequence of digital images, at least one block of an image being encoded by inter prediction with respect to a reference image block, comprising a generator which generates a set of motion vector predictors for a block to decode of a current frame, the set of motion vector predictors being permitted to include at least one spatial motion vector predictor and no more than one temporal motion vector predictor, the generator comprising a spatial predictor selector which selects the at least one spatial motion vector predictor and a temporal predictor selector which selects as said temporal motion vector predictor the motion vector at a predetermined position in the vicinity of a bottom right position of an area of the reference frame collocated with said block to decode of the current frame, and in a block of the reference frame neighboring the collocated area and further comprising a motion vector predictor selector which selects a motion vector predictor for the block to decode from the generated set based on information decoded from the bitstream;

and a motion vector decoder which determines a motion vector for the block to decode based on the selected motion vector predictor.

15. An apparatus as claimed in claim 14, wherein the spatial predictor selector selects at least one said spatial predictor before the temporal predictor is determined, the temporal predictor selector being operable to determine the temporal predictor in dependence upon the selected spatial predictor(s).

16. An apparatus as claimed in claim 14, wherein the temporal predictor selector is operable to determine the temporal predictor in dependence upon the availability of the selected spatial predictor(s).

17. A method as claimed in claim 14, wherein said block of the reference frame is diagonally below and to the right of said collocated area, and the predetermined position is a top left position in said block of the reference frame.