APPARATUS, A METHOD AND A COMPUTER PROGRAM FOR VIDEO CODING AND DECODING

• US 20140133567A1
• Filed: 04/16/2013
• Published: 05/15/2014
• Est. Priority Date: 04/16/2012
• Status: Active Grant

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Corporation
• Inventors: RUSANOVSKYY, Dmytro, HANNUKSELA, Miska Matias, LAINEMA, Jani
• Granted Patent: US 10,863,170 B2
• Time in Patent Office: Days
• US Class Current: 375/240.16
• CPC Class Codes: H04N 19/102 characterised by the element, parameter or selection affected or controlled by the adaptive coding
• 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 19/13 Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
• CPC Class Codes: H04N 19/159 Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/30 using hierarchical techniques, e.g. scalability H04N19/63 takes precedence
• CPC Class Codes: H04N 19/513 Processing of motion vectors
• CPC Class Codes: H04N 19/517 by encoding
• CPC Class Codes: H04N 19/573 Motion compensation with multiple frame prediction using two or more reference frames in a given prediction direction
• CPC Class Codes: H04N 19/597 specially adapted for multi-view video sequence encoding
• CPC Class Codes: H04N 19/70 characterised by syntax aspects related to video coding, e.g. related to compression standards

Abstract

There is disclosed a method, apparatus and computer program product in which a set of valid motion vector values for encoding and decoding may depend on the reference picture used. A current block of a frame is selected for encoding, and a reference block for the current block is selected. On the basis of the selected reference block a reference type is determined. On the basis of the reference type and the reference block a motion vector for the current block is determined. Motion vector information is encoded and decoded on the basis of the determined motion vector.

Claims

1. A method comprising:

selecting a current block of a picture for encoding; and

selecting a reference block for the current block;

determining a reference type on the basis of the selected reference block or determining a reference picture index identifying the picture the reference block belongs to;

determining a motion vector for the current block on the basis of the reference type and the reference block or on the basis of the reference picture index; and

encoding motion vector information on the basis of the determined motion vector.

2. The method according to claim 1 further comprising providing one or more reference pictures for the selecting of the reference block, wherein the one or more reference pictures comprises at least one of the following:

a view synthesized picture;

an inter-view picture;

an inter-layer picture;

or

an inter-predicted picture.

3. The method according to claim 1, wherein the determining a motion vector comprises determining a horizontal motion vector component and a vertical motion vector component for the motion vector, further comprising:

restricting the vertical motion vector component within a first range [a1,b1], if the selected reference block is from the view synthesized picture, the inter-view picture or the inter-layer picture; and

restricting the horizontal motion vector component within a second range [a2,b2], if the selected reference block is from the view synthesized picture or the inter-layer picture.

4. The method according to claim 1 further comprising defining a fixed motion vector for reference blocks selected from the view synthesized picture, the inter-view picture or the inter-layer picture;

and providing a motion vector syntax element for the fixed motion vector.

5. The method according to claim 4 further comprising determining the fixed motion vector based on a global disparity for multiview coding.

6. The method according to claim 1 further comprising:

determining a first entropy coding context and a second entropy coding context;

using the second entropy coding context in encoding motion vectors, when the reference block is selected from the view synthesized picture, the inter-view picture or the inter-layer picture; and

using the first entropy coding context in encoding motion vectors, when the reference block is not selected from the view synthesized picture, the inter-view picture or the inter-layer picture.

7. An apparatus comprising at least one processor and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to:

select a current block of a picture for encoding;

select a reference block for the current block;

determine a reference type on the basis of the selected reference block or a reference picture index identifying the picture the reference block belongs to;

determine a motion vector for the current block on the basis of the reference type and the reference block or on the basis of the reference picture index; and

encode motion vector information on the basis of the determined motion vector.

8. The apparatus according to claim 7, wherein said at least one memory stored with code thereon, which when executed by said at least one processor, further causes the apparatus to determine a horizontal motion vector component and a vertical motion vector component for the motion vector, and to restrict the vertical motion vector component within a first range [a1,b1], if the selected reference block is from the view synthesized picture, the inter-view picture or the inter-layer picture;

and

restrict the horizontal motion vector component within a second range [a2,b2], if the selected reference block is from the view synthesized picture or the inter-layer picture.

9. A method comprising:

receiving a bit stream comprising encoded information relating to a current block of a picture;

decoding a reference type for the current block from the encoded information;

using the reference type to determine how to obtain motion vector information relating to the current block; and

obtaining the motion vector information.

10. The method of claim 9 wherein said decoding of the reference type for the current block comprises

decoding into a decoded reference indication a reference index or another kind of an encoded reference indication included in the encoded information relating to the current block, the decoded reference indication indicating a reference picture associated with the motion vector information, and

determining the reference type on the basis of the decoded reference indication.

11. The method according to claim 9, wherein the reference type is at least one of the following:

view synthesis prediction;

inter-view prediction;

or

inter-layer prediction.

12. The method according to claim 10, wherein the reference picture is of at least one of the following types:

a view synthesized picture;

an inter-view picture;

or

an inter-layer picture

13. The method according to claim 10 further comprising

determining a motion vector comprises determining at least one of a horizontal motion vector component and a vertical motion vector component for the motion vector;

restricting the vertical motion vector component within a first range [a1,b1]; and

restricting the horizontal motion vector component within a second range [a2,b2].

14. The method according to claim 10 further comprising:

determining that the reference picture is associated with a fixed motion vector component on the basis of at least one of the following;

decoding an indication from the bitstream that the reference picture is associated with the fixed motion vector component;

inferring that the reference picture is associated with the fixed motion vector component based on one or more of the following

a type of the reference picture;

a scalability layer of the current picture and a scalability layer of the reference picture;

a view of the current picture and a view of the reference picture;

a property of the current picture and/or a property of the reference picture;

and determining a fixed motion vector component value to be used as the motion vector information relating to the current block.

15. The method according to claim 14, wherein the determining the fixed motion vector component value for the current block comprises inferring the fixed motion vector component value on the basis of the reference type.

16. The method according to claim 9 further comprising:

determining a first entropy coding context and a second entropy coding context;

using the second entropy coding context in decoding motion vectors, when the reference block is selected from a view synthesized picture, an inter-view picture or an inter-layer picture; and

using the first entropy coding context in decoding motion vectors, when the reference block is not selected from the view synthesized picture, the inter-view picture or the inter-layer picture.

17. An apparatus comprising at least one processor and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to:

receive a bit stream comprising encoded information relating to a current block of a frame;

decode the encoded information;

examine the received information to determine whether the decoded information contains an indication of a reference type for the current block or an indication of a reference picture index identifying the picture the reference block belongs to;

if the received information contains the indication of a reference type for the current block or the indication of a reference picture index, use the reference type or the reference picture index to determine how to obtain motion vector information relating to the current block; and

obtain the motion vector information.

18. An apparatus comprising:

means for receiving a bit stream comprising encoded information relating to a current block of a frame;

means for decoding the encoded information;

means for examining the received information to determine whether the decoded information contains an indication of a reference type for the current block or an indication of a reference picture index;

means for using the reference type or the reference picture index to determine how to obtain motion vector information relating to the current block, if the encoded information contains indication of a reference type for the current block; and

means for obtaining the motion vector information.

19. An apparatus comprising:

means for selecting a current block of a frame for encoding;

means for selecting a reference block for the current block;

means for determining a reference type on the basis of the selected reference block or a reference picture index identifying the picture the reference block belongs to;

means for determining a motion vector for the current block on the basis of the reference type and the reference block or on the basis of the reference picture index; and

means for encoding motion vector information on the basis of the determined motion vector.