Apparatus, a method and a computer program for video coding and decoding

1. A method comprising:

encoding an input picture into a coded constituent picture;

reconstructing, as a part of said encoding, a decoded constituent picture corresponding to the coded constituent picture;

encoding a spatial region of the input picture into a coded tile, the encoding comprising:

determining a horizontal offset and a vertical offset indicative of a region-wise anchor position of the spatial region within the decoded constituent picture;

encoding the horizontal offset and the vertical offset;

determining that a prediction unit at position of a first horizontal coordinate and a first vertical coordinate of the coded tile is predicted relative to the region-wise anchor position, wherein the first horizontal coordinate and the first vertical coordinate are horizontal and vertical coordinates, respectively, within the spatial region;

indicating that the prediction unit is predicted relative to a prediction-unit anchor position that is relative to the horizontal offset and the vertical offset;

deriving the prediction-unit anchor position equal to sum of the first horizontal coordinate and the horizontal offset, and the first vertical coordinate and the vertical offset, respectively;

determining a motion vector for the prediction unit; and

applying the motion vector relative to the prediction-unit anchor position to obtain a prediction block; and

encoding, in response to said coded constituent picture and said coded tile comprising different sampling densities, information indicative of a sampling ratio between the coded constituent picture and the coded tile into a bitstream.

2. The method according to claim 1 , further comprising:

scaling the first horizontal coordinate and the first vertical coordinate of the prediction unit according to the sampling ratio for the derivation of the prediction-unit anchor position.

3. The method according to claim 2 , further comprising:

scaling the motion vector according to the sampling ratio for obtaining the prediction block.

4. The method according to claim 3 , further comprising:

identifying a source block for obtaining the prediction block, comprising applying the motion vector relative to the prediction-unit anchor position.

5. The method according to claim 1 , further comprising:

partitioning the prediction unit to motion units; and

deriving a respective motion vector for respective ones of the motion units from the motion vector of the prediction unit according to the sampling ratio.

6. The method according to claim 1 , further comprising:

indicating for said coded tile that a motion vector anchor position offset mechanism is applied for motion vectors of the coded tile.

7. An apparatus comprising:

at least one processor and

at least one non-transitory memory, said at least one memory stored with code thereon, which when executed by said at least one processor, causes the apparatus to perform:

encode an input picture into a coded constituent picture;

reconstruct, as a part of said encoding, a decoded constituent picture corresponding to the coded constituent picture;

encode a spatial region of the input picture into a coded tile, comprising causing the apparatus to:

determine a horizontal offset and a vertical offset indicative of a region-wise anchor position of the spatial region within the decoded constituent picture;

encode the horizontal offset and the vertical offset;

determine that a prediction unit at position of a first horizontal coordinate and a first vertical coordinate of the coded tile is predicted relative to the region-wise anchor position, wherein the first horizontal coordinate and the first vertical coordinate are horizontal and vertical coordinates, respectively, within the spatial region;

indicate that the prediction unit is predicted relative to a prediction-unit anchor position that is relative to the horizontal offset and the vertical offset;

derive the prediction-unit anchor position equal to sum of the first horizontal coordinate and the horizontal offset, and the first vertical coordinate and the vertical offset, respectively;

determine a motion vector for the prediction unit; and

apply the motion vector relative to the prediction-unit anchor position to obtain a prediction block; and

encode, in response to said coded constituent picture and said coded tile comprising different sampling densities, information indicative of a sampling ratio between the coded constituent picture and the coded tile into a bitstream.

8. The apparatus according to claim 7 , further comprising code which when executed by said at least one processor, causes the apparatus to:

scale the first horizontal coordinate and the first vertical coordinate of the prediction unit according to the sampling ratio for the derivation of the prediction-unit anchor position.

9. The apparatus according to claim 8 , further comprising code which when executed by said at least one processor, causes the apparatus to:

scale the motion vector according to the sampling ratio for obtaining the prediction block.

10. The apparatus according to claim 9 , further comprising code which when executed by said at least one processor, causes the apparatus to:

identify a source block for obtaining the prediction block, comprising applying the motion vector relative to the prediction-unit anchor position.

11. The apparatus according to claim 7 , further comprising code which when executed by said at least one processor, causes the apparatus to:

partition the prediction unit to motion units; and

derive a respective motion vector for respective ones of the motion units from the motion vector of the prediction unit according to the sampling ratio.

12. The apparatus according to claim 7 , further comprising code which when executed by said at least one processor, causes the apparatus to:

indicate for said coded tile that a motion vector anchor position offset mechanism is applied for motion vectors of the coded tile.

13. A method comprising:

decoding, from a bitstream, a coded constituent picture;

decoding a coded tile into a decoded tile, the decoding comprising:

decoding a horizontal offset and a vertical offset;

decoding an indication that a prediction unit at position of a first horizontal coordinate and a first vertical coordinate of the coded tile is predicted relative to a prediction-unit anchor position that is relative to the horizontal offset and the vertical offset;

deriving the prediction-unit anchor position equal to sum of the first horizontal coordinate and the horizontal offset, and the first vertical coordinate and the vertical offset, respectively;

determining a motion vector for the prediction unit; and

applying the motion vector relative to the prediction-unit anchor position to obtain a prediction block;

decoding, from the bitstream, information indicative of a sampling ratio between the coded constituent picture and the coded tile; and

scaling the first horizontal coordinate and the first vertical coordinate of the prediction unit according to the sampling ratio for the derivation of the prediction-unit anchor position.

14. The method according to claim 13 , further comprising:

scaling the motion vector according to the sampling ratio for obtaining the prediction block.

15. The method according to claim 13 , further comprising:

partitioning the prediction unit to motion units; and

deriving a respective motion vector for respective ones of the motion units from the motion vector of the prediction unit according to the sampling ratio.

16. The method according to claim 13 , further comprising:

decoding an indication for said coded tile that a motion vector anchor position offset mechanism is applied for motion vectors of the coded tile.

17. An apparatus comprising:

at least one processor and

at least one non-transitory memory, said at least one memory stored with code thereon, which when executed by said at least one processor, causes the apparatus to perform:

decode, from a bitstream, a coded constituent picture;

decode a coded tile into a decoded tile, comprising causing the apparatus to:

decode a horizontal offset and a vertical offset;

decode an indication that a prediction unit at position of a first horizontal coordinate and a first vertical coordinate of the coded tile is predicted relative to a prediction-unit anchor position that is relative to the horizontal offset and the vertical offset;

derive the prediction-unit anchor position equal to sum of the first horizontal coordinate and the horizontal offset, and the first vertical coordinate and the vertical offset, respectively;

determine a motion vector for the prediction unit; and

apply the motion vector relative to the prediction-unit anchor position to obtain a prediction block;

decode, from the bitstream, information indicative of a sampling ratio between the coded constituent picture and the coded tile; and

scale the first horizontal coordinate and the first vertical coordinate of the prediction unit according to the sampling ratio for the derivation of the prediction-unit anchor position.

18. The apparatus according to claim 17 , further comprising code which when executed by said at least one processor, causes the apparatus to:

scale the motion vector according to the sampling ratio for obtaining the prediction block.

19. The apparatus according to claim 17 , further comprising code which when executed by said at least one processor, causes the apparatus to:

partition the prediction unit to motion units; and

derive a respective motion vector for respective ones of the motion units from the motion vector of the prediction unit according to the sampling ratio.

20. The apparatus according to claim 17 , further comprising code which when executed by said at least one processor, causes the apparatus to:

decode an indication for said coded tile that a motion vector anchor position offset mechanism is applied for motion vectors of the coded tile.