Tile partitions with sub-tiles in video coding

1. A method of decoding a picture, the method comprising:

receiving a bitstream comprising a plurality of coded segments, and information from a parameter set associated with the plurality of coded segments;

deriving, using the information from the parameter set:

a spatial partition structure that divides the picture into a plurality of picture segments, wherein

each picture segment corresponds to one of the plurality of coded segments and comprises one or more subsegments,

at least one picture segment comprises at least two subsegments, and

each subsegment comprises a plurality of units with each unit corresponding to a region of the picture of a spatial size corresponding to a unit size of the unit;

a subsegment size of a subsegment of the spatial partition structure; and

the unit size of the units of the spatial partition structure; and

decoding the plurality of coded segments received in the bitstream in accordance with the spatial partition structure, wherein derivation of an intra prediction mode for a second unit of a given one of the picture segments depends on a derived intra prediction mode for a first unit of the given one of the picture segments and is independent of any intra prediction mode for units of any other picture segments.

2. The method of claim 1 , further comprising deriving a quantization parameter value for the second unit based on a quantization parameter value for the first unit, and independently of any quantization parameter value for units of other picture segments.

3. The method of claim 1 , wherein deriving the spatial partition structure comprises deriving the spatial partition structure responsive to receiving an indication that an encoder sending the bitstream is using flexible partitioning to divide the picture into a plurality of picture segments.

4. The method of claim 1 , wherein deriving the spatial partition structure comprises deriving the spatial partition structure responsive to receiving an indication that an encoder sending the bitstream is using subsegments.

5. The method of claim 1 , wherein decoding the plurality of coded segments received in the bitstream comprises decoding each picture segment according to a predefined decoding order, wherein the predefined decoding order is a raster scan order.

6. The method of claim 1 , wherein deriving a subsegment size comprises deriving a first subsegment size for a first subsegment and a second subsegment size for a second subsegment, wherein the first subsegment size and the second subsegment size are different sizes.

7. The method of claim 1 , further comprising deriving a spatial size of a segment based on a subsegment size.

8. The method of claim 1 , wherein an edge of a first picture segment borders edges of two or more adjacent picture segments.

9. The method of claim 1 , wherein the information indicates a first subsegment size for a first subsegment of the spatial partition structure and a second subsegment size for a second subsegment of the spatial partition structure, and wherein the first subsegment size and the second subsegment size are different sizes.

10. The method of claim 1 , wherein the information indicates one of a height, a width, and an area of a subsegment of the spatial partition structure as an integer multiple of a respective one of a height, a width, and an area of a unit of the spatial partition structure.

11. The method of claim 1 , wherein the information indicates a single subsegment size for all the subsegments of the spatial partition structure.

12. The method of claim 1 , wherein each subsegment of the spatial partition structure corresponds to one of a rectangular region of the picture and a square region of the picture.

13. The method of claim 1 , wherein the spatial partition structure divides the picture segments by arranging corners of each picture segment on a grid that defines, for each picture segment, corresponding values for a start corner and an end corner.

14. A method of encoding a picture, the method comprising:

defining a spatial partition structure that divides a picture into a plurality of picture segments, wherein

each picture segment comprises one or more subsegments with at least one picture segment comprising at least two subsegements; and

each subsegment comprises a plurality of units with each unit corresponding to a region of the picture;

encoding the picture segments in accordance with the spatial partition structure to generate a plurality of coded segments, wherein each coded segment corresponds to one of the picture segments of the spatial partition structure, and wherein each coded segment is independent such that derivation of an intra prediction mode for a second unit of a given one of the picture segments depends on a derived intra prediction mode for a first unit of the given one of the picture segments, and is independent of any intra prediction mode for units of any other picture segment;

generating a bitstream comprising the plurality of coded segments, and a parameter set associated with the plurality of coded segments including information indicating the spatial partition structure used to divide the picture into the picture segments, wherein the information indicates a unit size of a unit of the spatial partition structure and a subsegment size of a subsegment of the spatial partition structure; and

transmitting the bitstream.

15. The method of claim 14 , wherein generating a bitstream further comprises generating the bitstream to comprise an indication that the spatial partition structure comprises subsegments.

16. The method of claim 14 , wherein an edge of a first picture segment borders edges of two or more adjacent picture segments.

17. The method of claim 14 , wherein the information indicates a first subsegment size for a first subsegment of the spatial partition structure and a second subsegment size for a second subsegment of the spatial partition structure, and wherein the first subsegment size and the second subsegment size are different sizes.

18. The method of claim 14 , wherein the information indicates one of a height, a width, and an area of a subsegment of the spatial partition structure as an integer multiple of a respective one of a height, a width, and an area of a unit of the spatial partition structure.

19. The method of claim 14 , wherein the information comprises a single subsegment size for all the subsegments of the spatial partition structure.

20. The method of claim 14 , wherein each subsegment of the spatial partition structure corresponds to one of a rectangular region of the picture and a square region of the picture.

21. The method of claim 14 , wherein the spatial partition structure divides the picture segments by arranging corners of each picture segment on a grid that defines, for each picture segment, corresponding values for a start corner and end corner.

22. The method of claim 21 , wherein the grid is defined with respect to subsegments of the spatial partition structure.

23. A decoder comprising:

communications circuitry configured to receive a bitstream comprising a plurality of coded segments, and information from a parameter set associated with the plurality of coded segments;

a memory configured to store instructions; and

processing circuitry operatively connected to the memory and the communications circuitry, and configured to execute the instructions stored in the memory whereby the decoder is configured to:

derive, using the information from the parameter set:

a spatial partition structure that divides the picture into a plurality of picture segments, wherein

each picture segment corresponds to one of the plurality of coded segments and comprises one or more subsegments,

at least one picture segment comprises at least two subsegments, and

each subsegment comprises a plurality of units with each unit corresponding to a region of the picture of a spatial size corresponding to a unit size of the unit;

a subsegment size of a subsegment of the spatial partition structure; and

the unit size of the units of the spatial partition structure; and

decode the plurality of coded segments received in the bitstream in accordance with the spatial partition structure, wherein derivation of an intra prediction mode for a first unit of a given one of the picture segments depends on a derived intra prediction mode for a second unit of the given one of the picture segments and is independent of any intra prediction mode for units of any other picture segments.

24. A non-transitory computer readable medium comprising executable instructions stored thereon that, when executed by a processing circuit in a decoder, causes the decoder to:

receive a bitstream comprising a plurality of coded segments, and information from a parameter set associated with the plurality of coded segments;

derive, using the information from the parameter set:

a spatial partition structure that divides the picture into a plurality of picture segments, wherein

each picture segment corresponds to one of the plurality of coded segments and comprises one or more subsegments,

at least one picture segment comprises at least two subsegments, and

each subsegment comprises a plurality of units with each unit corresponding to a region of the picture of a spatial size corresponding to a unit size of the unit;

a subsegment size of a subsegment of the spatial partition structure; and

unit size of the units of the spatial partition structure; and

decode the plurality of coded segments received in the bitstream in accordance with the spatial partition structure, wherein derivation of an intra prediction mode for a second unit of a given one of the picture segments depends on a derived intra prediction mode for a first unit of the given one of the picture segments and is independent of any intra prediction mode for units of any other picture segments.

25. An encoder comprising:

a memory configured to store instructions; and

processing circuitry operatively connected to the memory, and configured to execute the instructions stored in the memory whereby the encoder is configured to:

define a spatial partition structure that divides a picture into picture segments, wherein each picture segment comprises one or more subsegments with at least one picture segment at least two subsegments, and wherein each subsegment of the spatial partition structure comprises a plurality of units, with each unit corresponding to a region of the picture;

encode the picture segments in accordance with the spatial partition structure to generate a plurality of coded segments, wherein each coded segment corresponds to one of the picture segments of the spatial partition structure, and wherein each coded segment is independent such that any derivation of any intra prediction mode for a second unit of a given one of the picture segments depends on a derived intra prediction mode for a first unit of the given one of the picture segments and is independent of any intra prediction mode for units of any other picture segments; and

generate a bitstream comprising the plurality of coded segments, and a parameter set associated with the plurality of coded segments including information indicating the spatial partition structure used to divide the picture into the picture segments, wherein the information indicates a size of a unit of the spatial partition structure and a size of a subsegment of the spatial partition structure; and

transmit the bitstream.

26. A non-transitory computer readable medium comprising executable instructions stored thereon that, when executed by a processing circuit in an encoder, causes the encoder to:

define a spatial partition structure that divides a picture into picture segments, wherein each picture segment comprises one or more subsegments with at least one picture segment at least two subsegments, and wherein each subsegment of the spatial partition structure comprises a plurality of units, with each unit corresponding to a region of the picture;

encode the picture segments in accordance with the spatial partition structure to generate a plurality of coded segments, wherein each coded segment corresponds to one of the picture segments of the spatial partition structure, and wherein each coded segment is independent such that any derivation of any intra prediction mode for a second unit of a given one of the picture segments depends on a derived intra prediction mode for a first unit of the given one of the picture segments and is independent of any intra prediction mode for units of any other picture segments; and

generate a bitstream comprising the plurality of coded segments and, a parameter set associated with the plurality of coded segments including information indicating the spatial partition structure used to divide the picture into the picture segments, wherein the information indicates a size of a unit of the spatial partition structure and a size of a subsegment of the spatial partition structure; and

transmit the bitstream.