Video data encoding and decoding circuity applying constraint data

1. An apparatus comprising:

video data decoder circuitry configured to decode an input video data stream, the video data decoder circuitry being responsive to parameter data associated with the input video data stream, the parameter data indicating a profile selected from a plurality of profiles, each profile defining a first decoding attribute comprising one or more of a bit depth and a chrominance subsampling format;

detector circuitry configured to detect constraint data associated with the input video data stream, the constraint data defining a difference between a second decoding attribute applicable to the input video data stream and the first decoding attribute defined by the profile indicated by the parameter data, in which the constraint data is configured to indicate a zero difference of the first and second decoding attributes by a zero value of the constraint data; and

control circuitry configured to control the video data decoder circuitry to decode the input video data stream to generate a decoded video data stream having a third decoding attribute defined by the profile provided by the parameter data, as modified by the difference defined by the constraint data.

2. The apparatus of claim 1 , wherein the constraint data is configured to indicate a non-zero difference of the first and second decoding attributes by a non-zero value of the constraint data.

3. The apparatus of claim 2 , wherein the detector circuitry is configured to generate the difference of the decoding attribute by mapping a set of candidate values of the constraint data to respective difference amounts.

4. The apparatus of claim 3 , wherein, when the decoding attribute is the bit depth, the respective difference amounts mapped to candidate values of the constraint data all represent negative differences in bit depth so that the bit depth defined by the encoding profile provided by the parameter data, as modified by the difference defined by the constraint data, is a bit depth no greater than the bit depth defined by the encoding profile provided by the parameter data.

5. The apparatus of claim 3 , wherein, when the decoding attribute is the chrominance subsampling format, the respective difference amounts mapped to candidate values of the constraint data all represent differences so that the chrominance subsampling format defined by the encoding profile provided by the parameter data, as modified by the difference defined by the constraint data, is a chrominance subsampling format no higher, in a predetermined hierarchy of chrominance subsampling formats, than the chrominance subsampling format defined by the encoding profile provided by the parameter data.

6. The apparatus of claim 5 , wherein the predetermined hierarchy of chrominance subsampling formats comprises, in an order from lower to higher in the predetermined hierarchy of chrominance subsampling formats:

i. a 4:0:0 chrominance subsampling format;

ii. a 4:2:0 chrominance subsampling format

iii. a 4:2:2 chrominance subsampling format; and

iv. a 4:4:4 chrominance subsampling format.

7. The apparatus of claim 1 , wherein:

the input video data stream has associated parameter sets; and

the video data decoder circuitry is configured to decode the parameter data from a parameter set and to decode the constraint data from a parameter set.

8. A video storage, capture, transmission or reception apparatus comprising the apparatus of claim 1 .

9. An apparatus comprising:

video data encoder circuitry configured to encode an input video data stream to generate an output encoded video data stream, the video data encoder circuitry being responsive to configuration data defining a second decoding attribute comprising one or more of a bit depth and a chrominance subsampling format; and

parameter encoder circuitry configured to encode the second decoding attribute to be associated with the output encoded video data stream in dependence upon the configuration data;

in which the parameter encoder circuitry is configured to encode parameter data indicating a profile selected from a plurality of profiles, each profile defining a first decoding attribute, and constraint data defining a difference between the second decoding attribute defined by the configuration data and the first decoding attribute defined by the profile indicated by the parameter data, in which the constraint data is configured to indicate a zero difference of the first and second decoding attributes by a zero value of the constraint data.

10. The apparatus of claim 9 , wherein the constraint data is configured to indicate a non-zero difference of the decoding attribute by a non-zero value of the constraint data.

11. The apparatus of claim 10 , wherein the parameter encoder circuitry is configured to generate the difference of the decoding attribute by mapping a set of candidate values of the constraint data to respective difference amounts.

12. The apparatus of claim 11 , wherein, when the decoding attribute is the bit depth, the respective difference amounts mapped to candidate values of the constraint data all represent negative differences in bit depth so that the bit depth defined by the encoding profile provided by the parameter data, as modified by the difference defined by the constraint data, is a bit depth no greater than the bit depth defined by the encoding profile provided by the parameter data.

13. The apparatus of claim 11 , wherein, when the decoding attribute is the chrominance subsampling format, the respective difference amounts mapped to candidate values of the constraint data all represent differences so that the chrominance subsampling format defined by the encoding profile provided by the parameter data, as modified by the difference defined by the constraint data, is a chrominance subsampling format no higher, in a predetermined hierarchy of chrominance subsampling formats, than the chrominance subsampling format defined by the encoding profile provided by the parameter data.

14. The apparatus of claim 13 , wherein the predetermined hierarchy of chrominance subsampling formats comprises, in an order from lower to higher in the predetermined hierarchy of chrominance subsampling formats:

i. a 4:0:0 chrominance subsampling format;

ii. a 4:2:0 chrominance subsampling format

iii. a 4:2:2 chrominance subsampling format; and

iv. a 4:4:4 chrominance subsampling format.

15. The apparatus of claim 9 , wherein:

the output encoded video data stream has associated parameter sets; and

the parameter data encoder circuitry is configured to encode the parameter data to a parameter set and to encode the constraint data to a parameter set.

16. A video storage, capture, transmission or reception apparatus comprising the apparatus of claim 9 .

17. A method comprising:

decoding an input video data stream in response to parameter data associated with the input video data stream, the parameter data indicating a profile selected from a plurality of profiles, each profile defining a first decoding attribute comprising one or more of a bit depth and a chrominance subsampling format;

detecting constraint data associated with the input video data stream, the constraint data defining a difference between a second decoding attribute applicable to the input video data stream and the first decoding attribute defined by the profile indicated by the parameter data, in which the constraint data is configured to indicate a zero difference of the first and second decoding attributes by a zero value of the constraint data; and

controlling the decoding to generate a decoded video data stream having a third decoding attribute defined by the profile provided by the parameter data, as modified by the difference defined by the constraint data.

18. A machine-readable non-transitory storage medium which stores computer software which, when executed by a computer, causes the computer to carry out the method of claim 17 .

19. A method comprising:

encoding an input video data stream to generate an output encoded video data stream, in response to configuration data defining a second decoding attribute comprising one or more of a bit depth and a chrominance subsampling format; and

encoding the second decoding attribute to be associated with the output encoded video data stream in dependence upon the configuration data, by encoding parameter data indicating a profile selected from a plurality of profiles, each profile defining a first decoding attribute, and constraint data defining a difference between the second decoding attribute defined by the configuration data and the first decoding attribute defined by the profile indicated by the parameter data, in which the constraint data is configured to indicate a zero difference of the first and second decoding attributes by a zero value of the constraint data.

20. A machine-readable non-transitory storage medium which stores computer software which, when executed by a computer, causes the computer to carry out the method of claim 19 .