Data processing apparatuses, methods, computer programs and computer-readable media

1. Apparatus comprising:

at least one processor; and

non-transitory system memory having stored thereon computer-executable instructions which, when executed by the at least one processor, cause the apparatus to perform the following:

obtain a first plurality of residual elements useable to reconstruct a first part of a first representation of a signal at a relatively high level of quality using a first part of a second representation of the signal at the relatively high level of quality, the first part of the second representation being derivable from a first set of one or more signal elements in a representation of the signal at a relatively low level of quality;

obtain a second plurality of residual elements useable to reconstruct a second, different part of the first representation of the signal using a second, different part of the second representation of the signal, the second part of the second representation being derivable from a second, different set of one or more signal elements in the representation of the signal at the relatively low level of quality; and

perform at least one transformation operation involving at least one residual element in the first plurality of residual elements and at least one residual element in the second plurality of residual elements to generate at least one correlation element, the at least one correlation element being dependent on an extent of correlation between the at least one residual element in the first plurality of residual elements and the at least one residual element in the second plurality of residual elements,

wherein the apparatus is configured to perform the at least one transformation operation prior to the at least one correlation element being encoded, and

the apparatus being configured to perform the at least one transformation operation by:

performing a transformation involving the first plurality of residual elements to generate a first set of correlation elements, at least one correlation element in the first set of correlation elements being dependent on an extent of correlation between at least some of the first plurality of residual elements; and

performing a transformation involving the second plurality of residual elements to generate a second set of correlation elements, at least one correlation element in the second set of correlation elements being dependent on an extent of correlation between at least some of the second plurality of residual elements.

2. Apparatus according to claim 1 , wherein the at least one transformation operation comprises at least one directional decomposition operation.

3. Apparatus according to claim 1 , the apparatus being configured to generate a plurality of correlation elements in performing the at least one transformation operation.

4. Apparatus according to claim 1 , wherein the at least one correlation element being encoded comprises quantisation being performed on the at least one correlation element.

5. Apparatus according to claim 1 , wherein different correlation elements in the first and second sets of correlation elements represent different types of correlation, the apparatus being configured to group correlation elements of the same type together in the first and second sets of correlation elements.

6. Apparatus according to claim 1 , wherein the at least one transformation operation involves all of the residual elements in the first plurality of residual elements and all of the residual elements in the second plurality of residual elements.

7. Apparatus configured to comprising:

at least one processor; and

non-transitory system memory having stored thereon computer-executable instructions which, when executed by the at least one processor, cause the apparatus to perform the following:

perform at least one transformation operation involving at least one correlation element to generate at least one residual element in a first plurality of residual elements and at least one residual element in a second plurality of residual elements, the at least one correlation element being dependent on an extent of correlation between the at least one residual element in the first plurality of residual elements and the at least one residual element in the second plurality of residual elements, the first plurality of residual elements being useable to reconstruct a first part of a first representation of a signal at a relatively high level of quality using a first part of a second representation of the signal at the relatively high level of quality, the second plurality of residual elements being useable to reconstruct a second, different part of the first representation of the signal using a second, different part of the second representation of the signal;

derive the first part of the second representation from a first set of one or more signal elements in a representation of the signal at a relatively low level of quality;

derive the second part of the second representation from a second, different set of one or more signal elements in the representation of the signal at the relatively low level of quality; and

use at least the first plurality of residual elements, the second plurality of residual elements, the first part of the second representation and the second part of the second representation to generate output data,

wherein the apparatus is configured to perform the at least one transformation operation following the at least one correlation element being decoded, and

the apparatus being configured to perform the at least one transformation operation by:

performing a transformation involving the first plurality of residual elements to generate a first set of correlation elements, at least one correlation element in the first set of correlation elements being dependent on an extent of correlation between at least some of the first plurality of residual elements; and

performing a transformation involving the second plurality of residual elements to generate a second set of correlation elements, at least one correlation element in the second set of correlation elements being dependent on an extent of correlation between at least some of the second plurality of residual elements.

8. Apparatus according to claim 7 , wherein the at least one transformation operation comprises at least one inverse directional composition operation.

9. A method comprising:

obtaining a first plurality of residual elements useable to reconstruct a first part of a first representation of a signal at a relatively high level of quality using a first part of a second representation of the signal at the relatively high level of quality, the first part of the second representation being derivable from a first set of one or more signal elements in a representation of the signal at a relatively low level of quality;

obtaining a second plurality of residual elements useable to reconstruct a second, different part of the first representation of the signal using a second, different part of the second representation of the signal, the second part of the second representation being derivable from a second, different set of one or more signal elements in the representation of the signal at the relatively low level of quality; and

performing at least one transformation operation involving at least one residual element in the first plurality of residual elements and at least one residual element in the second plurality of residual elements to generate at least one correlation element, the at least one correlation element being dependent on an extent of correlation between the at least one residual element in the first plurality of residual elements and the at least one residual element in the second plurality of residual elements,

wherein the at least one transformation operation is performed prior to the at least one correlation element being encoded,

wherein performing the at least one transformation operation comprises:

performing a transformation involving the first plurality of residual elements to generate a first set of correlation elements, at least one correlation element in the first set of correlation elements being dependent on an extent of correlation between at least some of the first plurality of residual elements; and

performing a transformation involving the second plurality of residual elements to generate a second set of correlation elements, at least one correlation element in the second set of correlation elements being dependent on an extent of correlation between at least some of the second plurality of residual elements.

10. A method according to claim 9 , wherein the at least one transformation operation comprises at least one directional decomposition operation.

11. A method according to claim 9 , wherein the at least one correlation element being encoded comprises quantisation being performed on the at least one correlation element.

12. A method according to claim 9 , wherein performing the at least one transformation operation comprises performing a transformation involving at least one correlation element in the first set of correlation elements and at least one correlation element in the second set of correlation elements to generate at least one correlation element in a third set of correlation elements, the at least one correlation element in the third set of correlation elements being dependent on an extent of correlation between the at least one correlation element in the first set of correlation elements and the at least one correlation element in the second set of correlation elements.

13. A method according to claim 12 , wherein performing the at least one transformation operation comprises performing a different transformation involving the at least one correlation element in the first set of correlation elements and the at least one correlation element in the second set of correlation elements to generate at least one other correlation element in the third set of correlation elements, the at least one other correlation element in the third set of correlation elements being dependent on an extent of correlation between the at least one correlation element in the first set of correlation elements and the at least one correlation element in the second set of correlation elements.

14. A method according to claim 9 , wherein the at least one transformation operation involves all of the residual elements in the first plurality of residual elements and all of the residual elements in the second plurality of residual elements.

15. A method comprising:

performing at least one transformation operation involving at least one correlation element to generate at least one residual element in a first plurality of residual elements and at least one residual element in a second plurality of residual elements, the at least one correlation element being dependent on an extent of correlation between the at least one residual element in the first plurality of residual elements and the at least one residual element in the second plurality of residual elements, the first plurality of residual elements being useable to reconstruct a first part of a first representation of a signal at a relatively high level of quality using a first part of a second representation of the signal at the relatively high level of quality, the second plurality of residual elements being useable to reconstruct a second, different part of the first representation of the signal using a second, different part of the second representation of the signal;

deriving the first part of the second representation from a first set of one or more signal elements in a representation of the signal at a relatively low level of quality;

deriving the second part of the second representation from a second, different set of one or more signal elements in the representation of the signal at the relatively low level of quality; and

using at least the first plurality of residual elements, the second plurality of residual elements, the first part of the second representation and the second part of the second representation to generate output data,

wherein the at least one transformation operation is performed following the at least one correlation element being decoded,

wherein performing the at least one transformation operation comprises:

performing a transformation involving the first plurality of residual elements to generate a first set of correlation elements, at least one correlation element in the first set of correlation elements being dependent on an extent of correlation between at least some of the first plurality of residual elements; and

performing a transformation involving the second plurality of residual elements to generate a second set of correlation elements, at least one correlation element in the second set of correlation elements being dependent on an extent of correlation between at least some of the second plurality of residual elements.

16. A method according to claim 15 , wherein the at least one transformation operation comprises at least one inverse directional composition operation.