Data encoding and decoding
A data encoding method includes encoding an array of data values as data sets and escape codes for values not encoded by the data sets, an escape code including a prefix portion and a non-unary coded suffix portion having a length, in bits, dependent upon a value encoded by the prefix portion according to a relationship such that, for at least some values encoded by the prefix portion, the length of the non-unary coded suffix portion is greater than the length, in bits, of the prefix portion.
1. A data decoding apparatus comprising:
a decoder configured to decode input encoded data values into decoded data values having a bit depth, wherein
the input encoded data values include
values encoded as data sets; and
escape codes for values not encoded by the data sets,
an escape code of the escape codes includes
a prefix portion having a prefix length capped at a maximum prefix length that is dependent upon the bit depth of the decoded data values; and
a non-unary coded suffix portion having a length, in bits, that is dependent upon a value encoded by the prefix portion, and
for at least some values encoded by the prefix portion, the length of the non-unary coded suffix portion is greater than the prefix length, in bits, of the prefix portion.
2. The apparatus according to claim 1 , wherein the prefix portion comprises a unary encoded value.
3. The apparatus according to claim 2 , wherein the prefix portion comprises a truncated unary encoded value.
4. The apparatus according to claim 1 , further comprising:
a controller configured to access one or more tables in which the value encoded by the prefix portion and the length of the non-unary coded suffix portion are associated.
5. The apparatus according to claim 4 , wherein the controller is configured to select one of the one or more tables associating the value encoded by the prefix portion and the length of the non-unary coded suffix portion according to one or more of: (i) a data flag associated with the encoded data values; and (ii) a parameter derived from one or more previously encoded data values.
6. The apparatus according to claim 1 , wherein the value encoded by the prefix portion is associated with the length of the non-unary coded suffix portion such that the length of the non-unary coded suffix portion is an exponential function of the value encoded by the prefix portion.
7. The apparatus according to claim 1 , wherein a relationship between the value encoded by the prefix portion and the length of the non-unary coded suffix portion is such that a maximum length of the non-unary coded suffix portion is no greater than a maximum value selected from one of: a maximum number of bits of each of the data values to be encoded; and a predetermined maximum value.
8. The apparatus according to claim 1 , wherein the prefix portion is encoded as an exponential Golomb code.
9. The apparatus according to claim 1 , wherein the maximum prefix length is dependent upon the bit depth of the decoded data values plus six.
10. The apparatus according to claim 1 , wherein the maximum prefix length is equal to a predetermined constant minus a value equal to a dynamic range of data values for encoding.
11. The apparatus according to claim 10 , wherein the predetermined constant is equal to 29.
12. The apparatus according to claim 10 , wherein the predetermined constant is equal to 28.
13. The apparatus according to claim 1 , wherein one of the data sets is a significance map indicative of positions, relative to an array of the encoded data values, of most-significant data portions which are non-zero.
14. The apparatus according to claim 13 , wherein the significance map comprises a data flag indicative of a position, according to a predetermined ordering of the array of encoded data values, of a last of the most-significant data portions having a non-zero value.
15. A method of operation of a data decoding apparatus, comprising:
decoding input encoded data values into decoded data values having a bit depth by the data decoding apparatus, wherein
the input encoded data values include
values encoded as data sets; and
escape codes for values not encoded by the data sets,
an escape code of the escape codes includes
a prefix portion having a prefix length capped at a maximum prefix length that is dependent upon the bit depth of the decoded data values; and
a non-unary coded suffix portion having a length, in bits, that is dependent upon a value encoded by the prefix portion, and
for at least some values encoded by the prefix portion, the length of the non-unary coded suffix portion is greater than the prefix length, in bits, of the prefix portion.
16. The method according to claim 15 , wherein the maximum prefix length is dependent upon the bit depth of the decoded data values plus six.
17. The method of claim 16 , wherein
the maximum prefix length is equal to a predetermined constant minus a value equal to a dynamic range of data values for encoding, and
the predetermined constant is equal to 28.
18. A non-transitory computer readable medium including computer program instructions, which when executed by a computer causes the computer to perform the method of claim 15 .
19. A data encoding apparatus comprising:
an encoder configured to encode an array of data values having a bit depth as data sets and escape codes for values not encoded by the data sets, wherein
an escape code of the escape codes includes
a prefix portion having a prefix length capped at a maximum prefix length that is dependent upon the bit depth of the data values; and
a non-unary coded suffix portion having a length, in bits, that is dependent upon a value encoded by the prefix portion, and
for at least some values encoded by the prefix portion, the length of the non-unary coded suffix portion is greater than the prefix length, in bits, of the prefix portion.
20. The apparatus according to claim 19 , wherein
the maximum prefix length is equal to a predetermined constant minus a value equal to a dynamic range of data values for encoding, and
the predetermined constant is equal to 28.
21. A method of operation of a data encoding apparatus, the method comprising:
encoding an array of data values as data sets having a bit depth and escape codes for values not encoded by the data sets by the data encoding apparatus, wherein
an escape code of the escape codes includes
a prefix portion having a prefix length capped at a maximum prefix length that is dependent upon the bit depth of the data values; and
a non-unary coded suffix portion having a length, in bits, that is dependent upon a value encoded by the prefix portion, and
for at least some values encoded by the prefix portion, the length of the non-unary coded suffix portion is greater than the prefix length, in bits, of the prefix portion.
22. The method according to claim 21 , wherein
the maximum prefix length is equal to a predetermined constant minus a value equal to a dynamic range of data values for encoding, and
the predetermined constant is equal to 28.
23. A non-transitory computer readable medium including computer program instructions, which when executed by a computer causes the computer to perform the method of claim 21 .
24. A video data capture, transmission, display and/or storage apparatus comprising the data decoding apparatus according to claim 1 .