Bit-depth scalability
To increase efficiency of a bit-depth scalable data-stream an inter-layer prediction is obtained by mapping samples of the representation of the picture or video source data with a first picture sample bit-depth from a first dynamic range corresponding to the first picture sample bit-depth to a second dynamic range greater than the first dynamic range and corresponding to a second picture sample bit-depth being higher than the first picture sample bit-depth by use of one or more global mapping functions being constant within the picture or video source data or varying at a first granularity, and a local mapping function locally modifying the one or more global mapping functions and varying at a second granularity smaller than the first granularity, with forming the quality-scalable data-stream based on the local mapping function such that the local mapping function is derivable from the quality-scalable data-stream.
1. A method for decoding a data stream into which picture data of a picture of a video is encoded, the method comprising:
obtaining a lower quality reconstructed picture based on a prediction signal and residual data;
obtaining a predetermined fixed value associated with a scaling parameter, wherein the predetermined fixed value is not obtained by decoding information from the data stream, and the scaling parameter and an offset parameter define a local mapping function corresponding to a first block of the lower quality reconstructed picture;
determining the scaling parameter based on the predetermined fixed value; and
forming a higher quality reconstructed picture by applying a global mapping function to modify sample values of the lower quality reconstructed picture, and applying the local mapping function using the scaling parameter and the offset parameter to further modify a set of sample values obtained after the application of the global mapping function, wherein the set includes the first block in the lower quality reconstructed picture.
2. The method of claim 1 , wherein sample values of the higher quality reconstructed picture are at a bit depth greater than the sample values of the lower quality reconstructed picture.
3. The method of claim 1 , wherein different local mapping functions are applied to different blocks corresponding to the lower quality reconstructed picture.
4. The method of claim 3 , wherein the different blocks are of different sizes.
5. The method of claim 1 , wherein the local mapping function and the global mapping function are decoded from the data stream.
6. The method of claim 1 , wherein the local mapping function is linear and the global mapping function is non-linear.
7. The method of claim 1 , wherein the local mapping function is used to further modify the set of samples by addition of an output value of the local mapping function to an output value of the global mapping function applied to the set of samples.
8. The method of claim 1 , further comprising extracting, from the data stream, a syntax element representing a difference value associated with the scaling parameter, wherein the scaling parameter is determined based on a combination of the predetermined fixed value and the difference value.
9. An apparatus to decode a data stream into which picture data of a picture of a video is encoded, the apparatus comprising:
a processor;
a combiner configured to, using the processor, combine a prediction signal and residual data to form a lower quality reconstructed picture; and
a mapper configured to, using the processor:
obtaining a predetermined fixed value associated with a scaling parameter, wherein the predetermined fixed value is not obtained by decoding information from the data stream, and the scaling parameter and an offset parameter define a local mapping function corresponding to a first block of the lower quality reconstructed picture;
determine the scaling parameter based on the predetermined fixed value; and
form a higher quality reconstructed picture by applying a global mapping function to modify sample values of the lower quality reconstructed picture and applying the local mapping function using the scaling parameter and the offset parameter to further modify a set of sample values obtained after the application of the global mapping function, wherein the set includes the first block in the lower quality reconstructed picture.
10. The apparatus of claim 9 , wherein sample values of the higher quality reconstructed picture are at a bit depth greater than the sample values of the lower quality reconstructed picture.
11. The apparatus of claim 9 , wherein different local mapping functions are applied to different blocks corresponding to the lower quality reconstructed picture.
12. The apparatus of claim 9 , wherein the local mapping function and the global mapping function are decoded from the data stream.
13. The apparatus of claim 9 , wherein the mapper comprises subroutines running on a CPU.
14. The apparatus of claim 9 , wherein the mapper comprises circuit parts of an ASIC.
15. The apparatus of claim 9 , wherein the mapper is configured to extract, from the data stream, a syntax element representing a difference value associated with the scaling parameter, wherein the scaling parameter is determined based on a combination of the predetermined fixed value and the difference value.
16. A method for encoding, into a data stream, picture data of a picture of a video, the method comprising:
entropy encoding, into a subset of the data stream, residual data of a lower quality reconstructed picture, wherein the residual data is obtained based on the picture and a prediction signal of the lower quality reconstructed picture; and
entropy encoding, into the data stream, data related to a higher quality reconstructed picture, wherein the data related to a higher quality reconstructed picture is obtained by applying a global mapping function to modify sample values of the lower quality reconstructed picture and applying a local mapping function using a scaling parameter and an offset parameter to further modify a set of sample values obtained after the application of the global mapping function; and
wherein a predetermined fixed value associated with the scaling parameter and the offset parameter of the local mapping function are used for coding the higher quality reconstructed picture.
17. The method of claim 16 , wherein sample values of the higher quality reconstructed picture are at a bit depth greater than the sample values of the lower quality reconstructed picture.
18. The method of claim 16 , wherein the local mapping function is linear and the global mapping function is non-linear.
19. The method of claim 16 , wherein the local mapping function is used to further modify the set of samples by addition of an output value of the local mapping function to an output value of the global mapping function applied to the set of samples.
20. The method of claim 16 , further comprising inserting, into the data stream, a syntax element representing a difference value associated with the scaling parameter, wherein the scaling parameter is determined based on a combination of the predetermined fixed value and the difference value.