Effective prediction using partition coding
The way of predicting a current block by assigning constant partition values to the partitions of a bi-partitioning of a block is quite effective, especially in case of coding sample arrays such as depth/disparity maps where the content of these sample arrays is mostly composed of plateaus or simple connected regions of similar value separated from each other by steep edges. The transmission of such constant partition values would, however, still need a considerable amount of side information which should be avoided. This side information rate may be further reduced if mean values of values of neighboring samples associated or adjoining the respective partitions are used as predictors for the constant partition values.
1. A decoder for reconstructing a depth map of a video signal using encoded information from a data stream, the decoder comprising a processor configured for:
deriving a bipartition of a block of the depth map into first and second portions;
associating each of neighboring samples of the depth map with a respective one of the first and second portions, the neighboring samples adjoining the block of the depth map;
predicting the block of the depth map by determining a first predicted value for the first portion based on values of a first set of the neighboring samples, or determining a second predicted value for the second portion based on values of a second set of the neighboring samples;
determining, from the data stream, one or more refinement values for the first or second predicted value, wherein the one or more refinement values include a first or second refinement value; and
refining the prediction of the block by applying the first refinement value to the first predicted value for the first portion or applying the second refinement value to the second predicted value for the second portion.
2. The decoder according to claim 1 , wherein the first predicted value includes an average of values of the first set of neighboring samples and the second predicted value includes an average of values of the second set of neighboring samples.
3. The decoder according to claim 1 , wherein the processor is configured for, in applying the first or second refinement value, scaling the first or second refinement value using a quantization step size depending on a reference quantization step size at which a predetermined spatially sampled component associated with the depth map is transmitted within the data stream.
4. The decoder according to claim 3 , wherein the processor is configured for using the reference quantization step size to reconstruct a texture sample array corresponding to the depth map.
5. The decoder according to claim 1 , wherein the processor is configured for, in deriving the bipartition of the block of the depth map,
predicting a position of a wedgelet separation line within the block of the depth map based on a wedgelet separation line of a neighboring block such that the wedgelet separation line at the predicted position forms an extension of the wedgelet separation line of the neighboring block into the block of the depth map, and
refining the predicted position of the wedgelet separation line using line refinement information obtained from the data stream, the wedgelet separation line dividing the block of the depth map into the first and second portions.
6. The decoder according to claim 1 , wherein the processor is configured for using the block of the depth map as a reference in a prediction loop of the decoder.
7. The decoder according to claim 1 , wherein the one or more refinement values include an absolute value and a sign value of the first refinement value, or an absolute value and a sign value of the second refinement value.
8. The decoder according to claim 1 , wherein the processor is configured for, in applying the first or second refinement value, linearly combining the first or second refinement value with the first or second predicted value, respectively.
9. An encoder for encoding into a data stream a depth map of a video signal, the encoder comprising a processor configured for:
deriving a bipartition of a block of the depth map into first and second portions;
associating each of neighboring samples of the depth map with a respective one of the first and second portions, the neighboring samples adjoining the block of the depth map;
predicting the block of the depth map by determining a first predicted value for the first portion based on values of a first set of the neighboring samples, or determining a second predicted value for the second portion based on values of a second set of the neighboring samples;
determining a first refinement value associated with the first portion based on a first original value associated with the first portion, or determining the second refinement value associated with the second portion based on a second original value associated with the second portion, wherein the first or second refinement value is applied to the first or second predicted value, respectively, for refining the prediction of the block of the depth map; and
encoding, into the data stream, one or more refinement values including the first or second refinement value.
10. The encoder according to claim 9 , wherein the first predicted value includes an average of values of the first set of neighboring samples and the second predicted value includes an average of values of the second set of neighboring samples.
11. The encoder according to claim 9 , wherein, to refine the prediction of the block of the depth map, the first or second refinement value is linearly combined with the first or second predicted value, respectively.
12. The encoder according to claim 9 , wherein the processor is configured for quantizing the first or second refinement value using a quantization step size depending on a reference quantization step size at which a predetermined spatially sampled component associated with the depth map is transmitted within the data stream.
13. The encoder according to claim 12 , wherein the processor is configured for using the reference quantization step size to encode a texture sample array corresponding to the depth map.
14. The encoder according to claim 9 , wherein the processor is configured for, in deriving the bipartition of the block of the depth map,
predicting a position of a wedgelet separation line within the block of the depth map based on a wedgelet separation line of a neighboring block such that the wedgelet separation line at the predicted position forms an extension of the wedgelet separation line of the neighboring block into the block of the depth map,
refining the predicted position of the wedgelet separation line using line refinement information, the wedgelet separation line dividing the block of the depth map into the first and second portions, and
encoding the line refinement information into the data stream.
15. The encoder according to claim 9 , wherein the processor is configured for using the block of the depth map as a reference in a prediction loop of the encoder.
16. The encoder according to claim 9 , wherein the one or more refinement values include an absolute value and a sign value of the first refinement value, or an absolute value and a sign value of the second refinement value.
17. A non-transitory computer-readable medium for storing data associated with a video, comprising:
a data stream stored in the non-transitory computer-readable medium, the data stream comprising one or more refinement values including a first or second refinement value associated with a respective first or second portion of a block of a depth map associated with the video, wherein the one or more refinement values are encoded using a plurality of operations including:
deriving a bipartition of a block of the depth map into the first and second portions;
associating each of neighboring samples of the depth map with a respective one of the first and second portions, the neighboring samples adjoining the block of the depth map;
predicting the block of the depth map by determining a first predicted value for the first portion based on values of a first set of the neighboring samples, or determining a second predicted value for the second portion based on values of a second set of the neighboring samples;
determining the first refinement value associated with the first portion based on a first original value associated with the first portion, or determining the second refinement value associated with the second portion based on a second original value associated with the second portion, wherein the first or second refinement value is applied to the first or second predicted value, respectively, for refining the prediction of the block of the depth map, and
encoding, into the data stream, the one or more refinement values including the first or second refinement value.
18. The computer-readable medium according to claim 17 , wherein the first predicted value includes an average of values of the first set of neighboring samples and the second predicted value includes an average of values of the second set of neighboring samples.
19. The computer-readable medium according to claim 17 , wherein the one or more refinement values include an absolute value and a sign value of the first refinement value, or an absolute value and a sign value of the second refinement value.
20. The computer-readable medium according to claim 17 , wherein, to refine the prediction of the block of the depth map, the first or second refinement value is linearly combined with the first or second predicted value, respectively.