Inheritance in sample array multitree subdivision
A better compromise between encoding complexity and achievable rate distortion ratio, and/or to achieve a better rate distortion ratio is achieved by using multitree sub-divisioning not only in order to subdivide a continuous area, namely the sample array, into leaf regions, but using the intermediate regions also to share coding parameters among the corresponding collocated leaf blocks. By this measure, coding procedures performed in tiles—leaf regions—locally, may be associated with coding parameters individually without having to, however, explicitly transmit the whole coding parameters for each leaf region separately. Rather, similarities may effectively exploited by using the multitree subdivision.
1. A decoder for reconstructing an array of information samples representing a video from a data stream encoded with an array of spatially sampled information samples with leaf regions of different sizes derived by subdivision, comprising:
an extractor configured for:
extracting, from the data stream, multi-tree subdivision information and inheritance information, wherein each of the leaf regions has associated therewith a hierarchy level out of a sequence of hierarchy levels according to the multi-tree subdivision information, each of the leaf regions corresponds to a first block of the video and is to be reconstructed based on one or more coding parameters represented by a set of syntax elements, each of which is of a respective syntax element type out of a set of syntax element types,
wherein the inheritance information indicates, with respect to an inheritance region, which corresponds to a second block of the video and has associated therewith a second hierarchy level out of the sequence of hierarchy levels according to the multi-tree subdivision information, whether inheritance is to be used for sharing at least one syntax element among a subset of leaf regions that compose the inheritance region, wherein the at least one syntax element represents a coding parameter used in an inter coding process of video coding; and
extracting, from the data stream, if the inheritance information indicates the use of the inheritance, the at least one syntax element corresponding to the inheritance region to be shared among the subset of leaf regions; and
a reconstructor configured for:
copying the at least one syntax element into the set of syntax elements corresponding to each of the subset of leaf regions, each of the set of syntax elements representing coding parameters used in the inter coding process,
determining, for each of the subset of leaf regions, at least one coding parameter to use in the inter coding process for the corresponding leaf region based on the copied at least one syntax element,
determining, for each of the subset of leaf regions in accordance with the inter coding process, a respective prediction signal based on the determined at least one coding parameter and neighboring samples of a reconstructed signal of an already reconstructed leaf region,
decoding, in a residual decoding order, a residual signal for each of the subset of leaf regions, and
reconstructing, for each of the subset of leaf regions, the corresponding first block of the video based on a combination of the respective prediction signal and the residual signal.
2. The decoder according to claim 1 , wherein
the extractor is configured to
for each defined by the multi-tree subdivision, extract an inheritance flag from the data stream associated with said region in a hierarchy level order from a lower hierarchy level to a higher hierarchy level;
wherein the decoder is configured to
check, for each region defined by the multi-tree subdivision, whether the inheritance flag prescribes inheritance or not for the region,
when a region in the multi-tree subdivision has an inheritance flag prescribing inheritance, the extractor is further configured to
extract an inheritance subset associated with the region and including at least one syntax element of a predetermined syntax element type from the data stream,
copy the inheritance subset to a corresponding inheritance subset of syntax elements associated with each of leaf regions which constitute the region, and
suppress further extraction and checking for each of the leaf regions which constitute the region.
3. The decoder according to claim 2 , wherein the decoder is a hybrid decoder.
4. The decoder according to claim 1 , wherein the extractor is configured to extract, from the data stream, at least one syntax element representing the coding parameters associated with one or more leaf regions which belong to a subset of leaf regions of a region which has its corresponding inheritance information indicating no use of inheritance.
5. The decoder according to claim 1 , wherein the extractor is configured to, if inheritance is indicated not to be used, extract at least one syntax element of the predetermined syntax element type within the set of syntax elements, the at least one syntax element representing the coding parameters associated with all leaf regions of the array of information samples.
6. The decoder according to claim 1 , wherein the decoder is configured to reconstruct the array information samples by prediction using a prediction mode determined based on at least one syntax element of the predetermined syntax element type.
7. The decoder according to claim 1 , the decoder is configured such that the residual decoding order is a traversal order of a depth order.
8. A method for reconstructing an array of information samples representing a video from a data stream encoded with an array of spatially sampled information samples with leaf regions of different sizes by subdivision, comprising:
extracting, from the data stream, multi-tree subdivision information and inheritance information, wherein each of the leaf regions has associated therewith a hierarchy level out of a sequence of hierarchy levels according to the multi-tree subdivision information, each of the leaf regions corresponds to a first block of the video and is to be reconstructed based on one or more coding parameters represented by a set of syntax elements, each of which is of a respective syntax element type out of a set of syntax element types,
wherein the inheritance information indicates, with respect to an inheritance region, which corresponds to a second block of the video and has associated therewith a second hierarchy level out of the sequence of hierarchy levels according to the multi-tree subdivision information, whether inheritance is to be used for sharing at least one syntax element among a subset of leaf regions that compose the inheritance region, wherein the at least one syntax element represents a coding parameter used in an inter coding process of video coding;
extracting, from the data stream, if inheritance indicates the use of the inheritance, the at least one syntax element corresponding to the inheritance region to be shared among the subset of leaf regions;
copying the at least one syntax element into the set of syntax elements corresponding to each of the subset of leaf regions, each of the set of syntax elements representing coding parameters used in the inter coding process;
determining, for each of the subset of leaf regions, at least one coding parameter to use in the inter coding process for the corresponding leaf region based on the copied at least one syntax element;
determining, for each of the subset of leaf regions in accordance with the inter coding process, a respective prediction signal based on the determined at least one coding parameter and neighboring samples of a reconstructed signal of an already reconstructed leaf region;
decoding, in a residual decoding order, a residual signal for each of the subset of leaf regions;
and
reconstructing, for each of the subset of leaf regions, the corresponding first block of the video based on a combination of the respective prediction signal and the residual signal.
9. An encoder for encoding into a data stream an array of information samples representing a video obtained by spatial sampling, according to subdivision information, with leaf regions of different sizes by subdivision, comprising:
an inserter configured for:
inserting multi-tree subdivision information relating to the subdivision and inheritance information into the data stream, the inheritance information indicating, with respect to an inheritance region, whether inheritance is to be used for sharing at least one syntax element among a subset of leaf regions that compose the inheritance region, wherein
each of the leaf regions corresponds to a first block of the video, has associated therewith a hierarchy level out of a sequence of hierarchy levels according to the multi-tree subdivision information and is to be reconstructed based on one or more coding parameters represented by a set of syntax elements,
the inheritance region corresponds to a second block of the video, and has associated therewith a second hierarchy level out of the sequence of hierarchy levels according to the multi-tree subdivision information, and
the at least one syntax element represents at least one coding parameter used to reconstruct the first block of the video corresponding to each of the subset of leaf regions according to an inter coding process of video coding, and
inserting, into the data stream, if inheritance is indicated to be used, the at least one syntax element associated with the inheritance region so that the at least one syntax element is to be shared among the subset of leaf regions, without inserting the at least one syntax element for each of the subset of leaf regions corresponding to the inheritance region,
wherein reconstructing the first block of the video corresponding to each of the subset of leaf regions according to the inter coding process includes:
copying the at least one syntax element into the set of syntax elements corresponding to each of the subset of leaf regions, each of the set of syntax elements representing coding parameters used in the inter coding process,
determining, for each of the subset of leaf regions, the at least one coding parameter to use in the inter coding process for the corresponding leaf region based on the copied at least one syntax element,
determining, for each of the subset of leaf regions in accordance with the inter coding process, a respective prediction signal based on the determined at least one coding parameter and neighboring samples of a reconstructed signal of an already reconstructed leaf region,
decoding, in a residual decoding order, a residual signal for each of the subset of leaf regions, and
reconstructing, for each of the subset of leaf regions, the corresponding first block of the video based on a combination of the respective prediction signal and the residual signal.
10. A method for encoding into a data stream an array of information samples representing a video obtained by spatial sampling, according to subdivision information, with leaf regions of different sizes by subdivision, comprising:
inserting multi-tree subdivision information relating to the subdivision and inheritance information into the data stream, the inheritance information indicating, with respect to an inheritance region, whether inheritance is to be used for sharing at least one syntax element among a subset of leaf regions that compose the inheritance region, wherein
each of the leaf regions corresponds to a first block of the video, has associated therewith a hierarchy level out of a sequence of hierarchy levels according to the multi-tree subdivision information and is to be reconstructed based on one or more coding parameters represented by a set of syntax elements,
the inheritance region corresponds to a second block of the video, and has associated therewith a second hierarchy level out of the sequence of hierarchy levels according to the multi-tree subdivision information, and
the at least one syntax element represents at least one coding parameter used to reconstruct the first block of the video corresponding to each of the subset of leaf regions according to an inter coding process of video coding; and
inserting, into the data stream, if inheritance is indicated to be used, the at least one syntax element associated with the inheritance region so that the at least one syntax element is to be shared among the subset of leaf regions, without inserting the at least one syntax element for each of the subset of leaf regions corresponding to the inheritance region,
wherein reconstructing the first block of the video corresponding to each of the subset of leaf regions according to the inter coding process includes:
copying the at least one syntax element into the set of syntax elements corresponding to each of the subset of leaf regions, each of the set of syntax elements representing coding parameters used in the inter coding process,
determining, for each of the subset of leaf regions, the at least one coding parameter to use in the inter coding process for the corresponding leaf region based on the copied at least one syntax element,
determining, for each of the subset of leaf regions in accordance with the inter coding process, a respective prediction signal based on the determined at least one coding parameter and neighboring samples of a reconstructed signal of an already reconstructed leaf region,
decoding, in a residual decoding order, a residual signal for each of the subset of leaf regions, and
reconstructing, for each of the subset of leaf regions, the corresponding first block of the video based on a combination of the respective prediction signal and the residual signal.
11. A non-transitory computer readable digital storage medium having stored thereon a computer program, wherein the computer program, when read by the computer, causes the computer to perform a method according to claim 8 .
12. A non-transitory computer readable digital storage medium having stored thereon a computer program, wherein the computer program, when read by the computer, causes the computer to perform a method according to claim 10 .