Scalable video coding using inter-layer prediction of spatial intra prediction parameters
The coding efficiency of scalable video coding is increased by substituting missing spatial intra prediction parameter candidates in a spatial neighborhood of a current block of the enhancement layer by use of intra prediction parameters of a co-located block of the base layer signal. By this measure, the coding efficiency for coding the spatial intra prediction parameters is increased due to the improved prediction quality of the set of intra prediction parameters of the enhancement layer, or, more precisely stated, the increased likelihood, that appropriate predictors for the intra prediction parameters for an intra predicted block of the enhancement layer are available thereby increasing the likelihood that the signaling of the intra prediction parameter of the respective enhancement layer block may be performed, on average, with less bits.
1. A scalable video decoder, comprising:
a block-based decoding unit including a processor configured to:
reconstruct a base layer signal from a data stream; and
reconstruct an enhancement layer signal of a video from the data stream based on intra prediction using a current intra prediction parameter to decode a current block of the enhancement layer signal, wherein the reconstruct of the enhancement layer signal is based on information about a co-located block of the base layer signal and information about a neighboring block in the enhancement layer signal, wherein the reconstruct of the enhancement layer signal includes:
checking whether the co-located block of the base layer signal is intra-decoded including checking whether a base-layer intra prediction parameter includes an angular intra prediction parameter, wherein the co-located block is co-located relative to the current block of the enhancement layer signal,
checking whether the neighboring block of the enhancement layer signal is intra-decoded including checking whether a neighboring intra prediction parameter of the neighboring block includes an angular intra prediction parameter, wherein the neighboring block spatially neighbors the current block of the enhancement layer signal,
responsive to checking the co-located block of the base layer signal, inserting a base-layer intra prediction parameter of the co-located block of the base layer signal into a set of intra prediction parameters for the current block,
responsive to checking the neighboring block of the enhancement layer signal, inserting the neighboring intra prediction parameter including the angular intra prediction parameter of the neighboring block into the set of intra prediction parameters for the current block,
extracting, from the data stream, a syntax element identifying at least one of the set of intra prediction parameters, wherein the current intra prediction parameter is determined based on the syntax element present by checking, based on the syntax element, as to whether the current intra prediction parameter is a member of the set of intra prediction parameters,
determining the current intra prediction parameter for the current block based on the syntax element,
obtaining an enhancement layer internal prediction of the current block based on the current intra prediction parameter, and
reconstructing the current block based on the reconstructed base layer signal and the enhancement layer internal prediction of the current block.
2. The scalable video decoder according to claim 1 , wherein the block-based decoding unit is configured to perform the checking the neighboring block and inserting in the set with respect to a set of neighboring blocks of the enhancement layer signal, which neighbor the current block.
3. The scalable video decoder according to claim 1 , wherein the set of intra prediction parameters for the current block includes a default intra prediction parameter.
4. The scalable video decoder according to claim 1 , wherein the base-layer intra prediction parameter is inserted in the set of intra prediction parameters for the current block if the neighboring block of the enhancement layer signal has not been intra-predicted.
5. The scalable video decoder according to claim 1 , wherein the base layer signal is reconstructed based on a spatial intra prediction mode or a temporal inter-prediction mode.
6. The scalable video decoder according to claim 1 , wherein:
the neighboring intra prediction parameter is inserted in the set of intra prediction parameters for the current block if the neighboring block of the enhancement layer signal has been intra-predicted and the intra prediction parameter of the neighboring block includes an angular intra prediction direction,
the base-layer intra prediction parameter inserted in the set of intra prediction parameters if the neighboring block of the enhancement layer signal has not been intra-predicted or the neighboring intra prediction parameter of the neighboring block does not include the angular intra prediction direction, but for the co-located block of the base layer signal, the base-layer intra prediction parameter includes the angular intra prediction parameter, and
neither the neighboring intra prediction parameter nor the base-layer intra prediction parameter is inserted in the set of intra prediction parameters for the current block if the neighboring block of the enhancement layer signal has not been intra-predicted or the neighboring intra prediction parameter does not include the angular intra prediction direction, and the co-located block of the base layer signal has not been intra-predicted or the base-layer intra prediction parameter does not include the angular intra prediction parameter.
7. The scalable video decoder according to claim 1 , wherein a default intra prediction parameter is included in the set of intra prediction parameters for the current block if neither the neighboring intra prediction parameter nor the base-layer intra prediction parameter has been selected.
8. The scalable video decoder according to claim 1 , wherein if the current intra prediction parameter is a member of the set of intra prediction parameters, then indexing one of the set of intra prediction parameters using the syntax element, and if not, then deriving another one of a set of possible intra prediction modes using the syntax element.
9. A scalable video decoding method, comprising:
reconstructing a base layer signal from a data stream; and
reconstructing an enhancement layer signal of a video from the data stream based on intra prediction using a current intra prediction parameter to decode a current block of the enhancement layer signal, wherein the reconstructing of the enhancement layer signal is based on information about a co-located block of the base layer signal and information about a neighboring block in the enhancement layer signal, the reconstructing of the enhancement layer signal including:
checking whether the co-located block of the base layer signal is intra-decoded including checking whether a base-layer intra prediction parameter includes an angular intra prediction parameter, wherein the co-located block is co-located relative to the current block of the enhancement layer signal,
checking whether the neighboring block of the enhancement layer signal is intra-decoded including checking whether a neighboring intra prediction parameter of the neighboring block includes an angular intra prediction parameter, wherein the neighboring block spatially neighbors the current block of the enhancement layer signal,
responsive to checking the co-located block of the base layer signal, inserting a base-layer intra prediction parameter of the co-located block of the base layer signal into a set of intra prediction parameters for the current block,
responsive to checking the neighboring block of the enhancement layer signal, inserting the neighboring intra prediction parameter including the angular intra prediction parameter of the neighboring block into the set of intra prediction parameters for the current block,
extracting, from the data stream, a syntax element identifying at least one of the set of intra prediction parameters, wherein the current intra prediction parameter is determined based on the syntax element present by checking, based on the syntax element, as to whether the current intra prediction parameter is a member of the set of intra prediction parameters,
determining the current intra prediction parameter for the current block based on the syntax element,
obtaining an enhancement layer internal prediction of the current block based on the current intra prediction parameter, and
reconstructing the current block based on the reconstructed base layer signal and the enhancement layer internal prediction of the current block.
10. The scalable video decoding method according to claim 9 , further comprising performing the checking the neighboring block and inserting in the set with respect to a set of neighboring blocks of the enhancement layer signal, which neighbor the current block.
11. The scalable video decoding method according to claim 9 , wherein the set of intra prediction parameters for the current block includes a default intra prediction parameter.
12. The scalable video decoding method according to claim 9 , wherein the base-layer intra prediction parameter is inserted in the set of intra prediction parameters for the current block if the neighboring block of the enhancement layer signal has not been intra-predicted.
13. A scalable video encoder, comprising:
a block-based encoding unit including a processor configured to:
encode a base layer signal of a video into a data stream; and
encode an enhancement layer signal of the video into the data stream based on intra prediction using a current intra prediction parameter to encode current block of the enhancement layer signal wherein the encode of the enhancement layer signal is based on information about a co-located block of the base layer signal and information about a neighboring block in the enhancement layer signal, the encode of the enhancement layer signal comprising:
checking whether the co-located block of the base layer signal is intra-encoded including checking whether a base-layer intra prediction parameter includes an angular intra prediction parameter, wherein the co-located block is co-located relative to the current block of the enhancement layer signal;
checking whether the neighboring block of the enhancement layer signal is intra-decoded including checking whether a neighboring intra prediction parameter of the neighboring block includes an angular intra prediction parameter, wherein the neighboring block spatially neighbors the current block of the enhancement layer signal,
responsive to checking the co-located block of the base layer signal, inserting a base-layer intra prediction parameter of the co-located block of the base layer signal into a set of intra prediction parameters for the current block,
responsive to checking the neighboring block of the enhancement layer signal, inserting the neighboring intra prediction parameter including the angular intra prediction parameter of the neighboring block into the set of intra prediction parameters for the current block,
determining the current intra prediction parameter for the current block as at least one of the set of intra prediction parameters, and
inserting into the data stream a syntax element, which indicates the at least one of the set of intra prediction parameters, wherein the current intra prediction parameter is determined based on the syntax element present by checking, based on the syntax element, as to whether the current intra prediction parameter is a member of the set of intra prediction parameters,
wherein the current block is to be reconstructed based on a reconstructed base layer signal and an enhancement layer internal prediction of the current block obtained using the current intra prediction parameter.
14. The scalable video encoder according to claim 13 , wherein the base-layer intra prediction parameter is inserted in the set of intra prediction parameters for the current block if the neighboring block of the enhancement layer signal has not been intra-predicted.