Method and apparatus for setting reference picture index of temporal merging candidate
The present invention relates to a method and apparatus for setting a reference picture index of a temporal merging candidate. An inter-picture prediction method using a temporal merging candidate can include the steps of: determining a reference picture index for a current block; and inducing a temporal merging candidate block of the current block and calculating a temporal merging candidate from the temporal merging candidate block, wherein the reference picture index of the temporal merging candidate can be calculated regardless of whether a block other than the current block is decoded. Accordingly, a video processing speed can be increased and video processing complexity can be reduced.
1. An image decoder comprising:
one or more processors configured to
select a collocated picture, the collocated picture having a different temporal order from a current picture that includes a current prediction block, and the collocated picture comprising a temporal neighboring block which is used to derive a temporal merging candidate of the current prediction block,
derive a spatial merging candidate by using a spatial neighboring block,
derive the temporal merging candidate by using the temporal neighboring block,
generate a merging candidate list including the spatial merging candidate and the temporal merging candidate,
determine a motion vector and a reference picture index of the current prediction block by using the merging candidate list, the reference picture index of the current prediction block specifying a reference picture of the current prediction block, wherein the reference picture of the current prediction block has a different temporal order from the current picture and the collocated picture, and
obtain prediction samples of the current prediction Nock by using reconstruction samples within the reference picture specified by the reference picture index of the current prediction block, the reconstruction samples being indicated by the motion vector of the current prediction blocks,
wherein while a reference picture index of the spatial merging candidate is determined based on a reference picture of the spatial neighboring block, a reference picture index of the temporal merging candidate is set to a fixed value of zero, the reference picture index of the temporal merging candidate being used to determine the reference picture index of the current prediction block, but not used to determine the collocated picture of the current prediction block, and
wherein the spatial neighboring block and the temporal neighboring block are determined based on: a position of a coding block, a size of a block on which a parallel merge processing is applicable, and a size of the coding block, wherein the coding block includes the current prediction block.
2. The image decoder of claim 1 , wherein the temporal neighboring block is representative of one of a first block or a second block in the collocated picture, the first block being located at a position corresponding to a bottom right position of the current prediction block or the coding block, and the second block being located at a position corresponding to a central position of the current prediction block or the coding block.
3. The image decoder of claim 1 , wherein a temporal motion vector of the temporal merging candidate is derived by scaling a motion vector of the temporal neighboring block, based on both a first picture distance and a second picture distance, wherein the first picture distance is defined as a temporal order difference between the collocated picture and a reference picture of the temporal neighboring block, and wherein the second picture distance is defined as a temporal order difference between the current picture and a reference picture specified by the reference picture index of the temporal merging candidate.
4. A method of decoding a video signal, comprising:
selecting a collocated picture, the collocated picture having a different temporal order from a current picture that includes a current prediction block, and the collocated picture comprising a temporal neighboring block which is used to derive a temporal merging candidate of the current prediction block;
deriving a spatial merging candidate from a spatial neighboring block;
deriving the temporal merging candidate by using the temporal neighboring block;
generating a merging candidate list including the spatial merging candidate and the temporal merging candidate;
determining a motion vector and a reference picture index of the current prediction block by using the merging candidate list, the reference picture index of the current block specifying a reference picture of the current prediction block, wherein the reference picture of the current prediction block has a different temporal order from the current picture and the collocated picture; and
obtaining prediction samples of the current prediction block by using reconstruction samples within the reference picture specified by the reference picture index of the current prediction block, the reconstruction samples being indicated by the motion vector of the current prediction block,
wherein while a reference picture index of the spatial merging candidate is determined based on a reference picture of the spatial neighboring block, a reference picture index of the temporal merging candidate is set to a fixed value of zero, the reference picture index of the temporal merging candidate being used to determine the reference picture index of the current prediction but not used to determine the collocated picture of the current prediction block, and
wherein the spatial neighboring block and the temporal neighboring block are determined based on: a position of a coding block, a size of a block on which a parallel merge processing is applicable, and a size of the coding block, wherein the coding block includes the current prediction block.
5. The method of claim 4 , wherein the temporal neighboring block is representative of one of a first block or a second block in the collocated picture, the first block including a position corresponding to a bottom right position of the current prediction block or the coding block, and the second block including a position corresponding to a central position of the current prediction block or the coding block.