Systems and methods for reducing a reconstruction error in video coding based on a cross-component correlation
A method of filtering reconstructed video data including inputting a reconstructed luma picture sample array, setting a luma location corresponding to a current chroma sample to a location defined by a horizontal location in the chroma sample multiplied by a sub-width value and a vertical location in the chroma sample multiplied by a sub-height value, deriving luma sample locations inside the reconstructed luma picture sample array by using the luma location, and deriving a variable by using cross-component filter coefficients and the reconstructed luma picture sample array defined by at least one of the luma sample locations. The variable is modified by using a current chroma block of samples.
1. A method of filtering reconstructed video data, the method comprising:
inputting a reconstructed luma picture sample array prior to a luma adaptive loop filtering process;
inputting a reconstructed chroma picture sample array filtered according to a chroma adaptive loop filtering process;
inputting a chroma location specifying a top-left sample of a current chroma coding tree block;
setting a luma location, corresponding to a current chroma sample, equal to a location defined by a horizontal location of the current chroma samples multiplied by a sub-width value and a vertical location of the current chroma sample multiplied by a sub-height value, wherein the horizontal location and the vertical location are derived from the chroma location;
deriving luma sample locations inside the reconstructed luma picture sample array by using the luma location;
deriving a variable by using cross-component filter coefficients and the reconstructed luma picture sample array defined by at least one of the luma sample locations; and
deriving a modified filtered reconstructed chroma picture sample array by using the reconstructed chroma picture sample array and the variable.
2. The method of claim 1 , wherein the luma sample locations are derived by clipping a sum of the luma location and a predetermined value.
3. The method of claim 1 , wherein the variable is derived by using clip position variables derived by an adaptive loop filter boundary position derivation process.
4. The method of claim 1 , wherein the sub-width value and the sub-height value are specified depending on a chroma format.
5. The method of claim 4 , wherein
the sub-width value and the sub-height value are specified as follows:
the sub-width value and the sub-height value are equal to 2 in a case that the chroma format is a 4:2:0 chroma format;
the sub-width value is equal to 2 and the sub-height value is equal to 1 in a case that the chroma format is a 4:2:2 chroma format; and
the sub-width value and the sub-height value are equal to 1 in a case that the chroma format is a 4:4:4 chroma format.
6. A decoder of decoding coded data, the decoder comprising:
a processor; and
a memory associated with the processor, wherein the processor is
configured to perform the following steps:
inputting a reconstructed luma picture sample array prior to a luma adaptive loop filtering process;
inputting a reconstructed chroma picture sample array filtered according to a chroma adaptive loop filtering process;
inputting a chroma location specifying a top-left sample of a current chroma coding tree block;
setting a luma location, corresponding to a current chroma sample, equal to a location defined by a horizontal location in chroma samples multiplied by a sub-width value and a vertical location of the current chroma sample multiplied by a sub-height value, wherein the horizontal location and the vertical location are derived from the chroma location;
deriving luma sample locations inside the reconstructed luma picture sample array by using the luma location;
deriving a variable by using cross-component filter coefficients and the reconstructed luma picture sample array defined by at least one of the luma sample locations; and
deriving a modified filtered reconstructed chroma picture sample array by using the reconstructed chroma picture sample array and the variable.
7. An encoder of encoding video data, the encoder comprising:
a processor; and
a memory associated with the processor, wherein the processor is configured to perform the following steps:
inputting a reconstructed luma picture sample array prior to a luma adaptive loop filtering process;
inputting a reconstructed chroma picture sample array filtered according to a chroma adaptive loop filtering process;
inputting a chroma location specifying a top-left sample of a current chroma coding tree block;
setting a luma location, corresponding to a current chroma sample, equal to a location defined by a horizontal location of the current chroma samples multiplied by a sub-width value and a vertical location of the current chroma sample multiplied by a sub-height value, wherein the horizontal location and the vertical location are derived from the chroma location;
deriving luma sample locations inside the reconstructed luma picture sample array by using the luma location;
deriving a variable by using cross-component filter coefficients and the reconstructed luma picture sample array defined by at least one of the luma sample locations; and
deriving a modified filtered reconstructed chroma picture sample array by using the reconstructed chroma picture sample array and the variable.