System and method for video coding
An encoder includes circuitry and memory. The circuitry, in operation, generates a first coefficient value by applying a CCALF (cross component adaptive loop filtering) process to a first reconstructed image sample of a luma component. The circuitry generates a second coefficient value by applying an ALF (adaptive loop filtering) process to a second reconstructed image sample of a chroma component. The circuitry generates a third coefficient value by adding the first coefficient value to the second coefficient value, and encodes a third reconstructed image sample of the chroma component using the third coefficient value. In the CCALF process, in response to a coordinate of the second reconstructed image sample being (x, y), coordinates of the first reconstructed image samples are (2x, 2y−1), (2x−1, 2y), (2x, 2y), (2x+1, 2y), (2x−1, 2y+1), (2x, 2y+1), (2x+1, 2y+1), and (2x, 2y+2).
1. An encoder, comprising:
circuitry; and
memory coupled to the circuitry;
wherein the circuitry, in operation:
generates a first coefficient value by applying a CCALF (cross component adaptive loop filtering) filter to first reconstructed image samples of a luma component;
generates a second coefficient value by applying an ALF (adaptive loop filtering) process to a second reconstructed image sample of a chroma component;
generates a third coefficient value by adding the first coefficient value to the second coefficient value, and
encodes a third reconstructed image sample of the chroma component using the third coefficient value:
wherein in applying the CCALF filter,
in response to a coordinate of the second reconstructed image sample being (x, y), coordinates of the first reconstructed image samples are (2x, 2y−1), (2x−1, 2y), (2x, 2y), (2x+1, 2y), (2x−1, 2y+1), (2x, 2y+1), (2x+1, 2y+1), and (2x, 2y+2).
2. The encoder of claim 1 , wherein,
the CCALF filter is 8 taps filter having a 3×4 diamond shape.
3. The encoder of claim 1 , wherein,
the first coefficient value is generated by multiplying a filter coefficient value of the CCALF filter to a result of subtraction of a value of one of the first reconstructed image samples (2x, 2y−1), (2x−1, 2y), (2x, 2y), (2x+1, 2y), (2x−1, 2y+1), (2x, 2y+1), (2x+1, 2y+1), and (2x, 2y+2) and a value of the first reconstructed image sample located at (2x, 2y).
4. An encoding apparatus, comprising:
a block splitter, which, in operation, splits a first image into a plurality of blocks;
an intra predictor, which, in operation, predicts blocks included in the first image, using reference blocks included in the first image;
an inter predictor, which, in operation, predicts blocks included in the first image, using reference blocks included in a second image different from the first image;
a loop filter, which, in operation, filters blocks included in the first image;
a transformer, which, in operation, transforms a prediction error between an original signal and a prediction signal generated by the intra predictor or the inter predictor, to generate transform coefficients;
a quantizer, which, in operation, quantizes the transform coefficients to generate quantized coefficients; and
an entropy encoder, which, in operation, variably encodes the quantized coefficients to generate an encoded bitstream including the encoded quantized coefficients and control information,
wherein the loop filter performs:
generating a first coefficient value by applying a CCALF (cross component adaptive loop filtering) filter to first reconstructed image samples of a luma component;
generating a second coefficient value by applying an ALF (adaptive loop filtering) process to a second reconstructed image sample of a chroma component;
generating a third coefficient value by adding the first coefficient value to the second coefficient value, and
encoding a third reconstructed image sample of the chroma component using the third coefficient value:
wherein in applying the CCALF filter,
in response to a coordinate of the second reconstructed image sample being (x, y), coordinates of the first reconstructed image samples are (2x, 2y−1), (2x−1, 2y), (2x, 2y), (2x+1, 2y), (2x−1, 2y+1), (2x, 2y+1), (2x+1, 2y+1), and (2x, 2y+2).
5. The encoding apparatus of claim 4 , wherein,
the CCALF filter is 8 taps filter having a 3×4 diamond shape.
6. The encoding apparatus of claim 4 , wherein,
the first coefficient value is generated by multiplying a filter coefficient value of the CCALF filter to a result of subtraction of a value of one of the first reconstructed image samples (2x, 2y−1), (2x−1, 2y), (2x, 2y), (2x+1, 2y), (2x−1, 2y+1), (2x, 2y+1), (2x+1, 2y+1), and (2x, 2y+2) and a value of the first reconstructed image sample located at (2x, 2y).
7. An encoding method, comprising:
generating a first coefficient value by applying a CCALF (cross component adaptive loop filtering) filter to first reconstructed image samples of a luma component;
generating a second coefficient value by applying an ALF (adaptive loop filtering) process to a second reconstructed image sample of a chroma component;
generating a third coefficient value by adding the first coefficient value to the second coefficient value, and
encoding a third reconstructed image sample of the chroma component using the third coefficient value:
wherein in applying the CCALF filter,
in response to a coordinate of the second reconstructed image sample being (x, y), coordinates of the first reconstructed image samples are (2x, 2y−1), (2x−1, 2y), (2x, 2y), (2x+1, 2y), (2x−1, 2y+1), (2x, 2y+1), (2x+1, 2y+1), and (2x, 2y+2).
8. A decoding method, comprising:
generating a first coefficient value by applying a CCALF (cross component adaptive loop filtering) filter to first reconstructed image samples of a luma component;
generating a second coefficient value by applying an ALF (adaptive loop filtering) process to a second reconstructed image sample of a chroma component;
generating a third coefficient value by adding the first coefficient value to the second coefficient value, and
decoding a third reconstructed image sample of the chroma component using the third coefficient value:
wherein in applying the CCALF filter,
in response to a coordinate of the second reconstructed image sample being (x, y), coordinates of the first reconstructed image samples are (2x, 2y−1), (2x−1, 2y), (2x, 2y), (2x+1, 2y), (2x−1, 2y+1), (2x, 2y+1), (2x+1, 2y+1), and (2x, 2y+2).