Apparatus, a method and a computer program for video coding and decoding
A method comprising: receiving an image block unit of a frame, the image block unit comprising samples in color channels comprising at least one chrominance channel and one luminance channel ( 1100 ); reconstructing samples of said luminance channels of the image block unit ( 1102 ); determining a reference area for predicting target samples of at least one color channel of the image block unit, wherein said reference area comprises one or more of reference samples in a neighboring block in current color channel/frame, in the neighboring of a co-located block in reference color channel/frame; and/or inside the co-located block in reference color channel/frame ( 1104 ); determining filter coefficients of a filter for said predicting based the reference samples and a shape of the filter ( 1106 ); reconstructing the target samples of at least one color channel of the image block unit using said prediction based on the samples of said reference area and the filter coefficients ( 1108 ); computing an autocorrelation matrix for the reconstructed target samples of the image block unit ( 1110 ); computing autocorrelation matrices for a plurality of neighboring image blocks units of said image block unit ( 1112 ); mixing the autocorrelation matrices of each of the plurality of neighboring image blocks units separately with the autocorrelation matrix of said image block unit ( 1114 ); and storing the mixed autocorrelation matrices for said image block unit ( 1116 ).
1 . An apparatus comprising a processor, a memory, and a computer program code residing in the memory, wherein the computer program code when executed by the processor, is configured to cause the apparatus to perform:
receiving an image block unit of a frame, the image block unit comprising samples in one or more color channels comprising at least one chrominance channel and a luminance channel;
reconstructing samples of said luminance channel of the image block unit to generate reconstructed samples;
determining a reference area for predicting target samples of at least one color channel of the image block unit, wherein said reference area comprises one or more of reference samples in a neighboring block in a current color channel or the frame, in the neighboring of a co-located block in a reference color channel or the frame, and/or inside the co-located block in the reference color channel or the frame;
determining filter coefficients of a filter for said predicting based on the one or more reference samples and a shape of the filter;
reconstructing the target samples of at least one color channel of the image block unit using said predicting based on the samples of said reference area and the filter coefficients to generate reconstructed target samples;
computing an autocorrelation matrix for the reconstructed target samples of the image block unit;
computing autocorrelation matrices for each plurality of neighboring image blocks units of said image block unit;
mixing the autocorrelation matrices of the each of the plurality of neighboring image blocks units separately with the autocorrelation matrix of said image block unit to generate mixed autocorrelation matrices; and
storing the mixed autocorrelation matrices for said image block unit.
2 . The apparatus according to claim 1 , wherein said plurality of neighboring image blocks units comprise at least a left, a left-above, an above and a right-above neighboring image block of said image block unit.
3 . The apparatus according to claim 1 , wherein the apparatus upon execution is further caused to perform:
applying weights for the autocorrelation matrices of the plurality of neighboring image blocks units upon mixing with the autocorrelation matrix of said image block unit.
4 . The apparatus according to claim 3 , wherein the apparatus upon execution is further caused to perform:
inferring the weights from properties of said image block unit.
5 . The apparatus according to claim 3 , wherein the apparatus upon execution is further caused to perform:
receiving the weights from an encoder.
6 . The apparatus according claim 1 , wherein the apparatus upon execution is further caused to perform:
converting the stored autocorrelation matrices into prediction coefficients.
7 . The apparatus according to claim 6 , wherein the apparatus upon execution is further caused to perform:
using one or more of the plurality of neighboring image blocks units as a directional predictor.
8 . The apparatus according to claim 1 , wherein to determining the filter coefficients, the apparatus upon execution further is caused to perform:
determining recursively the filter coefficients for a successive filter orders of the filter for said predicting based on the one or more reference samples and the shape of the filter.
9 . The apparatus according to claim 1 , wherein to compute the autocorrelation matrix, the apparatus upon execution is further caused to perform:
computing the autocorrelation matrix for the reconstructed samples of the image block unit using sub-sampling determined based on a size and a shape of the image block unit.
10 . A method comprising
receiving an image block unit of a frame, the image block unit comprising samples in one or more color channels comprising at least one chrominance channel and a luminance channel;
reconstructing samples of said luminance channel of the image block unit to generate reconstructed samples;
determining a reference area for predicting target samples of at least one color channel of the image block unit, wherein said reference area comprises one or more of reference samples in a neighboring block in current color channel or the frame, in the neighboring of a co-located block in a reference color channel or the frame; and/or inside the co-located block in the reference color channel or the frame;
determining filter coefficients of a filter for said predicting based on the one or more reference samples and a shape of the filter;
reconstructing the target samples of at least one color channel of the image block unit using said predicting based on the samples of said reference area and the filter coefficients to generate reconstructed target samples;
computing an autocorrelation matrix for the reconstructed target samples of the image block unit;
computing autocorrelation matrices for each plurality of neighboring image blocks units of said image block unit;
mixing the autocorrelation matrices of the each of the plurality of neighboring image blocks units separately with the autocorrelation matrix of said image block unit to generate mixed autocorrelation matrices; and
storing the mixed autocorrelation matrices for said image block unit.
11 . The method according to claim 10 , wherein said plurality of neighboring image blocks units comprise at least a left, a left-above, an above and a right-above neighboring image block of said image block unit.
12 . The method according to claim 10 further comprising:
applying weights for the autocorrelation matrices of the plurality of neighboring image blocks units upon mixing with the autocorrelation matrix of said image block unit.
13 . The method according to claim 10 , comprising:
inferring the weights from properties of said image block unit.
14 . The method according to claim 10 , comprising:
receiving the weights from an encoder.
15 . The method according to claim 10 comprising
converting the stored autocorrelation matrices into prediction coefficients.
16 . The method according to claim 10 , comprising:
using one or more of the plurality of neighboring image blocks units as a directional predictor.
17 . The method according to claim 10 , comprising
determining recursively the filter coefficients for successive filter orders of the filter for said predicting based on the one more reference samples and the shape of the filter.
18 . The method according to claim 10 , comprising
computing the autocorrelation matrix for the reconstructed samples of the image block unit using sub-sampling determined based on the size and the shape of the said image block unit.