Unequal weight planar prediction
A method of decoding JVET video includes receiving a bitstream and calculating a final planar prediction in planar mode to predict pixel values for a current coding block. The final planar prediction may rely on using unequal weights applied to each of a horizontal and vertical predictor, where such predictors may be generated by interpolating neighboring pixels for each predicted pixel within a coding block. The computation may be made more accurate by deriving a value for a bottom right neighboring pixel.
1. A method for using planar mode to predict pixel values for a current coding block having height H, width W, and a top-left (TL) pixel within the current coding block is defined by coordinates x=0 and y=0, where constructed or reconstructed neighboring pixels form rows of horizontal boundary pixels on an upper side of the current coding block and constructed or reconstructed neighboring pixels form a column of vertical boundary pixels on a left side of the current coding block, the method configured to:
calculate an intensity value of a bottom right neighboring pixel of the current coding block;
using the calculated bottom right neighboring pixel value, calculate intensity values for the neighboring pixels in a row along the lower side of the current coding block and in a column along the right side of the current coding block;
calculate a horizontal predictor P h (x,y) and a vertical predictor P v (x,y) for a pixel at coordinate (x,y) in the current coding block by interpolating between corresponding neighboring pixels in neighboring rows and by interpolating between corresponding neighboring pixels in neighboring columns, respectively;
calculating a final planar prediction P(x,y) using unequal weights applied to each of the horizontal and vertical predictors, respectively, is determined in accordance with:
P ( x,y )=( A ( x,y )* P h ( x,y )+ B ( x,y )* P v ( x,y )+ c ( x,y ))/( D ( x,y ))
where A(x,y) and B(x,y) are position dependent weighting factors for the horizontal and vertical predictors, respectively, c(x,y) is a position dependent rounding factor, and D(x,y) is a position dependent scaling factor.
2. The method of claim 1 , wherein unequal weights A(x,y) and B(x,y) are assigned for prediction of each pixel within the coding block.
3. The method of claim 1 , wherein unequal weights A(x,y) and B(x,y) are each assigned to a distance ratio from a reliable neighboring pixel for each of the horizontal predictor and the vertical predictor.
4. The method of claim 1 , further comprising applying unequal weights to at least one of the horizontal predictor and/or the vertical predictor.
5. The method of claim 1 , further comprising applying unequal weights at horizontal and vertical predictor computations.
6. The method of claim 1 , using bottom right position adjustment and unequal weight assignment in combination.
7. A method for calculating a final planar prediction in planar mode to predict pixel values for a current coding block having height H, width W, and a top-left (TL) pixel within the current coding block is defined by coordinates x=0 and y=0, the method comprising:
receiving a video bitstream including encoded video data;
from the encoded video data, reconstructing neighboring pixels that form a row of horizontal boundary pixels on an upper side of the current coding block and reconstructing neighboring pixels that form a column of vertical boundary pixels on a left side of the current coding block;
calculating a first predictor for a pixel at coordinate (x,y) in the current coding block by interpolating between an intensity value of a respective horizontal neighboring pixel in the row of neighboring pixels along the upper side of the current coding block and an intensity value of at least one replicated neighboring pixels in the row along the lower side of the current coding block;
calculate a second predictor for the pixel at coordinate (x,y) in the current coding block by interpolating between an intensity value of a respective vertical neighboring pixel from the column of neighboring pixels along the left side of the current coding block and an intensity value of at least one replicated neighboring pixel in the column along the right side of the current coding block;
calculating a final planar prediction P(x,y) using unequal weights applied to each of the first and second predictors is determined in accordance with:
P ( x,y )=( A ( x,y )* P h ( x,y )+ B ( x,y )*( x,y )+ c ( x,y ))/( D ( x,y ))
where A(x,y) and B (x,y) are position dependent weighting factors for horizontal and vertical predictors, respectively, c(x,y) is a position dependent rounding factor, and D(x,y) is a position dependent scaling factor.