Method for chroma upsampling with luma reference
Chroma upsampling is performed by setting a chroma of a target pixel according to luma of neighboring pixels. When a luma of the target pixel differs from the luma of both of the reference pixels, the chroma of the target pixel is set to a value of (k*C 1+ (m−k)*C 3+ m/2) shifted n bits to the right. In this formula, n is an integer, m is equal to 2 n , and k is equal to {0˜m, min(abs(abs(Y 1− Y 2 )*k−abs(Y 2 −Y 3 )*(m−k)))}. Since luma are considered, and a precise calculation is used in this method, the calculations required are simplified and reduced, and video quality is improved.
1. A chroma upscaling method comprising:
comparing a luma Y 1 of a first reference pixel and a luma Y 2 of a target pixel for equality, and comparing a luma Y 3 of a second reference pixel and the luma Y 2 of the target pixel for equality; and
if the luma Y 1 of the first reference pixel is not equal to the luma Y 2 of the target pixel and the luma Y 2 of the target pixel is not equal to the luma Y 3 of the second reference pixel, setting a chroma C 2 of the target pixel based on a chroma C 1 of the first reference pixel and a chroma C 3 of the second reference pixel, as:
C 2=( k*C 1+( m−k )* C 3 +m/ 2)>> n;
wherein n is a positive integer, m=2 n , “>>” represents a shift calculation, and
k={ 0 ˜m , min(abs( D 1 *k−D 2*( m−k )))},
where D 1 =Abs(Y 1 −Y 2 ), D 2 =Abs(Y 2 −Y 3 ).
2. The method of claim 1 , wherein the first reference pixel, the target pixel, and the second reference pixel are neighboring pixels.
3. The method of claim 2 , wherein the first reference pixel, the target pixel, and the second reference pixel are neighboring pixels in a same row.
4. The method of claim 2 , wherein the first reference pixel, the target pixel, and the second reference pixel are neighboring pixels from a plurality of neighboring rows.
5. The method of claim 1 , wherein the positive integer n is 2.
6. The method of claim 1 , wherein the positive integer n is 3.
7. The method of claim 1 , wherein the positive integer n is 4.
8. A chroma upscaling method comprising:
comparing a luma Y 1 of a first reference pixel and a luma Y 2 of a target pixel for equality, and comparing a luma Y 3 of a second reference pixel and the luma Y 2 of the target pixel for equality; and
if the luma Y 1 of the first reference pixel is not equal to the luma Y 2 of the target pixel and the luma Y 2 of the target pixel is not equal to the luma Y 3 of the second reference pixel, setting a chroma C 2 of the target pixel based on a chroma C 1 of the first reference pixel and a chroma C 3 of the second reference pixel, as:
C 2=( D 2 *C 1 +D 1 *C 3+( D 1+ D 2)/2)/( D 1 +D 2);
wherein D 1 =Abs(Y 1 −Y 2 ), and D 2 =Abs(Y 2 −Y 3 ).
9. The method of claim 8 , wherein the first reference pixel, the target pixel, and the second reference pixel are neighboring pixels.
10. The method of claim 9 , wherein the first reference pixel, the target pixel, and the second reference pixel are neighboring pixels on a same line.
11. The method of claim 9 , wherein the first reference pixel, the target pixel, and the second reference pixel are neighboring pixels from a plurality of neighboring rows.