Method and apparatus for transform coefficient coding of non-square blocks
A method and apparatus for transform coefficient coding of image and video data for a video encoder or decoder are disclosed. The method determines a CG (coding group) size adaptively based on the current TU. The current TU is divided into one or more current CGs (coding groups) according to the CG size. Bins associated with the coefficients of the current TU are then encoded or decoded according to a selected CG scan path through the current TU and one or more coefficient scan paths within each CG. If TU width is larger or smaller than TU height for the current TU, then CG width is selected to be larger or smaller than CG height accordingly. According to another method, all bypass-coded bins associated with coefficients in the current TU are grouped to improve the parsing throughput rate.
1. A method for transform coefficient coding of image and video data for a video encoder or decoder, the method comprising:
receiving input data associated with a current TU (transform unit) corresponding to a block of a current picture; and
encoding or decoding all bypass-coded bins associated with coefficients in current CGs (coding groups) of the current TU without any context-coded bin associated with coefficient using
a first individual CG (coding group) scan path through the current TU, wherein all the bypass-coded bins associated with the coefficients of the current TU are determined using one or more first coefficient scan paths within each of the current CGs.
2. The method of claim 1 , further comprising a step of encoding or decoding all context-coded bins associated with the coefficients of the current TU without any bypass-coded bin associated with the coefficient using a second individual CG scan path through the current TU, wherein all the context-coded bins associated with the coefficients of the current TU are determined using one or more second coefficient scan paths within each of the current CGs.
3. The method of claim 2 , wherein the current TU is divided into one or more first CGs for the first individual CG scan path according to a first CG size and the current TU is divided into one or more second CGs for the second individual CG scan path according to a second CG size, and wherein the first CG size is different from the second CG size.
4. The method of claim 3 , wherein the second CG size corresponds to 4×4 and the first CG size corresponds to 4×2 or 2×4.
5. The method of claim 3 , wherein the second CG size corresponds to 4×2 or 2×4 and the first CG size corresponds to 4×4.
6. The method of claim 2 , wherein the bypass-coded bins associated with the coefficients of the current TU comprise first syntax elements and second syntax elements of the current TU, wherein each of the first syntax elements corresponds to a sign flag of one coefficient and each second syntax element corresponds to a remaining value of one coefficient level.
7. The method of claim 2 , wherein the context-coded bins associated with the coefficients of the current TU comprise third syntax elements, fourth syntax element and fifth syntax elements of the current TU, wherein each of the third syntax elements corresponds to a significance flag indicating whether if there is any non-zero coefficient in one CG, the fourth syntax element corresponds to a first level flag indicating whether an absolute value of one coefficient level is greater than one, and the fifth syntax element corresponds to a second level flag indicating whether the absolute value of one coefficient level is greater than two.
8. The method of claim 2 , wherein the current TU is divided into one or more first CGs for the first individual CG scan path, and wherein each of the one or more CGs corresponds to N consecutive coefficients of the current TU in a predefined coefficient scan order and N is a positive integer.
9. The method of claim 2 , wherein the current TU is divided into one or more first CGs for the first individual CG scan path according to a first CG size, and sign data hiding is applied to the current TU depending on the first CG size.
10. The method of claim 9 , wherein said sign data hiding is applied to the current TU if the first CG size is 24 and distance between a beginning non-zero coefficient and an ending non-zero coefficient is larger than a threshold.
11. An apparatus for transform coefficient coding of image and video data performed by a video encoder or decoder, the apparatus comprising one or more electronic circuits or a processor arranged to:
receive input data associated with a current TU (transform unit) corresponding to a block of a current picture; and
encode or decode all bypass-coded bins associated with coefficients in CGs (coding groups) of the current TU without any context-coded bin associated with coefficient using a first individual CG (coding group) scan path through the current TU, wherein all the bypass-coded bins associated with the coefficients of the current TU are determined using one or more first coefficient scan paths within each of the CGs.