US 12,301,854 B2
Image encoding/decoding method using secondary transform based on a transform skip mode flag and a transform matrix index
Sung Chang Lim, Daejeon (KR); Jung Won Kang, Daejeon (KR); Soo Woong Kim, Sejong (KR); Gun Bang, Daejeon (KR); Jin Ho Lee, Daejeon (KR); and Ha Hyun Lee, Seoul (KR)
Assigned to Electronics and Telecommunications Research Institute, Daejeon (KR)
Appl. No. 17/773,747
Filed by Electronics and Telecommunications Research Institute, Daejeon (KR)
PCT Filed Nov. 26, 2020, PCT No. PCT/KR2020/016991
§ 371(c)(1), (2) Date May 2, 2022,
PCT Pub. No. WO2021/107648, PCT Pub. Date Jun. 3, 2021.
Claims priority of application No. 10-2019-0153330 (KR), filed on Nov. 26, 2019; and application No. 10-2020-0004406 (KR), filed on Jan. 13, 2020.
Prior Publication US 2023/0007290 A1, Jan. 5, 2023
Int. Cl. H04N 19/46 (2014.01); H04N 19/176 (2014.01); H04N 19/186 (2014.01); H04N 19/96 (2014.01)
CPC H04N 19/46 (2014.11) [H04N 19/176 (2014.11); H04N 19/186 (2014.11); H04N 19/96 (2014.11)] 18 Claims
OG exemplary drawing
 
1. A video decoding method, the method comprising:
decoding a transform skip mode flag indicating whether an inverse transform is skipped for a luma component block;
in response to the transform skip mode flag indicating that the inverse transform is not skipped for the luma component block, determining, based on a LFNST (Low Frequency Non-Separable Transform) index, whether a secondary inverse transform is performed on the luma component block or not;
in response to a determination that the secondary inverse transform being performed on the luma component block, obtaining transform coefficients of the luma component block by performing the secondary inverse transform on the luma component block; and
obtaining residual samples of the luma component block by performing a primary inverse transform on transform coefficients of the luma component block,
wherein the secondary inverse transform is a non-separable inverse transform while the primary inverse transform comprises a horizontal primary inverse transform and a vertical primary inverse transform,
wherein a transform skip mode flag is decoded for each of the luma component block, a Cb component block and a Cr component block,
wherein in response to a tree structure, relating to the luma component block, the Cb component block and the Cr component block, being a single tree type, the LFNST matrix index is decoded from a bitstream in response that not only the transform skip mode flag of the luma component block but also transform skip mode flags for the Cb component block and the Cr component block indicates that the inverse transform is not skipped,
wherein in response to the tree structure being the single tree type, even though the transform skip mode flag of the luma component block indicates that the inverse transform is not skipped, decoding the LFNST index is omitted when at least one of the transform skip mode flags for the Cb component block and the Cr component block indicates that the inverse transform is skipped,
wherein the secondary inverse transform is performed on the luma component block when a value of the LFNST index is greater than 0,
wherein in response to decoding the LFNST index from the bitstream being omitted, the secondary inverse transform being not performed on the luma component block, and
wherein whether to decode an MTS (Multiple Transform Selection) index for the luma component block from the bitstream or not is determined based on the value of the LFNST index.