CPC H04N 19/132 (2014.11) [H04N 19/105 (2014.11); H04N 19/176 (2014.11); H04N 19/186 (2014.11); H04N 19/46 (2014.11); H04N 19/70 (2014.11)] | 10 Claims |
1. An image decoding method performed by a decoding apparatus, the method comprising:
obtaining length information of a chroma Quantization Parameter (QP) offset list;
obtaining chroma QP offset index information for a current chroma block based on the length information;
deriving a chroma QP offset for the current chroma block based on the chroma QP offset index information;
deriving a chroma QP of the current chroma block based on the chroma QP offset;
deriving a residual sample of the current chroma block based on the chroma QP; and
generating a reconstructed sample of the current chroma block based on the residual sample,
wherein the length information is related to a number of QP offset list for Cb, a number of QP offset list for Cr and a number of QP offset list for joint CbCr,
wherein the QP offset list for the joint CbCr is signaled based on joint CbCr QP offset present flag being 1,
wherein the chroma QP is derived based on a following equation:
Qp′Cb=Clip3(−QpBdOffset,63,qPCb+slice_cb_qp_offset+CuQpOffsetCb)+QpBdOffset
Qp′Cr=Clip3(−QpBdOffset,63,qPCr+slice_cr_qp_offset+CuQpOffsetCr)+QpBdOffset
Qp′CbCr=Clip3(—QpBdOffset,63,qPCbCr+slice_joint_cbcr_qp_offset+CuQpOffsetCbCr)+QpBdOffset
and
wherein, Qp′Cb, Qp′Cr, Qp′CbCr represent the chroma QP, qPCb, qPCr, and qPCbCr represent variables derived based on a luma QP offset of a luma block for the current chroma block, slice cb qp offset, slice cr qp offset, slice joint cbcr qp offset represent a slice level chroma QP offset, and CuQpOffsetCb, CuQpOffsetCr, CuQpOffsetCbCr represent the chroma QP offset.
|