Method and Apparatus of Delta Quantization Parameter Processing for High Efficiency Video Coding
In one implementation, a method codes video pictures, in which each of the video pictures is partitioned into LCUs (largest coding units). The method operates by receiving a current LCU, partitioning the current LCU adaptively to result in multiple leaf CUs, determining whether a current leaf CU has at least one nonzero quantized transform coefficient according to both Prediction Mode (PredMode) and Coded Block Flag (CBF), and incorporating quantization parameter information for the current leaf CU in a video bitstream, if the current leaf CU has at least one nonzero quantized transform coefficient. If the current leaf CU has no nonzero quantized transform coefficient, the method excludes the quantization parameter information for the current leaf CU in the video bitstream.
1 . A method for coding of video pictures, wherein each of the video pictures is partitioned into LCUs (largest coding units), the method comprising:
receiving a current LCU;
partitioning the current LCU adaptively to result in multiple leaf CUs;
determining whether a current leaf CU has at least one nonzero quantized transform coefficient according to both Prediction Mode (PredMode) and Coded Block Flag (CBF);
if the current leaf CU has at least one nonzero quantized transform coefficient, incorporating quantization parameter information for the current leaf CU in a video bitstream; and
if the current leaf CU has no nonzero quantized transform coefficient, excluding the quantization parameter information for the current leaf CU in the video bitstream.
2 . The method of claim 1 , wherein incorporating quantization parameter information for the leaf CU comprises transmitting the quantization parameter information for the leaf CU in the video bitstream corresponding to the video pictures.
3 . The method of claim 1 , wherein incorporating quantization parameter information for the leaf CU comprises deriving the quantization parameter information for the leaf CU from information of at least another leaf CU.
4 . The method of claim 3 , wherein the information of at least another leaf CU comprises quantization parameter information, PredMode, CBP, CBF, leaf CU position, or a combination of quantization parameter information, PredMode, CBP, CBF, and leaf CU position.
5 . The method of claim 1 , further comprising determining a QP (Quantization Parameter) minimum CU size to transmit the quantization parameter information for the current leaf CU, and only incorporating the quantization parameter information if the current leaf CU is larger than or equal to the QP minimum CU size and if the current leaf CU has at least one nonzero quantized transform coefficient.
6 . The method of claim 5 , wherein the QP minimum CU size is derived from a largest CU size.
7 . The method of claim 6 , wherein a syntax element qp_max_depth specifies a depth of the QP minimum CU size from the largest CU size.
8 . The method of claim 7 , wherein the syntax element qp_max_depth is incorporated in a sequence header, picture header or slice header.
9 . A method for decoding of a video bitstream corresponding to video pictures, wherein each of the video pictures is partitioned into LCUs (largest coding units), each LCU is adaptively partitioned into smaller CUs and results in multiple leaf CUs, the method comprising:
receiving coded data associated with a current leaf CU from the video bitstream;
detecting whether the current leaf CU has at least one nonzero quantized transform coefficient according to both Prediction Mode (PredMode) and Coded Block Flag (CBF); and
if the current leaf CU has at least one nonzero quantized transform coefficient:
deriving said at least one nonzero quantized transform coefficient from the coded data;
obtaining quantization parameter information for the current leaf CU from the video bitstream; and
reconstructing transform coefficients for the current leaf CU by applying the quantization parameter information to said at least one nonzero quantized transform coefficient; and
if the current leaf CU has no nonzero quantized transform coefficient:
reconstructing all zero transform coefficients for the current leaf.
10 . The method of claim 9 , wherein the quantization parameter information for the leaf CU is obtained explicitly from the video bitstream.
11 . The method of claim 9 , wherein the quantization parameter information for the leaf CU is obtained by deriving from information of at least another leaf CU.
12 . The method of claim 11 , wherein the information of at least another leaf CU comprises quantization parameter information, Prediction Mode (PredMode), Coded Block Pattern (CBP), Coded Block Flag (CBF), leaf CU position, or a combination of quantization parameter information, PredMode, CBF, CBP, and leaf CU position.
13 . The method of claim 9 , further comprising determining a QP (Quantization Parameter) minimum CU size to obtain the quantization parameter information for the current leaf CU from the video bitstream, and only obtaining the quantization parameter information if the current leaf CU is larger than or equal to the QP minimum CU size and if the current leaf CU has at least one nonzero quantized transform coefficient.
14 . The method of claim 13 , wherein the QP minimum CU size is derived from a largest CU size.
15 . The method of claim 14 , further comprising obtaining a syntax element qp_max_depth specifies a depth of the QP minimum CU size from the largest CU size.
16 . The method of claim 15 , wherein the syntax element qp_max_depth is obtained from a sequence header, picture header or slice header.