Method and apparatus for decoded picture buffer management in video coding system using intra block copy
Method and apparatus of managing a DPB (decoded picture buffer) for a video coding system are disclosed. Whether the IntraBC mode is used for a current picture is determined and a maximum allowed number of decoded pictures in the DPB is allocated based on whether the IntraBC mode is used for the current picture. The current picture is then encoded or decoded using decoded pictures stored in the DPB as reference data. In another method, a maximum number of reordered pictures in the DPB is determined. If certain conditions are true, one or more decoded pictures stored in the DPB will be emptied until none of the conditions is true. One condition corresponds to a number of decoded pictures in the DPB marked as “needed for output” being greater than the maximum number of reordered picture modified according to whether the IntraBC mode is used for the current picture.
1. A method of managing a DPB (decoded picture buffer) for a video coding system, wherein the video coding system uses coding modes including an Inter prediction mode and an IntraBC (Intra Block Copy) mode, comprising:
determining whether the IntraBC mode is used for a current picture, wherein decoded data of the current picture is used as reference data for the current picture if the current picture is coded using the IntraBC mode;
allocating, in the DPB, a memory space having a first size for storing at most a first maximum allowed number of decoded pictures in response to the IntraBC mode being determined to be used for the current picture;
allocating, in the DPB, the memory space having a second size for storing at most a second maximum allowed number of decoded pictures in response to the IntraBC mode being determined not to be used for the current picture, the second maximum allowed number being less than the first maximum allowed number; and
encoding or decoding the current picture using decoded pictures stored in the allocated memory space in the DPB as reference data.
2. The method of claim 1 , wherein whether the IntraBC mode is used for the current picture is indicated by a syntax flag or a variable, and a value of the syntax flag or the variable is related to whether two versions of decoded current picture need to be stored.
3. The method of claim 2 , further comprising emptying one or more decoded pictures stored in the allocated memory space in the DPB when one or more conditions are true, wherein the one or more conditions include a condition corresponding to a total number of decoded pictures in the allocated memory space in the DPB that is marked as needed for output being greater than or equal to
a first maximum number of reordered pictures, when the syntax flag or the variable indicates that two versions of decoded current picture are not need to be stored, and
a second maximum number of reordered pictures that is modified according to the first maximum number of reordered pictures, when the syntax flag or the variable indicates that two versions of decoded current picture are need to be stored.
4. The method of claim 3 , wherein a syntax element indicating the first maximum number of reordered pictures is signaled in a Sequence Parameter Set (SPS).
5. The method of claim 3 , wherein the second maximum number of reordered pictures is less than the first maximum number of reordered pictures.
6. The method of claim 3 , wherein the second maximum number of reordered pictures corresponds to reducing the first maximum number of reordered pictures by the value of the syntax flag or the variable.
7. The method of claim 1 , wherein a syntax element indicating the first maximum allowed number of decoded pictures is signaled in a Sequence Parameter Set (SPS).
8. An apparatus for managing a DPB (decoded picture buffer) in a video coding system, wherein the video coding system uses coding modes including an Inter prediction mode and an IntraBC (Intra Block Copy) mode, the apparatus comprising:
one or more electronic circuits or processors configured to:
determine whether the IntraBC mode is used for a current picture, wherein decoded data of the current picture is used as reference data for the current picture if the current picture is coded using the IntraBC mode;
allocate, in the DPB, a memory space having a first size for storing at most a first maximum allowed number of decoded pictures in response to the IntraBC mode being determined to be used for the current picture;
allocate, in the DPB, the memory space having a second size for storing at most a second maximum allowed number of decoded pictures in response to the IntraBC mode being determined not to be used for the current picture, the second maximum allowed number being less than the first maximum allowed number; and
encode or decode the current picture using decoded pictures stored in the allocated memory space in the DPB as reference data.