Moving picture coding method and moving picture decoding method
A moving picture coding apparatus includes a co-located block information determination unit which determines which one of a forward reference block and a backward reference block will be a co-located block and further determines whether only the unidirectional motion vector of the motion vectors of the co-located block is to be stored in a colPic memory, a temporal motion vector predictor calculation unit which derives a candidate motion vector predictor in temporal motion vector predictor mode using the colPic information stored in the colPic memory; and an inter prediction control unit which determines to code a motion vector using a candidate motion vector predictor having least error from the motion vector derived by motion estimation among candidate motion vector predictors.
1. A moving picture coding method of coding a current block included in a current picture using a reference motion vector of a reference block included in a reference picture different from the current picture, the reference block being co-located, in the reference picture, with the current block in the current picture, the moving picture coding method comprising:
determining a value of a predetermined flag which indicates whether or not reference block information is to be read from a memory, the reference block information including, among reference motion vectors of the reference block in a first prediction direction and a second prediction direction, the reference motion vector in the first prediction direction;
reading, from the memory, the reference block information including the reference motion vector according to the value of the predetermined flag;
coding a motion vector of the current block using the read reference block information;
writing, to the memory, the reference block information including the motion vector of the current block according to the value of the predetermined flag; and
adding the predetermined flag to a bitstream.
2. The moving picture coding method according to claim 1 ,
wherein the memory includes a first storage area for storing the reference block information of the first prediction direction, and a second storage area for storing the reference block information of the second prediction direction, and
in the reading, when the predetermined flag indicates ON, the reference block information including the reference motion vector is read from the first storage area, and when the predetermined flag indicates OFF, the reference block information including the reference motion vector is read from the first storage area and the second storage area.
3. The moving picture coding method according to claim 1 ,
wherein the memory includes a first storage area for storing the reference block information of the first prediction direction, and a second storage area for storing the reference block information of the second prediction direction, and
in the writing, when the predetermined flag indicates ON, and (i) when the current block includes at least one reference motion vector in the first prediction direction, the reference block information including the reference motion vector in the first prediction direction is written to the first storage area, and
(ii) when the current block includes only the reference motion vector in the second prediction direction, the reference block information including the reference motion vector in the second prediction direction is written to the first storage area.
4. The moving picture coding method according to claim 1 ,
wherein the memory includes a first storage area for storing the reference block information of the first prediction direction, and a second storage area for storing the reference block information of the second prediction direction, and
in the writing, when the predetermined flag indicates OFF, and
(i) when the current block includes the reference motion vector in the first prediction direction, the reference block information including the reference motion vector in the first prediction direction is written to the first storage area, and
(ii) when the current block includes the reference motion vector in the second prediction direction, the reference block information including the reference motion vector in the second prediction direction is written to the second storage area.
5. The moving picture coding method according to claim 1 ,
wherein, when the reference block includes two or more reference motion vectors, the coding includes:
selecting one of the two or more reference motion vectors based on whether the reference picture is located before or after the current picture; and
coding the motion vector of the current block using the selected reference motion vector.
6. The moving picture coding method according to claim 5 ,
wherein, in the selecting, when the reference block includes a forward reference motion vector and a backward reference motion vector, and
(i) when the current block is located before the reference block, the forward reference motion vector is selected from the forward reference motion vector and the backward reference motion vector, and
(ii) when the current block is located after the reference block, the backward reference motion vector is selected from the forward reference motion vector and the backward reference motion vector.
7. The moving picture coding method according to claim 5 ,
wherein, in the selecting, when the reference block includes one of a forward reference motion vector and a backward reference motion vector, the one of the forward reference motion vector and the backward reference motion vector in the reference block is selected regardless of a positional relation between the reference block and the current block.
8. A moving picture decoding method of decoding a current block included in a current picture using a reference motion vector of a reference block included in a reference picture different from the current picture, the reference block being co-located, in the reference picture, with the current block in the current picture, the moving picture decoding method comprising:
decoding a value of a predetermined flag which indicates whether or not reference block information is to be read from a memory, the reference block information including, among reference motion vectors of the reference block in a first prediction direction and a second prediction direction, the reference motion vector in the first prediction direction;
reading, from the memory, the reference block information including the reference motion vector according to the value of the predetermined flag;
decoding a motion vector of the current block using the read reference block information; and
writing, to the memory, the reference block information including the motion vector of the current block according to the value of the predetermined flag.
9. The moving picture decoding method according to claim 8 ,
wherein the memory includes a first storage area for storing the reference block information of the first prediction direction, and a second storage area for storing the reference block information of the second prediction direction, and
in the reading, when the predetermined flag indicates ON, the reference block information including the reference motion vector is read from the first storage area, and when the predetermined flag indicates OFF, the reference block information including the reference motion vector is read from the first storage area and the second storage area.
10. The moving picture decoding method according to claim 9 ,
wherein the memory includes a first storage area for storing the reference block information of the first prediction direction, and a second storage area for storing the reference block information of the second prediction direction, and
in the writing, when the predetermined flag indicates ON, and
(i) when the current block includes at least one reference motion vector in the first prediction direction, the reference block information including the reference motion vector in the first prediction direction is written to the first storage area, and
(ii) when the current block includes only the reference motion vector in the second prediction direction, the reference block information including the reference motion vector in the second prediction direction is written to the first storage area.
11. The moving picture decoding method according to claim 9 ,
wherein the memory includes a first storage area for storing the reference block information of the first prediction direction, and a second storage area for storing the reference block information of the second prediction direction, and
in the writing, when the predetermined flag indicates OFF, and
(i) when the current block includes the reference motion vector in the first prediction direction, the reference block information including the reference motion vector in the first prediction direction is written to the first storage area, and
(ii) when the current block includes the reference motion vector in the second prediction direction, the reference block information including the reference motion vector in the second prediction direction is written to the second storage area.
12. The moving picture decoding method according to claim 9 ,
wherein, when the reference block includes two or more reference motion vectors, the decoding includes:
selecting one of the reference motion vectors based on whether the reference picture is located before or after the current picture; and
decoding the motion vector of the current block using the selected reference motion vector.
13. The moving picture decoding method according to claim 12 ,
wherein, in the selecting, when the reference block includes a forward reference motion vector and a backward reference motion vector, and
(i) when the current block is located before the reference block, the forward reference motion vector is selected from the forward reference motion vector and the backward reference motion vector, and
(ii) when the current block is located after the reference block, the backward reference motion vector is selected from the forward reference motion vector and the backward reference motion vector.
14. The moving picture decoding method according to claim 12 ,
wherein, in the selecting, when the reference block includes one of a forward reference motion vector and a backward reference motion vector, the one of the forward reference motion vector and the backward reference motion vector in the reference block is selected regardless of a positional relation between the reference block and the current block.
15. A moving picture decoding method of decoding a current block included in a current picture using a reference motion vector of a reference block included in a reference picture different from the current picture, the reference block being co-located, in the reference picture, with the current block in the current picture, the moving picture decoding method comprising:
decoding a value of a predetermined flag which indicates whether or not reference block information is to be read, the reference block information including, among reference motion vectors of the reference block in a first prediction direction and a second prediction direction, the reference motion vector in the first prediction direction;
reading the reference block information including the reference motion vector according to the value of the predetermined flag;
decoding a motion vector of the current block using the read reference block information; and
writing the reference block information including the motion vector of the current block according to the value of the predetermined flag.
16. A moving picture coding method of coding a current block included in a current picture using a reference motion vector of a reference block included in a reference picture different from the current picture, the reference block being co-located, in the reference picture, with the current block in the current picture, the moving picture coding method comprising:
reading reference block information including, among reference motion vectors of the reference block in a first prediction direction and a second prediction direction, only the reference motion vector in the first prediction direction when the reference block includes reference motion vectors in the first prediction direction and the second prediction direction; and
coding a motion vector of the current block using the read reference block information.
17. A moving picture decoding method of decoding a current block included in a current picture using a reference motion vector of a reference block included in a reference picture different from the current picture, the reference block being co-located, in the reference picture, with the current block in the current picture, the moving picture decoding method comprising:
reading reference block information including, among reference motion vectors of the reference block in a first prediction direction and a second prediction direction, only the reference motion vector in the first prediction direction when the reference block includes reference motion vectors in the first prediction direction and the second prediction direction; and
decoding a motion vector of the current block using the read reference block information.