Method for decoding image and apparatus using same
A method or coding image information, according to the present invention, comprises the steps of: binarizing according to different techniques, index values of forward prediction, backward prediction, and bidirectional prediction, depending on whether the bidirectional prediction is applied when inter-predicting a current block; and entropy coding a binarized codeword, wherein whether to apply the bidirectional prediction when inter-predicting the current block can be determined on the basis of the size of the current block. As a result, provided are a method for binarizing an inter-prediction direction of a prediction unit having a specific size, and an apparatus using same.
1. A method of decoding video, the method comprising:
receiving, by a decoding apparatus, a bitstream including inter prediction type information indicating whether list0 prediction, list1 prediction or bi-prediction is applied to a current block;
deriving, by the decoding apparatus, a bin string of the inter prediction type information;
deriving, by the decoding apparatus, a value of the inter prediction type information based on the bin string;
determining, by the decoding apparatus, an inter prediction type for the current block based on the value of the inter prediction type information;
deriving, by the decoding apparatus, a prediction sample of the current block based on the inter prediction type; and
generating, by the decoding apparatus, a reconstructed sample based on the prediction sample,
wherein whether the bi-prediction is not available for the current block is determined based on a size of the current block.
2. The method of claim 1 , wherein when a current coding unit has an 8×8 size and a partition mode of the current block is 2N×N or N×2N, the bi-prediction is not available for the current block.
3. The method of claim 1 , wherein when the current block has a sum of width and length of 12, the bi-prediction is not available for the current block.
4. The method of claim 2 , wherein the current block is a prediction block.
5. The method of claim 1 , wherein if the bi-prediction is available for the current block, the bin string for the list0 prediction or the list1 prediction consists of 2 bits, and
wherein if the bi-prediction is not available for the current block, the bin string for the list0 prediction or the list1 prediction consists of 1 bit.
6. The method of claim 5 , wherein if the bi-prediction is available for the current block, the bin string for the bi-prediction consists of 1 bit.
7. The method of claim 1 , wherein the list0 prediction is based on a reference picture list0, and the list1 prediction is based on a reference picture list1, and the bi-prediction is based on both the reference picture list0 and the reference picture list1.
8. An apparatus for decoding video, the apparatus comprising:
an entropy decoder configured to receive a bitstream including inter prediction type information indicating whether list0 prediction, list1 prediction or bi-prediction is applied to a current block, derive a bin string of the inter prediction type information, and derive a value of the inter prediction type information based on the bin string;
a predictor configured to determine an inter prediction type for the current block based on the value of the inter prediction type information, and to derive a prediction sample of the current block based on the inter prediction type; and
an adder configured to generate a reconstructed sample based on the prediction sample,
wherein whether the bi-prediction is not available for the current block is determined based on a size of the current block.
9. The apparatus of claim 8 , wherein when a current coding unit has an 8×8 size and a partition mode of the current block is 2N×N or N×2N, the bi-prediction is not available for the current block.
10. The apparatus of claim 8 , wherein when the current block has a sum of width and length of 12, the bi-prediction is not available for the current block.
11. The apparatus of claim 9 , wherein the current block is a prediction block.
12. The apparatus of claim 8 , wherein if the bi-prediction is available for the current block, the bin string for the list0 prediction or the list1 prediction consists of 2 bits, and
wherein if the bi-prediction is not available for the current block, the bin string for the list0 prediction or the list1 prediction consists of 1 bit.
13. The apparatus of claim 12 , wherein if the bi-prediction is available for the current block, the bin string for the bi-prediction consists of 1 bit.
14. The apparatus of claim 8 , wherein the list0 prediction is based on a reference picture list0, and the list1 prediction is based on a reference picture list1, and the bi-prediction is based on both the reference picture list0 and the reference picture list1.