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 information on an inter prediction type and information on a residual sample, wherein the information on the inter prediction type indicates whether list0 prediction, list1 prediction or bi-prediction is used as the inter prediction type for to a current prediction unit;
deriving, by the decoding apparatus, a bin string of the information on the inter prediction type;
deriving, by the decoding apparatus, a value of the information on the inter prediction type based on the bin string;
determining, by the decoding apparatus, the inter prediction type for the current prediction unit based on the value of the information on the inter prediction type;
deriving, by the decoding apparatus, a prediction sample of the current prediction unit based on the inter prediction type;
deriving, by the decoding apparatus, the residual sample based on the information on the residual sample; and
generating, by the decoding apparatus, a reconstructed sample based on the prediction sample and the residual sample,
wherein whether the bi-prediction is not available for the current prediction unit is determined based on a size of the current prediction unit,
wherein the current prediction unit is derived from a current coding unit based on a partition mode, and
wherein when the current coding unit has an 8×8 size and the partition mode is 2N×N or N×2N, the bi-prediction is not available for the current prediction unit.
2. The method of claim 1 , wherein when the current coding unit has the 8×8 size and the partition mode is 2N×2N, the bi-prediction is available for the current prediction unit.
3. The method of claim 1 , wherein when the current prediction unit has a sum of width and length of 12, the bi-prediction is not available for the current prediction unit.
4. The method of claim 1 , wherein if the bi-prediction is available for the current prediction unit, the bin string for the list0 prediction or the list1 prediction consists of 2 bins, and
wherein if the bi-prediction is not available for the current prediction unit, the bin string for the list0 prediction or the list1 prediction consists of 1 bin.
5. The method of claim 4 , wherein if the bi-prediction is available for the current prediction unit, the bin string for the bi-prediction consists of 1 bin.
6. 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.
7. A decoding apparatus for decoding video, the apparatus comprising:
an entropy decoder for receiving a bitstream including information on an inter prediction type and information on a residual sample, wherein the information on the inter prediction type indicates whether list0 prediction, list1 prediction or bi-prediction is used as the inter prediction type for the current prediction unit, for deriving a bin string of the information on the inter prediction type, and for deriving a value of the information on the inter prediction type based on the bin string;
a predictor for determining the inter prediction type for the current prediction unit based on the value of the information on the inter prediction type, and to derive a prediction sample of the current prediction unit based on the inter prediction type;
an inverse transformer for deriving the residual sample, wherein the residual sample is derived based on information on the residual sample; and
an adder configured to generate a reconstructed sample based on the prediction sample and the residual sample,
wherein whether the bi-prediction is not available for the current prediction unit is determined based on a size of the current prediction unit,
wherein the current prediction unit is derived from a current coding unit based on a partition mode, and
wherein when the current coding unit has an 8×8 size and the partition mode is 2N×N or N×2N, the bi-prediction is not available for the current prediction unit.
8. The apparatus of claim 7 , wherein when the current coding unit has the 8×8 size and the partition mode is 2N×2N, the bi-prediction is available for the current prediction unit.
9. The apparatus of claim 7 , wherein when the current prediction unit has a sum of width and length of 12, the bi-prediction is not available for the current prediction unit.
10. The apparatus of claim 7 , wherein if the bi-prediction is available for the current prediction unit, the bin string for the list0 prediction or the list1 prediction consists of 2 bins, and
wherein if the bi-prediction is not available for the current prediction unit, the bin string for the list0 prediction or the list1 prediction consists of 1 bin.
11. The apparatus of claim 10 , wherein if the bi-prediction is available for the current prediction unit, the bin string for the bi-prediction consists of 1 bin.
12. The apparatus of claim 7 , 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.