Encoder, decoder, encoding method, and decoding method
Provided is an encoder which includes circuitry and memory. Using the memory, the circuitry splits an image block into a plurality of partitions, obtains a prediction image for a partition, and encodes the image block using the prediction image. When the partition is not a non-rectangular partition, the circuitry obtains (i) a first prediction image for the partition using a first motion vector for the partition, (ii) a second motion vector for the partition using the first prediction image, and (iii) a second prediction image for the partition as the prediction image using the second motion vector. When the partition is a non-rectangular partition, the circuitry obtains the first prediction image as the prediction image using the first motion vector, without using the second motion vector.
1. An encoder, comprising:
circuitry; and
memory, wherein
using the memory, the circuitry:
splits an image block into a plurality of partitions;
obtains a prediction image for a partition included in the plurality of partitions; and
encodes the image block using the prediction image,
in obtaining the prediction image, the circuitry:
determines whether the partition is a non-rectangular partition;
when the partition is determined not to be a non-rectangular partition, obtains (i) a first prediction image for the partition using a first motion vector for the partition, (ii) a second motion vector for the partition using the first prediction image, and (iii) a second prediction image for the partition as the prediction image using the second motion vector; and
when the partition is determined to be a non-rectangular partition, obtains the first prediction image as the prediction image using the first motion vector, without using the second motion vector.
2. The encoder according to claim 1 , wherein
the circuitry determines that the partition is a non-rectangular partition when the partition is a triangular partition.
3. The encoder according to claim 1 , wherein
the prediction image obtained when the partition is determined not to be a non-rectangular partition is same as a portion corresponding to the partition, of a prediction image obtained for the image block without splitting the image block into the plurality of partitions in a determined prediction mode.
4. The encoder according to claim 1 , wherein
the circuitry obtains the second motion vector by performing motion estimation using the first prediction image.
5. A decoder, comprising:
circuitry; and
memory, wherein
using the memory, the circuitry:
splits an image block into a plurality of partitions;
obtains a prediction image for a partition included in the plurality of partitions; and
decodes the image block using the prediction image,
in obtaining the prediction image, the circuitry:
determines whether the partition is a non-rectangular partition;
when the partition is determined not to be a non-rectangular partition, obtains (i) a first prediction image for the partition using a first motion vector for the partition, (ii) a second motion vector for the partition using the first prediction image, and (iii) a second prediction image for the partition as the prediction image using the second motion vector; and
when the partition is determined to be a non-rectangular partition, obtains the first prediction image as the prediction image using the first motion vector, without using the second motion vector.
6. The decoder according to claim 5 , wherein
the circuitry determines that the partition is a non-rectangular partition when the partition is a triangular partition.
7. The decoder according to claim 5 , wherein
the prediction image obtained when the partition is determined not to be a non-rectangular partition is same as a portion corresponding to the partition, of a prediction image obtained for the image block without splitting the image block into the plurality of partitions in a determined prediction mode.
8. The decoder according to claim 5 , wherein
the circuitry obtains the second motion vector by performing motion estimation using the first prediction image.
9. An encoding method, comprising:
splitting an image block into a plurality of partitions;
obtaining a prediction image for a partition included in the plurality of partitions; and
encoding the image block using the prediction image, wherein
the obtaining of the prediction image includes:
determining whether the partition is a non-rectangular partition;
when the partition is determined not to be a non-rectangular partition, obtaining (i) a first prediction image for the partition using a first motion vector for the partition, (ii) a second motion vector for the partition using the first prediction image, and (iii) a second prediction image for the partition as the prediction image using the second motion vector; and
when the partition is determined to be a non-rectangular partition, obtaining the first prediction image as the prediction image using the first motion vector, without using the second motion vector.
10. A decoding method, comprising:
splitting an image block into a plurality of partitions;
obtaining a prediction image for a partition included in the plurality of partitions; and
decoding the image block using the prediction image, wherein
the obtaining of the prediction image includes:
determining whether the partition is a non-rectangular partition;
when the partition is determined not to be a non-rectangular partition, obtaining (i) a first prediction image for the partition using a first motion vector for the partition, (ii) a second motion vector for the partition using the first prediction image, and (iii) a second prediction image for the partition as the prediction image using the second motion vector; and
when the partition is determined to be a non-rectangular partition, obtaining the first prediction image as the prediction image using the first motion vector, without using the second motion vector.