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`An encoder includes circuitry and memory connected to the
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`circuitry, and the circuitry,
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`in operation: determines, based on a
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`width and a height of a block, whether or not to disable a prediction
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`mode in which the block is split along a partitioning line defined by a
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`distance and an angle and then prediction is performed; and encodes
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`the block with the prediction mode disabled or not disabled according
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`to a result of the determination on whether or not to disable the
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`prediction mode.
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`Here,
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`the distance is
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`the shortest distance
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`10
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`between the center of the block and the partitioning line, and the
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`angle is an angle representing a direction from the center of the block
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`toward the partitioning line in the shortest distance. The circuitry
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`determines to disable the prediction mode when (i) a width-to-height
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`ratio is at least 8 or (ii) a height-to-width ratio is at least 8.
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`- 163 -
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