| CPC H04N 19/46 (2014.11) [H04N 19/176 (2014.11); H04N 19/184 (2014.11); H04N 19/189 (2014.11)] | 4 Claims |

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1. An image decoding method performed by an image decoding apparatus, the image decoding method comprising:
receiving a bitstream generated as a result of encoding an image sequence;
obtaining, from a sequence parameter set of the bitstream, a first tool set index and a second tool set index for indicating a tool allowed to decode the bitstream among a first tool and a second tool;
obtaining, from the sequence parameter set, a first tool flag indicating whether the first tool is used for the image sequence, and a second tool flag indicating whether the second tool is used for the image sequence;
from the first tool flag and the second tool flag, identifying a tool that is used for the image sequence; and
reconstructing the image sequence based on the identified tool,
wherein when a value of a first bit included in the first tool set index is 1 and a value of a first bit included in the second tool set index is 1, a value of the first tool flag is 1,
when the value of the first bit included in the first tool set index is 1 and the value of the first bit included in the second tool set index is 0, the value of the first tool flag is 0 or 1,
when the value of the first bit included in the first tool set index is 0 and the value of the first bit included in the second tool set index is 0, the value of the first tool flag is 0,
when a value of a second bit included in the first tool set index is 1 and a value of a second bit included in the second tool set index is 1, a value of the second tool flag is 1,
when the value of the second bit included in the first tool set index is 1 and the value of the second bit included in the second tool set index is 0, the value of the second tool flag is 0 or 1, and
when the value of the second bit included in the first tool set index is 0 and the value of the second bit included in the second tool set index is 0, the value of the second tool flag is 0,
wherein when the value of the first bit included in the first tool set index is 0, the value of the first bit included in the second tool set index is set to 0.
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