Encoder using a flag indicating whether temporal motion vector prediction is enabled, decoder, and medium

A non-transitory computer readable medium storing a bitstream,

• the bitstream including a sequence parameter set including a parameter, the parameter indicating that a change in a picture resolution is allowed for any of pictures, the parameter being provided for a decoder to perform a decoding process, wherein
• in the decoding process, a flag indicating whether temporal motion vector prediction is enabled or disabled is decoded, and
• when a reference picture having a same resolution as a current picture is not available to decode the current picture, the flag indicates that the temporal motion vector prediction is disabled.