| 摘要 |
PROBLEM TO BE SOLVED: To provide an encoding and decoding method capable of efficiently applying a direct mode.SOLUTION: Information indicating whether or not a backward reference frame set by default can be utilized for a direct mode is provided to a decoder. Also, a switching procedure to switch to an alternative mode applicable when a collocated block has no effectively usable forward motion vector, and the alternative mode are provided. Thereby, it can be clearly determined whether or not the reference frame can be utilized for the direct mode. Furthermore, when a frame number does not have time information, information indicating relation between the reference frame and a current frame can be efficiently transmitted. Moreover, prediction performance when the direct mode cannot be applied can be improved by the alternative mode and its switching procedure. |
