Video encoder and video encoding method

A video encoding method for encoding a plurality of pictures included in a video in an intra-refresh scheme comprising:

• determining, by a processor, according to a position of a boundary between a refreshed region through which a slice to which an intra-refresh is applied has traversed and an unrefreshed region through which the slice to which the intra-refresh is applied has not traversed, in a first picture, which has been encoded, among the plurality of pictures, and a refresh update size being a ratio of a size of the pictures in a moving direction of the boundary to a refresh cycle, a position of the boundary in a second picture, which is an encoding target, subsequent to the first picture;
• identifying, by the processor, based on the position of the boundary of the first picture and the position of the boundary of the second picture, among a plurality of first sub-blocks being units of motion compensation included in the second picture, as a first restriction target sub-block, a first sub-block which is included in the refreshed region in the second picture and is possible to select a motion vector of a sub-block included in the unrefreshed region of the first picture as a prediction vector of the motion vector of the first sub-block when the first sub-block is encoded in an inter prediction coding mode referring to another encoded picture;
• generating, by the processor, encoded data by encoding, among a plurality of second sub-blocks which are obtained by dividing the second picture and are units to be applied in the inter prediction coding mode or in an intra prediction coding mode in which only a coding target picture is referred to, a second restriction target sub-block, which is a second sub-block including the first restriction target sub-block, in the inter prediction coding mode without using the prediction vector with respect to the first restriction target sub-block, or by encoding the second restriction target sub-block in the intra prediction coding mode;
• and
• entropy-encoding the encoded data by the processor.

A non-transitory computer-readable recording medium having recorded thereon a video encoding computer program that causes a computer to execute encoding of a plurality of pictures included in a video in an intra-refresh scheme, the video encoding computer program that causes the computer to execute a process comprising:

• determining, according to a position of a boundary between a refreshed region through which a slice to which an intra-refresh is applied has traversed and an unrefreshed region through which the slice to which the intra-refresh is applied has not traversed, in a first picture, which has been encoded, among the plurality of pictures, and a refresh update size being a ratio of a size of the pictures in a moving direction of the boundary to a refresh cycle, a position of the boundary in a second picture, which is an encoding target, subsequent to the first picture;
• identifying, based on the position of the boundary of the first picture and the position of the boundary of the second picture, among a plurality of first sub-blocks being units of motion compensation included in the second picture, as a first restriction target sub-block, a first sub-block which is included in the refreshed region in the second picture and is possible to select a motion vector of a sub-block included in the unrefreshed region of the first picture as a prediction vector of the motion vector of the first sub-block when the first sub-block is encoded in an inter prediction coding mode referring to another encoded picture;
• generating encoded data by encoding, among a plurality of second sub-blocks which are obtained by dividing the second picture and are units to be applied in the inter prediction coding mode or in an intra prediction coding mode in which only a coding target picture is referred to, a second restriction target sub-block, which is a second sub-block including the first restriction target sub-block, in the inter prediction coding mode without using the prediction vector with respect to the first restriction target sub-block, or by encoding the second restriction target sub-block in the intra prediction coding mode;
• and
• entropy-encoding the encoded data.