Method for adaptively setting resolution, and image decoding apparatus

A method of encoding a video sequence of pictures by adaptively setting a picture resolution, the method comprising:

• encoding, into a sequence parameter set (SPS) referred by all of the pictures belonging to the video sequence, a flag indicating that it is allowed that at least one picture of the sequence has a different size than a reference picture referred by the at least one picture;
• encoding maximum resolution information into the sequence parameter set, wherein the maximum resolution information specifies a maximum size of each decoded picture referring to the SPS;
• encoding resolution information for a current picture into a picture parameter set which is a lower level than the sequence parameter set,
• wherein the picture parameter set is a parameter set referred by one or more pictures belonging to the video sequence, and
• wherein the resolution information for the current picture specifies a size of the current picture which are less than or equal to the maximum size, and includes a first syntax element specifying a width of the current picture and a second syntax element specifying a height of the current picture;
• for encoding a current block within the current picture in an inter-prediction, comparing the size of the current picture with a size of a reference picture to be referenced by the current block;
• determining a motion vector of the current block;
• based on the size of the current picture and the size of the reference picture, resampling a sample location in the reference picture indicated by the motion vector and resampling sample locations in a reference block which is positioned at the sample location in the reference picture;
• and
• predicting the current block using samples which correspond to the sample locations in the reference picture.

A method of transmitting video data to a video decoding apparatus, the method comprising:

• encoding a video sequence of pictures with adaptively setting a picture resolution to generate a bitstream containing the encoded video sequence;
• and
• transmitting the bitstream to a video decoding apparatus,
• wherein encoding the video sequence of pictures comprises:
• encoding, into a sequence parameter set (SPS) referred by all of the pictures belonging to the video sequence, a flag indicating that it is allowed that at least one picture of the sequence has a different size than a reference picture referred by the at least one picture;
• encoding maximum resolution information into the sequence parameter set, wherein the maximum resolution information specifies a maximum size of each decoded picture referring to the SPS;
• encoding resolution information for a current picture into a picture parameter set which is a lower level than the sequence parameter set,
• wherein the picture parameter set is a parameter set referred by one or more pictures belonging to the video sequence, and
• wherein the resolution information for the current picture specifies a size of the current picture which are less than or equal to the maximum size, and includes a first syntax element specifying a width of the current picture and a second syntax element specifying a height of the current picture;
• for encoding a current block within the current picture in an inter-prediction, comparing the size of the current picture with a size of a reference picture to be referenced by the current block;
• determining a motion vector of the current block;
• based on the size of the current picture and the size of the reference picture, resampling a sample location in the reference picture indicated by the motion vector and resampling sample locations in a reference block which is positioned at the sample location in the reference picture;
• and
• predicting the current block using samples which correspond to the sample locations in the reference picture.