Video processing methods and apparatuses for horizontal wraparound motion compensation in video coding systems

An apparatus of processing video data in a video coding system, the apparatus comprising one or more electronic circuits configured to:

• receive input video data associated with a current block in a current picture;
• determine a reference picture for the current block stored in a reference picture buffer of the video coding system;
• determine whether the reference picture stored in the reference picture buffer is scaled with respect to the current picture;
• determine whether horizontal wraparound motion compensation is enabled for predicting the current block, wherein the one or more electronic circuits are configured to:
• determine that the horizontal wraparound motion compensation is enabled for predicting the current block in response to a wraparound enable flag indicating that the horizontal wraparound motion compensation is enabled and the reference picture being determined as not scaled with respect to the current picture, and
• determine that the horizontal wraparound motion compensation is disabled for predicting the current block in response to the reference picture being determined as scaled with respect to the current picture;
• perform motion compensation for the current block to obtain a reference block from the reference picture, wherein when the horizontal wraparound motion compensation is determined as enabled for predicting the current block, an out-of-boundary part is located within the reference picture toward a right boundary when a part of the reference block is outside of a left boundary of the reference picture or an out-of-boundary part is located within the reference picture toward a left boundary when a part of the reference block is outside of a right boundary of the reference picture;
• and
• encode or decode the current block according to the reference block.

A non-transitory computer readable medium storing program instruction causing a processing circuit of an apparatus to perform video processing method, and the method comprising:

• receiving input video data associated with a current block in a current picture;
• determining a reference picture for the current block stored in a reference picture buffer of the video coding system;
• determining whether the reference picture stored in the reference picture buffer is scaled with respect to the current picture;
• determining whether horizontal wraparound motion compensation is enabled for predicting the current block, including
• determining that the horizontal wraparound motion compensation is enabled for predicting the current block in response to a wraparound enable flag indicating that the horizontal wraparound motion compensation is enabled and the reference picture being determined as not scaled with respect to the current picture, and
• determining that the horizontal wraparound motion compensation is disabled for predicting the current block in response to the reference picture being determined as scaled with respect to the current picture;
• performing motion compensation for the current block to obtain a reference block from the reference picture, wherein when the horizontal wraparound motion compensation is determined as enabled for predicting the current block, an out-of-boundary part is located within the reference picture toward a right boundary when a part of the reference block is outside of a left boundary of the reference picture or an out-of-boundary part is located within the reference picture toward a left boundary when a part of the reference block is outside of a right boundary of the reference picture;
• and
• encoding or decoding the current block according to the reference block.