Method and apparatus for global motion compensation in video coding system

A method of Inter prediction for video coding performed in a video encoder or a video decoder, the method comprising:

• receiving input data related to a current processing unit in a region at a video encoder side or receiving a video bitstream corresponding to compressed data including the current processing unit within the region at a video decoder side, wherein the current processing unit consists of a set of pixels from video data;
• if a GMC (global motion compensation) mode is enabled for the region:
• determining a first number of multiple global motion models allowed for encoding processing units in the region using multiple global motion models at the video encoder side or for decoding the processing units in the region using the multiple global motion models at the video decoder side;
• and
• encoding the current processing unit at the video encoder side or decoding the current processing unit at the video decoder side using one or more coding modes including the GMC mode with one global motion model selected from the multiple global motion models, wherein more than one set of parameters for said one global motion model selected from the multiple global motion models is allowed for the current processing unit and an indication for selecting among said more than one set of parameters is signalled at a level of the current processing unit in the video bitstream.

An apparatus of Inter prediction for video coding performed in a video encoder or a video decoder, the apparatus comprising one or more electronic circuits or processors configured to:

• receive input data related to a current processing unit in a region at a video encoder side or receive a video bitstream corresponding to compressed data including the current processing unit within the region at a video decoder side, wherein the current processing unit consists of a set of pixels from video data;
• if a GMC (global motion compensation) mode is enabled for the region:
• determine a first number of multiple global motion models allowed for encoding processing units in the region using multiple global motion models at the video encoder side or for decoding the processing units in the region using the multiple global motion models at the video decoder side;
• and
• encode the current processing unit at the video encoder side or decode the current processing unit at the video decoder side using one or more coding modes including the GMC mode with one global motion model selected from the multiple global motion models, wherein more than one set of parameters for said one global motion model selected from the multiple global motion models is allowed for the current processing unit and an indication for selecting among said more than one set of parameters is signalled at a level of the current processing unit in the video bitstream.

A method of Inter prediction for video coding performed in a video encoder or a video decoder, the method comprising:

• receiving input data related to a current processing unit in a region at a video encoder side or receiving a video bitstream corresponding to compressed data including the current processing unit within the region at a video decoder side, wherein the current processing unit consists of a set of pixels from video data;
• if a GMC (global motion compensation) mode is enabled for the region:
• determining a first number of multiple global motion models allowed for encoding processing units in the region using multiple global motion models at the video encoder side or for decoding the processing units in the region using the multiple global motion models at the video decoder side, wherein parameters for each of the multiple global motion models are signalled in the video bitstream at a high level syntax associated with the region at the video encoder side or parsed from the video bitstream at the high level syntax at the video decoder side, wherein the parameters for a given global motion model are signalled predictively in the high level syntax using other parameters for the given global motion model associated with a previous coded region, wherein the previous coded region corresponds to a left region, a top region or a temporally collocated region, wherein a flag is used to indicate whether the parameters for the given global motion model are exactly predicted by said other parameters for the given global motion model associated with the previous coded region;
• and
• encoding the current processing unit at the video encoder side or decoding the current processing unit at the video decoder side using one or more coding modes including the GMC mode with one global motion model selected from the multiple global motion models.