Global motion models for motion vector inter prediction

1. A decoder, the decoder configured to:

receive a bit stream including a current frame comprising at least one 128×128 block and a picture header associated with the entire current frame;

determine, as a function of the picture header, that one global motion mode is enabled for the entire current frame, the enabled global motion mode being selected from a group including translational motion, 4-parameter affine motion, and 6-parameter affine motion;

detect, based on the enabled global motion mode, a plurality of parameters applicable to the entire frame, wherein:

if the enabled global motion mode is translational motion:

detecting the plurality of parameters further comprises detecting, in the picture header, a x direction translational motion vector component and a y direction translational motion vector component; and

the x direction translational motion vector component and the y direction translational motion vector component apply to the entire frame;

if the enabled global motion mode is 4-parameter affine motion:

detecting the plurality of parameters further comprises detecting, in the picture header, four explicit affine motion parameters; and

the four explicit affine motion parameters apply to the entire frame;

and if the enabled global motion mode is 6-parameter affine motion:

detecting the plurality of parameters further comprises detecting, in the picture header six explicit affine motion parameters; and

the six explicit affine motion parameters apply to the entire frame; and

decode the current frame using the detected parameters.

2. The decoder of claim 1 , wherein if the enabled global motion mode is translational motion, the decoder is further configured to detect that affine global motion modes are disabled for the current frame.

3. The decoder of claim 1 wherein if the enabled global motion mode is 4-parameter affine motion and if coordinates of the current frame are denoted x and y, x′ and y′ are coordinates of a reference frame, and the four 4-parameter affine motion parameters are denoted a, b, c and f, then x′=ax+by+c and y′=−bx+ay+f.

4. The decoder of claim 1 wherein if the enabled global motion mode is 6-parameter affine motion and if coordinates of the current frame are denoted x and y, x′ and y′ are coordinates of a reference frame, and the six 6-parameter affine motion parameters are denoted a, b, c, d, e and f, then x′=ax+by+c and y′=dx+ey+f.

5. A method, the method comprising:

receiving, by a decoder, a bit stream including a current frame comprising at least one 128×128 block and a picture header associated with the entire current frame;

determining, by the decoder and as a function of the picture header, that one global motion mode is enabled for the entire current frame, the enabled global motion mode being selected from a group including translational motion, 4-parameter affine motion, and 6-parameter affine motion;

detecting, by the decoder and based on the enabled global motion mode, a plurality of parameters applicable to the entire frame, wherein:

if the enabled global motion mode is translational motion:

detecting the plurality of parameters further comprises detecting, in the picture header, a x direction translational motion vector component and a y direction translational motion vector component; and

the x direction translational motion vector component and the y direction translational motion vector component apply to the entire frame;

if the enabled global motion mode is 4-parameter affine motion:

detecting the plurality of parameters further comprises detecting, in the picture header, four explicit affine motion parameters; and

the four explicit affine motion parameters apply to the entire frame;

and if the enabled global motion mode is 6-parameter affine motion:

detecting the plurality of parameters further comprises detecting, in the picture header six explicit affine motion parameters; and

the six explicit affine motion parameters apply to the entire frame;

and decoding, by the decoder, the current frame using the detected parameters.

6. The method of claim 5 , wherein if the enabled global motion mode is translational motion, the decoder is further configured to detect that affine global motion modes are disabled for the current frame.

7. The method of claim 5 , wherein if the enabled global motion mode is 4-parameter affine motion and if coordinates of the current frame are denoted x and y, x′ and y′ are coordinates of a reference frame, and the four 4-parameter affine motion parameters are denoted a, b, c and f, then x′=ax+by+c and y′=−bx+ay+f.

8. The method of claim 5 wherein if the enabled global motion mode is 6-parameter affine motion and if coordinates of the current frame are denoted x and y, x′ and y′ are coordinates of a reference frame, and the six 6-parameter affine motion parameters are denoted a, b, c, d, e and f, then x′=ax+by+c and y′=dx+ey+f.