Method of predicting motion and texture data

1. Method as part of a scalable encoding or decoding method, for generating for at least one block of pixels of a picture of a high resolution sequence of high resolution interlaced pictures at least one motion predictor from motion data associated with the pictures of a low resolution sequence of low resolution progressive pictures each interlaced picture comprising a top field interlaced with a bottom field, a temporal reference being associated with each progressive picture and each field of an interlaced picture, wherein the method comprises:

generating at least one frame motion predictor from motion data associated with at least one block of pixels of the low resolution picture with the same temporal reference as the top or bottom field of said high resolution picture; and

generating at least one field motion predictor from motion data associated with at least one block of pixels of the low resolution picture with the same temporal reference as the top field or bottom field of said high resolution picture.

2. Method according to claim 1 , wherein generating said at least one frame motion predictor comprises subsampling said motion data associated with said at least one block of pixels of the low resolution picture with the same temporal reference as the top or bottom field of said high resolution picture with a horizontal inter-layer ratio in the horizontal direction of the picture and a vertical inter-layer ratio in the vertical direction of the picture,

said horizontal inter-layer ratio being equal to the width of the high resolution picture divided by the width of the low resolution pictures and said vertical inter-layer ratio being equal to the height of the high resolution pictures divided by the height of the low resolution pictures.

3. Method according to claim 1 , wherein the method further comprises:

when the temporal frequency of the high resolution sequence is equal to the temporal frequency of the low resolution sequence, generating at least one texture predictor for said at least one block of pixels from at least one of:

texture data associated with said at least one block of pixels of the low resolution picture with the same temporal reference as the top field of said high resolution picture; and

texture data associated with said at least one block of pixels of the low resolution picture with the same temporal reference as the bottom field of said high resolution picture; and

texture data associated with each of said at least one block of pixels of the low resolution pictures with the same temporal reference as one of the bottom or top fields of said high resolution picture; and

when the temporal frequency of the high resolution sequence is equal to twice the temporal frequency of the low resolution sequence, generating at least one texture predictor for said at least one block of pixels from texture data associated with said at least one block of pixels of the low resolution picture with the same temporal reference as the top field of said high resolution picture.

4. Method according to claim 1 , wherein the motion data associated with the low resolution pictures comprises motion vectors.

5. Method according to claim 4 , wherein said method is used by a method of encoding high resolution pictures from low resolution pictures encoded according to the MPEG-4 AVC standard.

6. Method according to claim 1 , wherein, when the temporal frequency of said high resolution sequence is equal to the temporal frequency of said low resolution sequence, the method comprises:

generating one top field motion predictor by subsampling said motion data associated with at least one block of pixels of the low resolution picture with the same temporal reference as the top field of said high resolution picture with a horizontal inter-layer ratio in the horizontal direction of the picture and a vertical inter-layer ratio in the vertical direction of the picture; and

generating one bottom field motion predictor by subsampling said motion data associated with at least one block of pixels of the low resolution picture with the same temporal reference as the bottom field of said high resolution picture with said horizontal inter-layer ratio in the horizontal direction of the picture and said vertical inter-layer ratio in the vertical direction of the picture, said horizontal inter-layer ratio being equal to the width of the high resolution picture divided by the width of the low resolution pictures and said vertical inter-layer ratio being equal to the height of the fields of the high resolution pictures divided by the height of the low resolution pictures.

7. Method according to claim 1 , wherein, when the temporal frequency of the high resolution sequence is equal to twice the temporal frequency of said low resolution sequence, the method comprises generating either one top field motion predictor or one bottom field motion predictor by subsampling motion data associated with at least one block of pixels of the low resolution picture with the same temporal reference as the top field respectively as the bottom field of said high resolution picture with a horizontal inter-layer ratio in the horizontal direction of the picture and a vertical inter-layer ratio in the vertical direction of the picture,

said horizontal inter-layer ratio being equal to the width of the high resolution picture divided by the width of the low resolution pictures and said vertical inter-layer ratio being equal to the height of the fields of the high resolution picture divided by the height of the low resolution pictures.