Patent ID: 7352810

Claim:
A coding device comprising: an MPEG coder; and a syntax modifier linked to the MPEG coder; for modifying the display-horizontal-size and display-vertical-size fields and the frame-centre-horizontal-offset and frame-center-vertical-offset fields of the MPEG data stream originating from the coder, respectively as a function of the amplitude and of the position of a desired zoom, wherein the syntax modifier (a) calculates the horizontal and vertical sizes of an initial display rectangle from which is obtained the sizes of a target display rectangle for a scaling ratio of a coded image, (b) stores in the fields display-horizontal-size and display-vertical-size of the MPEG bitstream, the horizontal and vertical size of the initial display rectangle, (c) calculates the corresponding position of the centre of the initial display rectangle with respect to the centre of the coded image so as to define a horizontal and vertical offset, and (d) stores an item of information defining the horizontal and vertical offset in the frame_centre_horizontal_offset and frame_centre_vertical_offset fields of the MPEG video data stream.