Television – Image signal processing circuitry specific to television – Special effects
Patent
1992-07-10
1994-03-08
Powell, Mark R.
Television
Image signal processing circuitry specific to television
Special effects
395125, G06F 1572, H04N 5262
Patent
active
052932338
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an apparatus for use with a digital video effects system, and, more especially, concerns improvements relating to apparatus of the kind described in International Application PCT/GB89/01116, the disclosure of which is incorporated herein by reference.
In Application No. PCT/GB89/01116 there is described an apparatus for producing a variety of curved surface effects by the use of a so-called intermediate address store wherein there is represented, for each pixel of the output picture, the co-ordinates of the point in an input picture which is to be seen at that point in the output. This store is filled by a control system which generates arbitrary functions which are used to address it, and linear functions which are written to it.
One drawback of such a system is that if the scale of the picture information to be stored is increased in relation to the scale of the original picture information, then it is possible for locations in the intermediate address store to be left unwritten and to appear as holes in the final picture. This occurs because as the scale of the curved surface function providing the coordinates used to address the intermediate address store is increased, the corresponding coordinate values are provided to a resolution that is not sufficiently great to provide coordinate values corresponding to all addresses of the store. Thus, during the process of filling the store, some addresses of the store are skipped and remain unwritten. When data is then read from the store to enable addressing of a store containing picture information, gaps will appear in the information necessary to address the picture store and corresponding holes will appear in the visible image retrieved from the picture store.
In theory it would be possible to overcome the above problem by computing, from the coordinate values generated to a given scale by the arbitrary curved function, intermediate coordinate values at a resolution sufficient to enable complete addressing of the relevant store. In practise, however, the volume of data that would need to be processed in such a computation is such that would not be feasible for any known general purpose data processor to carry out the required computation in the real time available, i.e. in the period between reproduction of consecutive frames of a television picture signal.
It is accordingly one object of the invention to devise a process enabling the resolution of coordinate values that have been transformed to define a curved surface to be increased in relation to that provided by the original series of coordinates, which process is organised into steps such that coordinate values of increased resolution can be generated in real time by a data processing apparatus having respective stages dedicated to carry out corresponding steps of that process.
It is a further object of the invention to provide corresponding, novel individual stages of such a data processing apparatus.
It is a yet further object of the invention to provide a data processing apparatus comprising an appropriate association of said individual stages.
According to one aspect of the invention there is provided a process for deriving, from a set of two dimensional co-ordinate signals that have been transformed according to curved functions in order to represent relatively to a video image frame positions to be occupied by an image of a curved surface, intermediate values of the transformed co-ordinate signals to a resolution greater than that provided by said set, characterised in that it comprises the steps of:
a)providing within a memory store a look up table containing for each of a given number of two dimensional geometric figures within a given range of sizes a corresponding distribution of values of co-ordinate positions within the figure, such that the stored distributions collectively include substantially all possible distributions of such values that can occur within a given incremental area or range of areas of the image frame;
b)processing a set of said transformed co-or
REFERENCES:
patent: 4751579 (1988-06-01), Okunishi et al.
patent: 4809070 (1989-02-01), Lake, Jr.
patent: 4965844 (1990-10-01), Oka et al.
Barton Nicholas
Billing Robert
Powell Mark R.
Questech Limited
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