Television – Format conversion – Changing number of fields for standard conversion
Patent
1995-02-16
1998-05-19
Kostak, Victor R.
Television
Format conversion
Changing number of fields for standard conversion
348447, 348701, H04N 701
Patent
active
057542465
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to video signal processing, and especially to processes which involve field interpolation, such as broadcast standards conversion.
It is a well recognised problem that such processes can introduce picture artifacts if there is motion in the video image. The seriousness of the problem will depend upon the nature and the resolution of the process involved and upon the type and degree of motion. A variety of techniques have been proposed for reducing the deleterious effects of motion, such techniques being referred to as motion compensation. Generally speaking, motion compensation will add significantly to the cost of the standards conversion or other process.
SUMMARY OF THE INVENTION
It is an object of this invention to provide at modest cost a method of reducing the deleterious effects of motion to a level which will be satisfactory in many applications.
Accordingly, the present invention consists in one aspect in a method of reducing the deleterious effects of motion in a video signal process, comprising the steps of conducting the video signal process on a video signal at high bandwidth without motion compensation; conducting a like video signal process without motion compensation at low bandwidth to produce a low bandwidth control signal; conducting a similar video signal process with motion compensation at low bandwidth to produce a low bandwidth motion compensated signal; comparing the control and motion compensated signals to produce an error signal and subtracting the error signal in the high bandwidth video signal process.
Since motion compensation is only conducted on a low bandwidth signal, it can be provided in relatively simple hardware. The resolution of the overall process is determined by the high bandwidth signal path and is not affected by the relatively coarse processing which produces the error signal. Although the motion compensation will not detect slow movement or movement involving small picture areas, it will respond to the types of motion which have the most serious effects on picture quality, the best example of this being panning. Indeed, it is possible to operate a method according to the present invention so as to detect horizontal motion only.
The low bandwidth motion compensated and non-motion compensated processes may have a large number of steps in common and may be conducted in tandem. Thus an error signal may be developed with the low bandwidth motion compensated and non-motion compensated signals being notional signals, not output as such.
Since the present invention in this aspect operates by removing a motion-related error from a "conventional" non-motion compensated process, it can be provided as an adjunct to existing designs and to existing equipment. If it is found that the approach contemplated by the present invention is unsuited to particular types of picture material, the error signal can simply be disabled for such categories of picture material. In a dynamically adapted arrangement, the amplitude of the error signal can be attenuated in circumstances where there is a lack of confidence in the motion compensation.
In an arrangement where the invention is embodied in freshly designed equipment, not as an adjunct to existing equipment, there is no requirement to develop an error signal as such. The present invention accordingly encompasses an alternative arrangement where the low bandwidth channel has no non-motion compensated processing, the need for this being obviated by confining the previously full bandwidth non-motion compensated processing, to high frequencies.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described by way of example with reference to the accompanying drawings in which:
FIG. 1 is a block diagram illustrating apparatus according to the present invention;
FIG. 2 and 2A are a more detailed diagram illustrating one embodiment according to the present invention;
FIGS. 3 and 4 are diagrams serving to clarify the method of operation of the apparatus shown in FIG. 2;
FIG. 5 is
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patent: 4612567 (1986-09-01), Pritchard
patent: 4780760 (1988-10-01), Waldman et al.
patent: 5140424 (1992-08-01), Yoshimura et al.
patent: 5175619 (1992-12-01), Willis
patent: 5225907 (1993-07-01), Casavant et al.
Kostak Victor R.
Snell & Wilcox Limited
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