Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1985-06-12
1988-03-08
Chin, Tommy P.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358105, 358140, 358167, H04N 514, H04N 521, H04N 701
Patent
active
047302178
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invntion relates to a movement detector for use in television signal processing.
2. Related Art
There are a number of applications in television signal processing which benefit from motion-adaptive processing. For example it is desirable to operate noise reduction methods in stationary parts of a scene but not in moving parts. In the field of digital television data rate reduction there are often different algorithms suitable for moving and for stationary picture areas. Also in line-rate conversion, different interpolation schemes are sometimes needed depending on scene motion. In each of these cases a number of difficulties arise in defining suitable movement detection processing. For example noise (or subcarrier in an environment where composite colour coding is used) can masquerade as scene movement. There is one area of difficulty however which arises specifically in the application of line-rate conversion. This will now be described for the specific application of up-conversion from a line-format with 2:1 interlace to a non-interlaced format, although conversion to other line formats will show one some difficulty.
In order to achieve improvement in picture quality it is possible to "upconvert" an interlaced signal for display with a higher line-rate.
This may take place, for example, in a satellite broadcasting receiver designed for displaying extended definition signals. The relationship between an incoming interlaced line-format and a resulting non-interlaced line format, for example, is illustrated in FIG. 1. Crosses indicate received interlace lines and circles indicate the additional lines which need to be interpolated to provide a non-interlaced scan. The dot is taken as an example line (in "field 0") to be interpolated and the "surrounding" (in space and time) received interlace lines are labelled A,B,C and D. If the appropriate area of the scene is stationary, then the best method of interpolation for the new line is to base it on values taken from the same vertical position. For example an average of A and B would be suitable (a form of "temporal interpolation"). This would enable the full vertical resolution capabilities of the received interlaced lines to be achieved. If there is some scene movement in the vicinity of lines A,B,C and D however then values from positions A and B would provide an erroneous interpolation and a better option would be to use lines from the same field. For example an average of C and D (a form of "vertical interpolation") could be suitable. If however C and D were used for interpolation in a stationary scene, then vertical resolution would be sacrificed and much of the picture quality improvement promised by this technique would be lost. A movement detection circuit is therefore required in order to provide a control signal for determining the appropriate interpolation procedure.
One approach would be to use an absolute frame difference signal i.e. k=1A-B1 where k provides the basis for this control signal. In general, movement will give rise to a significant frame difference value while stationary picture detail will yield a zero frame-difference value. Thus a large frame difference signal is required and a very small frame difference signal could be used to indicate that temporal interpolation is required. Usually there will be more than two options for interpolation so that the transition in a scene from one type to the next would not be so abrupt. Typically there could be a number of options ranging from purely vertical interpolation at one extreme to purely temporal interpolation at the other. Intermediate interpolators would use lines displaced both vertically and temporally.
There is a fundamental difficulty which arises with such movement detection. This is because certain types of movement "bypass" the detector and result in a zero frame-difference signal. This difficulty does not arise in the systems based on a single scanning standard, such as noise reducers, and is thus specific to the
REFERENCES:
patent: 4232338 (1980-11-01), Netravali
patent: 4296436 (1981-10-01), Achiha
patent: 4322750 (1982-03-01), Lord
patent: 4393396 (1983-07-01), Raven
Digital Standards Converter by Adaptive Intra-Frame Line Interpolation, by K. Kinuhata, et al., IEEE Transactions on Communications, vol. COM-26, No. 10, Oct. 1978, pp. 1413-1419.
Flannigan Barry A.
Tonge Gary J.
Chin Tommy P.
Independent Broadcasting Authority
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