Television – Format conversion – Line doublers type
Reexamination Certificate
1999-06-07
2001-05-15
Kostak, Victor R. (Department: 2711)
Television
Format conversion
Line doublers type
C348S448000
Reexamination Certificate
active
06233018
ABSTRACT:
This invention relates to video signal processing and more particularly to the interpolation of picture lines in, for example, an interlace-to-progressive conversion.
Many techniques have been proposed for interlace-to-progressive conversion.
An interpolation filter which takes information from both the current and adjacent fields will perform well on stationary pictures but performance will generally be degraded in the presence of motion. Adaption has been proposed, with a motion detector arranged to switch from temporal to vertical interpolation in the presence of detected motion. A particular spatio-temporal interpolation filter has been proposed which provides similar performance without the need for adaption.
It is an object of this invention to provide an improved method of interpolating picture lines in a video signal, which takes advantage of motion compensation to offer improved interpolation performance without substantial processing overhead.
Accordingly, the present invention consists in one aspect in a motion compensated method of interpolating picture lines in a video signal, utilising an interpolation aperture taking information from current and adjacent fields, arranged such that the contributions from adjacent fields sum substantially to zero at low frequencies, characterised in that vertical motion information is rounded to the nearest two picture lines (per field period) and vertical motion compensation conducted through vertical shifting of the aperture.
In a further aspect, the present invention consists in apparatus for the interpolation of picture lines in a video signal, comprising delay means for providing simultaneous access to a current field and at least two adjacent fields; a source of vertical motion vectors rounded to even numbers of picture lines; shift means for shifting the adjacent fields in accordance with rounded vertical motion vectors and an interpolation filter taking information from at least three lines of each of the current and shifted adjacent fields, the contributions from said adjacent fields summing substantially to zero at low frequencies.
There is disclosed in EP 0 266 079 and in: Weston, M. 1988.
Fixed, adaptive and motion compensated interpolation of interlaced TV pictures.
2nd International Workshop on Signal Processing for HDTV (L'aquila, Italy) Feb. 2-Mar. 29 1988, a fixed spatio-temporal interpolation which reduces the deleterious effects of motion by arranging that the contributions from adjacent fields sum substantially to zero at low frequencies.
It has surprisingly been found that a significant improvement to the performance of the fixed filter can be achieved with vertical motion compensation restricted to vertical units of even numbers of picture lines per field period. The performance of a filter according to this invention is clearly no better than that of the fixed filter at vertical motions of one picture line per field. However, it has been recognised by the present inventor that no system can deal satisfactorily with this “strobe” speed. At speeds greater than one picture line per field, filters according to the present invention offer much better performance than the known fixed filter. At high speeds, camera integration blurs the image to the extent that lack of accuracy in determining vertical motion has no material effect.
In accordance with the present invention, this vertical-temporal filter is steered to follow vertical motion in steps of two picture lines per field. That is, for vertical motion speeds below one picture line per field, it is unchanged from the fixed filter. For speeds between one and three picture lines per field, the coefficients in the outer fields are moved up and down by two picture lines in the direction of motion, and so on. Thus the coefficients in the outer fields always act on existing field lines, never on the inserted lines of zero.
Comparisons have been made between a filter according to the present invention and complex vertical interpolation filters which attempt to follow vertical motion accurately at all speeds other than those close to the strobe speed. It is found that in the presence of uncertainties in motion vectors, the performance of filters according to the present invention is in fact superior to the more complex and supposedly more accurate vertical interpolators.
The present invention is particularly suitable for use with motion information decoded from an MPEG2 or other bit rate reduced signal where uncertainties in motion vectors are to be expected.
REFERENCES:
patent: 5119193 (1992-06-01), Noji
patent: 5177610 (1993-01-01), Wilkinson
patent: 5410356 (1995-04-01), Yasuhiro
patent: 5534946 (1996-07-01), De Haan et al.
patent: 5786852 (1998-07-01), Kim et al.
patent: 0 179 594 (1986-04-01), None
patent: 0 266 079 (1988-05-01), None
patent: 0 294 874 (1988-12-01), None
“Fixed, Adaptive, and Motion Compensated Interpolation of Interlaced TV Pictures”, by M. Weston, 2ndInternational Workshop on Signal Processing for HDTV, Feb. 29th-Mar. 2, 1988.
British Broadcasting Corporation
Kostak Victor R.
McDermott & Will & Emery
LandOfFree
Video signal processing does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Video signal processing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Video signal processing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2561872