Television – Format conversion – Line doublers type
Reexamination Certificate
1999-03-05
2001-04-17
Kostak, Victor R. (Department: 2611)
Television
Format conversion
Line doublers type
C348S452000
Reexamination Certificate
active
06219102
ABSTRACT:
DESCRIPTION
The invention relates to a weighted median filter interpolator, in particular for an interlaced to progressive conversion process of video signals.
Weighted median filters are known in the art (see e.g. Lit. [1]). They represent a more general approach to rank dependent median operators. The generalization relates to (a) sample dependent weight(s), which can be seen as a repetition operator of the respective samples. Following this understanding, a weight of “0” means, the respective sample is not considered in the ranking operation.
Interlaced to progressive conversion refers to the problem of interpolating the missing lines in an interlaced scanned video signal by use of a signal interpolation algorithm (IPC algorithm) to represent a resulting signal in a progressive scan raster. More or less motion insensitive methods for the scan raster conversion have been proposed and are known (see e.g. Lit. [2] and [3]).
For the IPC interpolation process, it is known to use so-called five-tap median filters. As disclosed in Lit. [2], the inputs to the filter are for example the corresponding pixels from the previous and the next frames, their linear average and the pixels from the line above and below. Similarly, three-tap median filters were also proposed for the 100 Hz interlaced to interlaced conversion (see Lit. [4]).
Problems with the known or formally proposed filters are their poor behaviour in either the temporal domain, i.e. poor motion portrayal and remaining flicker artifacts in progressive display modes, or in the spatial domain the loss of resolution and fuzzy vertical edges.
Based on the known proposal of weighted median filter approaches, it is an object of the present invention to improve interpolation filters proposed for the interlaced to progressive conversion of video signals in the direction of more flexibility depending on available source fields at a certain time.
A weighted median filter interpolator for the interlaced to progressive conversion of video signals is characterized according to the invention by means for adjusting specific filter modes by setting the weights such that the number of median samples to be processed at a certain time is always an odd number. Preferably, the weight of a single sample is either “0” or “1”. As a most preferred embodiment, according to the invention a five-tap median filter is used of which the actual filter aperture depends on the selected filter mode defined by the respective number of sample weights according to the available source fields at a certain time.
According to the invention a specific set of weights is selected to define a specific IPC interpolation filter. Thus a general IPC interpolation filter provides according to a selected mode a specific output quality depending on the available source fields.
In particular, for a five-tap median interpolator, two sub-sets define two alternative interpolation filters included in a five-tap weighted median filter structure. For example, in the case of a five-tap weighted median IPC filter, a three-dimensional filter aperture is realizable spreading over a horizontal, a vertical and a temporal dimension of three consecutive fields of an incoming interlaced video signal, in particular if a spatial linear filter output sample is used. The actual filter aperture depends on the filter mode, and thus on the respective sample weights.
The filter behaviour varies with the modes depending on the weights of the source signal samples, which preferably are a top pixel T, a bottom pixel B, a previous (field) pixel P, a successive (field) pixel S and a linear source signal sample, which preferably is a horizontal/vertical linear filter sample.
The weight of a single sample can be either “0” or “1”. The weight settings specified by the present invention are such that the number of median samples is always an odd number, i.e. preferably and in the case of a five-tap median filter “1”, “3” or “5”. By this selection according to the invention, the median operator becomes unambiguous. For example, if the number of weights=“1” is three, then the median is derived from these three samples, whereas if the number of weights=“1” is five, the median is derived from said five samples.
REFERENCES:
patent: 5126843 (1992-06-01), Tanaka
patent: 5488421 (1996-01-01), Hwang et al.
patent: 5889890 (1999-03-01), Heimburger
patent: 5995163 (1999-11-01), Fossum
patent: 0 610 701 (1994-08-01), None
patent: 0 629 083 (1994-12-01), None
Erdler Oliver
Schwendowius Joerg
Wagner Peter
Zimmerman Klaus
Frommer William S.
Frommer Lawrence & Haug LLP.
Kostak Victor R.
Simon Darren M.
Sony International (Europe) GmbH
LandOfFree
Weighted median filter interpolator does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Weighted median filter interpolator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Weighted median filter interpolator will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2486374