Television – Format conversion – Conversion between standards with different aspect ratios
Reexamination Certificate
1998-11-23
2001-07-17
Eisenzopf, Reinhard J. (Department: 2614)
Television
Format conversion
Conversion between standards with different aspect ratios
C348S556000, C348S558000, C348S913000, C348S469000, C348S173000
Reexamination Certificate
active
06262772
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of The Invention
The subject invention relates to displaying images having a certain aspect ratio on display screens having a different aspect ratio.
2. Description of The Related Art
With the advent of widescreen displays in which the display screen has an aspect ratio of 16:9, a problem has arisen when images having an aspect ratio of 4:3 are displayed on the screen. In particular, as shown in
FIG. 1A
, the 4:3 aspect ratio image
1
is displayed on the screen with vertical black bands
2
and
3
. Since at the present time, most video signals have the 4:3 aspect ratio, “burn in” may occur on the display screen where the screen phosphors are aged only in the area where the image is displayed. This then leads to distortions when viewing a true 16:9 image on the display.
Similarly, motion pictures are generally shot in a 16:9 aspect ratio. However, when that picture is reformatted for the standard 4:3 aspect ratio, information is lost. Now many motion picture studios release these motion pictures also in “letterbox” format in which the 16:9 image is compressed such that it fits the 4:3 aspect ratio. This is shown in
FIG. 1B
where the 16:9 image
4
appears between two horizontal black bands
5
and
6
.
In addition to being detrimental to the display, the appearance of these vertical or horizontal black bands is disturbing to the user of the display and detracts from the viewing experience.
Conversion circuitry is know that is capable of expanding a displayed image both horizontally and vertically in order to eliminate these black bands. However, it is up to the user to decide when and which of these conversions is to be used.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method and apparatus for automatically eliminating both horizontal and vertical black bands from the borders of displayed images.
This object is achieved in a method for automatically eliminating horizontal and vertical black bands from the borders of a displayed video image, the method comprising the steps of performing a first detection of the occurrence of a black level in an input video signal for at least n lines at the beginning and end of a frame in the input video signal; performing a second detection of the occurrence of a black level in said input video signal for at least m pixels at the beginning and end of each line in a frame of the input video signal; vertically up-converting the lines in the input video signal in dependence on said first detection; and horizontally expanding the lines in the input video signal in dependence on said detection.
An apparatus for automatically eliminating horizontal and vertical black bands from the borders of a displayed video image, comprises first means for performing a first detection of the occurrence of a black level in an input video signal for at least n lines at the beginning and end of a frame in the video signal; second means for performing a second detection of the occurrence of a black level in an input video signal for at least m pixels at the beginning and end of each line in the video signal; means for vertically up-converting the lines in the video signal in dependence on said first detection; and means for horizontally expanding the lines in the video signal in dependence on said detection.
In a preferred embodiment of the invention, the first and second detections are performed for a predetermined number of fields (or frames) to insure that the black bands consistently persist. It should be understood that with this preferred embodiment, the black bands will appear on the display at least temporarily.
In order to prevent the black bands from being temporarily visible, the above method may alternatively include delaying the input video signal for at least one field (or frame) while the black level detection is being performed.
REFERENCES:
patent: 4556906 (1985-12-01), Dischert et al.
patent: 5223929 (1993-06-01), Sugimori et al.
patent: 5249049 (1993-09-01), Kranawetter et al.
patent: 5442403 (1995-08-01), Yasumoto et al.
patent: 5760840 (1998-06-01), Tani et al.
patent: 0514819A2 (1992-11-01), None
patent: 0800311A1 (1997-10-01), None
Cavallerano Alan
Shen Richard C.
Eisenzopf Reinhard J.
Goodman Edward W.
Philips Electronics North America Corporation
Tran Trang U.
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