Television – Image signal processing circuitry specific to television – Transition or edge sharpeners
Reexamination Certificate
1998-05-18
2001-01-30
Peng, John K. (Department: 2714)
Television
Image signal processing circuitry specific to television
Transition or edge sharpeners
C348S631000, C348S606000, C348S624000, C348S630000, C348S382000, C348S266000
Reexamination Certificate
active
06181385
ABSTRACT:
The invention relates to a method for processing transitional regions in a digital picture signal.
PRIOR ART
The invention is based on a method for processing transitional regions in a picture signal, of the generic type of the independent Claim
1
. A method for picture signal edge correction has been disclosed, for example, in German Patent Specification DE 40 39 122 C2. In the case of the method which is known from this patent, a digitized luminance signal of a video signal is delayed in four series-connected delay circuits. The delayed luminance signals are processed in downstream stages, namely subtraction circuits, absolute-value circuits, comparators and multiplying circuits. These processing stages are used to define the start of an edge and the end of an edge. When the start of an edge is identified, control signals are produced such that one of the delayed luminance signals is output instead of the undelayed luminance signal. This results in an increase in the gradient of a transition in the picture signal since the upper luminance value of the transition from one sample value to the next is virtually output without having to output intermediate values.
INVENTION
On the basis of the prior art cited above, the object of the invention is to specify a method for processing transitional regions in a digital picture signal, which operates as far as possible at the sampling clock rate of the respective picture signal, is easy to implement in terms of circuitry and, in particular, manages without complex circuits to identify transitions (edges) in the picture signal.
In contrast to the method known from the prior art, the method according to the invention and having the features of Claim
1
has the advantage that it processes each pixel individually at the normal sampling clock rate and, to this extent, is easy to implement in terms of circuitry. With regard to the processing of a pixel, the position of this pixel within a transition is irrelevant. There is no need for circuit elements for definition of what is a transition in the picture signal and to detect such a transition in the picture. This characteristic of the method also provides insensitivity to noise occurring in the picture signal.
The measures described in the dependent claims allow further improvements in the method. On the basis of the method according to the invention, a transitional region is defined simply by the maximum and minimum pixel values in the processing block under consideration. Splitting the transitional region defined in this way into upper and lower sections according to Claim
2
makes it easy to allocate correction values to increase the gradient of the transition. In this case, the processing pixel value is allocated a positive correction value if said processing pixel is located in one of the upper sections of the transition and, accordingly, is allocated a negative correction value if said processing pixel value is in one of the lower sections of the transition. This results in the gradient of the transition being increased in a simple manner.
The splitting of the defined transitional region into upper and lower sections is accomplished in a simple manner by determining the mean value between the minimum and maximum pixel values in the processing block and using this mean value as a boundary between the upper and lower sections.
The method can advantageously be used to increase the edge gradient in a picture signal. In this case, the picture signal is predominantly a luminance signal of a video signal.
For the situation where the edge gradient of a luminance signal is increased, it is advantageous if the respective correction value for the processing pixel value is chosen as a function of the difference between the maximum and minimum pixel values. In this case, the edge gradient increasing function can gradually tend to zero if the difference between the maximum and minimum pixel values likewise tends to zero. This also makes it possible to use the edge gradient increasing measure to avoid the undesirable effect of unnaturally acting human faces in a video picture.
The measures according to Claim
6
are advantageous for a specific implementation of the method for luminance signals. As a result of the fact that the specified transfer function, with whose aid the pixel values of the transition are corrected, has sections with different gradients, in particular two gradients which differ substantially from zero, undesirable aliasing effects at the higher frequencies are avoided in the picture.
The method can also advantageously be used to improve the colour transitions in a picture signal, as is claimed in Claim
9
. Aliasing effects at the higher horizontal frequencies of the chrominance signal are less easily visible by the human eye, so that in this case it is possible to simplify the method. A simplified method, which is easy to implement, is claimed in Claim
10
.
The measure according to Claim
11
leads to a further simplification of the downstream switching units. The increase in the number of sample values by a factor of 2 specifically results in the capability to use the same processing clock rate in the downstream circuit parts for processing the luminance and chrominance signals (for example conversion of these signals into corresponding RGB signals).
REFERENCES:
patent: 4935806 (1990-06-01), Rabii
patent: 5029004 (1991-07-01), Shibayama
patent: 5151787 (1992-09-01), Park
patent: 5159442 (1992-10-01), Mizuta
patent: 5237414 (1993-08-01), Faroudja
patent: 5304854 (1994-04-01), Aoki et al.
patent: 5311328 (1994-05-01), Murata
patent: 5374964 (1994-12-01), Rzeszewski
patent: 5412432 (1995-05-01), Hong
patent: 5467145 (1995-11-01), Limberg
patent: 5469225 (1995-11-01), Hong
patent: 5515112 (1996-05-01), Penney
patent: 5699126 (1997-12-01), Hong
patent: 5848181 (1998-12-01), Ogata
patent: 5920357 (1999-07-01), Ohara
patent: 5926577 (1999-07-01), Kasahara et al.
patent: 5936682 (1999-08-01), Thomas et al.
patent: 6043853 (2000-03-01), Shimazaki et al.
patent: 3943307A1 (1990-07-01), None
patent: 3919817C2 (1990-12-01), None
patent: 4039122C2 (1991-06-01), None
patent: 4340687C2 (1994-07-01), None
patent: 0094597A2 (1983-11-01), None
patent: 0384718B1 (1990-08-01), None
patent: 0805603A1 (1997-11-01), None
German Search Report dated: Feb. 5, 1998.
Deutsche Thomson-Brandt GmbH
D{acute over (e)}sir Jean W.
Herrmann Eric P.
Peng John K.
Tripoli Joseph S.
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