Television – Basic receiver with additional function – Multimode
Reexamination Certificate
1998-02-24
2001-08-28
Powell, Mark R. (Department: 2672)
Television
Basic receiver with additional function
Multimode
C348S441000, C348S453000, C382S260000, C382S298000
Reexamination Certificate
active
06281938
ABSTRACT:
The invention relates to a signal processing system.
Images can be represented in an electrical environment by signals that define such image attributes as the intensity and colour of elements of the images. In the past, television pictures were represented by analog signals defining the luminance (Y) and the colour difference (R−Y) and (B−Y), ie chrominance, of the picture elements. More recently digital signals have been used to represent television pictures. Digital signals are highly resistant to degradation and can be readily processed to create special effects in the television picture.
In one digital standard, the so-called D
1
standard, a component signal is used consisting of luminance (Y) and chrominance (U, V) signals that are sampled at a ratio of 4:2:2. The luminance signal is sampled at a rate of 13.5 MHz and the two chrominance signals are each sampled at a rate of 6.75 MHz. The bandwidth is a measure of the detail in the picture. Sampling in the 4:2:2 ratio means that the horizontal resolution of the colour in the television picture is halved, but because it is the luminance that contains the picture detail this reduction in horizontal colour resolution is an acceptable compromise that enables the data rate to be reduced.
As a component signal, the D
1
signal is well suited to studio and post-production work. However, under some circumstances unacceptable image degradation can occur as a direct consequence of the reduced chrominance bandwidth.
FIG. 1
of the accompanying drawings illustrates a simple picture
1
comprising two areas of different colours
2
,
3
, say yellow and black, with an abrupt transition
4
between the two areas.
FIG. 2
of the accompanying drawings shows a signal
5
of infinite bandwidth representing a line
6
in the picture
1
. The infinite bandwidth of the signal
5
means that signal can represent exactly the transition
4
between the two areas
2
,
3
. Ideally, the luminance (Y) and chrominance (U, V) signals would represent the line
6
in this manner. However, this does not happen in practice because of the limited bandwidth of the signals.
FIG. 3
of the accompanying drawings shows a luminance signal
7
comprising multiple sample values at evenly spaced intervals. The effect of limiting the bandwidth in the signal
7
is to produce a transitional zone
9
in the signal extending to each side of the boundary
4
in the picture.
FIG. 4
of the accompanying drawings shows a signal
10
having half the bandwidth of the signal
7
and corresponding to one of the chrominance signals (U or B). The effect of halving the bandwidth of the signal
10
as compared to that of the signal
7
is to halve the number of sampling points
11
that comprise the signal
10
and to increase the size of the transitional zone
12
on each side of the boundary
4
in the picture.
When the picture represented by the luminance signal
7
and chrominance signals
10
is displayed on a monitor the boundary
4
between the two areas
2
,
3
will not be seen as a sharp line but will instead be seen as a blurred region that may contain unwanted colours between yellow and black. In some situations, especially when the image is static as opposed to part of a video sequence, this blurring of the boundary
4
is unacceptable.
In British Patent Application No. 9607910.8, the teachings of which are incorporated herein by reference, there is described a processing system for converting the 4:2:2 signals into 4:4:4 signals. That is to say, the system converts the initial chrominance (UV) data that are shared between two adjacent pixels into respective chrominance (UV) data for each pixel. This overcomes the above-discussed problems and thus facilitates processing of the signals.
Naturally, once the 4:4:4 signals have been processed it is necessary to convert them back into the 4:2:2 format so that they can be stored in D
1
equipment and/or broadcast. Many television companies insist that there should be no difference between the initial 4:2:2 signals and the 4:2:2 signals that have been processed. Of course there will be some differences where the pixel values have been intentionally changed as part of the processing, but the differences must be limited to such intentional changed and it is impermissible to create differences that are solely as a result of converting from 4:2:2 into another format and back again.
The invention addresses these problems.
According to one aspect of the invention there is provided a signal processing apparatus comprising: a source of a plurality of video signals that each contain an equal amount of data for a given pixel in a video image; a first filter for filtering the plurality of video signals to produce first filtered signals; a second filter for filtering the plurality of video signals to produce second filtered signals; a selector connected to the first and second filters for selecting between portions of the first and second filtered signals, and thereby outputting a plurality of video signals in which at least one of the signals contains less data for a given pixel in a video image than at least one other of the signals.
According to another aspect of the invention there is provided a signal processing method comprising: filtering a plurality of video signals that each contain an equal amount of data for a given pixel in a video image to produce first filtered signals; filtering the plurality of video signals to produce second filtered signals; selecting between portions of the first and second filtered signals; and outputting a plurality of video signals in which at least one of the signals contains less data for a given pixel in a video image than at least one other of the signals.
The invention also provides a signal processing system in which initial signals in one standard comprising plural signals of equal bandwidth are converted into resultant signals in another standard comprising plural signals of differing bandwidths by processing the initial signals to produce processed signals and selecting portions of the initial signals or of the processed signals for output as the resultant signals depending on a comparison between the processed signals and the initial signals.
The above and further features of the invention are set forth with particularity in the appended claims and together with advantages thereof will become clearer from consideration of the following detailed description of exemplary embodiments of the invention given with reference to the accompanying drawings.
REFERENCES:
patent: 4602285 (1986-07-01), Beaulier
patent: 5384869 (1995-01-01), Wilkinson
patent: 5528301 (1996-06-01), Hau
patent: 5537157 (1996-07-01), Washino
patent: 5550936 (1996-08-01), Someya
patent: 5852470 (1998-12-01), Kondo
patent: 5920654 (1999-07-01), Someya
patent: 469892A3 (1992-02-01), None
patent: 2286943 (1995-08-01), None
Cooper & Dunham LLP
Powell Mark R.
Quantel Limited
Sajous Wesner
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