Television – Basic receiver with additional function – For display of additional information
Reexamination Certificate
1998-07-13
2001-11-27
Eisenzopf, Reinhard J. (Department: 2614)
Television
Basic receiver with additional function
For display of additional information
C348S565000, C348S638000, C348S659000
Reexamination Certificate
active
06323913
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a circuit configuration for color decoding and decimation for a video signal. Such a circuit configuration is particularly suitable for inserting a reduced picture into a main picture or parent picture, i.e. so-called picture-in-picture insertion.
Picture-in-picture insertion requires that the picture to be inserted is reduced from its original, input size to the picture size to be inserted. In other words, the picture signal is to be decimated. Moreover, in the course of the picture processing, it is expedient for the brightness and color signal components to be processed separately. These signal components are combined in the video signal at the receiving end. The luminance and two chrominance signal components are obtained from the video signal, i.e. the color decoding, is carried out prior to the decimation.
A prior art circuit configuration for picture-in-picture insertion is described in the SIEMENS product description “ICs for Entertainment Electronics; Picture-in-Picture System,” Issue May 1991, in particular page 8 and pages 42-43. A digitally operating color decoder generates a digital luminance signal Y and two digital chrominance signals U, V which are fed to a picture-in-picture processor. The latter contains, on the input side, a decimator which decimates the picture to be inserted with regard to its size. The decimated picture is then buffer-stored in a frame memory. A commercially available module which is not necessarily adapted to the specific application of picture-in-picture insertion is proposed as color decoder. Therefore, the signal components Y, U, V with the largest possible signal bandwidth in each case are fed to the input side of the decimation device. For the purpose of decimation, horizontal and vertical averaging of pixels is carried out for each signal component. For picture-size reduction by the factor 1/9, 9 pixels are averaged to form a single pixel for the picture to be inserted.
As a result of the decimation by means of averaging, the sampling rate of the picture to be inserted is reduced. In order to satisfy the sampling/Nyquist theorem after decimation as well, thereby preventing interfering effects in the decimated picture, corresponding band limiting of the signal components to be decimated is necessary. For this purpose, the averaging operation does actually include low-pass filtering, but the passband thereof is indeterminately delimited such that the decimated picture nevertheless contains interfering effects.
An example of a conventional digital color decoder is described in Fernseh- und Kino-Technik, Ton Nillesen: “Digitaler TV-Farbdecoder mit Zeilenfrequenzverkopplung” [Digital TV Color Decoder With Line Frequency Locking], No. 4/1986, pages 141 to 146. In order to keep the bandwidth of the color-decoded output signals Y, U, V as large as possible, the color decoder has high-quality filters on the output side, namely a respective low-pass filter in the path of the chrominance signals, which filter out the respective mixed products at multiples of the carrier frequency, and a notch filter in the path of the luminance signal component, which filters out the color subcarrier. The entire picture-in-picture system thus has a relatively high outlay on circuitry. A fully integrated implementation of a color decoder and picture-in-picture processor on a single integrated circuit chip would be correspondingly complex.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a circuit configuration for color decoding and decimation for a video signal, which overcomes the above-mentioned disadvantages of the prior art devices and methods of this general type and which has as few functional blocks as possible and, consequently, a low outlay on circuitry.
With the foregoing and other objects in view there is provided, in accordance with the invention, a circuit configuration for color coding and decimation for a video signal having a color component, comprising:
an analog-to-digital converter receiving a video signal with a color component, the analog-to-digital converter generating a digitized video signal and having an output; a recovery device connected to the analog-to-digital converter
for recovering from the video signal a carrier coupled to a color subcarrier frequency;
a multiplier connected to the recovery device for multiplicatively combining the carrier recovered in the recovery device with a digitized video signal generated by the analog-to-digital converter, and for thereby generating a first signal component and a second signal component;
a first low-pass filter having an input connected directly to the output of the analog-to-digital converter, the first low-pass filter having a passband below the color component in a frequency spectrum of the video signal, filtering the digitized video signal, and generating a luminance signal component;
a second low-pass filter having an input connected directly to the multiplier, the second low-pass filtering the first signal component and generating therefrom a first chrominance signal component;
a third low-pass filter having an input connected directly to the multiplier, the third low-pass filter filtering the second signal component and generating therefrom a second chrominance signal component;
wherein the luminance signal component and the first and second chrominance signal components output by the first, second and third low-pass filters, respectively, have sampling rates which are reduced relative to sampling rates of their respective input signals, as defined by a degree of decimation.
In accordance with an added feature of the invention, a sampling of the video signal in the analog-to-digital converter is coupled to the color subcarrier frequency, and wherein the multiplier includes a first device enabling a sign of the digitized video signal to be altered in a manner coupled to the color subcarrier frequency, and a changeover device enabling an output signal of the first device to be passed to the second or third low-pass filter means with coupling to the color subcarrier frequency.
In accordance with an additional feature of the invention, the first device is controlled by a signal at twice the color subcarrier frequency and the changeover device is controlled by a signal at four times the color subcarrier frequency.
In accordance with another feature of the invention, the video signal contains a luminance spectral component and a chrominance spectral component modulated on a color subcarrier, and wherein the first low-pass filter has a spectral passband below the chrominance spectral components, and a spectral stop band.
In accordance with a further feature of the invention, the video signal contains a picture with a given size which is decimated by a factor N
2
, and wherein the sampling rate of an output signal of the first low-pass filter amounts to a factor 1/N
2
of a sampling rate of an input signal of the first low-pass filter.
In accordance with again an added feature of the invention, the sampling rates for the chrominance signal components amount to a factor 1/M times a sampling rate for the luminance signal component, and wherein respective passbands of the second and third low-pass filters substantially amount to a factor 1/M times the passband of the first low-pass filter means.
In accordance with again an additional feature of the invention, the first, second, and third low-pass filters each comprise horizontally acting low-pass filters.
With the above and other objects in view there is provided, in accordance with the invention, a television set which comprises the above-described circuit configuration, a screen displaying a main picture generated by a further video signal, and a second picture, decimated by the circuit configuration and inserted into the main picture.
According to the invention, the filters required for color decoding and the filters required for decimation are combined. A notch filter in the luminance path is no longer necessary sinc
Eisenzopf Reinhard J.
Greenberg Laurence A.
Infineon - Technologies AG
Lerner Herbert L.
Stemer Werner H.
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