JPS6174491A - Chrominance signal processor - Google Patents

Abstract

PURPOSE:To always obtain the frequency characteristic of a required chrominance signal when any of a high frequency signal and a video signal is received by switching and using plural BPFs. CONSTITUTION:A BPF2 has a characteristic to make a color subcarrier wave high-peak and a BPF4 has a symmetrical characteristic about the subcarrier. Since the high frequency part of a color signal such as a TV signal is reduced because of the filter characteristic of an IF, the TV signal is supplied to the BPF2, but at the input of a reference NTSC signal such as a video input signal, the BPF2 is switched to the BPF4 by switches 5, 6. The switching signal is supplied from a CPU7. Consequently, a chrominance signal is always provided with ideal filter characteristic and its color reproducibility can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a color signal processing device for a television receiver having a tuner and a video detection circuit, to which video signals from a VTR, video disk, etc. can be connected at the same time. Regarding.

Conventional Structure and Problems Conventionally, band pass filters (hereinafter referred to as BPF) have been commonly used both when receiving high frequency television signals and when receiving video signals from VTRs and the like. However, when receiving a high frequency signal, it passes through a high frequency filter during movie production, so the color signal components are lower in the high range than in the low range. The situation is shown in Figure 2. Therefore, in current television receivers, the situation is shown in Figure 3.
The characteristics of the BPF were changed to an ibeaker, and the characteristics were synthesized to obtain the color signal band characteristics shown in Fig. 4.

However, for example, the frequency characteristics of the video signal output from a VTR or the like are flat in the color signal portion, as shown in FIG. As a result, when a video signal from a VTR or the like is received, there is a problem in that color transients and color tone are lost.

OBJECTS OF THE INVENTION The present invention eliminates the above-mentioned conventional drawbacks, and aims to provide a device that can always obtain desired color signal frequency characteristics regardless of whether it receives a high frequency signal or a video signal. . ``Structure of the Invention The present invention configures a BDF having the characteristics of a no-beaker when receiving a high frequency signal of 1N, and when receiving a video signal, switches to a BPF having characteristics symmetrical about the subcarrier, Even when receiving the color signal, the color signal band characteristics as shown in Figure 4 are always maintained, and the color signal is faithfully reproduced and color transients are reproduced.

It is designed to prevent deterioration of color 17 and the like.

DESCRIPTION OF ACTUAL CASE Figure 6 shows an embodiment of the invention. In the figure, 1 is an analog-to-digital converter that converts the input video signal from analog to digital, 2 is the first BPF, 3 is the digital signal processing circuit, 4 is the 20th BPF, and 5°6 is the first BPF 2 and the second BPF.
A changeover switch 7 is used to change over the BPF 4, and 7 is a calculation processing circuit (cpw).

Now, it is assumed that the first BPF 2 has a characteristic of high beaker on the color subcarrier, and the second BPF 4 has a characteristic of being symmetrical about the subcarrier. The television signal passes through the 10th BPF as mentioned above (because of the IF filter characteristics (Figure 1), the high frequency range of the color signal is lowered,
When a standard NTSC signal such as a video input signal is input, the switch 5 and 6 switch to the second BPF (symmetrical type) 4. This switching signal is generated by the CPU 7.

Effects of the Invention As described above, according to the present invention, ideal filter characteristics as shown in FIG. 4 are always obtained for color signals, and color transients,
It is possible to improve color reproduction characteristics such as color gloss.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram of the video intermediate frequency filter, Figure 2 is a frequency characteristic diagram of the video detection output, Figure 3 is an amplitude characteristic diagram after passing through the BPF when the frequency characteristic of the color signal input is flat, and 4
The figure is a frequency characteristic diagram of the color signal after passing through an ideal PF, Figure 5 is a characteristic diagram of the BPF when the input signal is flat, and Figure 6 is a block diagram of the color signal processing device in an embodiment of the present invention. It is a diagram. 1... Analog-digital converter, 2... First BPF 13... Color signal processing circuit, 4...
...Second BPF, 5.6...Switch switch,
7...CPU. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure closed between 1 and 2 Figure 2 Kite Seikin Figure 3 eyebrow wave

Claims (1)

[Claims] Analog converts decoded video signals from analog to digital
a digital converter, a first digital filter constituting a bandpass filter for extracting a color signal from an analog-to-digital converted composite video signal, and a second digital filter having different characteristics from the first digital filter. and a switching circuit for the first digital filter and the second digital filter, and configured to switch between the first digital filter and the second digital filter depending on the difference in frequency characteristics of the color signal of the input composite video signal. A color signal processing device characterized by: