JPH03158092A - Video signal processor unit - Google Patents

Abstract

PURPOSE:To attain color demodulation normally by using a selector in response to a burst switching signal generated from a deflection processing circuit so as to select a digital video signal outputted from an A/D converter for a burst period and selecting a chroma signal outputted from a frame comb-line filter for a period other than the burst period. CONSTITUTION:A selector 4 which selects a digital video signal outputted from an A/D converter 1 with a burst switching signal generated from a deflection processing circuit 3 and a C signal outputted from a frame comb-line filter 2 is provided. Thus, a digital video signal of the A/D converter 1 not causing a delay in the frame is selected from the burst signal portion and a PLL is formed in a path for the burst signal and the clock signal. Thus, the input composite video signal is sampled by a clock signal phase-locked with a burst signal of the same frame as the input video signal and the time constant of the PLL for clock generation for sampling the composite video signal is decreased. Thus, the color demodulation is implemented normally.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video signal processing device for a digital television receiver.

C. Prior Art] In recent years, digital television receivers have become commercially available, and the image quality has continued to improve, and frame comb filters that use frame memory to separate the luminance signal and chroma signal of the NTSC signal, that is, Y/C separation, have also become available. It has been put into practical use. The video signal processing device that is the basis of this is also being developed frequently.

An example of a conventional video signal processing device will be described below with reference to the drawings.

FIG. 3 is a block diagram of a conventional video signal processing device.
In FIG. 3, 1 is an A/D converter that converts an analog composite video signal into a digital video signal. 2 is a frame comb filter that uses a frame memory and performs Y/C separation; 3 is a deflection processing circuit that detects a synchronization signal from a composite video signal and performs signal processing for deflection; 5 is a chroma trap This is a circuit for completely removing the C (chroma) signal component in the Y (luminance) signal which is the output of the frame comb filter 2. 6 is a chroma band pass filter 2 that extracts only chroma signal components. 7 is a color decoder that demodulates the color (No. 8); 8 is a phase comparator that detects the phase difference between the burst signal and the clock signal; 9 is a clock generator that A clock signal whose output phase is controlled is generated based on the output. This clock signal is used, for example, as a sampling clock of the A/D converter 1. 10 is a crystal resonator.

The operation of the video signal processing device configured as described above will be described below.

First, the input composite video signal is converted from an analog signal to a digital signal by an A/D converter, and is input to a frame comb filter 2 and a deflection processing circuit 3, respectively.

Next, the deflection processing circuit 3 detects horizontal and vertical synchronizing signals from the input signal, and generates a horizontal deflection signal I and a vertical deflection signal V synchronized therewith.

In addition, in the frame comb filter 2, Y/C using a frame memory takes advantage of the fact that there is a correlation between frames in a still image of a television signal.
Separation is performed to output a Y (luminance) signal and a C (chroma) signal, respectively.

Next, in the chroma trap 5, the residual C signal component that could not be completely separated by the Y/C separation in the frame comb filter 2 is dropped and outputted as Y (No. 8).
'becomes a signal. Further, the C signal of the frame comb filter 2 is filtered in a chroma band pass filter 6 to remove components other than the C signal component, and then color demodulated in a color decoder 7 to produce an R-Y signal and a B-Y signal which are color difference signals. are output as, respectively. At the same time, the RY signal and the BY signal are each input to a phase comparator 8 and used to detect the phase difference between the burst signal and the clock signal.

Next, a clock signal for sampling is generated in a clock generator 9 using the phase difference detected by the phase comparator 8 and the crystal resonator 10.

[Problem to be solved by the invention]

However, in the above configuration, the clock signal is generated based on the phase difference between the burst signal color-demodulated from the C signal output from the frame comb filter 2 and the clock signal, and phase synchronization is applied. In contrast, the input composite video signal is sampled with a clock signal that is phase-locked to the burst signal one frame before, and the time constant of the clock generation PLL for sampling the composite video signal increases, resulting in normal color reproduction. The problem was that it could not be demodulated.

An object of the present invention is to provide a video signal processing device in which the time constant of a clock generation PLL is small and color demodulation can be performed normally even when a frame comb filter is used.

[Means to solve the problem]

The video signal processing device of the present invention selects the output signal of the A/D converter during the burst signal period using the burst switching signal generated from the deflection processing circuit, and selects the output chroma of the frame comb filter during the period other than the burst signal period. It is characterized by providing a selector for selecting a signal.

[Operation] According to the configuration of the present invention, the burst signal portion of the chroma signal output from the frame comb filter is converted into a signal before being input to the frame comb filter, that is, a digital video signal output from the A/D converter. will be switched to. As a result, the input composite video signal is
It is possible to perform A/D conversion by sampling with a clock signal phase-locked to the burst signal of the same frame. Therefore, the time constant of the clock generation PLL for sampling the composite video signal can be reduced, and color demodulation can be performed normally.

〔Example〕

Hereinafter, a video signal processing device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a video signal processing apparatus according to an embodiment of the present invention, and FIG. 2 is a waveform diagram of FIG. 1.

In Fig. 1, l is an A/D converter, 2 is a frame comb filter using frame memory, 5 is a chroma trap, 6 is a chroma band pass filter, 7 is a color decoder, 8 is a phase comparator, and 9 is a clock. The generator 10 is a crystal oscillator, and the above structure is similar to that shown in FIG.

What is different from the configuration shown in FIG. 3 is that the deflection processing circuit 3 generates a burst switching signal that is at L level during the burst signal period and at H level during the rest of the period, and the A/D converter 1 The difference is that a selector 4 is provided for switching between the output digital video signal and the C signal output from the frame comb filter 2 in response to a burst switching signal generated by the deflection processing circuit 3.

The operation of the video signal processing apparatus configured as described above will be described below with reference to FIGS. 1 and 2.

First, the input composite video signal is converted from an analog signal to a digital signal by an A/D converter, and is input to a frame comb filter 2 and a deflection processing circuit 3.

Next, in the deflection processing circuit 3, from the composite video signal converted into a digital video signal,
The horizontal and vertical 31Jl signals are detected, and a horizontal deflection signal H and a vertical deflection signal V synchronized therewith are generated, and the image display device is controlled by the horizontal deflection signal H and the vertical deflection signal (2). In addition, in the frame comb filter 2, by utilizing the fact that there is a correlation between frames when the composite video signal is close to a still image, Y/C separation is performed using a frame memory, and Y (luminance) A signal and a C (chroma) signal are output respectively.

Accordingly, in No. 718, in the chroma trap 5, the residual C signal component that could not be completely separated by Y/(d[ in the frame comb filter 2) is dropped and output,
This becomes the Y' signal. Further, the frame comb filter 2
C signal (Fig. 2 141)! ! , in selector 4,
Composite video signal after 1 frame (Fig. 2(b)
) and the burst switching signal (
FIG. 2(C))
become that way. In other words, only the burst portion is a signal one frame later.

Next, the output of the selector 4 is passed through a chroma band pass filter 6, in which components other than the C signal component are removed, and the output is sent to a color decoder 7.
Color demodulation is performed at , and output as RY signal and BY signal, which are color difference signals. Further, the RY signal and the BY signal are simultaneously input to the phase comparator 8 and used to detect the phase difference between the burst signal and the clock signal.

Next, using the phase difference detected by the phase comparator 8 and the crystal oscillator 1O, a clock signal whose phase is locked to the burst signal in the color difference signal is generated in the clock generator 9. This clock signal is then supplied to the A/D converter 1 as a sampling clock.

As described above, according to this embodiment, the burst switching signal (FIG. 2(C)) generated from the deflection processing circuit 3 causes the digital video signal output from the A/D converter 1 and the frame comb filter 2 to By providing a selector 4 for switching between the burst signal and the C signal output from the A/D converter 1, the digital video signal of the A/D converter 1 with no frame delay is selected for the burst signal portion, and the difference between the burst signal and the clock signal is selected. A PLL will be configured. As a result, the input composite video signal is sampled with a clock signal that is phase-locked to the burst signal of the same frame, and the time constant of the clock generation PLL for sampling the composite video signal becomes smaller, resulting in normal color reproduction. Demodulation can be performed.

〔Effect of the invention〕

According to the video signal processing device of the present invention, the selector responsive to the burst switching signal generated from the deflection processing circuit selects the digital video signal output from the A/D converter during the burst period, and selects the digital video signal output from the A/D converter during the burst period, and selects the chroma signal output from the frame comb filter, so even if the frame comb filter is used, the input composite video signal will still be sampled with a clock signal phase-locked to the burst signal of the same frame. Therefore, the time constant of the clock generation PLL for sampling the composite video signal is small (this makes it possible to perform color demodulation normally).

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a video signal processing device according to an embodiment of the present invention, FIG. 2 is a waveform diagram of each part of FIG. 1, and FIG. 3 is a block diagram of a conventional video signal processing device. l...A/D! IJR12...Frame comb filter, 3...Deflection processing circuit, 4...Selector, 5...
...Chroma) U7p, 6...Chroma band pass filter, 7...Color decoder, 8...Phase comparator, 9
...Clock generator, lO...Crystal oscillator

Claims (1)

[Claims] an A/D converter that converts a composite video signal into a digital video signal; a frame comb filter that separates and extracts a luminance signal and a chroma signal from the digital video signal output from the A/D converter; The burst signal period is determined by a deflection processing circuit that receives the digital video signal output from the converter and outputs a horizontal deflection signal and a vertical deflection signal as well as outputs a burst switching signal, and a burst switching signal output from this deflection processing circuit. a selector that selects a digital video signal output from the A/D converter and selects a chroma signal output from the frame comb filter during periods other than the burst period; and a chroma signal is extracted from the output signal of this selector. A chroma bandpass filter, a color decoder that demodulates a color signal from the output signal of the chroma bandpass filter, a phase comparator that detects the phase difference between a clock signal and a burst signal using the output signal of this color decoder, and this phase comparator. a clock generator that generates the clock signal whose output phase is controlled based on the output of the clock generator and supplies the clock signal as a sampling clock to the A/D converter.