JPH047994A - Y/c separator circuit - Google Patents

Abstract

PURPOSE:To reduce beats at the boundary of colors by narrowing the frequency band of a chroma signal before demodulation when inputting a standard signal, and enlarging the frequency band of the chroma signal before demodulation when inputting a non-standard signal. CONSTITUTION:A control signal is sent to a switch circuit 109 so as to show whether the input signal is the standard signal or the non-standard signal by detecting phase relation between a synchronizing signal and a subcarrier by a control circuit 110. According to the control signal, the switch circuit 109 switches the frequency band of the chroma signal corresponding to the quality of the signal to be inputted such as the two-step cascade connection of band pass filters 105 and 106 in the case of the standard signal input or the one-step connection of the band pass filter 106 in the case of the non-standard signal input. Thus, the beats at the boundary of colors can be decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to separation of a luminance signal (Y) and a carrier color signal (C) in a magnetic recording and reproducing device that records and reproduces video signals using a recording medium such as a magnetic tape. It is related to circuits.

2. Description of the Related Art In general, the configuration of a magnetic recording/reproducing apparatus is as shown in FIG. 2, for example.

In FIG. 2, 201 is a composite color video signal (hereinafter referred to as composite signal) input, 202 is a Y/C separation circuit, 203 is a time axis compression circuit, 204° and 205 are FM modulation circuits, and 206 and 207 are recording amplifier circuits. , 208, 209
, 212, 213 are magnetic heads, 210, 211 are magnetic tapes, 214° 216 is an FM equalizer circuit, 216
, 217 is an FM demodulation circuit, 218 and 219 are time axis correction circuits, 220u encoder, 221 is a composite signal output, and 221 is a component system.

Next, the conventional configuration of the Y/C separation circuit 2 shown in FIG. 1 will be explained using FIG. 3. In Fig. 3, 301 is a composite signal input, 302゜303 is a 1H (H is horizontal period) delay circuit, 304 is a vertical correlator, 305.306
307 is a bandpass filter that passes signals near the subcarrier frequency; 307 is a demodulation circuit that converts the chroma signal into a PB signal 30ya and a PR signal 307b, which are color difference signals defined by SMPTE; and 30B is a subtracter.

The signal 302 that has passed through the 1H delay circuit 302 & the signal 306a that has passed through the horizontal band pass filter 306 are subtracted at 308 to obtain a luminance signal 308+L. At this time, in a place where the color border equalization color signal band is wide, the luminance signal 30
A subcarrier remains on 8a (carrier leak).

The luminance signal 3081 separated here! L%PB signal 30
7&, the PR signal 307b is sent to the encoder 22 shown in FIG.
When converting to a composite signal at 0, if the subcarrier in the encoder and the carrier on the luminance signal are in phase with the phase during demodulation, the composite signal can be reproduced without deterioration. , if they are not in phase, they will deteriorate. Therefore, when the composite signal input is a standard composite signal (a composite signal in which the phase relationship between the synchronization signal and the subcarrier is maintained every 1H, hereinafter referred to as the standard signal), the Y/C separation circuit 202 demodulates the signal. The subcarrier information of the previous chroma signal is transferred to the luminance signal 30B.
It is superimposed on &.

An example of the frequency characteristics of the chroma signal 306 & before demodulation in FIG. 3 is shown in FIG. 4 401.

PB signal 307 & or PR signal 30 after demodulation in FIG.
An example of the frequency characteristic of 'γb is shown in FIG. 5 601.

An example of frequency characteristics of a component system is shown in FIG. 5 502.

In FIG. 2, the time axis correction circuits 218 and 219 configure a PLL using a composite synchronization signal of the recorded and reproduced luminance signal 216a with jitter, and write to the memory using the write clock generated thereby. By using a readout clock that does not have jitter, sick correction is performed in the reproduced video signal.

Problems to be Solved by the Invention However, in the conventional configuration, the composite signal input to the magnetic recording/reproducing device is a non-standard composite signal, that is, a composite signal in which the phase relationship between the synchronization signal and the subcarrier is not maintained (hereinafter referred to as non-standard composite signal). 308 signal), there is jitter between the luminance signal component and the color signal component of the input signal, so the luminance signal 308&
Interference occurs between the subcarriers remaining above and the subcarriers in the encoder, resulting in beats at the color boundaries.

This beat can be achieved at the same time by expanding the frequency band of the chroma signal before demodulation as shown in FIG.
3, the demodulated PB signal 5072L or PR
It is also possible to improve this by expanding the frequency band of the signal 507b and reducing carrier leakage. However, in that case, since the portion shown at 504 in FIG. 5 is not transmitted, the image quality deteriorates when the standard signal is input.

Means for Solving the Problems As mentioned above, expanding the frequency band of the chroma signal before demodulation causes deterioration in image quality when a standard signal is input. However, when a non-standard signal is input, when it is converted into a composite signal, the phase relationship between the luminance signal and the modulated subcarrier is not in phase, resulting in deterioration in image quality.

Focusing on this point, the Y/C separation circuit of the present invention switches the frequency band of the chroma signal before demodulation using a control signal indicating whether the two input signals are standard signals or non-standard signals.

Operation The Y/C separation circuit of the present invention can suppress image quality deterioration by narrowing the frequency band of the chroma signal before demodulation when a standard signal is input, and can suppress image quality deterioration by narrowing the frequency band of the chroma signal before demodulation when inputting a non-standard signal. By widening the frequency band, it is possible to reduce beats at color boundaries.

Embodiment Hereinafter, one embodiment of the Y/C separation circuit of the present invention will be described with reference to the drawings. In FIG. 1, 1o1 is a composite signal input, 102 and 103 are 1H (H is horizontal period) delay circuits, 104 is a vertical correlator, 105 and 106 are bandpass filters that pass signals near the subcarrier frequency, and 107 is a The chroma signal is the FB signal 107a, which is a color difference signal specified by SMPTIC, and the PR signal 1.
07b demodulation path, 108 is a subtracter, 109
110 is a switch circuit for switching the band pan filter, and 110 is a control circuit for switching the switch.

With this configuration, the control circuit 110 sends a control signal indicating whether the input is a standard signal or a non-standard signal to the switch circuit 109 by detecting the phase relationship between the synchronization signal and the subcarrier. In the switch circuit 109, when the standard signal is input, the control signal is used to connect the 2-stage cascade connection of the 105 band PANU filter and the 106 band PANU filter, and when the non-standard signal is input, the 106 band bus filter + 7 is connected. )1
As described in step 1, the frequency band of the chroma signal is switched depending on the quality of the input signal.

Effects of the Invention As described above, the Y/C separation circuit of the present invention switches the frequency band of the chroma signal according to the quality of the input signal, so when the standard signal is input, the chroma signal before demodulation is By narrowing the frequency band of the chroma signal, image quality deterioration can be suppressed, and when non-standard signals are input, by widening the frequency band of the chroma signal before demodulation, it is possible to reduce beats at color boundaries. d) is extremely advantageous in practice.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the Y/C separation circuit of the present invention, Fig. 2 is a block diagram showing the configuration of a single-vehicle magnetic recording/reproducing device, and Fig. 3 is a conventional Y10 separation circuit. Fig. 4 is a frequency characteristic diagram showing an example of the frequency characteristics of the chroma signal before demodulation, and Fig. 6 is a diagram showing the frequency characteristics of the chroma signal after demodulation.
FIG. 3 is a frequency characteristic diagram showing an example of frequency characteristics of a B-time signal or a PR signal. 104... Vertical correlator, 10δ, 1o6...
BPF, 107... Demodulation circuit, 110...
control circuit. Name of agent: Patent attorney Shigetaka Awano and 1 other person 1st
Figure N Figure 3 +, 152 L'4 Figure 4 Figure 5

Claims (1)

[Claims] Supplying the composite color video signal to a bandpass filter,
A Y/Y signal configured to separate a chroma signal from the composite color video signal and obtain a luminance signal by subtracting the separated chroma signal from the composite color video signal.
1. A Y/C separation circuit, which is characterized in that the frequency band of at least a bandpass filter is switched according to the quality of an input signal.