JPS62264794A - Color video signal reproducing device - Google Patents

Abstract

PURPOSE:To facilitate dropout compensation even for a carrier chrominance signal by converting a reproduced carrier chrominance signal into a color difference signal whose color information is hardly affected due to phase changes. CONSTITUTION:The reproduced carrier chrominance signal is converted into the color difference signal whose color information is hardly affected by phase changes. Each signal before 1H retarded by one horizontal scanning period is outputted at changeover switches 18a, 18b by 1H delay circuits 17a, 17b while a dropout takes place and the signal having the dropout is outputted while being interpolated by the signal before 1H. The timing correction of color difference signals R-Y, B-Y is applied before the conversion into the carrier chrominance signal from the color difference signal, then the deterioration such as color shift of the generated carrier signal chrominance is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color video signal reproducing device for reproducing color video signals from a recording medium.

[Conventional technology]

Conventionally, when recording and reproducing color image signals, for example, a luminance signal Y and a color difference signal (R-Y) are generated by a matrix circuit from R, G, and B signals obtained in a reproducible camera-integrated video cheap recorder.

B-Y), the luminance signal Y is subjected to processing such as pre-emphasis, and then subjected to FM modulation. Also, the color difference signal (R-Y
, B-Y) is subjected to quadrature two-phase modulation to become a carrier color signal, and then low-band converted to become a low-band converted carrier color signal. and F
The M-modulated luminance signal and the low frequency-converted carrier color signal are frequency multiplexed to become a recording signal, which is recorded on the tape by a rotating head.

On the other hand, during reproduction, the reproduced signal is separated into an FM-modulated luminance signal and a low-pass converted carrier color signal using a low-pass filter and a band-pass filter, and the FM-modulated luminance signal is demodulated to the original luminance signal. The low-pass converted carrier color signal is frequency-converted to become the original carrier color signal, and these luminance signals and carrier color signals are multiplexed and output as a reproduced video signal.

[Problem that the invention seeks to solve]

By the way, conventionally when correcting color information during playback,
The color information must be corrected in the form of a carrier color signal. However, since the carrier color signal also includes hue information in its phase, it is difficult to perform correction while maintaining the continuity of the phase change. There is a problem in that it is not possible to compensate for omissions or to remove noise using a feedback type noise removal circuit, which inevitably causes deterioration of color information such as color unevenness during reproduction.

The present invention has been made in view of the above-mentioned problems, and is capable of correcting a reproduced color video signal with a simple configuration without deterioration of color information due to a phase change of a carrier color signal. The purpose is to provide equipment.

[Means to solve the problem]

The color video signal reproducing apparatus of the present invention includes a reproducing means for reproducing a color video signal from a recording medium, a separating means for separating a luminance signal and a carrier color signal from the color video signal reproduced by the reproducing means, and the separating means. The present invention is equipped with a conversion means for converting a carrier color signal generated by a carrier color signal into a plurality of types of baseband signals, and a correction means for correcting a mutual time difference between the plurality of types of baseband signals.

[Effect]

With the above configuration, by converting the carrier color signal into multiple types of baseband signals, it is possible to create a signal in which the color information does not change due to phase change, and furthermore, the correction means can take correspondence between each baseband signal. I can do it.

〔Example〕

The present invention will be explained below using examples.

FIG. 1 shows a VT to which the present invention is applied as an embodiment of the present invention.
3 is a diagram showing a schematic configuration of a dropout compensation circuit of R. FIG.

In Fig. 1, la and lb are magnetic heads, 2 is a head selection switch, 3 is a regenerative amplifier, and 4 is a bypass filter (H
P F ), 5 is an FM demodulation circuit, 6 is a luminance signal processing circuit, 25 is a luminance signal delay circuit, 7 is a mixer that multiplexes the luminance signal and carrier color signal, and 8 is a carrier color signal that has been low-frequency converted. a low-pass filter (LPF) for separating the signals; 9 is a frequency conversion circuit for converting the low-pass converted carrier color signal separated by the LPF 8 into a normal carrier color signal; 1;
0 is a band pass filter (BPF) 11. 12 is an automatic phase control circuit (APC) 11 for the signal output from a voltage controlled oscillator (VCO) 13, and an automatic frequency control circuit (AF).
C) 12.

Further, 14 is a reference signal generator, 15 is a mixer, and 16 is a B
17a and 17b are delay circuits that delay the horizontal scanning period (LH) signal; 18a and 18b are changeover switches; 19
20 is a timing correction circuit that corrects the color difference signals R-Y and B-Y through the changeover switches 18a and 18b so that they correspond to each other; and 20 is the timing correction circuit 1.
9 is a carrier color signal modulation circuit that converts the corrected color difference signal into a carrier color signal, and 21 is a dropout cancellation circuit (DOC) that detects a dropout of the FM-modulated luminance signal separated in the HPF 4. Interpolation processing is performed on the luminance signal using a one-horizontal scanning period delay line (not shown), and a switching pulse is output to the changeover switches 18a, 18b and the timing correction circuit 19.

In FIG. 1, a reproduced composite video signal reproduced from a magnetic tape (not shown) by magnetic heads la and lb is supplied to a changeover switch 2. In FIG. The magnetic head
Reference characters a and lb are rotating heads, and the changeover switch 2 connects the magnetic heads la and lb using changeover switch pulses (for example, 60 Hz in the case of an NTSC television signal) generated in accordance with the rotation period of the magnetic heads la and lb. The signals reproduced by the magnetic heads la and Ib alternately switched between the A side and the B side are alternately supplied to the reproducing amplifier 3, where they are amplified and then sent to the HPF 4. LPF8° is supplied to AFC12.

Then, the HPF 4 separates the luminance signal distributed on the high frequency side of the reproduced composite video signal and supplies it to the DOC 21. If a dropout is detected in the luminance signal in the DOC 21, well-known compensation processing is performed to interpolate the dropout in the luminance signal, and if no dropout is detected, the dropout is directly demodulated by the FM demodulation circuit 5, and the luminance signal is processed. After the circuit 6 performs general signal processing on the luminance signal during reproduction, the signal is delayed for a predetermined time by the delay circuit 25 and then supplied to the mixer 7 . On the other hand, LPF
Frequency conversion circuit 9 separates the low frequency conversion carrier color signal placed on the low frequency side of the reproduced composite video signal by 8.
is converted into a normal carrier color signal by The operation of the frequency conversion circuit 9 during conversion will be described below. During conversion, the VCO 13 is controlled by the AFC 12 to generate a low-pass conversion color subcarrier signal (fs±Δf) that includes a frequency shift (±Δf) due to time axis fluctuation during reproduction, and is further controlled by the reference signal generator 14 by APCII. The phase shift between the reference signal fc generated by the frequency converter 9 and the signal after frequency conversion by the frequency converter 9 is detected, and the VCO
13, the phase of the low-pass conversion color subcarrier signal fs±Δf output from the VCO 13 is determined by controlling the reproduction low-pass conversion carrier color signal (fs±Δf) manually input to the frequency conversion circuit 9.
) is controlled so as to cancel out the phase fluctuations.

After this, it is mixed with the reference signal fc in the mixer 15,
The signal becomes fc+fs±Δ, and the frequency conversion circuit 9
In this case, the frequency conversion circuit 9 outputs a carrier color signal from which the difference from the reproduced low-pass converted carrier color signal (fs±Δr), that is, the frequency fluctuation during reproduction has been removed. The chroma signal "C" output from the frequency conversion circuit 9 is supplied to the color difference signal demodulation circuit 16 after passing through the BPFIO.

Note that the reference signal f generated by the reference signal generator 14
c is a color subcarrier signal (for example, 3.58 MHz in the case of NTSC television signal compatibility).

The carrier color signal is converted into a color difference signal (R-Y, B-Y signal) in a color difference signal demodulation circuit 16 to which a reference signal fc is supplied from a reference signal generator 14, and then sent to IH delay circuits 17a, 17b and Changeover switch 18a.

18b, respectively.

The changeover switches 18a and 18b are normally connected to the L side in the figure, and supply the color difference signal demodulated in the color difference signal demodulation circuit 16 to the timing correction circuit 19.

The timing correction circuit 19 receives the input R-Y signal,
This is to correct the mutual temporal correspondence error of the B-y signals.

The timing correction circuit 19 is composed of, for example, a fixed delay line and a variable delay line, and the fixed delay line delays the color difference signal so that it can correspond to the luminance signal delayed by the delay circuit 25 in the mixer 7. Also,
The variable delay line usually has the same delay time as the fixed delay line, and the color difference signals R-Y and B-Y passed through the changeover switches 18a and 18b are delayed by the timing correction circuit 19 as described above. Thereafter, a carrier color signal is generated using the supplied color difference signal in a carrier color signal modulation circuit 20, and the generated carrier color signal is multiplexed with a luminance signal in a mixer 9 and outputted as an output component video signal.

In addition, when a dropout occurs, the reproduced luminance signal separated from the reproduced composite video signal by the HPF 4 is monitored at the DOC 21 for the envelope of the signal, detects the occurrence of a sudden level change, and detects the occurrence of a sudden level change. Assume that a dropout has occurred, and at the same time the well-known dropout compensation of the luminance signal is performed, the sudden change in the envelope returns to normal.
A high level switching pulse is output to each changeover switch 18a, 18b and the timing correction circuit 19, and the changeover switch 18a, 18b switches the switch connection to the H side in the figure while the high level changeover pulse is being input. . As a result of this operation, during the period when dropout occurs, the output from each selector switch 18a, 18b is a pre-IH signal delayed by one horizontal scanning period by IH delay circuits 17a, 17b, and dropout occurs. The signal that is generated is interpolated with the signal before IH and output.

However, the above-described dropout compensation processing is performed using signals delayed by the 2@IH delay circuits 17a and 17b. Now, each IH delay circuit 1
7a and 17b do not necessarily have the same delay time, and if the delay times of the respective lH delay circuits 17a and 17b are different, the color difference signals R-Y and B-Y of the portions subjected to the dropout compensation process will have different delay times. Since a time lag occurs, the carrier color signal modulation circuit 2 uses this signal as is.
The carrier color signal generated by 0 may suffer deterioration such as color shift, and in the carrier color signal modulation circuit 20,
The color difference signal R-Y before conversion from the color difference signal to a carrier color signal.

By performing B-Y timing correction, it is possible to suppress deterioration such as color shift of the conveyed color signal that occurs.

Now, if the delay time of the IH delay circuit 17b is longer than that of the IH delay circuit 17a, the RY signal delayed by the IH delay circuit 17a is delayed by a fixed delay line in the timing correction circuit 19 for a predetermined time, Further, the BY signal delayed by the lH delay circuit 17b is delayed by a variable delay line. Note that the delay time at dropout of the variable delay line is the IH delay line 17a.

IH delay circuit 17a so that R-Y and B-Y input to 17b are simultaneously output from timing correction circuit 19.

The variable delay line is controlled in such a way that the delay time is switched by a switching pulse generated by the DOC 21, and as mentioned above, it is usually the same as the fixed delay line. However, when a dropout occurs, the delay time of the variable delay line is switched to the delay time at the time of dropout, and the IH delay circuit 17a,
By correcting the difference in delay time of 17b, the color difference signal R
After the timing deviation between -Y and B-Y is corrected, the signal is supplied to the carrier color signal modulation circuit 20.

Then, the carrier color signal modulation circuit 20 generates a carrier color signal using the supplied color difference signal, and the generated carrier color signal is multiplexed with the luminance signal in the mixer 9 and output as an output composite signal.

As explained above, dropout compensation can be easily achieved for the carrier color signal by converting the reproduced carrier color signal into a color difference signal whose color information is less affected by phase changes. By correcting the timing of the delayed signal, the deterioration of the color information due to the use of the color information can be suppressed by correcting the timing of the delayed signal, and the color information can be faithfully reproduced even in the event of dropout.

Further, in this embodiment, the dropout cancellation circuit detects the occurrence of dropout only in the reproduced luminance signal, and performs dropout compensation processing on the luminance signal accordingly, and the lH delay circuits 17a, 17
Color difference signal R-Y via b.

Dropout compensation is performed using B-Y. By doing this, the reproduced luminance signal, R-Y signal, B
It is possible to solve the problem that occurs when a dropout detection circuit is provided for each of the -Y signals. In other words, if a dropout detection circuit is provided for each of the reproduced luminance signal, R-Y signal, and B-Y signal, and each delay circuit is switched and controlled independently, all dropout detection circuits will be activated when a dropout occurs. Dropouts are not always detected, and a signal with and without dropout correction occurs at the same time, and these signals have a large phase shift and are not matched, so the output composite at the time of restoration This is because the video signal deteriorates.

Note that if a dropout detection circuit is provided for each signal, even if a dropout is detected in any one of the dropout detection circuits, a control pulse is sent that causes all dropout detection circuits to perform dropout correction processing. The above problem can be solved by allowing this to occur.

Further, in this embodiment, dropout compensation is performed using an IH delay circuit, etc., assuming that the signal from one horizontal scanning period ago has the highest correlation with the current signal, but the present invention is not limited to this. 1 field or! The image quality after dropout compensation can be further improved by using a frame period delay circuit or by controlling the delay amount of the delay circuit in accordance with the correlation of the image signals handled.

Further, in this embodiment, dropout compensation is performed by demodulating the carrier color signal into a color difference signal, but this is not limited to this. For example, after demodulating into other baseband signals such as R, G, and B signals, Needless to say, it would be good to provide dropout compensation.

Further, although the present embodiment has been explained using a VTR, the present invention is not limited to this, and the present invention can also be applied to a playback device such as a video disc device.

〔Effect of the invention〕

As described above, the present invention provides a color video signal reproducing device capable of correcting a reproduced color video signal with a simple configuration without deterioration of color information due to a phase change of a carrier color signal. I can do it.

[Brief explanation of drawings]

FIG. 1 shows a VT to which the present invention is applied as an embodiment of the present invention.
3 is a diagram showing a schematic configuration of a dropout compensation circuit of R. FIG. 16...Color difference signal demodulation circuit,

Claims (1)

[Claims] a reproduction means for reproducing a color video signal from a recording medium;
separation means for separating a luminance signal and a carrier color signal from the color video signal reproduced by the reproduction means; a conversion means for converting the carrier color signal generated by the separation means into a plurality of types of baseband signals; 1. A color video signal reproducing device comprising: a correction means for correcting mutual time differences between a plurality of types of baseband signals.