JPH0470184A - Reproduction device for color video signal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a color video signal reproducing device for reproducing a color video signal consisting of a frequency multiplexed signal of an FM modulated luminance signal and a chromaticity signal on the lower frequency side thereof. Regarding.

[Summary of the invention]

The present invention provides a color video signal reproducing device for reproducing a color video signal consisting of a frequency multiplexed signal of an FM modulated luminance signal and a chromaticity signal on the lower frequency side thereof, in which the level of the reproduced chromaticity signal is higher than a reference level. is detected, the characteristics of the color field noise reducer are controlled according to the level of the reproduced luminance signal obtained by FM demodulating the reproduced FM modulated luminance signal. /N and color reproducibility can both be improved.

[Conventional technology]

In conventional VTRs, when recording, the luminance signal is FM modulated and the carrier color signal is low frequency converted so that it is on the lower frequency side of the FM modulated luminance signal, and the FM modulated luminance signal and the low frequency converted signal are A color video signal consisting of a frequency multiplexed signal of a carrier color signal is recorded on a magnetic tape so as to form an inclined track.

In conventional VTRs, during playback, the FM modulated luminance signal is supplied to the FM demodulation circuit for fftm, and the low frequency converted carrier color signal is converted to a high frequency to convert the carrier color signal at the original frequency. The carrier color signal is then supplied to a color field noise resonator to remove (reduce) noise.
I was trying to do that.

Such a color field noise reducer obtains a difference signal between a current carrier color signal and a carrier color signal from one field period ago, supplies the difference signal to a limiter, and determines whether the level of the input difference signal is inside a positive or negative reference level. , the input difference signal is output as the output difference signal, and when the level of the input difference signal is outside the positive and negative reference levels, the output difference signal is set to zero, and the output of the limiter is set to noise. , and is subtracted from the current carrier color signal or the carrier color signal one field period ago.

According to such a conventional VTR, high S.
A reproduced carrier color signal of /H can be obtained.

[Problem to be solved by the invention]

However, 1. Since the frequency of the FM modulated luminance signal changes in accordance with the level change of the luminance signal, the bias effect on the carrier color signal also changes. That is, the higher the frequency of the FM modulated luminance signal, the higher the bias effect becomes, and the lower the frequency, the lower the bias.

Therefore, if the reproduced carrier color signal is supplied to the color field noise reducer and the noise is removed (reduced) regularly, when the frequency of the FM modulated luminance signal during recording is high,
Especially when the high frequency period is long to some extent, the S/N of the reproduced carrier color signal becomes high. Therefore, when the reproduced carrier color signal is supplied to a color field noise reducer to remove noise, the effective component of the reproduced carrier color signal There is a possibility that even the particles may be removed and color reproducibility may deteriorate. Also, when the frequency of the FM modulated luminance signal during recording is low, especially when the low frequency period is long to some extent, the S/N of the reproduced carrier color signal is low, so the reproduced carrier color signal is used in the color field noise reducer. When the signal is supplied and noise removed, the S/N of the reproduced carrier color signal may not improve as much.

In view of the above, the present invention provides a method for reproducing a color video signal consisting of a frequency multiplexed signal of an FM modulated luminance signal and a chromaticity signal on the lower frequency side thereof, by adjusting the S/N and the S/N of the reproduced chromaticity signal. The purpose is to propose something that can improve color reproducibility at the same time.

[Means to solve the problem]

The present invention provides color field noise resonance + (13) and a first level detection circuit (
17, 18), an FM demodulation circuit (3) to which the reproduced FM modulated luminance signal is supplied, and a second level detection circuit (9, 18) that detects the level of the reproduced luminance signal from the FM demodulation circuit (3). 10), and a first level detection circuit (17,
18) detects that the level of the reproduced chromaticity signal is higher than the reference level, the second detection circuit (9,
10), the characteristics of the color field noise reducer (13) are controlled.

[Effect]

According to the present invention, the first bell detection circuit (17
, 18) detects that the level of the reproduced chromaticity signal is higher than the reference level, the second detection circuit (9
, 10), the characteristics of the color field noise reducer (13) are controlled.

〔Example〕

The present invention will be described in detail below with reference to FIG.

This embodiment shows a helical scan type VTR playback system that is compatible with the present invention. On a magnetic tape (not shown), a color video signal consisting of a frequency multiplexed signal of an FM modulated luminance signal and a low frequency converted carrier color signal on the lower frequency side thereof is stored.
A color video signal recorded on this magnetic tape is recorded so that an inclined track is formed for each field, and is reproduced by a rotating magnetic head (1 (11 or a pair of rotating magnetic heads) H. This reproduction The resulting color video signal is supplied to a bypass filter (2) and a low-pass filter (5) through a regenerative amplifier (1), and is separated into an FM-modulated luminance signal and a low-pass-converted carrier chrominance signal, respectively.

The FM modulated luminance signal from the bypass filter (2) is
The signal is supplied to a luminance signal processing circuit, where it undergoes amplitude suppression by limiter and receiver, FM demodulation by an FM demodulator, de-emphasis by an 8-de-enhancement circuit, etc., and is outputted to an output terminal (4) as a luminance signal.

The luminance signal from this luminance signal processing circuit (3) is supplied to a pedestal clamp circuit (6) and subjected to pedestal clamping. White side clip and sync signal removal circuit (7
), and is clipped at 50% of the white level to avoid malfunctions due to high brightness peak waveforms or overlevels of the brightness signal, and is clipped at 50% of the white level. Accordingly, the horizontal and vertical synchronization signals are removed.

The brightness signal from the white side clip and synchronization signal removal circuit (7) is passed through the on/off switch (8) to the integrator circuit (9).
), and after being integrated over a predetermined field period of 10 fields, the signal is supplied to a level discrimination circuit (10) including a hysteresis circuit to avoid malfunctions due to unnecessary noise, and its level is discriminated. The characteristics of the color field noise reducer (13) are controlled by the determined output having hysteresis characteristics.

On the other hand, the low-pass converted carrier color signal (including the burst signal) from the low-pass filter (5) is supplied to the ACC circuit (11). The output of the ACC circuit (11) is supplied to the carrier color signal processing circuit (12), where processing such as high frequency conversion (inverse conversion) is performed, and the output of the carrier color signal (including burst signals) is output from this circuit. is supplied to color field noise reduce+ (13).

The output of the color field noise reducer (13) is
It is supplied to the output terminal (14). Regarding the specific configuration example of the color field noise reducer (13),
This will be described later with reference to FIGS. 2 and 3.

The carrier color signal from the carrier color signal processing circuit (12) is passed through a burst signal extraction circuit (15) and an envelope detection circuit (
17). The burst signal output from the burst signal extraction circuit (15) is supplied to the burst signal level detection circuit (16), and its level is detected.
The detection output is integrated over a predetermined number of field periods, and the integrated output is supplied as a gain am signal to the ACC circuit (11) so that the burst signal level is constant.
The gain of the CC circuit (16) is controlled.

The detection output from the envelope detection circuit (17) is supplied to a level discrimination circuit (18) for level discrimination, and the discrimination output is supplied to the on/off switch (8) as a switch control signal. And on/off switch (8)
is turned on when the level of the carrier color signal is above a sufficiently high predetermined level, and when it is below the predetermined level,
turned off.

Next, a specific example of the color field noise reducer (13) shown in FIG. 1 will be described with reference to FIG. 2.

The carrier color signal (including the burst signal) from the carrier color signal processing circuit (12) is supplied to the A/D converter (21) through the input terminal (20) and converted into a parallel 8-pino digital signal. be done. The digital carrier color signal from the A/D converter (21) is fed directly to the subtractor (23) and also to the field memory (22) where it is delayed by l field period and then sent to the subtracter (23). ), the latter is subtracted from the former, and the parallel 9-bit subtraction output is used as an address signal to R O which constitutes the limiter.
M (24).

As shown in FIG. 4, the ROM (24) as a limiter changes the level of the input signal when the level of the input signal supplied to the ROM (24) as an address signal is inside the positive and negative reference levels. The relationship between the level of the input signal and the level of the output signal is linear, and when the level of the input signal is outside the positive and negative standards L/-. is 0
And, from the level discrimination circuit (10) to the input terminal (
7 in response to a control signal as an address signal supplied to the ROM (24) through 24a).
An 8-bit digital output signal is stored in which the output signal is made variable.

In this case, the lower the luminance signal level, the more positive and negative base IL
・-・The absolute value of L becomes larger, that is, the noise reduction effect of Color Field 2 Noise Reducer (8) increases, and the brightness (the higher the l/□＼ of No. 3, the positive and negative base t$L
・When the level of the luminance signal changes or at every predetermined period, the positive and negative reference levels are It is made to vary discretely.

In this case, when switch (8) in Figure 1 is off,
A curved line is selected as the input/output characteristic of the ROM (24) as a limiter, and when the switch (8) is on and the level of the luminance signal is above a predetermined level, the noise removal effect is smaller than that of the curved line. When curve a is selected and the level of the luminance signal is less than the predetermined level, curve C, which has a greater noise removal effect than curve A, is selected.

Incidentally, the number of input/output characteristic curves of the ROM (24) serving as a limiter may be increased to more than three so that switching can be performed in more stages.

The parallel 8-bit digital output signal from the ROM (24) is then considered as a noise signal and is supplied to the subtracter (25) together with the digital carrier color signal from the two-field memory (22) to convert the latter from the former. is subtracted. The parallel 9-bit subtraction output from the subtracter (9) is
The signal is supplied to the compressor (26), bit-compressed into a parallel 8-bit digital carrier color signal (including a digital burst signal), and supplied to the D/A converter (27), where it is converted into an analog signal. , the converted carrier color signal (including the burst signal) is passed through the output terminal (28) to the first
It is supplied to the output terminal (14) in the figure.

Next, another specific example of the color field noise resolution user (13) in FIG. 1 will be explained with reference to FIG. 3. In FIG. 3, parts corresponding to those in FIG. Some redundant explanations will be omitted.

The parallel 8-bit digital carrier color signal from the A/D converter (21) is fed directly to subtractors (29) and (30). The parallel 9-bit subtraction output from the subtracter (29) is
After being supplied to the bit compressor (26) and bit-compressed into a parallel 8-bit digital signal, it is sent to the field memory (26).
22) and is delayed by one field period. The output of the field memory (22) is fed to a D/A converter (27) and also to a subtracter (30) to convert the digital carrier color signal (digital burst) from the A/D converter (21). The parallel 9-bit subtraction output is subtracted from the ROM (including the signal) as a limiter.
24).

The parallel 8-bit digital output signal from the ROM (24) is regarded as a noise signal and is sent to the subtracter (29).
) and subtracted from the digital carrier color signal (including the digital burst signal) from the A/D converter (21).

According to the color video signal reproducing apparatus described above, in reproducing a color video signal consisting of a frequency multiplexed signal of an FM modulated luminance signal and a low-frequency-converted carrier chrominance signal on the lower frequency side thereof, the reproduced carrier is When it is detected that the color signal level is higher than the reference level, the characteristics of the color field noise reducer are controlled according to the level of the reproduced luminance signal obtained by FM demodulating the reproduced FM modulated luminance signal. Therefore, both the S,/N and color reproducibility of the reproduced chromaticity signal can be improved.

[Effects of the Invention] According to the present invention as described above, in a color video signal reproducing device that reproduces a color video signal consisting of a frequency multiplexed signal of an FM modulated luminance signal and a chromaticity signal on the lower frequency side thereof, the reproduced color When it is detected that the level of the brightness signal is higher than the reference level, the characteristics of the color field noise reducer are controlled according to the level of the reproduced brightness signal obtained by FM demodulating the reproduced wave FM Henoka brightness signal. This makes it possible to improve both the S/N and color reproducibility of the reproduced chromaticity signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIGS. 2 and 3 are block diagrams showing specific examples of a color field noise reducer, and FIG. 4 is a curve diagram showing the characteristics of a limiter. . (3) is a luminance signal processing circuit (including an FM demodulator), (6
) is a clamp circuit, (7) is a white side clip and synchronization signal removal circuit, (8) is an on/off switch, 9) is an integration circuit, (10) is a level discrimination circuit, (II) is an ACC circuit, (12) is carrier color signal processing circuit (including high frequency converter)
, (1, 3) is a color field noise reducer,
(17) is an enrobe detection circuit, and (18) is a level discrimination circuit.

Claims (1)

[Scope of Claims] A color video signal reproducing device that reproduces a color video signal consisting of a frequency multiplexed signal of an FM modulated luminance signal and a chromaticity signal on the lower frequency side thereof, comprising: a color field to which the reproduced chromaticity signal is supplied; a noise reducer, a first level detection circuit that detects the level of the reproduced chromaticity signal, an FM demodulation circuit to which the reproduced FM modulated luminance signal is supplied, and detects the level of the reproduced luminance signal from the FM demodulation circuit. and a second level detection circuit that detects a detection output from the second detection circuit when the first level detection circuit detects that the level of the reproduced chromaticity signal is higher than the reference level. A reproduction device for a color video signal, characterized in that the characteristics of the color field noise reducer are controlled based on the following.