JPH02128592A - Circuit for removing noise of vtr - Google Patents

Abstract

PURPOSE:To prevent the deterioration of the waveform characteristics and a decline in the resolution of luminance signals by detecting whether or not the phase relation between horizontal synchronizing signals and subcarriers is in a prescribed relation and, when a non-standard signal is discriminated, performing noise removing operations on a recording side. CONSTITUTION:Luminance signals Y are supplied to both of a delay circuit 2 and a high-pass filter 3 through a terminal 1 and a separated residual subcarrier component CS is supplied to a limiter 4 where the subcarrier component is limited to a fixed level and passed through an amplifier 5 and attenuator 6 where the component is adjusted in level. After level adjustment, the subcarrier component is supplied to one terminal of a switch 7. The switch 7 is controlled by a switch controlling signal SW supplied from a system controller 9 based on the output signal of dn SCH phase discrimination circuit 8 which detects the phase relation between horizontal synchronizing signals and the subcarriers whether or not the relation is in a prescribed relation and turns on/off noise removing operations. Therefore, when a non-standard composite signal is discriminated, the noise removing operations are performed and flickers are eliminated at the reproducing time. Thus the deterioration of the picture quality of pictures can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a VTR noise removal circuit, and particularly to a VTR noise removal circuit suitable for being provided on the recording side of a VTR.

[Summary of the invention]

This invention provides Y/C in a VTR noise removal circuit.
Separate the residual subcarrier component from the separated Y signal,
A circuit system that adjusts the level, a detection means that detects whether the phase of the horizontal synchronization signal and the phase of the subcarrier are in a predetermined relationship, and noise removal operation using the output signal of the circuit system based on the output of the detection means. By having means for controlling the on/off of the The subcarrier component can be removed, thereby eliminating flicker and preventing image quality deterioration during playback.

[Conventional technology]

Conventionally, a noise removal circuit such as that disclosed in Japanese Patent Laid-Open No. 60-66363, for example, has been used in a VTR that records and reproduces a composite signal by separating Y/C signals. A noise removal circuit is often used on the reproduction side of a VTR to remove residual subcarrier components contained in the Y signal when the Y/C separation is incomplete during boat fishing.

VT that separates Y/C composite signals and records/plays them
In R, if the Y/C separation is incomplete, residual subcarrier components in the Y signal may interfere with the subcarriers of the chroma signal, causing deterioration in the quality of the reproduced image.

Even if a residual subcarrier component is superimposed on the Y signal due to incomplete Y/C separation, each of the composite signals recorded and reproduced will contain the residual subcarrier component of the Y signal and the subcarrier of the chroma signal. If it is a so-called standard composite signal in which the phase is locked,
Since the phases of the two interfering waves are locked, the deterioration in image quality does not appear as a flicker and is not visually a problem.

On the other hand, in special playback (slow or double speed playback), the residual subcarrier component of the Y signal and the subcarrier of the chroma signal interfere on the playback side, causing flicker. However, by passing the Y signal through a noise filter, the residual subcarrier component The carrier component can be removed, and therefore flicker can be eliminated.

[Problem to be solved by the invention]

By the way, when residual subcarrier components are superimposed on the Y signal due to incomplete Y/C separation, the phases of the residual subcarrier components of the Y signal and the subcarriers of the chroma signal are not locked, so-called. When a non-standard composite signal is recorded, there is a problem in that flicker occurs not only during special playback but also during standard playback.

Therefore, it may be possible to always pass the Y signal through a noise filter for removing residual subcarrier components on the playback side, but in this case, even during standard playback of a standard composite signal, the waveform There was a problem that the characteristics deteriorated and the resolution of the Y signal decreased.

Therefore, on the playback side, it is possible to determine whether the recorded signal is a standard composite signal or a non-standard composite signal, and take appropriate measures in each case. This is possible, but there was a problem in that it was difficult for the player to distinguish between standard and non-standard.

In order to improve the problem of image quality deterioration, it has been desired to record the Y signal by removing the residual subcarrier component in the Y signal in advance only when a non-standard composite signal is detected on the recording side.

Therefore, an object of the present invention is to enable the recording side of a VTR to determine whether or not it is a non-standard composite signal.
In the case of non-standard composite signals, VT can remove residual subcarrier components from the Y signal before recording.
An object of the present invention is to provide an R noise removal circuit.

[Means to solve the problem]

The present invention includes a circuit system that separates residual subcarrier components from a Y/C separated Y signal and adjusts the level, and a circuit system that determines whether the phase of a horizontal synchronization signal and the subcarrier are in a predetermined relationship. The configuration includes a detection means for detecting the detection, and a means for controlling on/off of the noise removal operation based on the output signal of the circuit system based on the output of the detection means.

[Effect]

On the recording side of the VTR, it is determined whether the phase of the horizontal synchronizing signal and the phase of the subcarrier have a predetermined relationship, that is, whether it is a standard composite signal or a non-standard composite signal. . Y
/C Only the residual subcarrier component is separated from the separated Y signal and the level is adjusted.

If it is determined to be a non-standard composite signal, a circuit system is connected and a noise removal operation is performed using the output signal of the circuit system, after which it is recorded. Therefore, even if the residual subcarrier component is superimposed on the Y signal due to incomplete Y/C separation and is a non-standard composite signal, it can be recorded with the residual subcarrier component in the Y signal removed. As a result, flicker can be eliminated during playback, and image quality deterioration can be prevented. Furthermore, since it is not necessary to pass the Y signal through a noise filter all the time, it is possible to prevent the resolution of the Y signal from decreasing and the waveform characteristics from deteriorating.

On the other hand, if it is determined to be a standard composite signal, it is recorded without connecting the circuit system and without performing any noise removal operation. Even when the noise removal operation is not performed, in the case of a standard composite signal, deterioration of waveform characteristics is prevented, and image quality deterioration that would cause problems during reproduction does not occur.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. Note that this VTR noise removal circuit is provided on the recording side of the VTR.

In FIG. 1, a Y/C separated luminance signal Y is supplied via a terminal 1 to a delay circuit 2 and a bypass filter 3, respectively.

Since the luminance signal Y mentioned above has incomplete Y/C separation,
As shown in FIG. 3A, the residual subcarrier component C8 is superimposed on the luminance signal component cy. This residual subcarrier component C3 is separated from the luminance signal Y by the bypass filter 3. Note that instead of the bypass filter 3, it is also possible to use a bandpass filter.

As shown in FIG. 3B, the separated residual subcarrier component C3 is supplied to the limiter 4.

If there is a residual subcarrier component C3 at a large level, the limiter 4 limits it to a partial level shown by the - dotted chain line in FIG. 3C. The residual subcarrier component C8 is
From the limiter 4, the signal further passes through an amplifier 5 and an attenuator 6, resulting in a level-adjusted residual subcarrier component C3 as shown in the third diagram. The residual subcarrier component C8 is supplied to one terminal of the switch 7. This switch 7 is operated based on the output signal from the SCH phase discrimination circuit 8.
System controller 9 [hereinafter abbreviated as system controller]
It is controlled by a switch control signal SW supplied from.

The configuration of the above-mentioned SCH phase discrimination circuit 8 is shown in FIG.

A horizontal synchronizing signal SH separated from the composite signal is supplied to a sawtooth wave generating circuit 12 via a terminal 11.

In response to this horizontal synchronizing signal SH, the sawtooth wave generating circuit 1
2 a sawtooth wave is formed and fed to the comparator 13. This sawtooth wave is compared with a reference voltage Vrl set by VR14 of the comparator 13. For example, when the voltage of the sawtooth wave exceeds a predetermined level, comparator 1
3 outputs a high level signal S1, and this signal Sl
is supplied to the phase comparison circuit 15.

On the other hand, the burst signal SB is supplied to one terminal of the exclusive OR gate 17 (hereinafter referred to as EX-OR gate) via the terminal 16, and the normal invert signal SNI whose level is inverted every IH is supplied to the terminal 18 to the other terminal of the EX-OR gate 17.

This EX-OR gate 17 allows each line to be compared at the same edge.
A signal S2 outputted from 7 is supplied to a phase comparator circuit 15.

The signal S1 supplied from the above-mentioned comparator 13 and 0
The signal S2 supplied from the X-OR gate 17 is phase-compared in the phase comparator circuit 15, and an error voltage Ver is formed according to the phase difference. This error voltage Ver is supplied to a sample and hold circuit 19 and a window comparator 20, respectively.

The error voltage Ver is the VR of the window comparator 20.
It is compared with reference voltages Vr2 and Vr3 set at 21. This window comparator 20 has an error voltage Ve
r is constantly monitored, and the error voltage Ver is equal to the reference voltage Vr.
2. When within the range of Vr3, for example, a high level control signal is output to the sample hold circuit 19. This control signal operates the sample-and-hold circuit 19 at a high level, and disables the sample-and-hold circuit 19 at a low level, for example.

When the error voltage Ver is within the range of the reference voltages Vr2 and Vr3, the error voltage Ver is held in the sample and hold circuit 19, and its voltage level is supplied to the integrating circuit 22. Note that 23 is VR of the integrating circuit 22. The output signal 5sch from the integrating circuit 22, ie, an analog signal having SCH phase information, is digitized by the A/D converter 25 via the terminal 24 and supplied to the system controller 9. Based on the output signal S sch from the integrating circuit 22, the system controller 9 determines whether it is a standard composite signal or a non-standard composite signal. As a result, the switch control signal SW is output from the system controller 9, and the switch 7 is controlled to be on/off.

If it is determined that it is a non-standard composite signal based on the output signal 5sch from the SCH phase discrimination circuit 8, the system controller 9 supplies, for example, a high level switch control signal S- to the switch 7, and the switch 7 is connected. It is turned on. The level-adjusted residual subcarrier component C8 described above is supplied to the subtraction circuit 26 via the switch 7.

In this example, the system controller 9 makes a judgment based on the output signal S sch from the SCH phase discrimination circuit 8 and outputs the switch control signal SW, but the present invention is not limited to this, and for example, The switch 7 may be directly controlled based on the output signal S sch from the SCH phase discrimination circuit 8.

On the other hand, the luminance signal Y supplied to terminal 1 has a delay amount ll1
At 12, bypass filter 3, limiter 4, amplifier 5
, and supplied to the subtraction circuit 26 with a delay equal to the sum of the delay amounts of the attenuator 6.

The residual subcarrier component C8 is subtracted from the luminance signal Y by a subtraction circuit 26. As a result, the residual subcarrier component C5 superimposed on the luminance signal component CY is canceled as shown in FIG. 3A, and a luminance signal jY (luminance signal component CY) as shown in FIG. 3A is obtained. , this luminance signal Y
is taken out from the terminal 27.

As a result, even if the residual subcarrier component C8 is superimposed on the luminance signal component CY and the supplied composite signal is non-standard, the recording side can easily and reliably determine that it is a non-standard composite signal. It is recorded with the residual subcarrier component C3 removed.

Therefore, during reproduction, interference between the residual subcarrier component C3 in the luminance signal Y and the subcarrier of the chroma signal is prevented, so flickering is not caused (and deterioration in the quality of the reproduced image is also prevented. Since it is not necessary to constantly pass the luminance signal Y through a noise filter on the reproduction side as in the conventional case, deterioration of the waveform characteristics of the luminance signal Y and reduction in resolution are prevented.

By the way, the output signal 5sc from the SCH phase discrimination circuit 8
If it is determined that the signal is a standard composite signal based on h, the system controller 9 supplies, for example, a low level switch control signal Sa, and the bypass filter 3
, the circuit system such as the limiter 4 and the subtraction circuit 26 are disconnected (off).

In this state, the luminance signal Y supplied to terminal 1 is taken out as it is from terminal 27 with a predetermined delay amount without being subjected to subtraction processing, thereby preventing deterioration of waveform characteristics and image quality. . In this case, the recorded composite signal and the reproduced composite signal are both standard composite signals, so the phases of the two interfering waves are locked, and the image quality deterioration does not appear as flicker, and is visually Above, it's not a problem.

In this embodiment, instead of the conventionally used trap, a noise removal circuit removes the residual subcarrier component C.
3 is removed, the band of the luminance signal Y is not restricted, and the waveform characteristics are not degraded (and the resolution of the luminance signal Y is not reduced. Since the residual subcarrier component C8 is removed by a noise removal circuit instead of the horizontal correlator,
The edge portion of the residual subcarrier component C8 can be removed, and the circuit scale does not increase.

〔Effect of the invention〕

According to this invention, the residual subcarrier component is separated from the Y/C separated Y signal and the level is adjusted;
It detects whether the phase of the horizontal synchronization signal and the subcarrier have a predetermined relationship, and if it is determined that the signal is non-standard, the circuit system is connected and the output signal of the circuit system is detected. Because the noise removal operation is performed on the recording side, the recording side can determine whether or not it is a non-standard composite signal, which has the effect of making the detection of non-standard composite signals more reliable and easier. . Due to the above-mentioned effect, even if the residual subcarrier component is superimposed on the Y signal and the signal is a non-standard composite signal, the signal can be recorded with the residual subcarrier component removed. In addition, since the signal is recorded with the residual subcarrier component in the Y signal removed, even if a non-standard composite signal is recorded, during playback [standard playback 1
．． [Either special playback] has the effect of eliminating flicker and preventing image quality deterioration.

Due to the above-mentioned effect, on the playback side, Y
Since it is not necessary to pass the signal through a noise filter all the time, it is possible to prevent the waveform characteristics of the Y signal from deteriorating and the resolution from decreasing.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing the SCH phase discrimination circuit shown in FIG. 1, and FIG. 3 is a waveform diagram illustrating the noise removal process. . Explanation of main symbols in the drawings 3: Bypass filter, 4: Limiter, 5: Amplifier, 6
: Attenuator, 7: Switch, 8: SCH phase discrimination circuit, 9 systems controller, Y, II double signal C8: Residual subcarrier component, SH horizontal synchronization signal. Agent Patent Attorney Masatoshi Sugiura

Claims (1)

[Claims] A circuit system that separates a residual subcarrier component from a Y/C separated Y signal and adjusts the level, and whether or not the phase of a horizontal synchronizing signal and the subcarrier have a predetermined relationship. 1. A noise removal circuit for a VTR, comprising: detection means for detecting whether the detection means is active, and means for controlling on/off of a noise removal operation based on an output signal of the circuit system based on the output of the detection means.