JPH0530394A - Noise detector in video signal - Google Patents

Abstract

PURPOSE:To detect a noise component such as discharge noise superimposed on a video signal reproduced from a VTR or the like. CONSTITUTION:A reproduction output from magnetic heads H1, H2 of a rotary head device 1 is demodulated by a demodulation section 5. The demodulated video signal passes through a subcarrier elimination section 10, in which a subcarrier signal component of 3.58MHz is eliminated from the video signal. A switching circuit 11 extracts a signal of a burst period from the video signal and the output of the burst period to be extracted is a signal of a DC component with a flat waveform resulting from eliminating a burst signal of the same frequency as the subcarrier signal. When a noise component is in existence in the burst period, the noise component is a component in which an edge waveform is left in the DC component whose waveform is flat. When the resulting output passes through an integration circuit 12, a DC voltage in response to the level and number of noise components is obtained and the voltage output is compared with a comparison voltage at a comparator 13 to detect whether or not the noise component is superimposed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise detecting device for a video signal for detecting a noise component superimposed on a video signal reproduced by a VTR or a video signal demodulated by a television receiver.

[0002]

2. Description of the Related Art As a cause of noise superimposed on a video signal reproduced from a VTR, for example, external noise given to a receiving section from an antenna, a magnetic head of a rotary head device and a magnetic tape at the time of recording or reproducing. There is sliding noise. A more significant influence is discharge noise when the charged magnetic tape is discharged in the vicinity of the head of the rotary head device.

Since the above noise appears in the reproduced image, the image quality is deteriorated. In particular, the discharge noise appears prominently in the image, and removing or preventing it is important for compensating the quality of the reproduced image by the VTR.

[0004]

[Problems to be Solved by the Invention] However, the VTR
The reproduced video signal from is a composite signal that is a superposition of an FM-modulated luminance and synchronization signal and a low-frequency converted color signal. Further, since there is level fluctuation due to uneven contact between the tape surface and the head, the reproduced video signal is reproduced. It is very difficult to detect the target noise component from the video signal.

The present invention solves the above-mentioned conventional problems, and makes it possible to detect the presence of a noise component superimposed on a video signal, and to implement interpolation in the presence of the noise component or a measure for preventing noise generation. It is an object of the present invention to provide a noise detection device for a video signal that is made possible.

[0006]

A noise detecting device for a video signal according to the present invention includes a means for extracting a DC component or a low frequency component having a flat waveform from a demodulated video signal, and a means for superimposing on the extracted component. And a means for detecting a noise component that is present.

Further, according to the present invention, the means for removing the frequency of the burst signal from the demodulated video signal, the means for extracting the area in which the burst signal was recorded, and the noise superimposed on the extracted area. And a means for detecting a component.

[0008]

According to the above means, in a region where a signal of a certain frequency can be removed, for example, a region where a burst signal is recorded, this frequency signal, such as a burst signal, is removed by a filter or the like, and a DC component or a low frequency component having a flat waveform is obtained. Take out. Then, the noise component superimposed on the flat DC component or the low frequency component is detected.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit block diagram showing a reproduction path of a video signal in a VTR and a noise detecting device according to the present invention added thereto, and FIG. 2 is a diagram showing waveforms appearing in respective parts of the noise detecting device.

In FIG. 1, reference numeral 1 is a two-head rotary head device, and H1 and H2 are reproducing magnetic heads mounted on the rotary drum 1a. Each magnetic head H1 and H2
The reproduced output from each head is amplified by amplifiers 2a and 2b, and the switcher 4 switches the reproduced signals from the respective heads H1 and H2. Then, the phase is adjusted by the equalizer 3 and demodulated by the demodulator 5. The timing of the switching in the switcher 4 is set in the timing setting unit 7. This timing setting unit 7
Then, the timing is set based on the output from the PG sensor 6 provided in the rotary head device 1. That is, based on the PG signal output from the PG sensor 6 every 1 rotation or 1/2 rotation of the rotary drum 1a, the timing setting section 7 generates a timing pulse for setting a certain period, and the timing pulse causes the switcher 4 to switch. The reproduction outputs from the magnetic heads H1 and H2 are switched under control. The video signal demodulated by the demodulation unit 5 is sent to the television receiver via the filter 8 and the like.

The noise detecting device of the present invention is provided in the branch output path of the signal demodulated by the demodulating section 5, and includes a buffer amplifier 9, a subcarrier removing section 10, and a switching circuit (gate circuit) 11. , An integrating circuit 12, a comparator 13, a comparison voltage setting unit 14, and the like. In the switching circuit (gate circuit) 11, the switching operation is performed or the window is opened based on the timing set by the timing setting unit 15. In the timing setting unit 15, the P
A timing pulse is generated based on the output from the G sensor 6 or based on the timing pulse generated by the timing setting unit 7, and the switching circuit 11 is operated by the timing pulse.

Next, the operation of the noise detecting device will be described with reference to the diagram of FIG. 2 (a) to 2 (e)
The output diagram of (1) shows the output signals of the respective parts shown in (a) to (e) of FIG. When the rotary drum 1a of the rotary head device 1 rotates, the magnetic heads H1 and H2 sequentially scan the tracks of the magnetic tape to perform reproduction, and the reproduction signal is reproduced by the amplifier 2a,
Amplified by 2b, switched by the switcher 4, and phase-adjusted by the equalizer 3.

The signal switched by the switcher 4, passed through the equalizer 3, and demodulated by the demodulator 5 is shown in FIG.
As shown in. This demodulated signal is the horizontal synchronization signal 2
1, a field region 22 FM-modulated by a luminance signal and a color signal, and this field region 22
And a burst area 23 which is located before and after and in which a burst signal is provided. The burst signal serves as a reference such as the phase of the color signal, and has the same frequency of 3.58 MHz as the subcarrier (subcarrier).

In the noise detecting device, the video signal passes through the buffer amplifier 9 and the subcarrier removing section 10. The subcarrier removing unit 10 is composed of a filter and removes the burst signal of 3.58 MHz.
FIG. 2B shows a state in which the burst signal is removed by the subcarrier removing unit 10. Note that FIG. 2 shows a state in which the discharge noise 24 is superimposed on the burst area 23. The discharge noise 24 is generated by the magnetic heads H1 and H2 in the rotary head device 1 from the charged magnetic tape.
This occurs when a discharge occurs in the vicinity of. The discharge noise 24 has a steep waveform, and when the burst signal is removed by the subcarrier removing section 10, the discharge noise 24 appears in a state in which the discharge noise 24 is superimposed on the DC component of the burst region 23.

Further, a switching circuit (gate circuit) 1
In No. 1, only the burst area 23 is taken out based on the timing pulse from the timing setting unit 15. The output from the switching circuit 11 is as shown in FIG. Next, by passing through the integrating circuit 12, a voltage output according to the number or level of the discharge noises 24 superimposed on the burst region 23 is obtained, and D shown in FIG.
It becomes C output. Further, the comparator 13 compares the output voltage from the integration circuit 12 shown in FIG. 2D with the comparison voltage. The voltage set in the comparison voltage setting unit 14 is set with reference to the voltage V0 of the DC component of the burst region 23, for example. In the comparator 13, the output of FIG. 2D is compared with the comparison voltage, and as shown in FIG. 2E, a high level output is produced when the discharge noise 24 is superimposed. From the output of FIG. 2E, it is detected whether or not the discharge noise 24 is included in the video signal.

As the processing after the detection, for example, a voltage of a certain level is set by the comparison voltage setting unit 14, and if the output of FIG. It is determined that there is a discharge noise or discharge noise, and interpolation such as ground connection of the rotary head device 1 is performed.

The integrating circuit 12 is omitted and the comparator 13
Edge waveform (24) in the waveform of FIG.
May be compared with the comparison voltage, and when the edge waveform equal to or higher than the comparison voltage is generated, a pulse is output from the comparator 13 and the number of the pulses may be counted to count the number of occurrences of discharge noise. .

In the above operation, the edge waveform (24) in FIG. 2 has been described as discharge noise, but head sliding noise other than discharge noise or external noise can be detected in the same manner.

In the above embodiment, the burst signal is removed by the subcarrier removing unit 10 and then the burst area 23 is taken out by the switching circuit 11. However, the switching circuit 11 is provided next to the buffer 9 to remove the burst area 23. The sub-carrier removing unit 10 is first taken out and then taken out.
The same applies even if the burst signal is removed by.

Further, the area for detecting the noise component is not necessarily limited to the burst area 23, and a DC component or a low waveform where the waveform becomes flat, such as an area immediately before and after the vertical synchronizing signal, is obtained. Noise can be similarly detected in a region where the frequency component can be easily extracted.

Further, it is possible to detect noise not only from the VTR reproduction signal but also from the video signal after being received and demodulated by the television receiver.

[0022]

As described above, according to the present invention, it is possible to detect a noise component such as discharge noise superimposed on a video signal.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing a reproduction path of a VTR and a noise detection device,

2 (a) to (e) are diagrams showing the output waveforms of the portions (a) to (e) in FIG.

[Explanation of symbols]

1 rotating head device 1a rotating drum H1, H2 magnetic head 5 Demodulator 10 Subcarrier removal unit 11 Switching circuit 12 Integrator circuit 13 Comparator

Claims (2)

[Claims] 1. A video signal comprising: means for extracting a DC component or low-frequency component having a flat waveform from a video signal; and means for detecting a noise component superimposed on the extracted component. Noise detector in. 2. A means for removing the frequency of a burst signal from a video signal, a means for extracting an area where the burst signal was recorded, and a means for detecting a noise component superimposed on the extracted area. A noise detection device in a video signal having.