JPH0193285A - Noise elimination circuit for video signal - Google Patents

Abstract

PURPOSE:To attain excellent noise reduction and to avoid precedence of voice by supplying an output of a mixture means directly to a phase inversion means in the normal reproduction mode and supplying the output of the phase inversion means directly to a mixture means as other input in the special reproduction mode. CONSTITUTION:In the case of the normal reproduction mode, an output of a chroma inverter circuit 5 is outputted from a changeover switch 8, an output of a mixing circuit 1 is outputted from a changeover switch 9 and an output of a 1 frame delay circuit 4 is outputted from a changeover switch 10 selectively and the output of the mixing circuit 1 is directly fed to the chroma inverter circuit 5 not through the 1 frame delay circuit 4, no voice precedence takes place. In the case of the special reproduction mode, the output of the mixing circuit 1 is outputted from the switch 8, the output of the 1 frame delay circuit 4 is outputted from the switch 9 and the output of the chroma inverter circuit 5 is outputted from the switch 10 selectively and the output of the chroma inverter circuit 5 is fed directly to a color frame comparator circuit 7 not via the 1 frame delay circuit 4 and the color frame comparison with the input video signal is applied, then noise rejection is implemented excellently.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a noise removal circuit for video signals, and more particularly to a noise removal circuit for a recorded information reproducing apparatus such as a video disc player.

A circuit as shown in FIG. 4, which is used in broadcasting equipment as a noise removal circuit for a video signal, is well known. In the same figure, the digitized video signal is input to the input terminal IN+.
is supplied to the mixing circuit 1 via. In the mixing circuit 1, the video signal is multiplied by the power R2!52 and then supplied to the adder 3.

The output of the adder 3 is supplied to the output terminal OUT+, and after being delayed by 17 frame periods by the 1-frame delay circuit 4, it is supplied to the chroma inverter circuit 5. The chroma inverter circuit 5 is configured to, for example, separate a video signal into a luminance signal and a chrominance signal, and then invert the phase of the chrominance signal and add to the luminance signal to generate a video signal with the chrominance signal phase inverted. ing. The output of this chroma inverter circuit 5 is multiplied by (1-K) by the q multiplier 6 in the mixing circuit 1, and then supplied to the pruner 3 and then the p multiplier 2.
is added to the output of

The above configuration is equivalent to the configuration of a circuit called a cyclic filter, and a video signal from which random noise has been removed is supplied to the output terminal OUT+. Note that since the video signal from which random noise has been removed is also output from the 1-frame delay circuit 4 and the chroma inverter circuit 5, the outputs of the 1-frame delay circuit 4 and the chroma inverter circuit 5 are supplied to the output terminal 01J T +. You may.

When the conventional noise removal circuit as described above is used in a recorded information reproducing apparatus such as a video disc player, the following problems occur. That is, in a video disc player, for example, the information reading point of the pickup is skipped in the radial direction by one track every time the disc rotates once, and the video signal of the same frame is repeatedly played back. In some cases, reproduction is performed, and when an l-rack interlacing movement II operation (hereinafter referred to as a jump operation) in such special reproduction is performed, color frames become discontinuous. This is because the color frame of the NTSC video signal is inverted every frame. As a result, the phases of the color signals in the video signals output from the projectors 2 and 6 and supplied to the adder 3 are opposite to each other, and the output terminal OUT+ receives a video signal with the amplitude of the color signal attenuated. This is not preferable because it will output the following. Therefore, it is possible to prevent the attenuation of the color signal amplitude by adding a color frame discrimination circuit to the circuit shown in FIG. 4 and turning on and off the operation of the chroma inverter 5. On/off control is difficult.

Therefore, a noise removal circuit as shown in FIG. 5 can be considered, which can match the phases of the color signals of the two video signals supplied to the addition Eii 33 even if the color frames of the input video signal are discontinuous. In the figure, mixing circuit 1.
The one-frame delay circuit 4 and the chroma inverter circuit 5 are connected in the same way as the circuit shown in FIG. However, in this example, the input video signal and the chroma inverter circuit 5
The video signal output from the color frame comparison circuit 7
is supplied to. The color frame comparison circuit 7 is configured to compare, for example, the phases of the colorverse 1-signals of the two supplied video signals and generate a color frame coincidence detection signal when the phases of both signals match. The color frame coincidence detection signal output from the color frame comparison circuit 7 is supplied to the chroma inverter circuit 5. The chroma inverter circuit 5 is configured not to invert the phase of the color signal when the color frame coincidence detection signal is present.

In the above circuit, the phase of the color subcarrier V of the video signal output from the chroma inverter circuit 5 and supplied to the mixing circuit 1 is the color subcarrier V of the input video signal supplied to the mixing circuit 1 via the input terminal IN+. Since it matches the phase of the carrier, in the adder 3 in the mixing circuit 1,
The phase of the color signal does not become reversed, and noise can be effectively removed from the video signal. However, by separately outputting the luminance signal and chrominance signal separated from the video signal in the chroma inverter circuit 5 and sending them to a video reproducing device such as a television receiver, deterioration of image quality can be prevented and the recorded information reproducing device To simplify the configuration, the luminance signal and chrominance signal output from the chroma inverter circuit 5 are delayed by about one frame period (1/30 second) with respect to the video signal supplied to the input terminal. , the signal is delayed by about one frame period with respect to the audio signal read from the disk together with the video signal.

The permissible time difference between video and audio depends on the content of the video, but in the case of an announcer-up, the permissible limit is reached when the audio precedes by one frame, according to the Journal of the Society of Television Engineers. Vo I, 36.
No. 9, page 776. Additionally, optical video disc players have been devised that use field or frame memory to perform special playback of CLV (constant linear velocity) discs, and in such players, video signals are supplied to a noise removal circuit. If the audio passes through an image memory such as a field memory beforehand, the lead of the audio will be 1.5 frames to 2 frames, which will be unbearable.

In order to prevent audio antecedents without deteriorating the sound quality, it is possible to digitize the audio signal and use memory to delay the audio signal, but in that case,
This makes the circuit configuration complicated, which is not desirable.

21/11 Therefore, an object of the present invention is to provide a luminance signal and a color signal that have a simple configuration, avoid the preceding phenomenon of audio, and have an improved S/N ratio even when the color frames of input video and other signals are discontinuous. An object of the present invention is to provide a video signal noise removal circuit that can obtain the following.

The video signal noise removal circuit according to the present invention delays the output of a mixing means that is supplied with a video signal read from a recording medium as one input and that mixes this one input with another input at a predetermined mixing ratio. The connection between the signal delay means and the phase inverting means for inverting the phase of the color signal being output from the mixing means based on the phase difference between the color signals in one input and the other input of the mixing means is changed according to the reproduction mode. The output of the mixing means which has passed through the signal delay means and the phase inverting means is inputted to the output of the mixing means, so that a luminance signal and a color signal from which noise has been removed are obtained from the phase inverting means.

Large-'L-± Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 3.

In FIG. 1, a mixing circuit 1, a color frame comparison circuit 7, and a chroma inverter circuit 5 are connected in the same way as the circuit shown in FIG. However, in this example, the output of the mixing circuit 1 is supplied to one input terminal of the changeover switches 8 and 9.

The output of the chroma inverter circuit 5 is supplied to the other input terminal of the changeover switch 8. A control input terminal of the changeover switch 8 is connected to a control circuit (not shown) to select either a normal playback mode in which recorded information is sequentially played back in the recorded order, or a special playback mode in which recorded information is played back in an order different from the recorded order. A mode control signal indicating the mode is supplied via the input terminal IN2.

The changeover switch 8 is configured to selectively output the output of the chroma inverter circuit 5 in the normal reproduction mode, and to selectively output the output of the mixing circuit 1 in the special reproduction mode. The output of the changeover switch 8 is delayed by the one-frame delay circuit 4 and then supplied to the other input terminals of the changeover switches 9 and 10. Changeover switch 9
Similarly to the changeover switch 8, the control input terminals 10 and 10 are supplied with a υItll signal indicating whether the mode is normal playback mode or special playback mode from a control circuit (not shown). The changeover switch 9 is configured to selectively output the output of the mixing circuit 1 in the normal reproduction mode, and to selectively output the output of the one-frame extension circuit 4 in the special reproduction mode. There is. The output of this changeover switch 9 is supplied to the chroma inverter circuit 5. Also,
The changeover switch 10 is configured to selectively output the output of the one-frame delay circuit 4 in the normal reproduction mode, and selectively output the output of the chroma inverter circuit 5 in the special reproduction mode. The output of this changeover switch 10 is supplied to the color frame comparison circuit 7 and the multiplier 6 in the mixing circuit 1.

Furthermore, the luminance signal and color signal generated in the chroma inverter circuit 5 are output to output terminals 0LJT2 and 0LJT2, respectively.
Supplied to UT3.

In the above configuration, in the normal playback mode, the output of the chroma inverter circuit 5 is selectively outputted from the changeover switch 8, the output of the mixing circuit 1 is selectively outputted from the changeover switch 9, and the output of the mixing circuit 1 is selectively outputted from the changeover switch 10, and the output of the mixing circuit 1 is selectively outputted from the changeover switch 9. The output of the one frame delay circuit 4 is selectively output. Therefore, since the output of the mixing circuit 1 is directly supplied to the chroma inverter circuit 5 without passing through the 1-frame delay circuit 4, the audio preceding phenomenon does not occur. In addition, the chroma inverter circuit 5
The output is delayed by one frame period and then supplied to the color frame delay circuit 7, but since no jump operation is performed in normal playback mode, the color frames of the input video signal are discontinuous. Therefore, the phase inversion operation of the chroma inverter circuit 5 is always performed, and noise removal from the video signal is performed satisfactorily.

In addition, in the special playback mode, the output of the mixing circuit 1 is selectively output from the changeover switch 8, the output of the 1 frame delay circuit 4 is selectively outputted from the changeover switch 9, and the output from the changeover switch 10 is selectively outputted. The output of the I-main inverter circuit 5 is selectively output. Therefore, the output of the chroma inverter circuit 5 is directly supplied to the color frame comparison circuit 7 via the changeover switch 10 without passing through the one-frame delay circuit 4, and color frame comparison with the input video signal is performed. Therefore, the phases of the color signals in the two video signals mixed by the mixing circuit 1 are reliably prevented from becoming opposite to each other, and noise removal from the video signals can be performed satisfactorily. Furthermore, in the special playback mode, the audio signal is discontinuous and is therefore not output from the recorded information playback device. Therefore, no voice precedent phenomenon occurs. Therefore, the 1 frame delay circuit 4
By supplying the video signal delayed by one frame period to the chroma inverter circuit 5 via the changeover switch 9,
The luminance signal and chrominance signal output from this chroma inverter circuit 5 have a period of one frame compared to the input video signalG)
There is no problem even if there is a delay.

FIG. 2 is a diagram showing a specific circuit example of the chroma inverter circuit 5. In the figure, the video signal is transmitted to the one-day delay circuit 1.
1 and is delayed by one day (one horizontal scanning period), and simultaneously supplied to the multiplier 12 and multiplied by 71/4.

11 (The output of the delay circuit 11 is supplied to the 1-day delay circuit 13 and delayed by 1H, and at the same time is supplied to the multiplier 14 and multiplied by 1/2. The output of the 1-day delay circuit 13 is 15 and multiplied by 11/4.
The outputs of the units 12, 14 and 15 are added and combined by an adder 16. The shore line output of the adder 16 is BPF (
The signal is outputted as a color signal through a bandpass filter (bandpass filter) 17 and simultaneously supplied to a multiplier 18 and a subtracter 19.

In multiplier 18, the color signal is doubled. This ride!
The output of triplex 18 is supplied to switch 20 . The output of the color frame comparison circuit 7 is supplied to the control input terminal of the switch, and the switch 20 is configured to perform on/off control based on the output of the color frame comparison circuit 7. The output of this switch 20 is the subtracter 21
is supplied to The output of the one-day delay circuit 11 is supplied to the subtracter 21, and in this subtracter 21, the output of the switch 20 is subtracted from the output of the one-day delay circuit 11, and the phase of the color signal is determined by the color frame comparison circuit 7. An inverted video signal is generated according to the output of the . Also, the subtractor 19
, the output of the BPF 17 is subtracted from the output of the 1Hff extension circuit 11 to generate a luminance signal.

In the chroma inverter circuit as described above, the signal delay time is 1H, so the signal delay time of the 1-frame delay circuit 4 is 524H (=5
25H-1H).

Furthermore, in the circuit shown in FIG. 1, the color frame of the input video signal is forcibly matched with the color frame of the cyclic video signal to prevent the color signal component from attenuating within the cyclic loop. Therefore, the color signal output from the chroma inverter circuit 5 matches the color frame of the input video signal, and if the color frame of the input video signal becomes discontinuous due to the jump operation,
It is necessary to correct the phase of the color signal output from the chroma inverter circuit 5. Therefore, the chroma inverter circuit 5
FIG. 3 shows a noise removal circuit according to the present invention, which is equipped with a circuit for correcting the phase of a color signal output from a color signal.

In FIG. 3, a mixing circuit 1.1 frame delay circuit 4,
chroma inverter circuit 5, color frame comparison circuit 7,
The changeover switches 8.9.10 are connected in the same way as in the circuit of FIG. However, in this example, the color signal output from the chroma inverter circuit 5 is
5, the phase inversion circuit 26 and the color frame comparison circuit 27. The color frame comparison circuit 27 includes a reference color frame pulse generation circuit 28.
A reference color frame pulse outputted from the reference color frame pulse is supplied. The reference color frame pulse generation circuit 28 is configured to output, as a reference color frame pulse, a pulse having the same phase as, for example, a color burst signal in the NTSC system. The color frame comparison circuit 27 compares the phase of the color subcarrier of the color signal outputted from the chroma inverter circuit 5 with the reference color frame pulse, and outputs a switching command signal according to the phase difference between the two signals. It is configured. The output of this color frame comparison circuit 27 serves as a control input for the changeover switch 25. The changeover switch 25 is configured to selectively output one of the input and output of the phase inversion circuit 26 in response to a switching command. The changeover switch 25 outputs a color signal in which phase disturbances caused by discontinuity of color frames have been corrected.

Although the case where the noise removal circuit is used in a video disc player has been described above, the present invention can also be applied to the case where it is used in other recorded information reproducing devices such as a video tape recorder.

Also, although the delay circuit 4 has been described as a frame memory,
Needless to say, it may also be used as field memory.

As described in detail above, the video signal noise removal circuit according to the present invention is supplied with a video signal read from a recording medium as one input, and mixes this one input with another input at a predetermined mixing ratio. connection between a signal delay means for delaying the output of the mixing means and a phase inversion means for inverting the phase of the color signal output from the mixing means based on the phase difference between the color signals in one input and each input of the mixing means; The output of the mixing means, which has passed through the signal delay means and the phase inverting means, is changed according to the playback mode of the recorded information playback device, and the output of the mixing means is used as the external power of the mixing means, and the luminance signal and color from which noise has been removed are obtained from the phase inverting means. Since the configuration is such that the signal is obtained, in the normal playback mode in which color frame discontinuity does not occur, the output of the mixing means is directly supplied to the phase inverting means, and from this phase inverting means, the signal is As a result, luminance signals and chrominance signal audio without time delay can be obtained, and it is possible to prevent audio preceding phenomena. In addition, in a special reproduction mode in which there is no need to reproduce audio, the output of the phase inverting means is directly supplied to the mixing means as an external signal, and the phase of the color signal of one input of the mixing means and the external input is inverted. This means that noise can be effectively removed. Therefore, the noise removal circuit according to the present invention can avoid the preceding sound phenomenon and obtain luminance and color signals with improved S/N ratios even when the color frames of the input video signal are discontinuous.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a circuit block diagram showing a specific circuit example of the chroma inverter circuit 5 in the circuit of FIG. 1, and FIG. FIGS. 4 and 5 are block diagrams showing conventional noise removal circuits. Explanation of symbols of main parts 1...Mixing circuit 4...1 frame delay circuit 5...Chroma inverter circuit 7...Color frame comparison circuit 9.10 ...
...Switch switch applicant Pioneer Corporation

Claims (1)

[Claims] A video signal noise removal circuit in a recorded information reproducing device having a normal mode in which recorded information on a recording medium is sequentially reproduced in the recording order and a special mode in which recorded information in the recording medium is reproduced in an order different from the recording order, the circuit comprising: Mixing means to which a video signal read from the recording medium is supplied as one input and mixes this one input and another input at a predetermined mixing ratio;
phase inverting means for inverting the phase of the color signal being output from the mixing means based on the phase difference between the color signals in one input and the other input of the mixing means; and a signal delaying means for delaying the output of the mixing means by a predetermined time. means, in said special mode, the output of said mixing means is supplied to said phase inverting means after passing through said signal delaying means, and in said normal mode, the output of said mixing means is supplied to said phase inverting means after passing through said phase inverting means; connection changing means for changing the connection so that the signal is supplied to the signal delaying means, and supplying the output of the mixing means that has passed through the phase inverting means and the signal delaying means as another input to the mixing means, thereby changing the phase of the signal. A video signal noise removal circuit configured to obtain a noise-free luminance signal and color signal from an inverting means.