JPH0638242A - Dropout compensation device - Google Patents

Abstract

PURPOSE:To obtain easy to see television pattern by eliminating black or white streaks caused just after a dropout period or at dropouts caused frequently in the case of compensating dropout. CONSTITUTION:A dropout detection circuit 4 detects a dropout period of a reproduction signal reproduced from a recording medium and a pulse generating circuit 12 generates a pulse signal with a prescribed width after the dropout period based on its detection signal. On the other hand, a color comb-line filter 6 uses a 1H delay line 21 to delay a reproduction signal from the recording medium by 1H, and a luminance component mixed in the reproduction signal is eliminated by using a subtractor means (22, 28) to subtract the 1H delay signal from the reproduction signal and only a chrominance carrier signal component is outputted. An output signal of the comb-line filter 6 is given to an amplifier 11, in which the signal is amplified by a gain corresponding to the output of the pulse generating circuit 12, and a dropout compensation circuit 7 uses the dropout detection signal to compensate the dropout.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dropout compensating device for compensating for a missing portion of a signal reproduced in a recording / reproducing device such as a video tape recorder (hereinafter referred to as VTR).

[0002]

2. Description of the Related Art Conventionally, in a magnetic recording / reproducing apparatus such as a VTR, white dots appear on the screen due to scratches or protrusions on the magnetic layer of the tape, or dropout of the reproduced signal caused by dust entering between the tape and the head. Alternatively, in order to eliminate the phenomenon in which a line appears, a dropout compensation circuit is used in which the signal missing portion is replaced with a signal one horizontal scanning period (1H) earlier. This dropout compensation circuit can be used both for the reproduced FM luminance signal and for the reproduced carrier chrominance signal.

Currently, there are various systems for recording video and audio on a magnetic tape or the like, but a VTR of a system for converting a color signal into a low frequency band and recording / reproducing it, for example, VHS (registered trademark) (Video Ho
In the me System) system and the 8 mm video format, in order to remove the crosstalk component of the color signal during playback, N
In the case of the TSC system, a color comb filter using one horizontal period delay line (1H delay line) is mounted. In addition, in order to improve the S / N ratio of the color signal, there is a circuit provided with a cyclic type color noise removing circuit (hereinafter referred to as a CNR circuit). In this CNR system, in addition to the type in which the 1H delay line of the color comb filter for color signal separation is also used as the 1H delay line for the CNR, and the 1H delay line for the color comb filter,
There are two types, 1H delay line dedicated to CNR.

FIG. 9 is a block diagram showing a conventional example of the latter type of dropout compensation device. That is, it shows a tribute to a dropout compensating device provided with a color comb filter for a carrier color signal.

In FIG. 9, the reproduction RF signal input to the input terminal 1 becomes a reproduction luminance signal of the base band in the reproduction luminance signal processing circuit 2. Further, the reproduction RF signal is supplied to the dropout detection circuit 4, where the dropout is detected and a dropout pulse is generated and sent to the reproduction luminance signal processing circuit 2 and the dropout changeover switch 31. Further, the reproduced RF signal is frequency-converted into a frequency (3.58 MHz) of the low-pass color signal by the frequency conversion circuit 5, and the 1H delay line 21, the adder 22, the attenuators 24, 25,
And the color comb filter 6 including the phase inversion circuit 28
Crosstalk (luminance component) is removed at. The signal from which crosstalk has been removed is dropout-compensated by the dropout compensating circuit 7 and becomes a reproduced color signal, which is output from the output terminal 8. The dropout compensation circuit 7 includes a dropout changeover switch 31, a 1H delay line 33, a phase inversion circuit 34, and a coefficient unit (feedback amplifier) 35.

The operation of FIG. 9 will be described. The color-converted carrier color signal is converted into 1 / thickness by the color comb filter 6.
The comb-shaped signal is obtained by adding the signal obtained by doubling and inverting the phase and the carrier color signal delayed by the 1H delay circuit 21 by a time corresponding to 1H and further halving the signal by the adder 22. After being processed, it is sent to the dropout changeover switch 31. The changeover switch 31 selects the output from the adder 22 in the normal time and selects and outputs the output from the coefficient unit 35 in the case of the dropout based on the dropout pulse output when the dropout is detected. To do. The 1H delay line 33 delays the output signal from the changeover switch 31 by a time corresponding to 1H. The phase inversion circuit 34 inverts the polarity of the output from the 1H delay circuit 33. The coefficient unit 35 multiplies the output from the phase inversion circuit 34 by K times (0
<K ≦ 1) and output. As described above, when a dropout occurs, the signal 1H before is replaced with a signal multiplied by K to perform dropout compensation.

Next, the dropout compensation operation will be specifically described with reference to FIG. A case will be described in which, as the input carrier color signal signal to the color comb filter 6, for example, a signal having a signal loss of 2H due to dropout as shown in FIG. 10A is input.

The input carrier color signal is combed by a signal delayed by a time corresponding to 1H by the 1H delay circuit 21 (see FIG. 10 (b)), and a signal as shown in FIG. 10 (c). And is sent from the adder 22 to the changeover switch 31. The changeover switch 31 determines that the dropout pulse is “L” based on the dropout pulse (see FIG. 10D) corresponding to the dropout section of FIG. 10A.
The output from the adder 22 is selected at (normal time), and the output from the coefficient unit 35 is selected and output when the dropout pulse is "H" (when dropout occurs). Therefore, the reproduced color signal becomes a signal as shown in FIG.
In the reproduced color signal shown in FIG. 10 (e), (n + 2) H
The signals of the (n + 3) th eye and the (n + 3) th eye are selected and output from the coefficient unit 35 because the dropout pulse is “H”. When the value of the coefficient K of the coefficient unit 35 is K = 0.98 and the level of the input carrier color signal is V, (n +
2) The signal levels of the Hth and (n + 3) Hth are 0.98 V and 0.96 V, respectively. On the other hand, (n + 4) H
Since the dropout pulse of the eye signal is "L", the signal from the adder 22 is selected and output. In the output signal of the adder 22, the (n + 4) Hth signal level is shown in FIG.
As shown in (c), since it is (1/2) V, the signal level of the (n + 4) Hth reproduced color signal is also (1/2) V. That is, with respect to the (n + 3) Hth signal level, (n + 4) H
Since the signal level of the eye drops sharply, the (n + 4) H eye looks like a black line when viewed on the screen, and there is a problem that the image quality is significantly deteriorated.

[0009]

As described above, in the conventional dropout compensating circuit having the color comb filter, the signal level immediately after the dropout section is drastically reduced, so that a black line appears on the screen. Looks like
There is a problem that the image quality is significantly deteriorated.

Therefore, in view of the above problems, the present invention provides a dropout compensator capable of eliminating a black line generated immediately after a dropout section or during frequent dropouts to provide an easy-to-view television screen. It is intended.

[0011]

According to a first aspect of the present invention, there is provided a dropout compensation device for detecting a dropout period of a reproduction signal reproduced from a recording medium, and the dropout detection device. After inputting the reproduction signal from the recording medium, a pulse generating means for generating a pulse signal having a predetermined width after the detection signal period
A first delay means for delaying a horizontal scanning period, subtracting or adding the reproduction signal and the signal delayed by one horizontal scanning period from the first delay means, and carrying color signal components mixed in the reproduction signal; A comb filter that outputs only one of the luminance signal components, gain varying means that varies the gain of the output signal of the comb filter using the output of the pulse generating means, and the output signal of this gain varying means are input. A second delay unit for delaying one horizontal scanning period is included, and the output signal of the gain varying unit is output for one horizontal scanning period from the second delay unit only during the dropout detection period detected by the dropout detecting unit. And a dropout compensating means for compensating for dropout based on the previous signal.

A dropout compensating apparatus according to the present invention is a dropout detecting means for detecting a dropout period of a reproduction signal reproduced from a recording medium,
First delay means for inputting a reproduction signal from the recording medium and delaying by one horizontal scanning period, and a dropout detection period provided at the input side of the first delay means and detected by the dropout detection means. Switching means for performing dropout compensation on the reproduced signal from the recording medium based on the signal from the first delay means one horizontal scanning period before, the output of the switch means and the first delay means. From 1
A comb filter that subtracts or adds a signal delayed in the horizontal scanning period, and outputs only one of the carrier color signal component and the luminance signal component mixed in the reproduction signal from the recording medium, and the output of this comb filter Second delay means for delaying one horizontal scanning period, and the output signal of the comb filter is passed through the second delay means for the dropout detection period detected by the dropout detection means.
A dropout compensating means for compensating for dropout based on a signal before the horizontal scanning period is provided.

A dropout compensating apparatus according to the present invention according to claim 3 is a dropout detecting means for detecting a dropout period of a reproduction signal reproduced from a recording medium,
The logical sum of the first delay means for delaying the detection signal from the dropout detection means for one horizontal scanning period, the detection signal from the dropout detection means and the signal delayed by the first delay means is calculated. A gate means and a second delay means for inputting a reproduction signal from the recording medium and delaying it by one horizontal scanning period; and the reproduction signal and the signal delayed by one horizontal scanning period from the second delaying means. A comb filter that subtracts or adds and outputs only one of a carrier color signal component and a luminance signal component mixed in the reproduction signal, and a third delay unit that inputs the output of the comb filter and delays for one horizontal scanning period. The output signal of the comb filter is dropout-compensated based on the signal of one horizontal scanning period before which has passed through the third delay means only during the detection signal period from the gate means. It is characterized in that it has and a dropout compensation means.

[0014]

According to the first aspect of the invention, the pulse generating means outputs a pulse having a predetermined width after the period of detecting the dropout. The gain varying means changes the gain based on the output signal from the pulse generating means. For example, the gain of the gain varying means is set to be large for a predetermined period after the period of detecting the dropout. That is, during the above-mentioned predetermined period, the level of the reproduced video signal is raised and output, so that the signal level immediately after dropout compensation does not suddenly decrease, and it looks like a black or white line on the screen. It is possible to eliminate the significant deterioration in image quality due to.

According to the second aspect of the present invention, since the signal circulates through the first delay means for the color comb filter even during dropout, the color comb filter output becomes 1/2 after the dropout interval. Can be prevented. Therefore, immediately after the dropout section that occurred conventionally,
It is possible to eliminate the blackish or whitish streaks that appear during frequent dropouts.

According to the third aspect of the present invention, the dropout compensating means is operated not only at the time of dropout, by using the signal obtained by ORing the dropout detection signal and the signal delayed by 1H period. Conventionally, the blackish or whitish horizontal stripe that has occurred after the dropout section can be replaced with a signal before 1H (and consequently 2H before) to be eliminated.

[0017]

EXAMPLES Examples will be described with reference to the drawings. 1 is a block diagram showing a dropout compensating apparatus according to a first embodiment of the present invention. The same parts as those in the conventional example shown in FIG.

In FIG. 1, the reproduction RF signal reproduced from the head at the time of reproduction is input to the input terminal 1, and the input reproduction RF signal becomes the reproduction luminance signal of the base band in the reproduction luminance signal processing circuit 2. Further, the reproduction RF signal is supplied to the dropout detection circuit 4, where the dropout is detected to generate a dropout pulse (d), which is sent to the reproduction luminance signal processing circuit 2 and the dropout changeover switch 31. Further, the reproduced RF signal is converted into the frequency conversion circuit 5.
The low-pass color signal is frequency-converted to a frequency (3.58 MHz) by the 1H delay line 21, the adder 22, and the attenuator 2.
Crosstalk (luminance component) is removed by the color comb filter 6 composed of 4, 25 and the phase inversion circuit 28.
The signal from which crosstalk has been removed passes through the amplifier circuit 11 and is then dropout-compensated by the dropout compensation circuit 7 to be a reproduced color signal, which is output from the output terminal 8. The dropout compensation circuit 7 includes a dropout changeover switch 31, a 1H delay line 33, a phase inversion circuit 34, and a coefficient unit (feedback amplifier) 35. The pulse generation circuit 12 generates a pulse having a predetermined width (for example, 1H) after the dropout period and supplies this to the amplification circuit 11 as a gain control signal.

The carrier color signal whose frequency has been converted by the frequency conversion circuit 5 is converted into 1 / x by the color comb filter 6.
The signal obtained by doubling and inverting by the phase inverting circuit 28 and the signal obtained by delaying the carrier color signal by the delay circuit 21 for a time corresponding to 1H and further halving the signal are added by the adder 22. After being processed by combing, the amplifier circuit 11
Sent to. The amplifier circuit 11 uses an amplification gain based on the control signal (e) output from the pulse generation circuit 12 to add the adder 22.
The output signal from is amplified and output. The gain of the amplifier circuit 11 is G1 (normal and when dropout occurs) or G2.
(Predetermined period after the dropout section) is set. However, G1 <G2. The switching circuit 31 selects the output from the amplifier circuit 11 when the dropout pulse (d) is "L", and selects the output from the coefficient unit 35 when the dropout pulse (d) is "H". Select and output. The delay circuit 33 delays the output signal from the switching circuit 31 by a time corresponding to 1H. The phase inversion circuit 34 is the delay circuit 3
Invert the polarity of the output from 3. The coefficient unit 35 multiplies the output from the phase inversion circuit 34 by K (0 <K ≦ 1) and outputs the output.
The dropout pulse (d) is normally "L", and becomes "H" when dropout is detected. When the falling edge of the dropout pulse (d) is input, the pulse generation circuit 12 generates a pulse having a pulse width (“H” period) corresponding to 1H, and outputs it as a gain control signal (e). Output to the amplifier circuit 11.

Next, the operation of the dropout compensating circuit thus constructed will be described with reference to the color signal levels shown in FIG.

FIG. 2 (a) shows (n +
2) FIG. 2B shows a delay circuit 2 for the input signal of the color comb filter in which the 2Hth and (n + 3) th Hths of the signal loss occur.
1 output, Fig. 2 (c) shows the output of the adder 22, and Fig. 2 (d)
Shows the dropout pulse, FIG. 2 (e) shows the control signal (e) from the pulse generation circuit 12, FIG. 2 (f) shows the output of the amplifier circuit 11, and FIG. 2 (g) shows the reproduced color signal output. ing.

The input carrier color signal shown in FIG. 2 (a) is multiplied by 1/2 and phase-inverted, and then input to the adder 22. on the other hand,
The input carrier color signal is also input to the delay circuit 21. The delay circuit 21 delays the reproduction input signal by a time corresponding to 1H and outputs the signal shown in FIG. 2 (b). The signal output from the delay circuit 21 is multiplied by 1/2 and input to the adder 22. The adder 22 adds these two signals, and
The signal shown in (c) is output to the amplifier circuit 11.

On the other hand, the dropout pulse is, for example, "L" in the normal state and becomes "H" when the dropout is detected. When the reproduction input signal is the signal shown in FIG. 2 (a), the dropout pulse becomes the signal shown in FIG. 2 (d) and is input to the pulse generation circuit 12. The pulse generation circuit 12 outputs after the fall of the dropout pulse,
For example, a pulse having a width corresponding to 1H as shown in FIG. 2 (e) is generated, and the gain control signal (e) is amplified by the amplifier circuit 11
Then, the amplification gain changes in the amplifier circuit 11 based on the control signal (e). For example, when the control signal (e) is "L", the gain is amplified by the gain G1, and when the control signal (e) is "H", the gain is amplified by the gain G2. Thus, the signal as shown in FIG. 2 (f) is output from the amplifier circuit 11 to the switching circuit 31.

After the signal output from the switching circuit 31 is delayed by the delay circuit 33 for a time corresponding to 1H, the other input of the switching circuit 31 is inverted in polarity by the phase inversion circuit 34. The signal multiplied by K in the coefficient unit 35 is input. The switching circuit 31 selects the output from the amplifier circuit 11 when the dropout pulse is “L”, and selects and outputs the output from the coefficient unit 35 when the dropout pulse is “H”. . Therefore, the reproduced color signal becomes the signal shown in FIG. 2 (g), and if the signal level of the (n + 1) Hth is G1V, the (n + 2) th Hth, (n + 3) th
The signal levels of the Hth and (n + 4) th H are KG1 respectively.
V, K2 G1 V, (G2 / 2) V. If the value of the coefficient K of the coefficient unit 35 is K = 0.98, the value of the gain G1 of the amplifier circuit 11 is G1 = 1, and the value of the gain G2 is G2 = 2, (n
The signal levels of +2) Hth eye, (n + 3) Hth eye, and (n + 4) Hth eye are 0.98V, 0.96V, and V, respectively.
The (n + 4) th H-th signal level does not suddenly decrease.

As described above, in the present embodiment, since the signal level immediately after the dropout section (the section where the dropout is "H") does not suddenly decrease, there is no deterioration in image quality such as a black line on the screen, and there is no dropout. Compensation can be made.

In the present embodiment, the dropout compensating device provided with the color comb filter for the carrier color signal has been described, but the present invention is not limited to this, and the luminance comb filter for the reproduced FM brightness signal is provided. Dropout compensator (in the reproduction luminance signal processing circuit 2 in FIG. 1)
Can also be used for. When the present invention is used for luminance dropout compensation, the inverting circuits 28 and 34 for phase adjustment shown in FIG. 1 are unnecessary.

FIG. 3 is a block diagram showing a dropout compensator according to the second embodiment of the present invention. The embodiment shown in FIG. 3 is provided with a circuit in which a switching circuit 13 and a coefficient unit 14 are combined instead of the amplifier circuit 11 in the embodiment of FIG. Other configurations are the same as those in FIG.

In FIG. 3, in the color comb filter 6,
The carrier color signal frequency-converted by the frequency conversion circuit 5 is
A signal obtained by delaying the signal halved by the attenuator 25 and inverted by the inverting circuit 28 and the carrier color signal by the delay circuit 21 by a time corresponding to 1H, and further halving the signal. After being subjected to comb processing by adding and in the adder 22, they are sent to the switching circuit 13 and the coefficient unit 14. The switching circuit 13 is, for example, a control signal from the pulse generating circuit 12.
When (e) is "L", the output from the adder 22 is selected, and when the control signal (e) is "H", the output from the coefficient unit 14 is selected and output. The delay circuit 33 is the switching circuit 31.
Delays the output signal from 1H by a time corresponding to 1H. The phase inversion circuit 34 inverts the polarity of the output from the delay circuit 33. The coefficient unit 35 multiplies the output from the phase inverting circuit 35 by K (0 <K ≦ 1) and outputs it.

The dropout pulse detected by the dropout detection circuit 4 is normally "L" and becomes "H" when a dropout is detected.
The pulse generation circuit 12 rises at the falling edge of the dropout pulse (d), generates a pulse whose pulse width (“H” period) is equivalent to 1H, and outputs it as the switching control signal (e). Output to 13.

Next, the dropout compensating apparatus having such a configuration will be described with reference to the diagram showing the color signal level in FIG.

FIG. 4 (a) shows (n +
2) The carrier color signal in which the 2H-th and (n + 3) -th H signals are missing, FIG. 4 (b) shows the output of the delay circuit 21, and FIG. 4 (c) shows the output of the adder 22. Figure 4 (d) shows the dropout pulse, Figure 4 (e) shows the switching control signal (e), and Figure 4 (f).
Shows the output of the switching circuit 13, and FIG. 4 (g) shows the reproduced color signal output.

The carrier color signal shown in FIG. 4A is multiplied by 1/2 and the phase thereof is inverted, and the result is input to the adder 22. On the other hand, the carrier color signal is also input to the delay circuit 21. Delay circuit 2
1 delays the input carrier color signal by a time corresponding to 1H and outputs the signal shown in FIG. 4 (b). The signal output from the delay circuit 21 is multiplied by 1/2 and input to the adder 22. The adder 22 adds these two signals, and the result is shown in FIG.
The signal indicated by is output to the switching circuit 13 and the coefficient unit 14.
The signal output from the adder 22 multiplied by N (N> 1) in the coefficient unit 14 is input to the other input of the switching circuit 13. The switching circuit 13 is, for example, a switching control signal.
When (e) is "L", the output from the adder 22 is selected and the signal shown in FIG. 4 (f) is output to the switching circuit 31.

On the other hand, the dropout pulse (d) is, for example, "L" in the normal state and becomes "H" when the dropout is detected. Figure 4 shows the input carrier color signal.
In the case of the signal shown in (a), the dropout pulse is as shown in Fig. 4 (d).
The signal shown in FIG. The pulse generation circuit 12 outputs to the switching circuit 13 the control signal (e) shown in FIG. 4 (e) which rises at the timing of the falling edge of the dropout pulse and falls after the time corresponding to 1H elapses.

After the signal output from the switching circuit 31 is delayed by the delay circuit 33 for a time corresponding to 1H, the polarity is inverted by the phase inverting circuit 34 to the other input of the switching circuit 31. The signal multiplied by K in the coefficient unit 35 is input. The switching circuit 31, for example, selects the output from the switching circuit 13 when the dropout pulse is “L”, and selects and outputs the output from the coefficient unit 14 when the dropout pulse is “H”. . Therefore, the reproduced color signal obtained at the output terminal 8 becomes the signal shown in FIG.
When the signal level of the (n + 1) th Hth is V, (n + 2)
The signal levels of the Hth, (n + 3) Hth, and (n + 4) Hth are KV, K2 V, and (N / 2) V, respectively. Coefficient unit 3
Assuming that the value of the coefficient K of 5 is K = 0.98 and the value of the coefficient N of the coefficient unit 14 is N = 2, (n + 2) th Hth and (n + 3) H
The signal levels of the eyes and (n + 4) H are 0.98, respectively.
V, 0.96V, V, and the signal level of the (n + 4) Hth eye after the dropout section does not suddenly decrease.

As described above, in this embodiment, since the signal level immediately after the dropout section (the section where the dropout is "H") does not suddenly decrease, there is no image deterioration such as a black line appearing on the screen and there is no drop. Out compensation can be done.

In the present embodiment, the dropout compensating device having the color comb filter for the carrier color signal has been described, but the present invention is not limited to this, and the luminance comb filter for the reproduced FM brightness signal is provided. Dropout compensator (in the reproduction luminance signal processing circuit 2 in FIG. 3)
Can also be used for. When the present invention is used for the dropout compensation of the luminance system, the inverting circuits 28 and 34 for phase adjustment in FIG. 3 are unnecessary.

FIG. 5 is a block diagram showing a dropout compensation circuit according to the third embodiment of the present invention. This example
An example is shown in which the 1H delay line for CNR is also used as the delay line for dropout compensation.

In FIG. 5, the reproduction RF signal reproduced from the head during reproduction is input to the input terminal 1 and the reproduction RF signal is reproduced.
The reproduction luminance signal processing circuit 2 converts the signal into a reproduction luminance signal in the base band. Further, the reproduction RF signal is supplied to the dropout detection circuit 4, where the dropout is detected and a dropout pulse is generated, and the reproduction luminance signal processing circuit 2, the dropout changeover switch 26, and the dropout changeover switch 31 are supplied. sending. Further, the reproduction RF signal is frequency-converted into the frequency (3.58 MHz) of the low-pass color signal by the frequency conversion circuit 5, and the 1H delay line 2
The crosstalk (luminance component) is removed by the color comb filter 6 including the adder 1, the attenuator 23, the dropout changeover switch 26, and the phase inversion circuits 27 and 28. The present embodiment is largely different from the embodiments of FIGS. 1 and 3 in that the above-described 1H delay line for CNR is used as a delay line for dropout compensation, and 1H for a color comb filter. A changeover switch 26 is provided at the input of the delay line 21, and this switch 26 is changed over at the time of dropout to output the output of the 1H delay line 21 to the phase inverting circuit 2
It is configured to return to the input through 7 for dropout compensation. The phase inverting circuit 27 is for adjusting the phase of the dropout compensation signal.

The signal from which crosstalk has been removed is subjected to noise removal by the CNR / dropout compensating circuit 7A and becomes a reproduced color signal, which is output from the output terminal 8. The CNR / dropout compensation circuit 7A includes a dropout changeover switch 31, a decorrelation noise subtractor 32, a 1H delay line 33, a phase inversion circuit 34, a coefficient unit (feedback amplifier) 35, and a subtractor 3.
6 and a coefficient multiplier (feedback amplifier) 37. Here, the input signal and the 1
The difference signal ΔC from the signal before H is generated by the subtractor 36, and the difference signal ΔC is supplied to the subtractor 32 through the coefficient 37.
The subtractor 32 subtracts from the input signal to reduce noise. It becomes the final reproduced color signal. Also, at the time of dropout, the changeover switch 31 is switched to the H side, and 1H
The previous signal is output as the reproduction color signal.

In the above structure, the changeover switch 26
If the phase inversion circuit 27 is not provided, at the time of dropout, a signal is not input to the 1H delay line 21 in the color comb filter 6, so that the dropout effect is affected. Therefore, on the television screen, the 1H period after releasing the dropout and the place where it is not compensated for even if dropouts occur frequently will appear, and it will be a dark line on the television screen and it will be an unsightly screen, but this implementation According to the example, at the time of dropout, the delay signal of the 1H delay line 33 for the color noise elimination circuit is output while circulating, and the 1H delay line 21 for the color comb filter is also provided by providing the changeover switch 26 and the phase inversion circuit 27. By circulating the color signal and performing dropout compensation, it is possible to prevent the output of the color comb filter 6 from becoming 1/2 immediately after the dropout section.
That is, the level of the reproduction color signal (e) is kept constant immediately after the dropout or when the dropout frequently occurs.

FIG. 6 shows the color signal levels of the respective parts in FIG. For example, “n” in FIG. 6 represents the color signal of the n-th line. FIG. 6 shows a case where signals are missing in a part of the (n + 2) Hth eye, a part of the (n + 3) Hth eye, and a part of the (n + 6) Hth eye. 6 (a) shows the carrier color signal input to the color comb filter 6, and FIG. 6 (b) shows the comb filter input (that is, the 1H delay line) when switching is performed by the switching circuit 26 at the time of dropout. 21 input signal)
6 (c) is the 1H delay signal output from the 1H delay line 21, and FIG. 6 (d) is the signal obtained by phase inversion of the signal of FIG. 6 (a) and the signal of FIG. 6 (c). The output of the color comb filter 6 obtained by multiplying by 1/2 is shown. Also, FIG. 6 (f) shows 1
6H shows a 1H delay signal for color noise removal that has passed through the H delay line 33, the phase inversion circuit 34, and the coefficient unit 34. FIG. 6E shows the reproduced color signal output to the output terminal 8 as shown in FIG. Indicates a dropout detection signal. As can be seen from FIG. 6, the level of the reproduced color signal (e) is kept constant immediately after the dropout or when the dropout frequently occurs.

In this embodiment, the dropout compensating device provided with the color comb filter of the carrier color signal has been described, but the present invention is not limited to this, and the luminance comb filter of the reproduced FM brightness signal is provided. Dropout compensator (in the reproduction luminance signal processing circuit 2 in FIG. 5)
Can also be used for. When the present invention is used for dropout compensation of a luminance system, a luminance comb filter is used instead of the color comb filter, and a simple dropout compensation circuit is used instead of the color noise removal / dropout compensation circuit, Inversion circuit 2 for phase adjustment in FIG.
Those corresponding to 8, 34 are unnecessary.

FIG. 7 is a block diagram showing a dropout compensator according to the fourth embodiment of the present invention. In FIG.
One of the reproduction RF signals input to the input terminal 1 becomes a reproduction luminance signal via the re-luminance signal processing circuit 2. Also, the dropout detection circuit 4 creates a dropout pal (i). On the other hand, a reproduced color signal processing circuit including a frequency conversion circuit 5 and a color comb filter 6 reproduces a color signal. The color comb filter 6 includes a 1H delay line 2
1, an adder 22 and a phase inversion circuit 28. As is well known, the color comb filter 6 has a characteristic of removing a crosstalk component and a characteristic that a color signal droops in the vertical direction. The reproduced color signal output from the adder 22 is used as a color noise removal and dropout compensation circuit 7 in the next stage.
Reach A. Color noise removal and dropout compensation circuit 7A
Is composed of subtractors 32, 36, 1H delay line 33, phase inverting circuit 34, and changeover switches 38, 39, 40. The switches 38, 39, 40 are normally switched to the L side. In the circuit 7A, the input signal and 1
A subtractor 36 produces a difference signal ΔC from the signal 1H before through the H delay line 33, and the subtractor 32 subtracts the difference signal ΔC from the input signal to reduce noise. It becomes the final reproduced color signal (h).

Further, one of the dropout detection signals (i) from the dropout detection circuit 4 is input to one input of the OR gate 10 and the other is sent to the signal through the 1H delay line 9.
(j) and reaches the other input terminal of the OR gate 10. The output (k) of the OR gate 10 is the switch 38, 3
It acts to control 9,40. During dropout, the gate output (k) becomes "H" and the switches 38 and 3
9 and 40 are switched to the H side and the signal before 1H is the reproduction color signal
With this configuration, the circuit 7A enters the dropout compensation mode again by the 1H delay pulse (j) even during the 1H period immediately after the dropout, and the signal 1H delay line 33 is circulated. Since the previously used signal is output again as the reproduction color signal, it is possible to eliminate the black streak that has conventionally occurred immediately after dropout. The part marked with * in FIG. 8 (h) is the part replaced with the signal delayed by pulse (j).

FIG. 8 shows the color signal level of each part in FIG. 8A shows the input carrier color signal of the color comb filter 6, and FIG. 8B shows the 1H delay signal from the 1H delay line 21.
8 (c) shows the output of the color comb filter 6, FIG. 8 (d) shows the output of the changeover switch 38, FIG. 8 (e) shows the output of the changeover switch 39, and FIG. 8 (f) shows the 1H delay line. FIG. 8 (g) shows the output of the subtractor 32, and FIG. 8 (h) shows the reproduced color signal output. 8 (i) shows the dropout detection signal, FIG. 8 (j) shows the 1H delay signal of (i), and FIG. 8 (k) shows the output of the OR gate 10. As can be seen from FIG. 8, the level of the reproduction color signal (h) is kept constant immediately after the dropout or even when the dropout frequently occurs.

In the present embodiment, the dropout compensating device provided with the color comb filter for the carrier color signal has been described, but the present invention is not limited to this, and the luminance comb filter for the reproduced FM brightness signal is provided. Dropout compensation device (in the reproduction luminance signal processing circuit 2 in FIG. 7)
Can also be used for. When the present invention is used for dropout compensation of a luminance system, a luminance comb filter is used instead of the color comb filter, and a simple dropout compensation circuit is used instead of the color noise removal / dropout compensation circuit, Inversion circuit 2 for phase adjustment in FIG.
Those corresponding to 8, 34 are unnecessary.

Further, the dropout compensating delay line 33 at the time of reproduction used in the present invention can also be used as the one used for Y / C separation at the time of recording, for example, so that the cost can be increased.

[0048]

As described above, according to the present invention, at the time of dropout compensation, the signal level does not suddenly decrease immediately after the dropout section, so that it looks like a black or white line on the screen. Image quality is not deteriorated, and the quality of the reproduced screen can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a dropout compensation device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing signal levels for explaining the operation of FIG.

FIG. 3 is a block diagram showing a dropout compensation device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing signal levels for explaining the operation of FIG.

FIG. 5 is a block diagram showing a dropout compensation device according to a third embodiment of the present invention.

6 is a diagram showing signal levels for explaining the operation of FIG.

FIG. 7 is a block diagram showing a dropout compensation device according to a fourth embodiment of the present invention.

8 is a diagram showing signal levels for explaining the operation of FIG. 7. FIG.

FIG. 9 is a block diagram showing a conventional dropout compensation device.

FIG. 10 is a diagram showing signal levels for explaining the operation of FIG. 9;

[Explanation of symbols]

 4 ... Dropout detection circuit 6 ... Comb filter for color signal separation 7 ... Dropout compensation circuit 7A ... Color noise removal and dropout compensation circuit 8 ... Reproduction color signal output terminal 9, 21, 33 ... 1H delay line 10 ... OR gate 11 ... Gain variable amplification circuit 12 ... Pulse generation circuit 13, 26, 31, 38, 39, 40 ... Changeover switch 14, 35, 37 ... Coefficient device 22 ... Adder 23, 24, 25 ... Attenuator 27, 28, 34 ... Phase inversion circuit 32, 36 ... Subtractor

Claims (3)

[Claims] 1. Dropout detection means for detecting a dropout period of a reproduction signal reproduced from a recording medium, and pulse generation means for generating a pulse signal of a predetermined width after the detection signal period from the dropout detection means. And a first delay means for inputting a reproduction signal from the recording medium and delaying it by one horizontal scanning period.
Comb filter for subtracting or adding the signal delayed by one horizontal scanning period from the delay means and outputting only one of the carrier color signal component and the luminance signal component mixed in the reproduction signal, and the output of this comb filter The dropout detecting means includes a gain varying means for varying the gain of the signal using the output of the pulse generating means, and a second delay means for receiving the output signal of the gain varying means and delaying it by one horizontal scanning period. Output signal of the gain varying means is set to 1 from the second delay means only during a dropout detection period detected by
A dropout compensating device comprising: dropout compensating means for compensating for dropout based on a signal before a horizontal scanning period. 2. A dropout detection means for detecting a dropout period of a reproduction signal reproduced from a recording medium, a first delay means for inputting the reproduction signal from the recording medium and delaying it by one horizontal scanning period, It is provided on the input side of the first delay means, and the reproduction signal from the recording medium is provided one horizontal scanning period before the horizontal delay period from the first delay means only for the dropout detection period detected by the dropout detection means. Switching means for performing dropout compensation based on a signal, the output of the switching means and 1 from the first delay means.
A comb filter that subtracts or adds the signal delayed in the horizontal scanning period and outputs only one of the carrier color signal component and the luminance signal component mixed in the reproduction signal from the recording medium, and the output of this comb filter Second horizontal delay for delaying one horizontal scanning period, and the output signal of the comb filter is passed through the second delay means for one horizontal period only during the dropout detection period detected by the dropout detection means. A dropout compensating device, comprising: dropout compensating means for compensating for dropout based on a signal before a scanning period. 3. A dropout detection means for detecting a dropout period of a reproduction signal reproduced from a recording medium, a first delay means for delaying a detection signal from the dropout detection means by one horizontal scanning period, and A gate means for taking a logical sum of a detection signal from the dropout detection means and a signal delayed by the first delay means, and a second signal for inputting a reproduction signal from the recording medium and delaying for one horizontal scanning period. A delay unit, the reproduction signal and the second signal
A comb filter for subtracting or adding the signal delayed by one horizontal scanning period from the delay means and outputting only one of the other carrier color signal component or luminance signal component mixed in the reproduction signal, and this comb filter The third delay means for inputting the output of FIG. 1 and delaying it for one horizontal scanning period is provided, and the output signal of the comb filter is passed through the third delay means for one horizontal scanning period only during the detection signal period from the gate means. A dropout compensating device comprising: dropout compensating means for compensating for dropout based on the previous signal.