JPS63269892A - Drop out correcting circuit - Google Patents

Abstract

PURPOSE:To reduce the quantity of a hardware by guiding out a chrominance signal by the use of the chrominance signal separating circuit of a chrominance signal phase inversion circuit. CONSTITUTION:Since a video signal passing through the chrominance signal phase inversion circuit 20 and a delay circuit 22 goes to a correction signal, when a drop out is generated, if this signal is selected by a selection circuit 21, a drop out corrected video signal can be obtained. By the use of a chrominance signal separating filter 201, a function for guiding out the chrominance signal to a drop out correcting circuit can be provided, so that the chrominance signal separating circuit is not required.

Description

[Detailed Description of the Invention] Flame Hill Light! The present invention is applicable to a dropout correction circuit in a recorded information reproducing apparatus such as a video disc player V, VTR, etc.
It is something to do.

In recorded information reproducing devices such as Ondo technology video disk players and VTRs, in order to make the system more compact and cost-effective, it is desirable to reduce the hardware load of the entire system, even if there is a J3 in the circuit system.

1.5.1 The present invention has been made in view of the above-mentioned points, and provides a drop error correction circuit 1 through which the hardware of the entire system can be reduced as much as possible by also having a function of deriving a color signal. The purpose is to provide.

The dropout correction circuit according to the present invention includes a color signal phase inversion circuit that inverts the phase of a color signal included in an input video signal, and uses a color signal separation circuit that constitutes the color signal phase inversion circuit to convert the color signal. It is configured to also perform derivation.

χ-Disaster-1 Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram of a recorded information reproducing apparatus having a dropout correction circuit according to the present invention and having a configuration in which, for example, signal processing is performed digitally.

In the figure, an FM video signal read from a recording medium such as a video disk is supplied to an A/D converter 2 via an analog LPF (low pass filter) 1. LPF
I is for removing aliasing distortion in A/D conversion. The digitized FM video signal output from the A/D converter 2 is supplied to a digital BPF (band pass filter) 3. This digital BPF3
extracts only the components necessary for detecting the video signal from the A/D conversion output that also includes the FM audio signal, and supplies the extracted components to the FM detection circuit 4 at the next stage. As the FM detection circuit 4, for example, one having the configuration proposed by the present applicant in Japanese Patent Application No. 59-262481 can be used.

From the detection output of the FM detection circuit 4, only the baseband component of the video signal is extracted by the video LPF 5.

A dropout detection circuit 6 for detecting a dropout of the video signal is provided, and the circuit 6 has, for example, a level comparator configuration, and is configured as a square of the envelope component of the digitized FM video signal in the FM detection circuit 4. It detects that the signal level of the signal is below a predetermined value and outputs a dropout detection signal. The digitized video signal that has passed through the video LPF 5 is supplied to a dropout correction circuit 7 and a sync separation circuit 8. The dropout correction circuit 7 performs dropout correction in response to the dropout detection signal supplied from the dropout detection circuit 6, and also has a function of deriving a color signal as will be explained in detail later. There is.

The synchronization separation circuit 8 separates and extracts synchronization signals such as horizontal synchronization signals contained in the digitized video signal and supplies them to the clock generation circuit 9. The clock generation circuit 9 generates 4 fsc (
fsc is subcarrier frequency) and 4N fsc (
N is an integer of 2 or more, for example, 3), which generates a clock, and has a PLl (phase locked loop) circuit configuration. The 4fsc and 4Nfsc clocks generated here are used as clocks for digital signal processing, and the sampling clock of the A/D converter 2 and the clock for signal processing up to the video LPF 5 are set to 4Nfsc, and the output from the video LPF 5 is 4f
Downsampling to the clock of sc.

The digitized video signal output from the dropout correction circuit 7 is generated by the clock generation circuit 9 based on the color burst signal extracted from the reproduced video signal.
The data is written into the buffer memory 11 using the fsc clock. Data is read from the buffer memory 11 using a 4fsc reference clock generated by the reference signal generation circuit 10. In this way, by reading data from the buffer memory 11 using a stable reference clock that is unrelated to the reproduced video signal, jitter (time axis fluctuation) of the reproduced video signal can be absorbed. The digitized video signal read from the buffer 7 memory 11 is converted into an analog signal by a D/A (digital/analog) converter 12 and becomes a reproduced video output.

FIG. 2 is a block diagram showing one embodiment of the dropout correction circuit 7 according to the present invention. In the figure, the digitized video signal is supplied to a color signal phase inversion circuit 20 and also serves as one input of a selection circuit 21. The color signal phase inversion circuit 20 includes, for example, a color signal pre-filter 201 that separates and extracts color signal components from an input video signal, and a color signal component separated by this separation filter 201 that is doubled (with a coefficient of 2).
) (actually multiplies by shifting one bit to the MSB side) 202, and the output of this multiplier r43202 is subtracted from the video signal delayed by the same delay time d as the color signal component by the separation filter 201. It derives a video signal with the phase of the color signal inverted as the output of the subtracter 203, and a separation filter 2.
The configuration is such that the color signal components separated at 01 are directly derived as color signal outputs.

A specific example of the circuit configuration of the color signal separation filter 201 is shown in FIGS. 3 and 4. As is clear from these figures, the color signal separation filter 201 has an FIR type bandpass filter configuration, and the video output ( It is configured so that the delayed output) and the color signal output can be taken out at the same time. Note that the operating clock frequency of the circuit is four times the frequency (4fs) of the color subcarrier (fsc).
c), where D is a delay circuit that delays the input signal by one clock, and 2'' is a multiplication coefficient (1 pixel shift to the LSB side).

The video signal with the phase of the color signal inverted in the color signal phase inversion circuit 20 is basically delayed by an amount equivalent to 1H (H: horizontal scanning period) in the delay circuit 22, and then sent to the selection circuit 21.
This is another input. The delay circuit 22 basically performs a delay equivalent to IH, but the input video signal is passed through the color signal separation filter 2 in the color signal phase inversion circuit 20.
01 has already been delayed by 1ffid, so a delay time of (IH-d) is set. The selection circuit 21 normally selects the directly supplied video signal (b side), and when a dropout occurs, the selection circuit 21 selects the video signal (b side) that is supplied directly, and when a dropout occurs, the video signal is passed through the delay circuit 22 in response to a dropout detection signal supplied from the dropout detection circuit 6 in FIG. The configuration is such that a video signal from one day ago (side a) is selected.

In other words, since the video signal from 1H before the input video signal has a strong correlation, by inverting the phase of the color signal which is shifted by 180 degrees every 1H, the video signal from 1H before is added to the input video signal's drop error 1 to 1. It can be used as a correction signal. The video signal that has passed through the color signal phase inversion circuit 20 and the delay circuit 22 is such a correction signal, so if this signal is selected by the selection circuit 21 when a dropout occurs, the dropout can be corrected. It is possible to obtain a video signal that is

Further, in the present invention, by using the color signal separation filter 201 constituting the color signal phase inversion circuit 20, the dropout correction circuit 7 is provided with the ability to derive a color signal, which is different from the conventional clock Since the color signal separation circuit that was separately required for extracting the color burst required by the generation circuit 9 and the like is no longer required, the amount of hardware for the entire system can be reduced.

FIG. 5 is a block diagram showing another embodiment of the present invention, in which parts equivalent to those in FIG. It has a set configuration.

That is, the configuration is such that a color signal is derived from the video signal after dropout correction, and this video signal is fed back to the selection circuit 21 via the Raon circuit 22.

According to this, since the color signal output is also subjected to dropout correction, it is possible to suppress disturbance of the color burst even if dropout occurs. Further, since the dropout aramill correction signal is fed back and inputted again to the d-spreading circuit 22, even if a dropout occurs at the same position in a plurality of consecutive horizontal scanning lines, it can be reliably corrected.

In each of the above embodiments, a case has been described in which the present invention is applied to a system in which signal processing is performed digitally, but the present invention can also be applied to a system in which signal processing is performed in an analog manner. However, since digital circuits can accurately perform processing such as multiplication, addition/subtraction, and delay, the present invention is particularly suitable for systems in which signal processing is performed digitally.

As explained above, the dropout correction circuit according to the present invention includes a color signal phase inversion circuit that inverts the phase of a color signal included in an input video signal, and this color signal phase inversion circuit is configured. Since the configuration also uses a color signal separation circuit to derive color signals, the color signal separation circuit that was previously provided separately is no longer necessary, and the hardware requirements for the entire system can be reduced accordingly. become.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of a recorded information reproducing apparatus having a dropout correction circuit according to the present invention, and FIG.
The figure is a block diagram showing an embodiment of the dropout correction circuit according to the present invention, FIGS. 3 and 4 are block diagrams showing a specific example of the circuit configuration of the color signal separation filter in FIG. 2, and FIG. FIG. 3 is a block diagram showing another embodiment of a dropout correction circuit according to the invention. Explanation of symbols of main parts

Claims (5)

[Claims] (1) A color signal phase inversion circuit that inverts the phase of the color signal included in the video signal, a delay circuit that delays the video signal output from the color signal phase inversion circuit by a predetermined time, and a color signal phase inversion circuit that inverts the phase of the color signal included in the video signal. the color signal phase inverting circuit includes a selection means having two inputs of a first video signal and a second video signal which is an input signal, and selecting and outputting the first video signal when a dropout occurs; Includes a color signal separation circuit that separates color signal components from the signal,
A dropout correction circuit characterized in that it also derives a color signal. (2) The color signal phase inversion circuit uses the second video signal as an input signal.
Dropout correction circuit described in section. (3) The dropout correction circuit according to claim 1, wherein the color signal phase inversion circuit uses the output signal of the selection means as an input signal. (4) The dropout according to claim 1, wherein the delay circuit has a delay time that is the delay time in the color signal phase inversion circuit subtracted from a time equivalent to 1H (H: horizontal scanning period). correction circuit. (5) The color signal phase inversion circuit is characterized in that, together with the color signal separation circuit, the color signal phase inversion circuit includes a subtracter that subtracts a signal obtained by doubling the color signal component separated by the separation circuit from the input video signal. A dropout correction circuit according to claim 1.