JPH0686231A - Video signal recording and reproducing device - Google Patents

Abstract

PURPOSE:To reproduce a video signal in recording with fidelity even when jitter is generated in a disk driving device in the recording and reproduction of the video signal by adding a burst signal on the addition signal of a luminance signal and a synchronizing signal. CONSTITUTION:The addition signal Y+S of the luminance signal Y and the synchronizing signal S is inputted from a camera part to a synchronizing signal separation circuit 10, and a horizontal synchronizing signal is separated. A burst gate pulse is generated at a prescribed timing at a pulse generation circuit 20. A burst signal outputted from a circuit 40 and the burst gate pulse are inputted to a gate circuit 30. The burst signal is inputted to an adder 35 in a period where the burst gate pulse is turned on, and the burst signal is added on the Y+S signal. A start flag is added on the signal at an adder 47, and frequency modulation processing, etc., is applied to the signal at a processing circuit 50, and it is recorded on a magnetic disk 70 by a magnetic head 60. The head 60 reads a recording signal, and it is demodulated at a circuit 90, and reproduction is performed by applying A/D and D/A conversion to the signal via a clock signal generated from an extracted burst signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal recording / reproducing apparatus, and more particularly to a video signal recording / reproducing apparatus for recording a video signal on a recording medium such as a magnetic disk or reproducing the recorded video signal. Regarding

[0002]

2. Description of the Related Art Conventionally, there has been known a video signal recording / reproducing apparatus for recording a video signal on a recording medium such as a magnetic disk and reproducing the video signal recorded on the recording medium.
In a recording / reproducing apparatus using a magnetic disk or the like, a signal obtained by subjecting a luminance signal (including a synchronization signal) and a color difference signal to FM modulation or the like is recorded on the magnetic disk.

[0003]

As described above, in the case of recording / reproducing a video signal on / from a recording medium such as a magnetic disk, a drive device for rotating the disk may cause jitter. This fluctuation can occur both during signal recording and during signal reproduction.
For this reason, there is a problem that the signal at the time of recording is not faithfully reproduced. That is, there is a problem that fluctuation occurs in a reproduced video or an image flickers.

In view of the above circumstances, the present invention is a video signal recording / reproducing apparatus capable of faithfully reproducing a video signal at the time of recording, even if jitter occurs in the disk drive at the time of recording or reproducing the video signal. The purpose is to provide.

[0005]

In order to achieve the above object, in the video signal recording / reproducing apparatus of the present invention, a reference signal having a predetermined frequency is added to a video signal including a sync signal in correspondence with the sync signal. And a voltage setting means for setting the DC component of the video signal in a predetermined period including at least the period to which the reference signal is added to a value different from the voltage of the DC component before and after the signal. Recording means for recording the generated video signal on a recording medium, reading means for reading the video signal recorded on the recording medium, to which the reference signal is added, and separating only the reference signal from the video signal to which the reference signal is added. Based on the separating means, the detecting means for detecting the end of the predetermined period, and the frequency of the reference signal separated by the separating means, the predetermined writing period and the video signal corresponding to the end of the predetermined period are recorded. And writing the write means, reading means for reading the video signal written in the storage means at a predetermined timing is provided to means.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an example of a video signal recording / reproducing apparatus 200. In the video signal recording / reproducing apparatus 200 shown in the figure, a luminance signal Y and a color difference signal R
-Y and BY are recorded on the magnetic disk 70 via the signal recording processing circuit 50. The output from the signal recording processing circuit 50 is applied to the magnetic head 60 and recorded on the magnetic disk 70 which is rotated by a spindle motor 80 as a drive device. In FIG. 1, as an example, the luminance signal Y
The case where the Y + S signal obtained by adding the synchronization signal S is recorded is shown.

First, a Y + S signal is input to the sync signal separation circuit 10 from a camera unit (not shown). The sync signal separation circuit 10 separates the horizontal sync signal from the Y + S signal. The burst gate pulse generation circuit 20 outputs a pulse having a predetermined width (burst gate pulse) necessary for writing the reference signal at a predetermined timing delayed by a certain time from the separated horizontal synchronizing signal. A reference signal (burst signal) for jitter correction output from the clock generation circuit 40 and the above burst gate pulse are input to the burst gate circuit 30. As the burst signal, for example, a sine wave having a frequency of 455/2 times the frequency of the horizontal synchronizing signal is used. The burst gate circuit 30 is a circuit that allows a signal to pass only during a period when the burst gate pulse is ON. Therefore, the burst gate pulse is ON.
Reference signal (burst signal) only during the period
Is input to the adder 35. The adder 35 adds the reference signal (burst signal) to the Y + S signal.

In the video signal recording / reproducing apparatus according to the present invention, when reproducing a video signal of a still image recorded on a recording medium, the video information is temporarily stored in the memory based on the reproduction signal, and then the memory is stored. The video information is read from and output to the display device.
In this way, when writing information based on the reproduction signal to the memory, a start flag for indicating the position to start writing the signal (starting point of the horizontal effective period) is added to the reproduction signal, and the horizontal flag is detected by detecting the start flag. A method of detecting a period is known.

Therefore, in the recording / reproducing apparatus of FIG.
Further, based on the horizontal synchronizing signal and the clock from the clock generation circuit 40, the start flag generation circuit outputs the start flag at a predetermined timing delayed from the burst gate pulse, and the addition 47 adds the burst-added Y + S signal. Further, a start flag is further added to the signal, the Y signal recording processing circuit 50 performs processing such as FM modulation, and the magnetic head 60 records the data on the magnetic disk 70.

FIG. 3 shows the relationship between the video signal to which the burst signal and the start flag are added and the outputs of the burst gate pulse generating circuit 20 and the start flag generating circuit 42. The horizontal effective period of the video signal is set between the start flag and the next horizontal synchronizing signal.

When reproducing the video signal recorded on the magnetic disk 70, the signal recorded by the magnetic head 60 is read, demodulated by the Y signal reproduction processing circuit 90, and the A / D converter 130, It is sent to the synchronization signal separation circuit 100, the clock recovery PLL circuit 120, and the start flag detection circuit 102. The sync signal separation circuit 100 separates the horizontal sync signal from the input Y + S signal. The burst gate pulse generation circuit 110 outputs a burst gate pulse which is ON for a predetermined time necessary to extract the burst signal after a certain time delay from the separated horizontal synchronization signal. Clock reproduction PLL circuit 120
Generates a clock by extracting a burst signal from the Y + S signal based on the Y + S signal and the burst gate pulse recorded on the disk 70 and synchronizing the burst clock frequency with the burst. The clock generated here is a clock that is affected by jitter during recording / reproduction, and is not a constant frequency but a clock that fluctuates in synchronization with the read video signal. In other words, this clock contains jitter information.

The start flag detection circuit 102 detects a start flag from the reproduced Y + S signal. When the start flag is detected, the memory write signal generation circuit 1
As a result of 04, a memory write signal for permitting data writing to the memory 140 is output for a predetermined period (horizontal effective period). That is, the read video signal is a clock reproduction PL.
Based on the clock including the jitter information output from the L circuit 120, the A / D converter 1 is operated during the horizontal effective period.
The data is A / D converted by 30 and recorded in the memory 140. Therefore, the video information is written in the memory 140 based on the clock synchronized with the fluctuation of the video signal, and the influence of the jitter is absorbed at the time of writing to the memory.

The data once stored in the memory 140 is
The D / A is read from the memory 140 on the basis of a constant frequency clock output from the clock generation circuit 160.
It is converted into an analog signal by the converter 150, is combined with the synchronization signal generated by the synchronization signal generation circuit 170 based on the clock similarly output from the clock generation circuit 160, and is output to a display device or the like not shown.

In the video signal handled by the video signal recording / reproducing apparatus configured as described above, it is necessary to secure a period for adding the burst signal and a period for adding the start flag, so that the horizontal effective period is only that much. It gets shorter. Therefore, the present invention proposes an improved recording / reproducing apparatus shown in FIG.

FIG. 2 shows an improved recording / reproducing apparatus of the present invention. In FIG. 2, the same circuits as in FIG. 1 have the same reference numerals. In the embodiment of FIG. 2, an offset bias circuit 45 is provided without using the start flag generation circuit 42 of FIG. Offset bias circuit 45
The output of the burst gate pulse generation circuit 20 and the output of the clock generation circuit 40 are applied to the. The offset bias circuit 45 counts the clock of the clock generation circuit 40 so that at least the burst gate pulse becomes O.
The bias voltage is added to the Y + S signal via the adder 47 for a predetermined period including the period of N. That is,
While the burst gate pulse is ON by the burst gate circuit 30, the output from the clock generation circuit 40 is added by the adder 35.
Is added to the Y + S signal, and at the same time, the DC level of the added bias voltage is increased.

The Y + S signal added with the burst signal of high DC level is FM-modulated by the Y-signal recording processing circuit and recorded on the magnetic disk 70 by the magnetic head 60, as in the recording / reproducing apparatus of FIG. .

FIG. 4 is a timing chart showing the relationship between the burst gate pulse and the Y + S signal to which the burst signal of high DC level is added as described above.

In FIG. 2, when reproducing the video signal recorded on the magnetic disk 70, the magnetic head 60 is used.
After demodulating the video signal read by the Y signal reproduction processing circuit 90, the synchronization signal separation circuit 100 and the clock reproduction P
The demodulated signal is input to the LL circuit 120 and the burst offset bias trailing edge detection circuit 105. The burst offset bias trailing edge detection circuit 105 replaces the start flag detection circuit 102 of FIG. 1 and detects the fall of the DC component of the burst signal shown in FIG. That is, the same effect as the start flag is obtained by the DC component of the burst signal. As in the case of FIG. 1, the video information is written in the memory 140 during the horizontal effective period based on the output signal of the memory write signal generation circuit 108 which is output by using the detection of the trailing edge of the burst offset bias as a trigger. Is.

FIG. 5 is a block diagram of the clock recovery PLL circuit 120. In the PLL circuit 120, the disk 7
The Y + S signal read from 0 and the burst gate pulse are input. Similar to the case of generating the burst gate pulse (by the sync signal separation circuit 10 and the burst gate pulse generation circuit 20) at the time of recording, the sync signal S in the Y + S signal is separated by the sync signal separation circuit 100 and burst The gate pulse generation circuit 110 generates a burst gate pulse having a predetermined timing and a predetermined pulse width based on the synchronization signal. The timing of the burst gate pulse generated here is the same as that of the burst gate pulse at the time of recording shown in FIG.

The burst extraction circuit 121 extracts a burst component from the Y + S signal based on the burst gate pulse. This burst component and the output of the voltage controlled oscillator (VCO) 124 are input to the frequency divider 1 to the phase comparator 122.
By inputting the signal divided into 1 / N by 25, the phase comparator 122, the low-pass filter 123, the VC
A reproduced clock frequency output locked to the burst signal is obtained by the PLL loop (phase locked loop) including the O124 and the N frequency divider 125. When there is no burst signal output from the burst extraction circuit, the phase comparator 1
If the phases are compared by 22, the clocks will be greatly deviated. Therefore, in the present invention, the burst gate pulse is also input to the phase comparator 122 so that the phases are compared only when the burst is extracted.

In this way, the writing to the memory 140 is performed based on the reproduction clock locked to the burst signal, so that the memory 140 stores a signal that faithfully reproduces the video signal at the time of recording. become.

[0023]

As described above, according to the present invention, by adding the burst signal, the fluctuation of the video signal due to the jitter is corrected, and further, the direct current level of the burst signal is increased to start the writing to the memory. By composing the start flag that indicates the time (horizontal effective period) with the burst signal, it is possible to faithfully reproduce the video signal at the time of recording, and the signal output for the start flag that was necessary in the past. Since the period can be omitted and the horizontal effective period is long, it is possible to obtain higher quality playback video.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating signal processing of a video signal recording / reproducing apparatus which is a basis of the present invention.

FIG. 2 is a block diagram showing an improved video signal recording / reproducing apparatus of the present invention.

3 is a timing chart showing a relationship among a video signal, a burst gate pulse, and a start flag handled by the device shown in FIG.

FIG. 4 is a timing chart showing a relationship among a video signal, a burst gate pulse and a start flag handled by the improved video signal recording / reproducing apparatus of the present invention.

FIG. 5 is a block diagram of a clock recovery PLL circuit.

[Explanation of symbols]

 20 burst gate pulse generation circuit 45 offset bias application circuit 105 burst offset bias trailing edge detection circuit 110 burst gate pulse generation circuit 120 clock recovery PLL circuit 160 clock generation circuit

Claims (3)

[Claims] 1. A signal adding means for adding a reference signal having a predetermined frequency to a video signal containing a sync signal, the video having a predetermined period including at least a period in which the reference signal is added. Voltage setting means for setting the direct current component of the signal to a value different from the voltage of the direct current component before and after the direct current component, recording means for recording the video signal to which the reference signal is added on a recording medium, and recording on the recording medium Read means for reading the video signal added with the reference signal, separation means for separating only the reference signal from the video signal added with the reference signal, and detection means for detecting the end of the predetermined period. Writing means for writing the video signal in the storage means for a predetermined writing period corresponding to the end of the predetermined period based on the frequency of the reference signal separated by the separating means; Having a reading means for reading the written video signal at a predetermined timing in a storage means, a video signal recording and reproducing apparatus. 2. A signal adding means for adding a reference signal of a predetermined frequency corresponding to the synchronizing signal to the video signal containing the synchronizing signal, and a video signal of a predetermined period including at least a period in which the reference signal is added. A video signal recording device, comprising: a voltage setting means for setting the DC component of the DC component to a value different from the voltage of the DC component before and after the DC component; and a recording means for recording the video signal to which the reference signal is added on a recording medium. apparatus. 3. A video signal recorded on a recording medium in which a reference signal of a predetermined frequency having a predetermined DC component is added to a video signal containing a synchronization signal for a predetermined period in response to the synchronization signal. A reading unit, a separating unit that separates only the reference signal from the video signal to which the reference signal is added, a detecting unit that detects the end of the predetermined period, and a frequency of the reference signal that is separated by the separating unit. A writing unit that writes the video signal in a storage unit for a predetermined writing period corresponding to the end of the predetermined period; and a reading unit that reads out the video signal written in the storage unit at a predetermined timing. Video signal playback device.