JP3260172B2 - Video signal recording and playback device - Google Patents

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. About.

[0002]

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

[0003]

As described above, in a device for recording / reproducing a video signal on a recording medium such as a magnetic disk, jitter (fluctuation) may occur in a driving device for rotating the disk. This fluctuation can occur at the time of signal recording and at the time of reproduction.
For this reason, there is a problem that a signal at the time of recording is not faithfully reproduced. That is, there is a problem that the reproduced video fluctuates or the image flickers.

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

[0005]

In order to achieve the above object, in a video signal recording / reproducing apparatus according to the present invention, a reference signal having a predetermined frequency is added to a video signal including a synchronization signal in accordance with the synchronization signal. Voltage setting means for setting a DC component of a video signal for a predetermined period including at least a period in which a reference signal is added to a value different from voltages of DC components before and after the video signal; Recording means for recording the recorded video signal on a recording medium, reading means for reading the video signal to which the reference signal has been added recorded on the recording medium, and separating only the reference signal from the video signal to which the reference signal has been added. Separating means, detecting means for detecting the end of the predetermined period, and recording the video signal 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. 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]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

FIG. 1 is a block diagram showing an example of a video signal recording / reproducing apparatus 200. In the illustrated video signal recording / reproducing apparatus 200, a luminance signal Y and a chrominance signal R
−Y and BY are recorded on the magnetic disk 70 via the signal recording processing circuit 50. An output from the signal recording processing circuit 50 is applied to the magnetic head 60, and is recorded on a magnetic disk 70 that is rotationally driven by a spindle motor 80 as a driving device. In FIG. 1, the luminance signal Y is used as an example.
5 shows a case in which a Y + S signal obtained by adding a synchronization signal S to a Y signal is recorded.

First, a Y + S signal is input to a synchronization signal separation circuit 10 from a camera unit (not shown). The synchronization signal separation circuit 10 separates a horizontal synchronization signal from the Y + S signal. The burst gate pulse generation circuit 20 outputs a pulse (burst gate pulse) having a predetermined width required for writing the reference signal at a predetermined timing delayed by a certain time from the separated horizontal synchronization signal. The burst gate circuit 30 receives a reference signal (burst signal) for jitter correction output from the clock generation circuit 40 and the burst gate pulse. As the burst signal, for example, a sine wave having a frequency of 455/2 times the frequency of the horizontal synchronization signal is used. The burst gate circuit 30 is a circuit that allows a signal to pass only while the burst gate pulse is ON.
The reference signal (burst signal) only during the period
Is input to the adder 35. The adder 35 adds a 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 reproduced signal, and then the memory is stored in the memory. The method employs a method of reading video information from a computer and outputting it to a display device.
As described above, when writing information based on a reproduction signal to the memory, a start flag for indicating a position at which the signal is to be written (a start point of a horizontal valid period) is added to the reproduction signal, and the horizontal flag is detected by detecting the start flag. A method for detecting a period is known.

Therefore, in the recording / reproducing apparatus shown in FIG.
Further, based on the horizontal synchronization signal and the clock from the clock generation circuit 40, the start flag generation circuit 42
A start flag is output at a predetermined timing delayed from the burst gate pulse, a start flag is further added to the Y + S signal to which the burst is added by the adder 47, and a process such as FM modulation is performed by the Y signal recording processing circuit 50. Then, the data is recorded on the magnetic disk 70 by the magnetic head 60.

FIG. 3 shows the relationship between the burst signal and the video signal to which the start flag is added, and the outputs of the burst gate pulse generation circuit 20 and the start flag generation circuit 42. The horizontal valid period of the video signal is set between the start flag and the next horizontal synchronization signal.

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

A 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, a memory write signal permitting data writing to the memory 140 is output for a predetermined period (horizontal valid period). That is, the read video signal is the clock reproduction PL.
During the horizontal effective period, the A / D converter 1 based on the clock including the jitter information output from the L circuit 120
The A / D conversion is performed by the A / D converter 30 and recorded in the memory 140. Therefore, the video information is written to 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 data is read out from the memory 140 based on a constant frequency clock output from the clock generation circuit 160, and the D / A
The signal is converted into an analog signal by the converter 150, is combined with a 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 in which a burst signal is added and a period in which a start flag is added. It will be shorter. Therefore, the present invention proposes an improved recording / reproducing apparatus shown in FIG.

FIG. 2 shows an improved recording and reproducing apparatus according to the present invention. 2, the same circuits as those in FIG. 1 are denoted by 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. The offset bias circuit 45 counts the clock of the clock generation circuit 40, and when at least the burst gate pulse
A bias voltage is added to the Y + S signal via the adder 47 for a predetermined time including the N period. 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 to the adder 35.
As a result, the DC level of the burst signal is increased at the same time as being added to the Y + S signal.

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

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

In FIG. 2, when reproducing a video signal recorded on a magnetic disk 70, a magnetic head 60 is used.
After the video signal read by the Y signal is demodulated 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 falling of the DC component of the burst signal shown in FIG. That is, the effect equivalent to that of the start flag is obtained by the DC component of the burst signal. The video information is written into the memory 140 during the horizontal effective period based on the output signal of the memory write signal generation circuit 108, which is output triggered by detection of the trailing edge of the burst offset bias, as in FIG. It is.

FIG. 5 is a block diagram of the clock recovery PLL circuit 120. The PLL circuit 120 includes a disk 7
A Y + S signal read from 0 and a burst gate pulse are input. In the same manner as in the case of the generation of the burst gate pulse (by the synchronization signal separation circuit 10 and the burst gate pulse generation circuit 20) at the time of recording, the synchronization signal S in the Y + S signal is separated by the synchronization signal separation circuit 100, and the 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.

A burst component is extracted from the Y + S signal by a burst extraction circuit 121 based on the burst gate pulse. The burst component and the output of the voltage controlled oscillator (VCO) 124 are supplied to the phase comparator 122 by the frequency divider 1.
By inputting the signal divided by 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 a PLL loop (phase locked loop) including the O 124 and the N frequency divider 125. When there is no burst signal output from the burst extraction circuit, the phase comparator 1
If the comparison of the phases by 22 is performed, the clock is greatly shifted. For this reason, in the present invention, a burst gate pulse is also input to the phase comparator 122, and the phase comparison is performed only at the time of burst extraction.

As described above, since the writing to the memory 140 is performed based on the reproduction clock locked to the burst signal, the memory 140 stores a signal obtained by faithfully reproducing the video signal at the time of recording. become.

[0023]

As described above, according to the present invention, by adding a burst signal, the fluctuation of the video signal due to jitter is corrected, and the DC level of the burst signal is further increased to start writing to the memory. The start flag indicating the timing (horizontal effective period) is superimposed on the burst signal, so that the video signal at the time of recording can be faithfully reproduced, and the signal output for the start flag which was conventionally required The period can be omitted, and by making the horizontal effective period longer, it is possible to obtain higher quality reproduced video.

[Brief description of the drawings]

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

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

FIG. 3 is a timing chart showing a relationship among a video signal, a burst gate pulse, and a start flag handled in the device of FIG. 1;

FIG. 4 is a timing chart showing a relationship between 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]

 Reference Signs List 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 regeneration PLL circuit 160 clock generation circuit

Claims (2)

(57) [Claims] 1. A signal adding means for adding a reference signal having a predetermined frequency to a video signal including a synchronization signal in accordance with the synchronization signal, and a video for a predetermined period including at least a period during which the reference signal is added. A voltage setting unit that sets a DC component of a signal to a value different from a voltage of a DC component before and after the signal, a recording unit that records a video signal to which the reference signal is added on a recording medium, and recording on the recording medium. Reading means for reading the video signal to which the reference signal has been added, separating means for separating only the reference signal from the video signal to which the reference signal has been added, and detection means for detecting the end of the predetermined period. Writing means for writing the video signal into 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 separation 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 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 including a synchronization signal for a predetermined period in correspondence with the synchronization signal. Reading means, separating means for separating only the reference signal from the video signal to which the reference signal is added, detecting means for detecting the end of the predetermined period, and based on the frequency of the reference signal separated by the separating means A predetermined writing period corresponding to the end of the predetermined period, a writing unit that writes the video signal to a storage unit, and a reading unit that reads out the video signal written to the storage unit at a predetermined timing. Video signal playback device.