JPS6313588A - Signal processing circuit for video signal recording and reproducing device - Google Patents

Abstract

PURPOSE:To insure noise against affecting a screen when a vertical emphasis circuit is loaded by providing a blanking processing circuit maintaining the level of a video signal in a blanking period at a prescribed blanking level. CONSTITUTION:The blanking processing circuit 9 processes an input video signal A so that said signal can be held at a fixed level during vertical and horizontal blanking periods, and a vertical emphasis circuit 10 further processes said signal A. Again a blanking processing circuit 11 processes said signal so as to maintain the vertical blanking period, FM-modulates and records the signal on a disk 1. A reproduction signal is FM-demodulated. A blanking processing circuit 23 processes a signal F including noise arising during a jump period or an address period, while a vertical deemphasis circuit 24 processes a signal G excluding noise. A blanking processing circuit 25 serves as eliminating the restoration error of vertical deemphasis.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention applies a vertical emphasis circuit to a video signal recording/reproducing device such as an optical video disk recorder that may generate large noise during the vertical retrace period of a reproduced signal. The present invention relates to a signal processing circuit for a video signal recording and reproducing device suitable for recording and reproducing video with a good signal-to-noise ratio.

[Prior Art] The characteristics of an optical video disc recorder will be explained as an example of a conventional video signal recording device.

FIG. 2 shows the appearance of a disc 1 used in a conventional optical video disc recorder. Concentric or spiral guide grooves are previously provided on the disk 1, and video signals are recorded along the guide grooves.

Further, an address recording area 32 is provided on the disk, and an address is assigned to each guide groove by, for example, discontinuing the guide grooves in correspondence with address information. If the rotation period of the disk is precisely selected to correspond to the period of one frame of the video signal, an address corresponding to each frame of the video will be assigned, so the address can be used as a key for searching the video signal. Furthermore, when reproducing a video signal along a spiral guide groove, in addition to being able to play back a moving image, it is possible to make the focusing position of the laser beam jump to the previous guide groove once per revolution. Still images of frames can be played back. Still images and moving images can be reproduced in the same manner using concentric guide grooves.

Incidentally, one of the factors that determines the quality of a video signal reproduced from a disc is the amount of noise in the video signal. As a conventional method for reducing noise contained in video signals, there is a vertical emphasis circuit that focuses on the vertical correlation of video signals. An example of a vertical emphasis circuit is shown in Japanese Patent Laid-Open No. 144288/1983. For example, as shown in FIG. 3, FIG. 4(A) shows the signal level along a vertical line on a screen where the center of the screen is black and the surrounding area is surrounded by white. The vertical emphasis circuit has the function of emphasizing uncorrelated parts in the vertical direction of the screen, and outputs a signal at a level as shown in FIG. 4(B) in response to an input as shown in FIG. 4(A).

During playback, a vertical de-emphasis circuit with characteristics that suppresses uncorrelated parts in the vertical direction is provided to cancel out the characteristics of the vertical emphasis circuit.
) is restored as shown in (A) of the same figure. As a result, components of noise included in the reproduced signal that have no correlation in the vertical direction are suppressed, so that the S/N of the reproduced video signal can be improved.

Vertical emphasis has similar effects not only in optical video disk recorders but also in video tape recorders and other video signal recording and reproducing devices.

[Problem that the invention seeks to solve]

The vertical emphasis circuit described above does not take into consideration the occurrence of large noise during the vertical retrace period of the video signal. There was a problem in that the generated noise caused interference on the screen.

FIG. 5(A) shows the portions before and after the jump period of a waveform obtained by F-scale demodulation of the signal reproduced from the disk. During the jump period, the laser beam moves to the adjacent guide groove, so the reproduced 1'M signal is interrupted, and a large level of noise appears in the demodulator output as shown in the figure. Therefore, in conventional optical video disc players, a jump period is provided within the video pause period or within the overscan period to prevent noise from appearing on the playback screen.

Similarly, regarding the address signal period, in order to prevent the address signal from interfering with the reproduction screen, the signal is recorded so that the address falls within the vertical retrace period or the overscan period of the video signal.

However, when a signal with a waveform as shown in FIG. 5(A) is processed by a vertical de-emphasis circuit, the response becomes as shown in FIG. 5(B). The vertical de-emphasis circuit acts as a kind of low-pass filter on the spatial frequency of the video signal in the vertical direction, and has a time constant of transient response to the pulse signal. Therefore, when a large level of noise is instantaneously applied as shown in FIG. 5(A), it takes time for the response of the vertical de-emphasis circuit to the noise to settle to a value sufficiently close to zero. In particular, since the level of noise during jump and address periods is high, the response to the noise is not sufficiently attenuated during the deferred retrace period, causing a problem such as flicker disturbance at the top of the screen.

This problem is not limited to optical video disc players.
Head switching noise also occurs in video tape recorders.

An object of the present invention is to prevent the noise from affecting the screen when a vertical emphasis circuit is installed in a video signal recording and reproducing device that may generate noise in the vertical retrace period or overscan area. That's true.

[Means for solving problems]

In order to achieve the above object, the present invention attempts to record on a recording medium. Or the period that is the sum of the vertical blanking period and overscan period of the video signal reproduced from the recording medium,
That is, a blanking period is determined within a period in which the screen is not displayed on the monitor screen.

A blanking processing circuit for maintaining the video signal level at a predetermined blanking level during the blanking period is installed before each of the vertical emphasis circuit of the recording signal processing system and the vertical de-emphasis circuit of the reproduction signal processing system. establish.

[Effect]

Playback 7 installed before the vertical de-emphasis circuit
- The side blanking processing circuit has the function of preventing noise present in the blanking period, such as jump and address period noise in an optical video disk recorder, and head switching noise in a video tape recorder, from being input to the vertical de-emphasis circuit. Motsu. Therefore, it is possible to prevent the noise from affecting the upper part of the reproduction screen due to the transient response of the vertical de-emphasis circuit.

On the other hand, the reason why a blanking processing circuit is provided on the recording side is as follows.

For example, if the input video signal during recording has information before the end of the predetermined blanking period, if blanking processing is provided only on the playback side, the information of the blanking period will be lost, so The video signal cannot be restored correctly by de-emphasis. Therefore, even if information exists during the blanking period, the blanking process on the recording side prevents this information from being involved in the vertical emphasis operation, and prevents the vertical de-emphasis from malfunctioning after the blanking process on the playback side.・I can prevent it from happening.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows a construction method when the present invention is applied to an optical video disc player.

The video signal input from the terminal 30 is converted into a digital signal by the AD converter 8, and then sent to the blanking processing circuit 9 and the screen emphasis circuit 10. Blanking processing circuit 1
1, which have undergone respective processing, are restored to analog signals by a DA converter 12. Adding a synchronization signal and a burst signal to the analog signal in an adder 13;
After the signal is subjected to li'M modulation in the FM modulator 14, intensity-modulated laser light is irradiated from the semiconductor laser 3 according to a signal applied to the laser drive circuit 15.

The laser beam passes through a collimating lens 4, an 8-7 mirror 5, and an objective lens 6, and is focused on a predetermined position on the disk 1, thereby recording information.

During reproduction, the photodiode 7 detects the reflected light when a certain amount of laser light is irradiated from the semiconductor laser 3 and reads information. The reproduced signal is amplified by a preamplifier 29, FM demodulated by a 2M demodulator 2o, and converted into a digital signal by an AD converter 21. The digital signal is processed by a time pace corrector ('FBC) 22 to remove fluctuations (jitter) on the time axis, and then sent to a blanking processing circuit 2.
5. The vertical de-emphasis circuit 24 and the blanking processing circuit 25 process the signal in this order, and the DA converter 26 restores it to an analog signal. The analog signal is outputted from a terminal 31 after adding a synchronization signal and a burst in an adder 27 .

On the other hand, the synchronizing signal is separated from the signal input from the terminal 30 in the synchronizing signal separation circuit 16, and the adders 13 and 27
The synchronizing signal is also supplied as a reference to the vertical blanking gate generating circuit 17 and the horizontal blanking gate generating circuit 18. Further, the reference synchronization signal of the burst generation circuit 19 is also separated by the synchronization signal separation circuit 16.

In addition, the average amount of reflected light on the surface of the disk 1 is observed using a photocoupler (not shown), the timing at which the address portion passes over the photocoupler is captured, and the motor control circuit 28 compares this timing with the phase of the synchronization signal. The rotation of the motor 2 is controlled so that the period falls within a predetermined position within the blanking period.

Figure 6 shows the signal waveform of the numbered part in Figure 1.
The symbols A) to (J) correspond to each other in both figures. However, portions where the signal is digitized are shown on the assumption that the signal is converted to analog according to the digital signal value of that portion. (A) is an input video signal, and the portion indicated by the arrow in FIG. 6 is processed as a vertical blanking period. The input video signal (A) is processed in the blanking processing circuit 9 so as to maintain a constant level during the vertical blanking period and the horizontal retrace period, resulting in a level as shown in FIG. 6(B). Next, the signal in (B) is subjected to a vertical enhancement circuit 10 in which the high-frequency component in the spatial frequency in the vertical direction of the screen is emphasized, and the signal is expressed as (
The signal shown in C) will be generated.

After that, in the blanking processing circuit 11 again, 1
1. Signal (D) is obtained by processing to maintain the vertical blanking period. A signal (E) obtained by adding a synchronization signal and a burst to the signal (D) by an adder 12 is recorded on the disk 1 by FM modulation.

FIG. 6 (F') is a waveform obtained by FU demodulating the signal reproduced from the disk, and includes noise generated in the jump period and address period. This signal (F') is processed by a blanking processing circuit 23 to obtain a noise-free signal as shown in (G). If the signal (G) is processed by the vertical de-emphasis circuit 24, it will become a signal as shown in (I()).If the signal (G) is compared with the signal (C), it will be found that the beginning of the blanking period is due to the blanking process. The portion protruding below the blanking level is missing, and as a result, in (H), a vertical de-emphasis restoration error occurs at the beginning of the vertical blanking period.

The blanking processing circuit 25 has the function of eliminating the above-mentioned restoration error, and its output waveform becomes as shown in (I).

A synchronizing signal and a burst are added to the signal (I) by an adder 27, and the vertical blanking period 12 is added as shown in (J).
- Play and output a waveform that is the same as the input except for the length between the two.

As described above, according to this embodiment, since the signal reproduced from the disk is subjected to vertical blanking processing and then vertical de-emphasis, large-amplitude noise that occurs during jumps and address periods is stretched out and reproduced. There is no interference on the screen. Further, since vertical blanking processing is performed in advance during signal recording, a video signal having a vertical blanking period with a timing different from the vertical blanking according to the present invention is received from an external signal source as shown in FIG. 6(A), for example. Even if input, information on the leading edge of the video signal will not be lost during blanking processing on the playback side and a restoration error due to vertical de-emphasis will not occur.

Further, after performing vertical emphasis or de-emphasis, a synchronization signal is added after a blanking process is performed, so that no distortion occurs in the vertical synchronization signal portion.

Further, even if the adder 13 adds a coded information signal or the like during the vertical retrace period and records it on the disk, it does not affect the vertical de-emphasis at all.

FIG. 7 shows a detailed configuration method of the blanking processing circuit. Digital data of a video signal is added to one input of the data selector 34, which has two inputs and one output, and data representing a blanking level is added to the other input. The OR circuit 33 calculates the logical sum of the vertical and horizontal gate signals and applies it to the select input terminal of the data selector, so that the blanking level is output during the blanking period, and the video signal data is output during the other periods.

Figure 1118 shows another method of configuring the blanking processing circuit. In this way, two sets of 3-state buffers 35 and 56 are used, and gate signals of opposite levels are applied to each control input. Good too.

Further, the blanking processing circuit can be configured to switch between the video signal and the DC voltage in an analog manner. In this case, the configuration shown in Figure 1 is
Changes are made so that the positions of the AD converter or DA converter and the blanking processing circuit are exchanged.

FIG. 9 shows the detailed configuration of the vertical emphasis circuit. A comb filter consisting of adders 37 and 41, coefficient units 59, 40 and 42, and 1H delay circuit 38 extracts high frequency components in the vertical spatial frequency of the video signal. Performs vertical emphasis processing in addition to the signal. The circuit of FIG. 10 also has the advantage that by choosing the sign of the coefficient of coefficient multiplier 42 to be negative,
It can also be used as a vertical de-emphasis circuit.

FIG. 10 shows another method of configuring the vertical emphasis circuit or vertical de-emphasis circuit.

In the figure, the same parts as in FIG. 9 are indicated by the same reference numerals. Adder 4
A switch 44 is provided on the output side of S, and is configured to directly lead the input signal to the output side during the vertical blanking period. This allows vertical emphasis or de-emphasis to be applied during the vertical blanking period.
15. It becomes possible to stop the operation of the system.

Further, FIG. 11 shows another method of configuring the vertical emphasis or vertical de-emphasis circuit. fs
The difference from the circuit shown in FIG. 9 is that a switch 44 is provided on the output side of the coefficient multiplier 42, and the vertical blanking gate signal is used to switch between the output of the coefficient multiplier 42 and a zero level signal. The same parts in FIG. 11 as in FIG. 10 are given the same reference numerals. The configuration shown in FIG. 11 also makes it possible to stop vertical emphasis or vertical de-emphasis processing during the vertical blanking period. Therefore, if the circuit of FIG. 10 or 11 is used as a vertical emphasis circuit, the signal of FIG.
The signal D) can be obtained as a vertical emphasis output. Therefore, the blanking processing circuit 11 shown in FIG. 1 becomes unnecessary.

Furthermore, if the circuit of FIG. 10 or 11 is used as a vertical de-emphasis circuit, the signal (I) can be obtained directly from the signal shown in FIG. 6(G). Therefore, the blanking processing circuit shown in figure W11 becomes unnecessary.

・16・ As described above, if the circuit shown in FIG. 10 or 11 is used, the output of the vertical emphasis circuit or vertical de-emphasis circuit will be at the level of - during the vertical blanking period, and when the synchronization signal is added, the vertical synchronization will be achieved. No distortion occurs in the part.

Figure 12 shows an example of how to configure a vertical blanking gate generation circuit, in which two monostable multi-45
and 46. FIG. 13 is a timing chart of the circuit of FIG. 12. In Figures 12 and 15 (a)
The symbols in (b) match each other. monostable multi 45
and 46 output pulse widths III, , III, respectively.
2, apply the vertical synchronizing signal (vn) to the trigger input of the monostable multi 45, and obtain the vertical blanking gate signal at the inverting output terminal Q of the monostable multi f-46.

FIG. 14 shows another method of configuring the vertical blanking gate generation circuit, and FIG. 15 is a timing chart thereof. The symbols (0) to (t) correspond to each other. The counter 47 reset by VD counts the number of rising edges of the horizontal synchronizing signal (HD), and when the value exceeds nl, the output output of the comparator 48 becomes IH, #, and when the value exceeds n2, the output of the comparator 49 The force becomes H11. Therefore, AND
A vertical blanking gate signal can be taken at the output of circuit 50.

Note that the horizontal blanking gate generation circuit may be the circuit shown in FIG. 12 or 14, and HD may be used instead of vD, and a higher frequency clock such as a sampling clock of an AD converter may be used instead of HD.

In the embodiment shown in FIG. 1, the input video signal is used as a synchronization reference during playback, but a reference synchronization signal generator may be provided instead, and this may also be used as a synchronization reference during playback.

Furthermore, depending on the external device connected to the input side, a video signal without a synchronization signal and a synchronization signal may be input separately. In this case, the synchronization signal separation circuit 16 may simply distinguish between the vertical synchronization signal and the horizontal synchronization signal of the input synchronization signal.

Similarly, if a device connected to the output side requires a video signal and a synchronization signal separately, the adder 27 can be omitted and the video signal and synchronization signal can be output independently. Further, in this case, even if the blanking processing circuit 25 is not particularly provided, no problem will occur on the playback screen.

Although the above description has been made by taking an optical video disk player as an example of a video signal recording/reproducing device, it goes without saying that the present invention can also be applied to a video tape recorder and the like.

〔Effect of the invention〕

As described above, according to the present invention, in a video signal recording and reproducing apparatus that generates noise during the vertical blanking period, such as jump or address period noise in an optical video disk recorder or head switching noise in a video tape recorder, A vertical emphasis circuit can be mounted without being affected by noise, and the SN ratio of the reproduced video signal can be improved.

[Brief explanation of the drawing]

Fig. 2 is a block diagram showing an optical video disc recorder as an embodiment of the present invention, Fig. 2 is a plan view showing the external appearance of the disc, and Fig. 3 is a front view of the screen for explaining the operation of vertical emphasis. , Fig. 4 is a signal voltage waveform diagram on the line segment E of the screen in Fig. 5, Fig. 1185 is a reproduction signal voltage waveform diagram in a conventional optical video disc recorder, and Fig. 6 is a signal voltage waveform at each part of the first part. Figure 7 is the first
A circuit diagram showing the configuration of the blanking processing circuit in the figure,
FIG. 8 is a circuit diagram showing another configuration of the blanking processing circuit, FIG. 9 is a block diagram showing the configuration of the vertical emphasis circuit or vertical de-emphasis circuit in FIG. 1, and FIG. FIG. 11 is a block diagram showing another configuration of the vertical emphasis circuit or vertical de-emphasis circuit, and FIG. 12 is a block diagram showing the configuration of the vertical blanking gate generation circuit in FIG. 1. 13 is an operation timing chart of the circuit shown in FIG. 12, FIG. 14 is a circuit diagram showing another configuration of the vertical blanking gate generation circuit, and FIG. 15 is a timing chart of the circuit shown in FIG. 14. be. Explanation of symbols 1...Disk, 9...Blanking processing circuit, 1
0... Vertical emphasis circuit, 11... Blanking processing circuit, 14... FM modulator, 17... Vertical blanking gate generation circuit, 20... FM demodulator, 2
3...Blanking processing circuit, 24...Vertical de-emphasis circuit, 25...Blanking processing circuit.

Claims (1)

[Claims] 1. A vertical emphasis circuit that emphasizes high-frequency components of an input video signal in a spatial frequency in the vertical direction of the screen and outputs it as a recording signal to a recording medium; In a signal processing circuit of a video signal recording and reproducing device, the signal processing circuit includes a vertical de-emphasis circuit that restores the original video signal by canceling out the portion emphasized by the vertical emphasis circuit, the input video signal to be recorded on the recording medium or Detecting that it is in a predetermined period of a combined period of a vertical blanking period of a video signal reproduced from the recording medium and an overscan period that is not displayed on the screen, and indicating that it is in the period. a vertical blanking gate generation circuit that generates a vertical blanking gate pulse as a signal; and a first block that maintains the level of the video signal input to the vertical emphasis circuit at a predetermined blanking level during the vertical blanking period. A video image characterized by being provided with a ranking processing circuit and a second blanking processing circuit that maintains the level of the reproduced video signal input to the vertical de-emphasis circuit at a predetermined blanking level during the vertical blanking period. Signal processing circuit for signal recording and reproducing equipment. 2. In the signal processing circuit of the video signal recording and reproducing apparatus according to claim 1, during the vertical blanking period, the level of the video signal output from the vertical emphasis circuit is set to a predetermined blanking level. and a fourth blanking processing circuit that maintains the level of the video signal output from the vertical de-emphasis circuit at a predetermined blanking level during the vertical blanking period. A signal processing circuit for a video signal recording and reproducing device, characterized in that: 3. In the signal processing circuit of the video signal recording and reproducing apparatus according to claim 1, during the droop blanking period, the vertical emphasis circuit stops its emphasis processing, and the vertical emphasis circuit stops its emphasis processing. The input is led as is to the output of the vertical emphasis circuit, and during the vertical blanking period, the de-emphasis process is stopped in the vertical de-emphasis circuit, and the input of the vertical de-emphasis circuit is directly passed to the output of the vertical de-emphasis circuit. 1. A signal processing circuit for a video signal recording and reproducing apparatus, characterized in that the vertical emphasis circuit and the vertical de-emphasis circuit are configured to lead to an output.