JPH04260289A - Video signal processing unit - Google Patents

Abstract

PURPOSE:To always obtain an excellent picture by providing a means adjusting automatically picture quality suitably based on plural sets of picture information representing S/N and lightness of a pattern with respect to a reproduction signal, a recording signal and an EE signal to the video signal processing unit for home use VTR or the like. CONSTITUTION:An average picture potential (APL) detector 13 detects APL information and an S/N detector 14 detect S/N information respectively from a video luminance signal outputted from a low pass filter(LPF) 9. A voltage controlled variable clip circuit 15 applies suitably arithmetic processing two sets of information and a picture quality adjustment circuit 10 implements optimum control by the result of calculation. Since the optimum picture quality adjustment is automatically implemented at all times depending on the state of the picture on each occasion, the user easily enjoys an excellent picture.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing apparatus, such as a video tape recorder (hereinafter abbreviated as VTR), which is equipped with an image quality adjustment means for automatically adjusting the image quality in a suitable manner.

0002

[Prior Art] As a prior art related to the present invention, "Video Technology Handbook" Monthly Audio Video
As described on pages 73 to 87 of the editorial department, a home VTR is an example. A brief explanation will be given below using FIGS. 15 and 16. To simplify the explanation, a case of VHS system compatible with NTSC signals will be taken as an example.

FIG. 15 is a block diagram of an example of a conventional home VTR playback system. In the figure, an FM brightness signal and a low-frequency color signal recorded on a magnetic tape 1 are detected by a magnetic head 2, amplified by a reproduction amplifier 3, and then passed through a low-pass filter (hereinafter abbreviated as LPF) 4 and a high-frequency signal. The signal is input to a pass filter (hereinafter abbreviated as HPF) 7. The LPF 4 selectively passes only the low-frequency color signal that spreads around 629 kHz, and the frequency converter 5 and band-pass filter (hereinafter abbreviated as BPF) 6 convert it into a high-frequency color signal centered on 3.58 MHz. After that, it is input to the adder 11. On the other hand, HPF
7, only the FM luminance signal whose carrier frequency is set to 3.4MHz to 4.4MHz is selectively passed through.
After being demodulated into a video luminance signal by the M demodulator 8 and LPF 9, it is input to the image quality adjustment circuit 10. The image quality adjustment circuit 10 has a function of reducing noise in a reproduced image and emphasizing contour information by changing the gain versus frequency characteristic of an input signal. The output of the image quality adjustment circuit 10 is input to an adder 11, where it is added to the high-frequency color signal, and then outputted from a terminal 12 as a reproduced video signal. Here, the characteristics of the image quality adjustment circuit 10 are usually changed by voltage control. To use it, a switch or volume was installed on the front of the VTR to vary the control voltage, and the user manually adjusted it according to their preference.

FIG. 16 is a block diagram of an example of a conventional home VTR recording system. In the figure, terminal 16
The video signal input from BPF17, LPF20
and is input to terminal 27. The terminal 27 is an EE output terminal for monitoring the input signal, and the input video signal is output almost unchanged. Only the high frequency color signal centered at 3.58 MHz is selectively passed through the BPF 17, converted into a low frequency color signal by the frequency converter 18 and the LPF 19, and then input to the recording amplifier 23. On the other hand, only the video luminance signal is selectively passed through the LPF 20, and the FM modulator 21 and HPF 22
After being modulated into an FM luminance signal at the recording amplifier 23
is input. In the recording amplifier 23, the FM luminance signal and the low frequency chroma signal are superimposed and moderately amplified, and then
It is recorded on the magnetic tape 25 via the magnetic head 24. As mentioned above, no image quality adjustment function was provided for the EE output signal and recording signal.

[0005]

[Problems to be Solved by the Invention] In the above-mentioned conventional technology, the image quality adjustment for the playback signal was manually performed by the user, so in order to enjoy good image quality, it was necessary to adjust the image quality each time the playback tape was replaced. It was very troublesome because it was necessary to readjust the adjustment state to the optimum point in response to changes in the signal-to-noise ratio (hereinafter abbreviated as S/N) caused by the deterioration state of the tape. In addition, even during continuous playback of the same tape, the visibility of noise varies depending on the brightness of the playback screen, so the optimal image quality adjustment state changes depending on the scene, but it is not possible to follow this. It was extremely difficult to manually fine-tune the adjustment status. In addition, since there was no image quality adjustment means for recording signals and EE signals, depending on the S/N of the input signal and the brightness of the screen,
It was not possible to suitably adjust the image quality.

[0006] The present invention provides means for suitably automatically adjusting the image quality of a reproduction signal, a recording signal, or an EE signal based on a plurality of image information such as S/N and screen brightness. The purpose is to provide

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a circuit that suitably processes a plurality of image information such as S/N and screen brightness. This was achieved by appropriately controlling an image quality adjustment circuit inserted in the signal path using the calculated output.

[0008]

[Operation] The image quality is continuously adjusted automatically based on the image information at the time, so the user can
You can easily enjoy good image quality.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below by taking as an example a case in which the present invention is applied to a home VTR.

FIG. 1 is a block diagram of an example system in which the present invention is applied to a home VTR playback system. In the figure, a magnetic tape 1, a magnetic head 2, a reproduction amplifier 3,
LPF4, frequency converter 5, BPF6, HPF7, FM
The functions of the part consisting of the modulator 8, LPF 9, image quality adjustment circuit 10, adder 11, and terminal 12 are the same as those explained using FIG. 15 in the conventional example section, so the explanation will be omitted. Omitted.

The video luminance signal output from the LPF 9 is input to an APL detector 13 and an S/N detector 14. APL information output from the APL detector 13 and S
The S/N information output from the /N detector 14 is input to the voltage control variable clipping circuit 15 and suitably subjected to arithmetic processing, and then the image quality adjustment circuit 10 is controlled using the arithmetic output.

FIG. 3 is a block diagram of an example of the configuration of the S/N detector 14, and FIG. 4 is a waveform diagram of an example of changes in signals at each part in the block diagram of FIG. The operation of the S/N detector 14 will be explained using FIGS. 3 and 4. The video luminance signal output from the LPF 9 is inputted from the terminal 28 as a waveform shown in a, and after being amplified by the amplifier 29, is inputted to the gate circuit 30. terminal 3
1, a gate pulse having a waveform as shown in b is applied and input to the gate circuit 30. It is desirable that the gate pulse waveform b rises at a timing slightly later than the start position of the horizontal synchronizing signal period of the video luminance signal a, and falls at a timing slightly earlier than the end position. In the gate circuit 30, during the period when the gate pulse b is at a high level, the signal sent from the amplifier 29 passes through as is and is input to the filter 32, and during the period when the gate pulse b is at a low level, the signal sent from the amplifier 29 is input to the filter 32. The incoming signal is blocked and not sent to the filter 32. The pass band of the filter 32 is selected so as to selectively pass the noise component to be detected. Typically, HPF or BPF is used. Waveform c is the output of filter 32, is smoothed by smoothing circuit 33, becomes waveform d, and is input to sample-and-hold circuit 34. A sample hold pulse e is applied to the terminal 35 and input to the sample hold circuit 34. The sample-and-hold circuit 34 performs a sampling operation while the sample-and-hold pulse e is at a high level, and performs a holding operation while the sample-and-hold pulse e is at a low level. As a result, the output of the sample and hold circuit 34 has a waveform as shown in f, and is input to the voltage conversion circuit 36. In the waveform f, the DC potential changes according to the amount of noise during the horizontal synchronization signal period of the video luminance signal a, and the information is held during one horizontal scanning period.
The information is updated when the next horizontal synchronization signal period arrives. Furthermore, the waveform f indicates a higher DC potential when the S/N value is higher, that is, when the amount of noise is larger. here,
Further, the voltage is converted in a voltage conversion circuit 36 so that the voltage changes are desirable for controlling the voltage control variable clip circuit connected to the subsequent stage, and the converted output is outputted from a terminal 37. A characteristic diagram of an example of the input/output characteristics of the S/N detector 14 is shown in FIG.

FIG. 6 is a block diagram of an example of the configuration of the APL detector 13. The video luminance signal output from the LPF 9 is input from the terminal 38 as a waveform shown in a, and the DC potential at the leading end of the synchronization signal is adjusted to a constant value in the clamp circuit 39. The output of the clamp circuit 39 becomes average DC potential information of the signal by passing through the LPF 9. This information is the average image potential (hereinafter referred to as APL).
(abbreviated as ) information.

This APL information has a high DC potential as the APL increases, but the clipping circuit 41 clips the APL information so that the potential does not fall below the potential equivalent to 50% of the APL. 50%
In the following cases, the output DC potential of the clip circuit 41 does not change. The output DC potential of the clip circuit 41 is further applied to the voltage controlled variable clip circuit 15 connected to the subsequent stage.
The voltage is converted in the voltage conversion circuit 42 so that the voltage change is desirable for the input, and the converted output is output from the terminal 43. A characteristic diagram of an example of the input/output characteristics of the APL detector 13 is shown in FIG.

FIG. 8 is a characteristic diagram showing an example of the characteristics of the voltage-controlled variable clip circuit 15. In the figure, the output DC potential of the S/N detector 14 is input as the control voltage on the horizontal axis. In addition, depending on the output clip potential on the vertical axis, APL
The output DC potential of the detector 13 is clipped so that it does not rise above this clip potential.

FIG. 9 is a characteristic diagram showing an example of the combined characteristics of the APL detector 13, the S/N detector 14, and the voltage control variable clip circuit 15. With respect to the output potential shown in the characteristic diagram of FIG. 7, a variable clipping effect using the input video signal luminance S/N as a parameter works by the output clipping potential of the characteristic diagram of FIG. 8, and the upper limit of the output voltage is suppressed.

FIG. 10 is a characteristic diagram showing an example of the characteristics of the image quality adjustment circuit 10. The control voltage emphasizes or suppresses a band centered around about 2.5 MHz, which is easily noticeable as minute signal information in an image. This image quality adjustment circuit 10
As the control voltage, the output voltage of the voltage-controlled variable clip circuit shown in FIG. 9 is applied. The change in image quality at this time is as follows. When the input video signal brightness S/N is good, for example, when the S/N value is 50 dB, the APL is 0 to 50%.
In the range of 2.5V, the control voltage of the image quality adjustment circuit 10 is 2.5V.
The gain vs. frequency characteristic of the image quality adjustment circuit is shown in Figure 1.
As shown at 0, the characteristic is flat. APL is 50-1
In the range of 00%, as the APL increases, the control voltage of the image quality adjustment circuit 10 increases almost linearly from 2.5 to 5.0V. Therefore, due to the effect of the image quality adjustment circuit, as the APL increases, the minute signal information of the image is gradually emphasized, and an image with enhanced contour information is obtained. In addition, when the input video signal brightness S/N is poor, for example, when the S/N value is 35 dB, the APL is 0 to 10.
0% range, the control voltage of the image quality adjustment circuit 10 is constant at 1.25V, and due to the effect of the image quality adjustment circuit, the A
Regardless of the PL, minute signal information of the image is suppressed, and an image with suppressed noise components can be obtained. As is clear from the characteristics shown in FIG. 9, in the above embodiment, control based on S/N information works preferentially over control based on APL information. This control is consistent with the fact that changes in the S/N value are easier to detect visually as noise, rather than the fact that the higher the APL, the harder it is to visually detect image noise. Yes, good image quality adjustment effects can be obtained.

FIG. 2 is a block diagram of an example system in which the present invention is applied to a home VTR recording system. In the figure, terminal 16, BPF 17, frequency converter 18, L
PF19, LPF20, FM modulator 21, HPF22,
The functions of the portion consisting of the recording amplifier 23, magnetic head 24, magnetic tape 25, adder 26, and terminal 27 are the same as those explained using FIG. 16 in the conventional example section, so the explanation will be omitted. omitted.

The video luminance signal output from the LPF 20 is sent to the image quality adjustment circuit 10, the APL detector 13 and the S/N
The signal is input to the detector 14. The APL information output from the APL detector 13 and the S output from the S/N detector 14
/N information is input to the voltage controlled variable clip circuit 15 and suitably processed, and then using the calculated output,
Controls the image quality adjustment circuit 10. The detailed operation of each block has already been explained, and the explanation will be omitted. The output of the image quality adjustment circuit 10 is sent to an FM modulator 21 and an adder 26. In the adder 26, the video luminance signal after image quality adjustment and the high-frequency color signal output from the BPF 17 are added together and sent to the EE signal output terminal 27. By the above-described operation, in the system configuration of FIG. 2, a good image quality adjustment effect can be obtained also for the recording signal and the EE signal.

FIG. 11 is a block diagram of an example system in which the present invention is applied to a home VTR playback system with an auto-tracking function. The difference from the example in FIG. 1 is that the function corresponding to the S/N detector 14 in FIG. omitted.

The operations of the blocks necessary to realize the auto-tracking function will be briefly explained below. The output of the reproducing amplifier 3 is converted by the FM amplitude detector 44 into DC potential information according to the FM amplitude, and the FM
This is input to the auto-tracking microcomputer 45 as amplitude information. With auto tracking microcomputer 45,
A command is sent to the capstan motor 48 to adjust it to the optimal tracking position where the FM amplitude is maximized.
Control tape advance speed. In the embodiment of FIG. 11, commands from the auto-tracking microcomputer 45 to the capstan motor 48 are sent via the system control microcomputer 46 and the servo circuit 47.

By the way, during VTR playback operation,
S/N deterioration of the reproduced video signal caused by tape demagnetization, poor tracking position, etc. is accompanied by a decrease in FM amplitude. That is, in this case, the FM amplitude detector 4
The FM amplitude information output from 4 can be substituted as S/N information. Therefore, the FM amplitude detector 44
By inputting the output to the voltage-controlled variable clipping circuit 15 as a substitute for S/N information, good image quality can be maintained against changes in image quality caused by tape demagnetization, poor tracking position, etc. Adjustment effects can be obtained.

FIG. 12 is a block diagram of an example system in which the present invention is applied to a home VTR recording system with a tuner. The difference from the example in Figure 2 is that the S/N in Figure 2 is
The function corresponding to the detector 14 is realized by different components, and the other parts operate in the same way, so the explanation will be omitted.

During tuner reception operation, terminal 4
The RF signal inputted from the tuner 9 is subjected to a tuning operation in the tuner 50 so as to pass only the signal transmitted from a specific broadcasting station, and only the selected signal is transmitted.
It is demodulated into a video signal by the demodulator 51 at the subsequent stage, and then the BPF
17 and LPF 20. FIG. 13 is a block diagram of an example of the configuration of the tuner 50. The RF signal inputted from the terminal 52 is controlled to have a constant amplitude by an automatic gain control circuit composed of a variable gain amplifier and a wave detector 54, and then output from the local oscillator 57 at the mixer 56. mixed with the signal. The mixer 56 outputs a sum frequency component and a difference frequency component of the two input signals. Only the difference frequency component is extracted by the BPF 58, amplified by the amplifier 59, and then output from the terminal 60 and sent to the demodulator 51. The terminal 55 is a detected potential output terminal of the detector 54, and the gain of the variable gain amplifier 53 is controlled by this detected potential.

FIG. 14 shows the variable gain amplifier 53 and the detector 5.
4 is a characteristic diagram of an example of the detected potential characteristics of the automatic gain control circuit configured by the circuit shown in FIG. As shown in FIG. 14, the detected potential output from the terminal 55 changes depending on the input RF signal field strength, that is, it includes input RF signal field strength information. By the way, when the input electric field strength becomes weaker and reaches a certain level, as the electric field strength becomes weaker,
The S/N ratio of the video signal output from the demodulator 51 deteriorates. Therefore, in this case, by inputting the detected potential output from the terminal 55 to the voltage control variable clip circuit 15 as a substitute for S/N information, a good image quality adjustment effect can be obtained during the tuner reception operation. be able to.

[0026]

Effects of the Invention As explained above, the present invention provides S/N
A circuit is installed to optimally process multiple image information, such as screen brightness, and the image quality adjustment circuit inserted in the signal path is continuously and automatically adjusted using the calculation output. Therefore, users can easily enjoy good image quality.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an example of a system in which the present invention is applied to a home VTR playback system.

[Fig. 2] A block diagram of an example of an embodiment system in which the present invention is applied to a home VTR recording system.

[FIG. 3] Block diagram of an example of the configuration of the S/N detector 14

[
Figure 4: Waveform diagram of an example of signal changes in each part in the block diagram of Figure 3

[Fig. 5] Characteristic diagram of an example of input/output characteristics of the S/N detector 14

FIG. 6 is a block diagram of an example of the configuration of the APL detector 13.

[
FIG. 7: Characteristic diagram of an example of input/output characteristics of the APL detector 13

[
FIG. 8: Characteristic diagram of an example of the characteristics of the voltage-controlled variable clip circuit 15

FIG. 9 is a characteristic diagram of an example of the combined characteristics of the APL detector 13, the S/N detector 14, and the voltage-controlled variable clip circuit 15.

FIG. 10 is a characteristic diagram of an example of the characteristics of the image quality adjustment circuit 10.

[Fig. 11] The present invention is applied to a home-use VT with an auto-tracking function.
Block diagram of an example of an embodiment system applied to an R regeneration system

FIG. 12 is a block diagram of an example of an embodiment system in which the present invention is applied to a home VTR recording system with a tuner.

[Figure 13
] Block diagram of an example of the configuration of tuner 50

[Figure 14]
A characteristic diagram of an example of the detection potential characteristics of the automatic gain control circuit configured by the variable gain amplifier 53 and the detector 54.

[Figure 15]
Block diagram of an example of a conventional home VTR playback system

[Figure 16] Block diagram of an example of a conventional home VTR recording system

[Explanation of symbols] 1...Magnetic tape 2...Magnetic head 3...Reproduction amplifier 4...LPF 5...Frequency converter 6...BPF 7...HPF 8...FM demodulator 9...LPF 10...Image quality adjustment circuit 11... Adder 12...Terminal 13...APL detector 14...S/N detector 15...Voltage control variable clip circuit 16...Terminal 17...BPF 18...Frequency converter 19...LPF 20...LPF 21...FM modulator 22...HPF 23...Recording amplifier 24...Magnetic head 25...Magnetic tape 26...Adder 27...Terminal 28...Terminal 29...Amplifier 30...Gate circuit 31...Terminal 32...Filter 33...Smoothing circuit 34...Sample hold circuit 35...Terminal 36...Voltage conversion circuit 37...Terminal 38...Terminal 39...Clamp circuit 40...LPF 41...Clip circuit 42...Voltage conversion circuit 43...Terminal 44...FM amplitude detector 45...Auto tracking microcomputer 46...System control microcomputer 47...Servo circuit 48...Capstan motor 49...Terminal 50...Tuner 51...Demodulator 52...Terminal 53...Variable gain amplifier 54...Detector 55...Terminal 56...Mixer 57...Local oscillator 58…BPF 59...Amplifier 60...Terminal

Claims (13)

[Claims] 1. A first detection means having a function of detecting first information included in a video signal; and a second detection means having a function of detecting first information included in a video signal and detecting second information different from the first information. detection means, and an image quality adjustment means having a function of varying the gain versus frequency characteristic of the input video signal, and further includes a first information detected by the first detection means and the second detection means. It has an arithmetic processing means for processing a plurality of pieces of information including the detected second information as input information, and controls the characteristics of the image quality adjustment means using the output information of the arithmetic processing means. A video signal processing device characterized by: 2. According to claim 1, noise amount information of the video signal is used as the first information or the second information to suppress noise components of the image when the amount of noise of the video signal is large. A video signal processing device, characterized in that the characteristics of the image quality adjustment means are controlled so as to. 3. According to claim 1, information on the amount of noise in the video signal is used as the first information or the second information to emphasize contour information of the image when the amount of noise in the video signal is small. A video signal processing device, characterized in that the characteristics of the image quality adjustment means are controlled so as to. 4. In claim 1, average image potential (hereinafter abbreviated as APL) information of the video signal is used as the first information or the second information, and when the APL of the video signal is low, the image potential A video signal processing device characterized in that characteristics of the image quality adjusting means are controlled so as to suppress noise components of the image quality adjusting means. 5. In claim 1, APL information of the video signal is used as the first information or the second information, so that when the APL of the video signal is high, contour information of the image is emphasized. A video signal processing device, characterized in that the characteristics of the image quality adjustment means are controlled. 6. In claim 1, the arithmetic processing means uses noise amount information of the video signal as the first information and uses APL information of the video signal as the second information, A video signal processing device characterized in that the video signal processing device is configured to operate with priority given to control based on noise amount information over control based on APL information. 7. The video signal processing apparatus according to claim 6, wherein when the amount of noise in the video signal is large, the characteristics of the image quality adjusting means are controlled so as to suppress noise components in the image. 8. The video signal processing apparatus according to claim 6, wherein when the amount of noise in the video signal is small, the characteristics of the image quality adjusting means are controlled so as to emphasize contour information of the image. 9. The video signal processing device according to claim 6, wherein when the APL of the video signal is low, the characteristics of the image quality adjusting means are controlled so as to suppress noise components of the image. 10. APL of the video signal according to claim 6;
2. A video signal processing apparatus, characterized in that when the image quality adjustment means is high, the characteristics of the image quality adjustment means are controlled so as to emphasize the contour information of the image. 11. In claim 1, the present invention is applied to a reproduction processing system of a video tape recorder using an FM modulation recording method, and reproduced FM signal amplitude information is used as the first information or the second information. A video signal processing device characterized by: 12. According to claim 1, the present invention is applied to a video signal processing device equipped with a tuner input method, and tuner input field strength information is used as the first information or the second information. video signal processing equipment. 13. According to claim 1, the present invention is applied to a video signal processing device equipped with a tuner input method, further comprising:
The tuner includes an automatic gain control circuit that has a function of absorbing changes in the input electric field strength and sends it to a subsequent circuit as a signal with a constant amplitude, and further includes a variable gain control circuit as a component of the automatic gain control circuit. It includes an amplifier and an amplitude detector, and further includes detected potential information of the amplitude detector,
A video signal processing device characterized in that the device is used as the first information or the second information.