JPH03228474A - Image signal processing circuit - Google Patents

Abstract

PURPOSE:To accurately separate only a synchronizing signal without receiving the influence of a noise when separating the synchronizing signal from an image signal by performing slicing with a level in the neighborhood of a pedestal level with a slice circuit in a period other than a blanking period. CONSTITUTION:A slicing means 71 which slices a part other than the blanking period of an input image signal with the level almost equal to the pedestal level of the input image signal is provided. Thereby, the noise can be eliminated with the slicing means 71 even when the noise with level lower than the pedestal level is mixed in the input image signal, and also, since no slicing is performed during the blanking period, no influence is applied to a synchronizing separator operation, and only a correct synchronizing signal can be outputted from a synchronizing separator means 72 provided at the rear stage of this image signal processing circuit 51, and malfunction can be prevented from occurring.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to an input image signal processing circuit, and particularly to a method for separating a synchronization signal without being affected by dropouts contained in a reproduced image signal read from a recording medium. The present invention relates to an image signal processing circuit that is capable of performing.

[Conventional technology]

For example, a luminance signal and a line-sequential color difference signal are formed from a color video signal, FM modulated and recorded on a recording medium such as a magnetic tape or magnetic disk, and the modulated signal read from this recording medium is adjusted by FMI to adjust the luminance. In an image signal recording and reproducing device that reproduces a signal and a color difference signal, converts the color difference signal into a color signal, and outputs a luminance signal and a color signal, an image is captured by an electronic still camera using a floppy disk. There are systems designed to record static color image signals. In such a system, an image signal read from a floppy disk is supplied to a signal processing circuit,
Various signal processing is performed here. One of these processes is to separate a synchronization signal from an image signal, supply this synchronization signal to a system controller, and generate various signals using the synchronization signal as a timing reference.

As mentioned above, in separating the synchronization signal from the reproduced image signal, conventionally, as shown in FIG. The synchronization signal is separated by slicing as shown in FIG. 5B.

[Problem to be solved by the invention]

However, as shown in FIG. 5A, the reproduced image signal contains noise such as dropouts, but the level of this noise may be lower than that of the slicing means, and in this case, as shown in FIG. As shown in the figure, an erroneous signal is output from the synchronization separation circuit in addition to the original synchronization signal. If such an erroneous signal is output from the sync separation circuit and given to the system controller, a signal created with the sync signal as a reference will also be generated at an erroneous timing. For example, when counting vertical synchronization signals and generating a pulse when a predetermined count value is reached, this pulse will be generated at a timing earlier than the predetermined timing due to the above-mentioned noise. It has also been proposed to detect the intervals between successive synchronization signals to distinguish image signals from other signals such as audio signals and data signals, but if an incorrect signal is output from the synchronization separation circuit, , the interval between synchronization signals cannot be detected accurately, and image signals cannot be accurately distinguished from other signals, so there is a risk of malfunction.

In order to eliminate such defects, the reproduced image signal is passed through a dropout compensation circuit, and when a dropout occurs in the image signal, the previous image signal is inserted. It is not possible to completely compensate for out, noise lower than the pedestal level is mixed into the image signal, and as mentioned above, there are disadvantages in that a signal other than the original synchronization signal is output from the synchronization separation circuit.

It is an object of the present invention to eliminate the above-mentioned drawbacks, reduce the influence of noise such as dropouts mixed in the input image signal, and in particular to correctly separate synchronization signals even when there is noise. The present invention aims to provide an image signal processing circuit as described above.

[Means and effects for solving the problem] The image signal processing circuit of the present invention includes slicing means for slicing a portion of the input image signal other than the blanking period at a level approximately equal to the pedestal level of the input image signal. It is characterized by this.

According to such an image signal processing circuit according to the present invention,
Even if noise at a level lower than the pedestal level is mixed into the input image signal, the noise is removed by the slicing means and this slicing is not performed during the blanking period, so there is no effect on the synchronization separation operation. Therefore, only the correct synchronization signal is output from the synchronization separation means provided at the subsequent stage of the image signal processing circuit. Therefore, various signals generated from this synchronization signal are also generated at correct timing, and malfunctions can be prevented.

〔Example〕

FIG. 1 is a block diagram showing the overall configuration of an embodiment of a color video signal recording and reproducing device equipped with an image signal processing circuit according to the present invention, and in this embodiment, it is used as a recording medium in an electronic still camera. It uses a floppy disk. In this example, three types of input terminal sections 11, 12 and 13 are provided so that various color video signals can be processed. The first input terminal section 11 is provided with a terminal to receive a so-called S input in which a luminance signal and a color signal are separated, and a second input terminal section 12 is provided with a terminal for receiving a so-called S input in which a luminance signal and a color signal are separated, and a terminal is provided at the second input terminal section 12 for receiving signals from a VTR or other video signal source. The third input terminal section 13 is provided with a terminal for receiving a composite color television signal based on the NTSC system. A color video signal supplied to one of the input terminals is selected by a manual switch provided in the input circuit 14, and from this selected video signal, a luminance signal Y and a color difference signal that appears line-sequentially, that is, an RY signal. and a BY signal. The luminance signal Y and the color difference signal are supplied to an FM modulation circuit 15, in which the luminance signal and the color difference signal are frequency-modulated and then supplied to a mixer 16. Here, the management information regarding the unit image of the video signal to be recorded supplied from the system controller 17 is sent to the DPSK modulation circuit (DifferentialPha).
(se 5hift Keying) Management information signals obtained by modulation by 1B are combined to generate a frequency multiplexed signal. Management information regarding this unit image includes, for example, an identification code of field recording or frame recording, track number to be recorded, date information, and the like.

The output signal of this mixer 16 is amplified to a predetermined level in a recording circuit 19 and subjected to predetermined processing, and then supplied to a magnetic head 21 via a recording/reproduction switch 20 controlled by a system controller 17. The information is recorded on a predetermined track of a magnetic recording medium, that is, a floppy disk 22. As mentioned above, since the brightness signal Y and the color difference signal RY or B-Y are mixed with the information signal in the mixer 16, they are recorded on the same track in a frequency multiplexed relationship. Become. The magnetic head 21 is connected to the floppy disk 2 by a head access mechanism 23 connected to the system controller 17.
2 predetermined tracks are accessed. Further, the floppy disk 22 is driven by a spindle motor 25 that is driven and controlled by a spindle motor drive circuit 24 connected to the system controller 17, for example, at a speed of 3600 RP.
It is rotated at a speed of M. In this way, unit images of the video signal can be recorded on predetermined tracks of the floppy disk 22. In this case, in field recording, one field of image signals is recorded on one track,
In frame recording, one frame of image signal is recorded using two tracks.

For reproduction, the recording/reproduction changeover switch 20 is switched to the reproduction side by the system controller 17 in response to the user's operation on the operation unit 40.

Mata, move the floppy disk 22 to the spindle motor 25
The head access mechanism 23
The magnetic head 21 is accessed to a predetermined track. A frequency multiplexed signal read by the magnetic head 21, that is, a luminance signal Y, a color difference signal R-Y or B-Y that appears line-sequentially, and a management information signal, that is, D
The PSK data is supplied to the reproduction circuit 41 via the switch 20. The reproducing circuit 41 is configured to supply a reproducing signal to the system controller 17 to detect whether or not there is recording. That is, if there is no reproduced signal, it can be determined that no signal is recorded on the track. On the other hand, if the reproduced signal is present, the reproduced signal is supplied to the FM demodulation circuit 42 and the DPSK demodulation circuit 43. The FM demodulation circuit 42 demodulates the reproduced signal to generate a luminance signal Y and a line sequential color difference signal R-.
A Y signal or a BY signal is obtained and supplied to input terminals 45 and 46, respectively, of an output signal processing circuit 44 including the reproduced signal processing circuit of the present invention. In the DPSK demodulation circuit 43,
In the reproduced RF signal, management information data subjected to DPSK modulation is demodulated on a carrier having a frequency of 13f* (h is a horizontal scanning frequency), and this demodulated management data signal is supplied to the system controller 17. This management data includes an identification code for field recording/frame recording, and the system controller 17 controls related circuits in accordance with this identification code. Recording and reproducing of management information data using the PSK modulation method is disclosed in, for example, Japanese Patent Laid-Open No. 62-219853.

FIG. 2 shows the detailed configuration of the output signal processing circuit 44. The luminance signal Y supplied from the FM demodulation circuit 42 to the input terminal 45 of the reproduced signal processing circuit 44 is supplied to the reproduced signal processing circuit 51 of the present invention. This reproduction signal processing circuit 51
The output luminance signal is converted into a digital signal by an A/■ converter 52, and further stored in a field memory 54 via a data conversion circuit 53. The output of this field memory 54 is in a normal mode in which one image is displayed on the screen of a playback display device (not shown), and in a multi-mode in which multiple images are reduced and displayed on the screen as a so-called multi-image. The signal is supplied to the multi-side contact of the normal/multi selector switch 55 that performs switching. The output signal of the A/D converter 52 is directly supplied to the normal side contact of this switch 550. Normal/multi changeover switch 55
The output signal is supplied to the D/A converter 56 to be converted into an analog signal, and this signal is outputted to the output terminal 57 as a luminance signal Y.

On the other hand, the color difference signal, R-Y signal, or B-Y signal supplied to the input terminal 46 of the output signal processing circuit 44 is converted into a digital signal by an A/D converter 58, and then converted to a digital signal by a color signal compensation circuit 59. After performing processing such as dropout compensation and skew correction, the data conversion circuit 60
The data is stored in the field memory circuit 61 via the field memory circuit 61. The color signal read from the field memory circuit 61 is supplied to the multi-side contact of the normal/multi changeover switch 62. The output signal of the signal compensation circuit 59 is directly supplied to the normal side contact of this switch 62. This switch 62
The color signal output from the color signal reproduction circuit 63 is supplied to the color signal reproduction circuit 63.

The color signal reproduction circuit 63 includes a synchronization circuit that converts line-sequential color difference signals into synchronized signals and an encoder that creates color signals from the color difference signals. The thus reproduced color signal is supplied to the output terminal 65 via the D/A converter 64.

The data conversion circuits 53 and 60 that process the luminance signal and color signal described above are connected to the system controller 1 which responds when the multi-screen function is selected on the operation unit 40.
According to the control signal from 7, the brightness signal and the color signal are compressed so as to correspond to each screen section corresponding to the type of multi-screen, for example, 2×2 or 5×5.

FIG. 3 shows a detailed configuration of the image signal processing circuit 51 according to the present invention. As shown in FIG. 4A, the luminance signal including the synchronization signal is supplied to the slice circuit 71. The slice level in this slice circuit 71 is set to a level approximately equal to the pedestal level of the luminance signal, as shown in FIG. 4A. The output luminance signal of the slice circuit 71 is supplied to a synchronization separation circuit 72 to separate vertical and horizontal synchronization signals. These synchronization signals are supplied to the system controller 17 shown in FIG. The horizontal and vertical synchronization signals separated by the synchronization separation circuit 72 are also supplied to a pulse generator 73, which generates a blanking signal as shown in FIG. 4B. In FIG. 4B, only the horizontal blanking signal is shown. This horizontal blanking signal is processed by a slice circuit 71.
to control the slicing operation. That is, when the horizontal blanking signal is at a high level, slicing is performed, but when the horizontal blanking signal is at a low level, no slicing operation is performed. Therefore, the slicing circuit 71 passes the luminance signal as is during the horizontal blanking period, and performs slicing at a level approximately equal to the pedestal level during periods other than horizontal blanking. Therefore, the fourth
Even if dropout occurs during the image signal period as shown in FIG. 4A, a signal lower than the slice level will not appear in the output signal of the slice circuit 71 during the image period as shown in FIG. 4C. Therefore, this slice circuit 7
The influence of dropout does not appear on the horizontal synchronization signal separated from the output signal of No. 1 by the synchronization separation circuit 72, as shown in the fourth diagram.

The output signal of the slice circuit 71 is further passed through a clamp circuit 74.
and fixes the bottom level of the horizontal synchronization signal to a predetermined value. In this way, the luminance signal output from the clamp circuit 74 is supplied to the A/D converter 52 and converted into a digital signal.

As shown in FIG. 1, the reproduced color signal C output from the output signal processing circuit 44 is supplied to a color signal output terminal 81 via a switch 80. Further, the reproduced luminance signal Y output from the output signal processing circuit 44 is supplied to a mixer 82, where it is superimposed with a character signal supplied from a character generator 83 controlled by the system controller 17, and is output to a luminance signal output terminal 84. supply to. The switch 80 is controlled by a character generator 83 so that the color signal is suppressed during the period in which the character signal is superimposed on the luminance signal. That is, during this period, a predetermined potential of the DC power supply 85 is supplied to the color signal output terminal 81. In this way, the output terminals 81 and 84 have a color signal C and a luminance signal Y separated from each other, that is, S
In order to obtain a composite color television signal of the NTSC system, the luminance signal and the color signal are supplied to a mixer 86 and combined, and the composite color television signal is outputted to an output terminal 87. Configure. In this way, the signals outputted to the output terminals 81, 84, and 87 can be supplied to a television monitor to reproduce a color image, or can be supplied to a color printer to create a color print.

The present invention is not limited to the embodiments described above, but can be modified and modified in many ways. For example, in the embodiment described above, the slice level is fixed and the operation of the slice circuit is controlled by the blanking signal shown in FIG. 4B, but the slice circuit is always operated and the slice level is blanked. It can also be changed in the same way as the signal. Furthermore, in the above embodiment, image signals reproduced from a floppy disk used in an electronic still camera are processed, but it is also possible to process image signals reproduced from other recording media. It is also possible to process image signals other than signals.

[Effects of the Invention] According to the image signal processing circuit of the present invention described above, even if noise such as dropout is included in the image signal,
Outside the blanking period, the slice circuit slices at a level near the pedestal level, so when separating the synchronization signal from the image signal that has passed through the slice circuit, the influence of noise does not appear, and only the synchronization signal can be accurately separated. be able to. Therefore, the timing of a signal created using this synchronization signal as a reference is not affected by noise, and malfunctions can be prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a recording/reproducing apparatus equipped with an image signal processing circuit according to the present invention, and FIG. 2 is a circuit diagram showing the detailed configuration of the output signal processing circuit shown in FIG. 1. , FIG. 3 is a block diagram showing the detailed configuration of the image signal processing circuit of the present invention, FIG. 4 is a signal waveform diagram for explaining its operation, and FIG. 5 is for explaining the operation of a conventional synchronous separation circuit. FIG. 3 is a signal waveform diagram for 14... Input circuit 15... FM modulation circuit 1
7...System controller 19...Recording circuit 20...Record/playback switch 21...Magnetic head 22...Floppy disk 23...Head access mechanism 24...Motor drive circuit 25... - Motor 41... Reproduction circuit 42... FM demodulation circuit 44... Output signal processing circuit 51... Reproduction image signal processing circuit 71... Slice circuit 72... Synchronization separation circuit 7
3... Pulse generator 74... Clamp circuit 81
... Color signal output terminal 84 ... Luminance signal output terminal 8
7...NTSC signal output terminal Fig.3

Claims (1)

[Claims] 1. An image signal processing circuit characterized by comprising slicing means for slicing a portion of an input image signal other than the blanking period at a level approximately equal to the pedestal level of the input image signal.