JPH03273570A - Image signal reproducing device - Google Patents

Abstract

PURPOSE:To obtain the frequency of the carrier signal of a reproduced FM signal and to judge the resolution of a signal recorded in a recording medium by successively switching the frequency for converting the reproduced FM signal in terms of frequency and obtaining a detection level for each frequency. CONSTITUTION:This device is provided with a frequency conversion means 32, frequency generation means 60-62 for generating plural frequency signals, detection means 64-68 for detecting a signal level and frequency discrimination means 52 and 68. The frequency of the frequency signal to the means 32 which converts the reproduced FM signal in terms of frequency is switched to detect the signal level of the component of the signal with a specified frequency of the FM reproduced signal which is converted in terms of frequency corresponding to each frequency. Then, the frequency of the carrier signal of the reproduced FM signal is obtained based on the frequency of the frequency signal inputted in the means 32 at such a time and the specified frequency at the time of being detected. Thus, the resolution of the reproduced FM signal is discriminated and the adjustment of an equalizer circuit 31 and a gain switching circuit 17 is executed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an image signal reproducing device for reproducing image signals and audio signals, and particularly for reproducing image signals and audio signals recorded on magnetic recording media, etc. The present invention relates to an image signal reproducing device.

[Prior Art] Conventionally known still video devices are capable of recording not only image signals but also audio signals for a certain period of time. The recording of such audio signals is
This is based on the still video floppy standard established by the Still Video Floppy Council, which compresses the audio signal in the time axis to raise the frequency band of the audio signal to the band of the image signal, and uses the same recording system as the image signal. One possible method is to record using . The center carrier frequency of FM modulation of such audio recording is set to approximately 5 MHz to 6 MH2.

On the other hand, the sync chip frequency of the luminance signal is 6 MHz, and the white beak frequency is 7.5 MHz, which is approximately 6.7 MHz when converted to the frequency of the center carrier wave. Among such devices, still video devices have been proposed that can record image signals and audio signals by further increasing the resolution of luminance signals, and in such devices, the sync chip frequency is 7.7.
MHz, the white beak frequency is 9.7MHz, which is approximately 8.7M when converted to the center carrier frequency.
It becomes Hz. Generally, a still video floppy has a recording area of 50 tracks, and images, signals, audio signals, and even high-resolution image signals can be arbitrarily recorded on each track.

[Problem to be solved by the invention] However, in the conventional video floppy playback device,
Since it is not possible to determine whether the recorded image signal is a high resolution image signal or a standard resolution image signal, the optimal equalizer cannot be selected during playback, resulting in an inversion phenomenon or deviation. Due to expansion, FM
There is a problem that the amplitude of the demodulated signal becomes excessively large.

The present invention has been made in view of the above-mentioned conventional example.
Image signal reproduction that makes it possible to determine the resolution of the signal recorded on the recording medium by determining the frequency of the carrier wave signal of the reproduced FM signal by sequentially switching the frequency for converting the signal and determining the detection level for each frequency. The purpose is to provide equipment.

[Means for Solving the Problems] In order to achieve the above object, the image signal reproducing device of the present invention has the following configuration. That is, it is an image signal reproducing apparatus that reproduces and outputs an image signal recorded on a recording medium, and includes a frequency converting means for converting the frequency of the reproduced FM signal, and a plurality of frequency signals supplied to the frequency converting means. selecting one of a frequency generating means to generate, a detecting means for detecting a signal level of a signal component of a predetermined frequency of an FM reproduction signal frequency-converted by the frequency converting means, and a frequency signal from the frequency generating means; A frequency determining means is provided for determining the frequency of the carrier wave signal of the reproduced FM signal from the frequency of the frequency signal detected by the detection means and the predetermined frequency for each frequency signal.

[Function] In the above configuration, switching the frequency of the frequency signal to the frequency conversion means that converts the frequency of the reproduced FM signal,
The signal level of the signal component of a predetermined frequency of the FM reproduction signal frequency-converted corresponding to each frequency is detected. The frequency of the carrier wave signal of the reproduced FM signal is determined from the frequency of the frequency signal input to the frequency conversion means at this time and the predetermined frequency at the time of detection.

This makes it possible to determine the resolution of the reproduced FM signal and adjust the equalizer circuit and gain switching circuit according to these resolutions.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the circuit configuration of a still video reproducing apparatus according to a first embodiment of the present invention.

The reproduced FM signal taken out from the magnetic disk 10 by the magnetic radar 1 is amplified by the preamplifier 12, and then
HPF (high pass filter) 13, BPF (band pass filter) 30. The signals are input to each of the switches 63. The HPF 13 is a filter for separating the luminance signal or time-compressed audio from the FM playback signal.
The signals separated by the equalizer (EQ) 14. Luminance FM demodulator 15. LPF (low pass filter) 16° After passing through the gain switching circuit 17, the de-emphasis circuit 18
．． 40 is input.

Here, in the case of reproducing a video track signal, the output of the de-emphasis circuit 18 is output from the luminance signal processing circuit 19. The signal is outputted from a video output terminal 22 via a video output circuit 21 .

The output of this de-emphasis circuit 18 is also input to a sync separation circuit 20, and the sync signal separated by this sync separation circuit 20 is also input to a control circuit 52.

On the other hand, in the case of reproducing the audio track signal, the output of the defancy circuit 40 is time-axis expanded by the audio reproducing circuit 41 and outputted from the audio output terminal 42.

The bandpass filter 30 to which the reproduced FM signal is input is an FM
This is a filter for separating the color difference FM playback signal from the playback signal.The separated color difference FM playback signal is passed through an equalizer (EQ).
)31. BPF via switch 631 frequency converter 32
33. It is input to BPF64.

Here, in the case of video track playback, the frequency converter 32 supplies color difference FM playback signals with center frequencies of 1.2 and 1.3 MHz to the frequency converter 32 from the oscillator 60 via the switch 62. Frequency conversion is performed using a signal of .579545MHz. Next, the BPF 33 separates the frequency-converted color-difference FM reproduction signal using a bandpass characteristic of, for example, 4.8 MHz, and the thus-separated color-difference FM signal is sent to the color-difference FM demodulator 34. De-emphasis circuit 351 Color difference signal processing circuit 36. Video output circuit 2
1 and then output from the video output terminal 22.

Here, in order to prevent the inversion phenomenon pointed out in the conventional example and the excessive amplitude of the FM demodulated signal, the equalizer 14 and the gain switching circuit 17 are configured to switch between the standard resolution image signal and the high resolution image signal according to instructions from the control circuit 52. Processing is in progress.

Next, the signal read and reproduced from the magnetic disk 10 is
The procedure of the control circuit 52 for determining whether the image signal is a standard resolution image signal or a high resolution image signal will be explained using the flowchart shown in FIG. Note that the processing described below is performed by the CPU 520.
．． CPU 520 (7) A ROM 521 that stores control programs and various data, a RAM 522 used as a work area for the CPU, etc., and a control program that executes the control procedure shown in the flowchart of FIG. 2 is stored in the ROM 521. has been done.

When reading from the magnetic disk 10 is instructed, the process advances to step S1, and the track movement of the magnetic head 11 on the magnetic disk 10 is performed. When it becomes necessary to determine the resolution of the image signal, the switches 62 and 63 are turned to b. Switch to input side.

From the oscillator 60 to the terminal 62a on the a side of the switch 62,
For example, a signal with a frequency f = 3.579545 MHz is input, and on the other hand, a signal of f = 1, which is the local frequency division of the oscillator 60, is input from the oscillator 61 to the input terminal 62b on the b side.
．． A signal of 7897725 MHz is input. If the eight input terminals 63a of the switch 63 are selected, only the color difference FM reproduction signal passes through the switch 63 and is input to the frequency converter 32, but if the b side input terminal 63b is selected, the luminance FM reproduction signal An FM reproduction signal including the FM signal is input to the frequency converter 32.

In this way, in step S2, both switches 62 and 63 are set to b.
The reproduced FM signal is frequency-converted by the frequency converter 32 using the frequency f of approximately 1.79 MHz, which is the signal from the oscillator 61, and is separated by the BPF 64, which has a bandpass characteristic of 10 MHz at the center frequency. and detected by the wave detector 65. This detector 65 has a frequency of 10MHz0 due to the bandpass characteristics of the BPF 64.
If the MH signal acid 0 minute is large, a large value will be output, and if it is small, a small value will be output.
If the signal component near z is large, a large value is output if it is a high-resolution image track, and if it is small, that is, if it is a standard-resolution image track or a time-compressed audio track, a small value is output. The output of this detector 65 is S/
It is input to H (sample and hold) circuits 66 and 67.

Next, in step S3, the magnetic disk lO rotates and the PG
When the PG pulse extracted by the coil 50 is input to the control circuit 52 via the PG pulse detection circuit 51, the process advances to step S4, and the process waits for 7 horizontal scanning times (7H) to elapse, that is, for the reproduced signal to reach the vertical synchronization period. wait. After seven horizontal scanning times have elapsed, the S/H circuit 66 is commanded to perform sampling. As a result, the sample-and-hold circuit 66 samples the detected output of the signal component around 8 MHz before frequency conversion, and holds that value.

Next, the process proceeds to step S6, and the switch 62 is switched to the a-side input terminal 63a. As a result, the reproduced FM signal has a frequency f, which is an output signal from the oscillator 60, and is approximately 3.5
The frequency of the 8 MHz signal is converted by the frequency conversion circuit 32. For this reason, the detector 65 detects a large value from the bandpass characteristic of the BPF 64 if the signal component near 6MHz in the signal before frequency conversion is large, that is, if it is a standard resolution image track or a time-compressed audio track. , on the other hand, if it is small, that is, if it is a high-resolution image track, a small value will be output.

Next, the process proceeds to step S7, in which a PG pulse is input from the PG pulse detection circuit 51 to the control circuit 52, and then in step S8, when 7H has elapsed and the vertical synchronization period begins, step S9
The control circuit 52 instructs the S/H circuit 67 to perform sampling. As a result, the S/H circuit 67 samples the detected output of the signal component around 6 MHz before frequency conversion, and holds that value.

Next, the process proceeds to step SIO, where the output of the S/H circuits 66 and 67 is input to the comparator 68, and the comparison result is input.

Thus, in step Sll, the control circuit 52 uses the comparator 68
Based on the comparison result, it is determined whether it is a high-resolution image track, a standard-resolution image, or a time-compressed audio track, and the equalizer 14. To optimally switch a gain switching circuit 17. Next, the process proceeds to step 313, where the switch 63 is switched to the input terminal 63a on the a side, so that the frequency conversion circuit 32 can be used for the color difference FM signal.

As explained above, the reproduction FM signal from the magnetic disk 10 is discriminated and the gain settings of the equalizer circuit 14 and the gain switching circuit 17 are performed.

FIG. 3 is a block diagram showing details of the discrimination circuit portion of the circuit shown in FIG. 1, and parts common to those in FIG. 1 are designated by the same numbers. Note that here, the brightness F is input from the terminal 70.
An FM reproduction signal including an M reproduction signal is input.

FIG. 4 is a block diagram showing a schematic configuration of a still video reproducing apparatus according to a second embodiment of the present invention.

This second embodiment includes the S/H circuits 66 and 67 and the comparison circuit 6 of the still video playback device of the first embodiment shown in FIG.
8 is replaced with an A/D converter 72 and a memory 73. Also. The operation of the control circuit 52a of this second embodiment will be explained with reference to the flowchart of FIG.

In FIG. 5, steps S21 to S24 are
Since they are the same as 81 to S4 of the first embodiment shown in FIG. 2, their explanation will be omitted.

After detecting the PG pulse in step S23, step S23
4, wait for 7H to pass and proceed to step S25, where the A/D
The converter 72 performs A/D conversion of the detection output of the signal component around 8 MHz before frequency conversion, and then the process proceeds to step S2.
6, the A/D converted value is written into the memory 73. Next, S
27 to S29 are similar to 86 to S8 of the first embodiment.

After detecting the PG pulse in step S28, step S29
After waiting for 7H to pass, the process proceeds to step S30, in which the A/D converter 72 performs A/D conversion of the detected output of the signal component around 6 MHz before frequency conversion, and in step S31, the signal is written to the previous part of the memory 73. Write that value to a different address than .

Next, the process advances to step S32, and from the memory 73 the step S
26 and step S31, and then in step S33, the magnitude of these two values is compared to determine whether it is a high-resolution image track, a standard-resolution image, or a time-compressed audio track. do. In this way, in step S34, according to the determination result, the equalizer 14. Gain switching circuit 17
In step S35, the switch 63 is switched to the a side (63a), and the process ends.

As described above, FM reproduction signal discrimination and equalization,
Gain switching settings are made.

FIG. 6 is a detailed block diagram of the determination circuit portion of the still video reproducing apparatus shown in FIG. 4, and parts common to those in FIG. 4 are designated by the same numbers.

FIG. 7 is a detailed block diagram of the judgment circuit portion of the third embodiment, which is a modification of the first embodiment (FIG. 1) of the present invention, and FIG. 8 is a detailed block diagram of the judgment circuit portion of the second embodiment (FIG. 4). FIG. 7 is a detailed block diagram of a judgment circuit portion of a fourth embodiment, which is a modification. Here, a bandpass filter (BPF) 75 with a pass band of 6 to 10 MHz is added to the front stage of the frequency conversion circuit 32 shown in FIG. 3 in FIG. 3 and in FIG. 8 in FIG. 6, respectively. As a result, F
F excluding the color difference FM modulation signal component included in the M reproduction signal
Only the M-modulated luminance signal component is frequency-converted by the frequency conversion circuit 32 and input to the determination circuit section.

In the above-mentioned embodiment, it was explained that the detection output is sampled after 7H has elapsed after the detection of the PG pulse, but sampling may be performed before or after that as long as it is during the vertical synchronization period of the image.

Further, this sampling may be performed in synchronization with the output of the synchronous separation circuit 20, or may be performed in combination with the PG pulse.

Furthermore, the sampling position may be either the horizontal synchronization period or the pedestal signal period.

Furthermore, in the explanation of the embodiments described above, the 525-60 system based on the NTSC system was explained, but the
Of course, it is possible to implement the same method even if the 625-50 system is based on the AL system.

As explained above, according to this embodiment, a plurality of frequencies are sequentially switched and supplied to the frequency converter that converts the frequency of the reproduced FM signal, and the detection level is recorded in the detection circuit each time. The frequency of the carrier signal of the reproduced FM signal is determined from the frequency at which the detection level was obtained and the center frequency of the bandpass filter. This makes it possible to determine whether the image signal recorded on the recording medium is a high-resolution image signal or a standard-resolution image signal, and to set the optimal equalizer that does not cause inversion and the optimal gain according to the deviation. can.

In particular, stable discrimination can be made by detecting the vertical synchronization signal portion, horizontal synchronization signal portion, or pedestal signal portion of the image signal.

[Effects of the Invention] As explained above, according to the present invention, the frequency of the carrier wave signal of the reproduced FM signal is determined and recorded by sequentially switching the frequency for converting the frequency of the reproduced FM signal and determining the detection level for each frequency. This has the effect of being able to determine the resolution of the signal recorded on the medium.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a still video playback device according to a first embodiment of the present invention, FIG. 2 is a flowchart showing processing of a control circuit according to a first embodiment of the present invention, and FIG. FIG. 4 is a block diagram showing a schematic configuration of a still video playback device according to the second embodiment of the present invention, and FIG. 5 is a detailed block diagram of the discrimination circuit portion of the first embodiment of the present invention. A flowchart showing the processing of the control circuit, FIG. 6 is a detailed block diagram of the discriminating circuit portion of the second embodiment of the present invention, FIG. 7 is a detailed block diagram of the discriminating circuit portion showing the third embodiment of the present invention, and FIG. 8 is a detailed block diagram of a discriminating circuit portion showing a fourth embodiment of the present invention. In the figure, 13... high pass filter (HPF), 14.
31... Equalizer circuit, 15... FM demodulator, 1
6...Low pass filter (LPF), 17...Gain switching circuit, 18, 35.40...Diffusion circuit, 19...Brightness signal processing circuit, 20...Synchronization separation circuit, 21 ...Video output circuit, 30.33,64゜7
5... Bandwidth filter (BPF), 32... Frequency conversion circuit, 34... FM demodulator, 36... Color difference signal processing circuit, 52... Control circuit, 60.61... Oscillator, 62.63...Switch, 65...Detector, 66
．． 67...Sample and hold circuit, 68...Comparator, 72...A/D converter, 73...Memory.

Claims (5)

[Claims] (1) An image signal reproducing device that reproduces and outputs an image signal recorded on a recording medium, comprising: a frequency converting means for frequency converting the reproduced FM signal; and a plurality of frequency signals supplied to the frequency converting means. a frequency generating means for generating a signal; a detecting means for detecting a signal level of a signal component of a predetermined frequency of the FM reproduction signal frequency-converted by the frequency converting means; and a frequency signal from the frequency generating means. , reproducing FM from the frequency of the frequency signal detected by the detection means and the predetermined frequency for each frequency signal.
An image signal reproducing device comprising: frequency determining means for determining the frequency of a carrier wave signal of a signal. (2) The image signal according to claim 1, wherein the frequency determining means determines whether the image signal is a high resolution image signal or a standard resolution image signal according to the frequency of a carrier wave signal of the reproduced FM signal. playback device. (3) Based on the output of the frequency determining means, it is determined whether the FM reproduction signal is a high resolution image signal or a standard resolution image signal, and the characteristics of the reproduction equalizer are switched accordingly, and the gain is switched according to the deviation. 3. The image signal reproducing apparatus according to claim 2, further comprising switching means. (4) The image according to claim 1, wherein the detection means detects the signal level of a signal component of a predetermined frequency of the frequency-converted FM reproduction signal in a vertical synchronization signal portion of the FM reproduction signal. Signal regenerator. (5) The image according to claim 1, wherein the detection means detects the signal level of a signal component of a predetermined frequency of the frequency-converted FM reproduction signal in a horizontal synchronization signal portion of the FM reproduction signal. Signal regenerator.