JPH0583036B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides a first carrier signal formed by frequency modulating a video signal including a synchronizing signal according to a first carrier signal having a first frequency. A second frequency modulated video signal formed by frequency modulating the frequency video signal or a second carrier signal having a higher frequency than the first carrier signal is input, and the input frequency modulated video signal is is the first frequency modulated video signal or the second frequency modulated video signal
The present invention relates to a determination device that determines whether a frequency modulated video signal is a frequency modulated video signal and determines whether a dropout has occurred in an input frequency modulated video signal.

[Conventional technology]

A still video floppy system (hereinafter referred to as still video) is known as a system for recording and reproducing FM modulated image signals on a 2-inch floppy disk. In this still video, the frequency allocation shown in FIG. 5 for the recorded signal on the disk is employed (hereinafter referred to as low-band FM signal frequency allocation). As shown in FIG. 5, in a still video, the luminance signal and color difference signal are each FM modulated and recorded. Further, as for the color difference signals, the R-Y signal and the B-Y signal are recorded alternately every horizontal period.

The FM luminance signal has a sync chip frequency of 6MHz and a white peak frequency of 7.5MHz.
The center frequency of the RY signal for the FM color difference signal is 1.2M.
Hz, the center frequency of the BY signal is 1.3MHz.
Furthermore, it is now possible to record ID signals using 204.5KHz as a carrier frequency. According to the frequency allocation described above, a luminance signal band of approximately 4.5 MHz and a horizontal resolution of approximately 350 TV lines are obtained for the reproduced signal. However, in recent years, as TV monitors have become higher in resolution and have larger screens, it has become desirable to have a wider band of luminance signals. In response to this demand, recording and reproduction based on frequency allocation as shown in FIG. 6, for example, is being considered as the performance of media, heads, etc. increases. In the high band FM signal frequency allocation shown in FIG. 6, the FM luminance signal has a sync chip frequency of 8 MHz and a white peak frequency of 10 MHz. The FM color difference signal and ID signal have not been changed in order to maintain compatibility with the low band FM signal frequency allocation shown in FIG. According to this high-band FM signal frequency allocation, the luminance signal band of the reproduced signal is approximately 6.5 MHz, and the horizontal resolution is approximately 520 TV lines. As the luminance signal becomes wider as described above, in order to maintain upward compatibility with conventional equipment, it is necessary to use a low-band
It is also necessary to reproduce the image signal recorded with the FM signal frequency allocation, and it is necessary to determine the recording conditions to determine which frequency allocation is being recorded on the medium. For this purpose, it has been considered to newly set a bit in the ID signal to indicate which recording condition is to be used for recording.

[Problem that the invention is trying to solve]

However, the above-described method of adding bits to the ID signal has the disadvantage that the determination of the recording conditions is delayed because the ID signal frequency is low.

The present invention solves such problems, and an input frequency modulated video signal is formed by frequency modulating a video signal including a synchronization signal according to a first carrier signal having a first frequency. 1st
The frequency video signal is a second frequency modulated video signal formed by frequency modulating according to a second carrier signal having a higher frequency than the first carrier signal, with good responsiveness,
It is an object of the present invention to provide a discriminating device capable of determining whether or not a dropout has occurred in an input frequency modulated video signal.

[Means for solving problems]

In order to achieve the above object, the present invention provides a first frequency modulated video signal formed by frequency modulating a video signal including a synchronization signal according to a first carrier signal having a first frequency; A second frequency modulated video signal formed by frequency modulating according to a second carrier signal having a higher frequency than the first carrier signal is input, and the input first or second frequency modulated video is input. Comparing means for comparing the level of the synchronous signal portion of the signal with a predetermined reference level signal and outputting a signal corresponding to the comparison result; and generating a pulse signal in synchronization with the signal output from the comparing means. a pulse signal generating means; a pulse width setting means for setting a pulse width of a pulse signal generated by the pulse signal generating means; and a pulse width setting means synchronized with the signal output from the comparing means by the pulse width setting means. is set to generate a pulse signal having a first pulse width, and depending on the generation state of the pulse signal output from the pulse signal generating means, the frequency modulated video signal input to the detecting means is set to generate a pulse signal having a first pulse width.
After outputting a first determination signal indicating whether the frequency modulated video signal is a frequency modulated video signal or a second frequency modulated video signal, the first determination signal is input to the detection means. 1, the pulse width setting means generates a pulse signal having a second pulse width in synchronization with the signal output from the comparison means. setting, and when the first determination signal indicates that the frequency modulated video signal input to the detection means is the second frequency modulation video signal, the pulse width setting means determines that the comparison means A pulse signal having a third pulse width is set to be generated in synchronization with a signal output from the pulse signal generating means, and the pulse signal is input to the detecting means according to the generation state of the pulse signal output from the pulse signal generating means. and determination signal generating means for outputting a second determination signal indicating whether or not dropout has occurred in the frequency modulated video signal.

[Effect]

According to the present invention, the input frequency modulated video signal is a first frequency video formed by frequency modulating a video signal including a synchronization signal according to a first carrier signal having a first frequency. signal or a second frequency modulated video signal formed by frequency modulating according to a second carrier signal having a higher frequency than the first carrier signal with good responsiveness, high speed and stability. Furthermore, it is also possible to determine whether or not dropout has occurred in the input frequency modulated video signal, making it possible to simplify the configuration of the device and reduce costs. be.

〔Example〕

FIG. 1 is a block diagram that best represents the features of the present invention, and shows the main parts of the present invention. In the figure, 1 and 2 are heads for reproducing odd and even fields of the recorded frame signal, respectively. Head 1 and head 2 are connected to preamplifiers 3 and 4, respectively, and the preamplifiers are 3. The output of the preamplifier 4 is connected to the head selector switch 5. 6 is a head switching signal from the system controller SC,
It is supplied to the head changeover switch 5. 7 is a high pass filter, 8 is an FM equalizer, and the output of the head selector switch 5 is the high pass filter 7.
The signal is supplied to an FM demodulator 9 and a comparator 10 via an FM equalizer 8. 11 is a low pass filter, 12 is a dropout switch, 13 is AGC, 14 is an IH delay line, and the dropout switch 12 receives the output of the FM demodulator 9 via the low pass filter 11,
The output of the dropout switch 12 is inputted via the 1H delay line 14, and 15 dropout pulses are supplied from the system controller SC. Further, the output of the dropout switch 12 is supplied to the de-emphasis L (16) and the de-emphasis H (17) via the AGC 13. Here, the de-emphasis amount of the de-emphasis H17 is set larger than that of the de-emphasis H16. The outputs of the de-emphasis L16 and de-emphasis H17 are connected to 18 de-emphasis changeover switches. A de-emphasis switching signal 19 is supplied from the system controller SC to the de-emphasis switching switch 18. The output of the de-emphasis selector switch 18 is a luminance signal of 20, and a luminance signal of 21.
is supplied to the sink separator and a monitor (not shown).

On the other hand, the output of the comparator 10 is input to a frequency detector 22, and a detection frequency switching signal 23 is supplied to the frequency detector 22 from the system controller SC. Frequency detector 22
are the monomulti of 22a, the latch of 22b and the 2
2c time constant switch. 2
7 is a pulse generator, 24 is a latch, 25 is a latch
It is an ON/OFF signal, and the latch 24 receives the output of the frequency detector 22, the output of the pulse generator 27, and the latch ON/OFF signal from the system controller SC.
signal 25 and the output of latch 24 is 26
as a frequency detection output of the system controller
Supplied to SC. The latch ON/OFF signal 25 is also supplied to the latch 22b. or,
PB is a playback switch, HS1 is a head shift instruction switch, and AI is an address instruction key for specifying the playback track address.

The system controller SC has a built-in CPU,
FIG. 4 shows a flowchart of the main part of the program.

Next, the operation of the embodiment shown in FIG. 1 will be described with reference to the operation flowchart shown in FIG.

Recorded on a floppy disk (not shown) by heads 1 and 2 in step S1.
The FM signal is reproduced and amplified by preamplifier 3 and preamplifier 4, respectively, and then supplied to head changeover switch 5. The head changeover switch 5 receives the head changeover signal 6 from the system controller SC.
Accordingly, the signal from head 1 and the signal from head 2 are alternately switched and output for each file.
The FM color difference signal is removed from the output of the head selector switch 5 by a high pass filter 7, the frequency characteristics of the FM signal are compensated by an FM equalizer 8, and the output is supplied to an FM demodulator 9 and a comparator 10. The output of FM demodulator 9 is passed through low pass filter 1
1, only the baseband signal passes through and is input to one input terminal of the dropout switch 12. Also, the output of the dropout switch 12 is connected to the other input terminal of the dropout switch 12.
The signal delayed by 1H by the 1H delay line 14 is input.

In step S2, it is determined whether or not a head shift is instructed by turning on the switch HS1. If so, heads S1 and S2 are simultaneously shifted to the track address specified by AI in step S3. Steps S3 and S4 are repeated until completion of the head shift is detected in a head moving mechanism (not shown) in step S4.
Upon completion of the head shift, the process advances to step S5.
Incidentally, if it is determined in step S2 that the switch HS1 is OFF, the process directly advances to step S5.

In step S5, the switch 12 is set to the a contact, the switch 18 is set to the b contact, the switch 22c is set to the a contact, and the latch ON/OFF signal is turned on.

As a result, the recording conditions are determined. That is, since the dropout switch 12 is connected to the a contact, it outputs the signal from the low-pass filter 11 for determining the recording conditions. The output of the dropout switch 12 passes through the AGC 13 and is made into a signal with a predetermined range of magnitude, and the de-emphasis L
16 and de-emphasis H17.
The de-emphasis L16 performs de-emphasis on the low band FM signal shown in FIG. 5, and the de-emphasis H17 performs de-emphasis on the high band FM signal shown in FIG. The outputs of the de-emphasis L16 and de-emphasis H17 are input to the de-emphasis changeover switch 18, but the system controller
According to the de-emphasis switching signal 19 from the SC, the switch 18 is connected to the b contact and selects the output of the de-emphasis H17 for determining the recording condition. During normal reproduction, according to the determination result, the output of the de-emphasis L16 is selected when the low-band FM signal is present, and the output of the de-emphasis H17 is selected when the high-band FM signal is present.

From the above results, the luminance signal 20 is obtained as the output of the de-emphasis changeover switch 18, and the horizontal synchronizing signal is separated from the luminance signal 20 by the sync separator 21.

A latch pulse for holding the determination result is generated by the pulse generator 27 and supplied to the latch 24. On the other hand, the comparator 10 compares the FM signal from the FM equalizer 8 at a constant level and
Alternatively, it is supplied to the frequency detector 22 as one signal.
The monomulti 22a of the frequency detector 22 is a retriggerable monomulti, and according to the detection frequency switching signal 23 from the system controller SC,
When determining the recording conditions, the switch 22 is set so that the time constant of CiR is selected by the time constant switch 22c.
C is connected to A contact. Therefore, the monomulti 22a outputs C ₁ R for the rising edge or falling edge of the 0 or 1 signal from the comparator 10.
A pulse with a predetermined time width τ determined by is generated.
Also, the latch 22b is connected to the latch ON/OFF signal 25.
Since it is ON, it is in an enabled state, and when determining the recording condition, the output state of the monomulti 22a is held at the rising edge or falling edge of the comparator 10. The output of latch 22b is enabled in latch 24 since latch ON/OFF signal 25 is also ON, and the pulse from pulse generator 27 holds the output state within horizontal synchronization.

Next, the frequency detection operation will be explained in detail with reference to FIG. FIG. 2 is an explanatory diagram of operations for low-band FM signals and high-band FM signals at the time of recording condition determination.

Figure 2 1 shows the waveform of the sync chip section of the output of the FM equalizer 8, and shows the waveform of the output of the FM equalizer 8.
At 0, the comparator level is as shown, and the FM
The signal is converted into a 0 or 1 signal to obtain FIG.
Furthermore, at the rising edge of the output of the comparator 10, the monomultiplier 22a has τ determined by C ₁ R.
generates a pulse with a time width of . This time width τ is set by the time constant switch 22c so that it is shorter than the period of the sync chip frequency of the low band FM signal and longer than the time width of the sync chip frequency of the high band FM signal. Therefore, the output of the mono multi 22a is a repetition of "0" and "1" for the low band FM signal, and the high band FM signal is
For FM signals, it is a continuous “1” and the second
The waveform shown in Figure 3 is obtained, and this waveform is further shown in Figure 2.
When latched at the rising edge of the comparator 10 output as shown in the figure, in the low band FM signal, consecutive "0"s due to the delay of the mono multi 22a will be output in the high band.
The FM signal outputs continuous "1"s, resulting in the waveform shown in Figure 2-4, which latches at the falling edge of the output waveform of the pulse generator 27 synchronized with the horizontal synchronizing signal shown in Figure 2-5. Therefore, the frequency detection output 26 shown in FIG. 26 is obtained. Through the above-described operation, the recording condition is determined as a low-band FM signal or a high-band FM signal by the frequency detection of the sync chip section. In this state, switch S6 controls the field, that is, 1 concentric circle on the magnetic disk.
Waits until the track is played.

The rotational speed of the disk motor is selected so that one field is recorded in one track.

Then, when one field has elapsed, the process proceeds to step S7, where it is determined whether the output of the latch 24, that is, the frequency detection output 26, is 1 (H) or 1 (L). 1 (H), that is, when a high band FM signal is detected as the recording condition, the process advances to step S8 and the switch 22c is turned to b.
Connect to the contact and turn off the latch ON/OFF signal.

As a result, the time constant of the monomulti 22a is switched to C ₂ R, the pulse width τ' is selected, the mode is switched to the dropout detection mode, and the latch 22a is switched to the dropout detection mode.
b, 24 does not operate, and the output signal of the monomulti 22a is output as is to the frequency detection output 26. Note that step S6 in this embodiment can be omitted.

Figure 3 (1) shows the output waveform of the FM equalizer 8 when a dropout occurs in the high band FM signal.
Obtain the comparator 10 output shown in Figure (2). Further, the monomulti 22a generates a pulse having a pulse width τ' determined by C ₂ R from the rising edge of the comparator 10. By setting the pulse width τ' to be slightly longer than the period of the peak frequency of the sync chip with emphasis applied, the waveform shown in Figure 3 (3) can be obtained, and the drop-out portion can be detected. The signal is output as is to the frequency detection output 26. Incidentally, when the output of 26 is at a low level in step S7, that is, when it is detected that it is a low band FM signal, the time constant switch 22c is connected to the c contact for the low band FM signal in step S9, thereby changing the time constant to _C3. R, the pulse width of the monomulti 22a is τ'', and the pulse width is set to the optimal detection frequency for each. In other words, τ'' is set to be slightly longer than the period of the peak frequency of the sync chip in the low band FM signal. Therefore, the dropout detection operation becomes reliable.

Also, in step S9, the switch 18 is connected to the a contact, so de-emphasis is optimized.
Further, the latch ON/OFF signal is turned OFF, and both latches 22b and 24 do not operate.

In this way, the mode is switched to the dropout detection mode in steps S8 and S9, and the optimum pulse width of the monomulti 22a is selected for the high band and low band FM signals, so that the detection output 26 has a low level at the dropout position. Otherwise, a high level signal is output.

Next, in step S10, it waits for the signal 26 to become low level, and when it becomes low level, in step S11, the switch 12 is connected to the b contact, and the signal from 1H ago is replaced.

Furthermore, this step S11 is continued until switch S12 determines that the output of 26 becomes high level
Repeat S12 and step when it reaches high level.
At S13, switch 12 is returned to the a contact side. In this way, only the portion where dropout has occurred is compensated using the signal from 1H earlier.

Next, in step S14, it is determined whether the playback switch PB is ON or not. If it is OFF, the program is terminated, and if it is still ON, it is determined in step S15.
, and turn on the head shift instruction switch HS1.
Determine whether or not. head shift instruction switch
If it is not ON, the process returns to step S10, and the sequence for dropout compensation is repeated again. If the head shift instruction switch is ON, the process returns to step S3, and the head shift operation and determination as to whether the recording signal of the new track is high band or low band are started again.

Although this embodiment has been described as an example for the two frequency allocations shown in FIGS. 5 and 6, the present invention is also effective for other allocations as long as their sync chip frequencies are different. It is also possible to determine the different frequency allocations as described above by installing a second frequency detector in this embodiment, or by increasing the types of mono-multi time constants and performing sequential determination.

As explained above, according to the embodiments of the present invention,
Since it is possible to quickly determine whether to record using a low-band FM signal or a high-band FM signal based on the FM signal, the optimum playback state can be quickly set without having to play back an ID signal or the like. Also, when inserting the jacket, the RF function plays back whether or not each track is recorded.
It is possible to judge the recording condition at the same time as making a judgment from the signal, and by storing this judgment result in memory, it has the effect of speeding up the subsequent operation of the playback device.It is also inexpensive because it can also be used for dropout detection. There is also the advantage of having one. still,
It goes without saying that the present invention is effective not only for determining the band of a recorded signal but also for determining the modulation conditions of a transmitted modulated signal.

〔Effect of the invention〕

According to the present invention, even without using an ID signal or the like, an input frequency modulated video signal can be frequency modulated by frequency modulating a video signal including a synchronization signal according to a first carrier signal having a first frequency. or a second frequency modulated video signal formed by frequency modulating according to a second carrier signal having a higher frequency than the first carrier signal. can be determined quickly and stably with good responsiveness without being affected by the brightness, contrast, etc. of the image indicated by the input frequency modulated video signal, so the reliability of the determination can be improved. Since it is also possible to determine whether or not dropout has occurred in the input frequency modulated video signal, the configuration of the device can be simplified and costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of frequency detection operation of the embodiment of the present invention, FIG. 3 is an explanatory diagram of dropout detection of the embodiment of the present invention, and FIG. Flowchart, Figure 5 shows low band FM signal frequency allocation, Figure 6
The figure is a diagram showing high band FM signal frequency allocation. 1 is the head, 2 is the head, 3 is the preamp, 4
is a preamplifier, 5 is a head switching switch, 6 is a head switching signal, 7 is a high pass filter, 8 is FM
Equalizer, 9 is FM demodulator, 10 is comparator, 11 is low pass filter, 12 is dropout switch, 13 is AGC, 14 is 1H delay line, 15 is dropout pulse, 16 is de-emphasis L, 17 is Dayenphasis H,
18 is a de-emphasis switching switch, 19 is a de-emphasis switching signal, 20 is a brightness signal, 21
is a sync separator, 22 is a frequency detector, 22
22b is a latch, 22c is a time constant switch, 23 is a pulse generator, 24 is a latch, 25 is a latch ON/OFF signal, and 26 is a frequency detection output.

Claims (1)

[Claims] 1. A first frequency modulated video signal formed by frequency modulating a video signal including a synchronization signal according to a first carrier signal having a first frequency; A second frequency modulated video signal formed by frequency modulating according to a second carrier signal having a higher frequency than the carrier signal is input, and the first or second input signal is
Comparing means for comparing the level of the synchronizing signal portion of the frequency modulated video signal with a predetermined reference level signal and outputting a signal corresponding to the comparison result, and generating a pulse in synchronization with the signal output from the comparing means pulse signal generation means for generating a signal; pulse width setting means for setting the pulse width of the pulse signal generated by the pulse signal generation means; and output from the comparison means by the pulse width setting means. A frequency modulated image is set to generate a pulse signal having a first pulse width in synchronization with the signal, and is input to the detection means according to the generation state of the pulse signal output from the pulse signal generation means. After outputting a first determination signal indicating whether the signal is a first frequency modulated video signal or a second frequency modulated video signal, the first determination signal is input to the detection means. When the signal indicates that the signal is the first frequency modulated video signal, the pulse width setting means generates a pulse signal having a second pulse width in synchronization with the signal output from the comparison means. and when the first determination signal indicates that the frequency modulated video signal input to the detection means is the second frequency modulated video signal, the pulse width setting means and a pulse signal having a third pulse width is generated in synchronization with the signal output from the comparison means, and the detection is performed according to the generation state of the pulse signal output from the pulse signal generation means. 1. A determination device comprising determination signal generating means for outputting a second determination signal indicating whether or not a dropout has occurred in a frequency modulated video signal input to the means.