JPH0291856A - Device for discriminating fm modulated video signal recording system - Google Patents

Abstract

PURPOSE:To discriminate normal-band recording and high-band recording from each other to easily control a record circuit by counting signals having a sink chip frequency component of FM modulated video signals over a specific period specified by a setting means and discriminating a recording system based on the counted results. CONSTITUTION:A magnetic head 10 reads FM modulated video signals from a recording medium and an FM demodulation circuit 22 demodulates the read FM modulated video signals. A synchronizing separator circuit 24 takes out vertical synchronizing signals which are delayed by about 1H from vertical synchronizing pulses. The taked out vertical synchronizing signals are supplied to a first monostable multivibrator 25 and H-level outputs are outputted to another monostable multivibrator 26 for a prescribed period so as to set the output of the multivibrator 25 to an 'L' level synchro nously to the fall of the output. By means of the outputs of the multivibrators 25 and 26 for the prescribed period, a prescribed period which is not influenced by pulses related to horizontal synchronizing signals is set in a counter 15 in the vicinity of the center of the vertical synchronizing signals and the recording system is discriminat ed based on a counted result of signals having a sink chip frequency component in the video signals.

Description

[Detailed Description of the Invention] Summary of the Invention An FM modulated video signal is read from a recording medium, its vertical synchronization signal is extracted, and a predetermined period is set near the center of the vertical synchronization signal and not affected by the horizontal synchronization signal. , the frequency of the signal component having the sync chip frequency of the FM modulated video signal read from the recording medium is counted over the above-mentioned predetermined period, and the recording method of the video signal on the recording medium is determined based on this counted value.

BACKGROUND OF THE INVENTION The present invention is aimed at determining which type of recording the video signal read from the recording medium is based on, among multiple types of recording methods in which FM modulation is performed using modulated waves of different frequencies when recording a video signal on a recording medium. The present invention relates to a device for automatically determining whether a still video signal is a normal band recording method or a high band recording method.

Recording methods for recording still video signals on high-density magnetic floppy disks using electronic still cameras (still video cameras) and other recording devices include the normal band recording method and the 71-band recording method.

A still video signal consists of a luminance signal (Y signal) and a color signal (C signal) (generally color difference signals R-Y and B-Y). In the normal band recording method, a carrier wave with a center frequency of 7 MHz is FM modulated by a luminance signal Y, and this FM modulated wave is abbreviated as Y-RF multiplied signal).One color difference signal R-Y, B-
Frequency 1.2 MHz, 1.3 M by Y respectively
FM modulates the Hz carrier wave and converts these FM modulated waves into C-
These Y-RF and C-RF multiplied signals are mixed and recorded on a video or floppy track. These Y-RF multiplied signal C-RF multiplied signal frequency allocations are shown in FIG. 5(A). Y-RF
Double signal sync-chip (synchronization tip) frequency is 6 MH
z, white peak frequency is 7.5M
Hz, and the frequency deviation is 1.5 MHz.

In the high-band recording method for recording high-resolution still video signals, the center frequency of the carrier wave for FM modulation of the luminance signal Y is set to 9 MHz. As shown in FIG. 5(B), the Y-RF multiplied signal sync chip frequency is 7.
7MHz, white peak frequency is 9.7MHz,
The frequency deviation is 2MHz. This is the same as the case of the C-RF multiplied signal normal band.

As described above, when the recording method of still video signals differs, the reproduction method, especially the configuration of the FM demodulation circuit, also differs. Therefore, in a device that can reproduce both normal band and high band.

An FM demodulation circuit for the normal band and an FM demodulation circuit for the 71st band are provided. It is not specified which method is used to record still video signals on the video floppy installed in the playback device or on each track of the video floppy.

It is necessary to determine the recording method from the video signal read from the video .phi. floppy in the reproducing device, and to switch the demodulation circuit etc. based on the result of this determination. This is why it is necessary to automatically determine the recording method of the RF video signal.

As mentioned above, the normal band and the normal band are FM.
Since the frequency of the modulated carrier wave is different, a difference occurs in the demodulated voltage when these RF video signals are demodulated. It is conceivable to use this demodulated voltage difference to discriminate between recording methods, but this method requires adjustment of the threshold voltage for discrimination, and it takes time to obtain a relatively stable demodulated voltage. There is a problem in that the determination process is slow because it takes time.

SUMMARY OF THE INVENTION An object of the present invention is to provide a device that can relatively quickly and accurately determine the recording method of an FM modulated video signal.

An apparatus for determining a recording method of an FM modulated video signal according to the present invention includes a reading head that reads an FM modulated video signal from a recording medium, a demodulation circuit that demodulates the FM modulated video signal read by the reading head, and a demodulation circuit that demodulates the FM modulated video signal by the demodulation circuit. a synchronization separation circuit for extracting a vertical synchronization signal from a video signal, and a period setting means for setting a predetermined period near the center of the vertical synchronization signal output from the synchronization separation circuit and not affected by pulses related to the horizontal synchronization signal. , a counting means for counting a signal having a sync chip frequency component in the FM modulated video signal read by the reading head over a predetermined period set by the setting means, and a recording method based on the counting result by the counting means. It is characterized by comprising means for determining.

Since the sync chip frequency differs depending on the recording method, the recording method can be determined by measuring this frequency. Moreover, in this invention, the measurement period of the sync chip frequency is set to a period near the center of the vertical synchronizing signal and excluding the pulse generation position related to the horizontal synchronizing signal, as described above, so that Accurate discrimination is possible without being affected by signal disturbances caused by horizontal synchronization signals and horizontal synchronization signals. Furthermore, according to the present invention, it is 0.5H (approximately 32μs) or less (3.5μs in the embodiment) at the latest.
s) makes it possible to determine the recording method, thereby increasing the speed of automatic determination.

Hereinafter, an embodiment in which the present invention is applied to distinguish between the above-mentioned normal band recording and high band recording of still video signals will be described in detail.
Needless to say, the present invention can also be applied to determining the recording format of a video signal of a movie recorded on a video tape.

DESCRIPTION OF THE EMBODIMENTS FIG. 1 is a block diagram showing a part of a reproducing apparatus for a still picture signal recorded on a video floppy, particularly a part of a recording system discrimination circuit. Figure 2 shows the main operations of the circuit shown in Figure 1 and the operation during the vertical retrace period, and Figure 3 shows the time axis of the time chart shown in Figure 2 extended. This is shown in more detail, and FIG. 4 conversely compresses the time axis of the time chart shown in FIG. 2 to show the operation over a period of IV or more.

Video floppy (magnetic recording medium) (path shown)
A still video signal recorded with M modulation (hereinafter referred to as RF
The multiplied signal) is read by the magnetic head 1o and then applied to the head amplifier 11. The amplified reproduced RF signal is applied to the amplifier 12 on the one hand to be further amplified, and on the other hand to the limiter 21 to limit its amplitude.

The reproduced RF signal amplified by the amplifier 12 is provided to a high-pass filter 13.

The recording method discrimination process is performed in a very small period (period T2, which will be described later) within the period in which the vertical synchronizing signal appears. During this period, the reproduced RF signal includes a Y-RF multiplied signal sync chip frequency component, a C-RF multiplied signal center frequency component, and a synchronization signal component. The high-pass filter 13 passes only the Y-RF multiplied signal sync chip frequency component, and has a cutoff frequency of 1, for example.
．． It is set to about 5MHz.

The signal that has passed through the high-pass filter 13 is applied to a Schmidt inverter 14, where it is level-discriminated using a zero-level threshold and shaped into a pulse signal (or square wave signal). This pulse signal is input to the counter 15. As will be described later, the counter 15 operates only during the period T2 and counts the input pulse signals. The input pulse signal (normal band sync chip component, high band sync chip component) of the counter 15 and the output signal of the counter 15 during this period T2 are shown in FIG.

RF multiplied signal FM demodulation circuit 22 given to limiter 21
The signal is demodulated by the de-emphasis circuit 23 and then input to the synchronization separation circuit 24 . The synchronization separation circuit 24 outputs a vertical synchronization signal V and a horizontal synchronization signal H8'/nC3)'ne. Since the synchronization signal is added to the Y signal, it is sufficient to handle only the Y signal here.

Therefore, strictly speaking, the output RF signal Y/ of the amplifier 11 is
The Y-RF multiplied signal is applied to a C separation circuit (shown in the figure) and outputted from this circuit, and is inputted to a demodulation circuit 22 via a Y-RF multiplied signal limiter 21.

As mentioned above, the normal band and high band dual-purpose playback device is provided with a normal band demodulation circuit and a high band demodulation circuit, and these two types of demodulation circuits are switched depending on the determination result of the normal band or high band. can be switched. The demodulation circuit 22 in FIG. 1 includes these two types of demodulation circuits and their switching circuits. The signal necessary for the operation of the recording format discrimination circuit is the vertical synchronization signal V,
Re-sync Whether the raw RF signal is a normal band signal or a high band signal, it is fully possible to extract the vertical synchronization signal V by demodulating it with either of the two types of demodulation circuits described above. In reality, until the process of determining whether it is a normal band or a high band is completed,
The switching circuit will be controlled so that one of the normal band demodulation circuit and the high band post-modulation circuit is operated according to the previous determination result.

FIG. 2 shows a composite synchronization signal C extracted from the demodulated video signal. The vertical synchronization pulse part of this hybrid synchronization signal C has a 3H sync width, and in order to prevent the horizontal synchronization signal from disappearing during that time, this pulse part is 0.07H wide and is divided into six pulses every 0.43H. It is a separation. This 0.07H width pulse portion will be referred to as a delimiter pulse portion a.

There are various types of synchronization separation circuit 24, but in this embodiment, this circuit 24 outputs a vertical synchronization signal V that is approximately IH delayed from the vertical synchronization pulse portion of the hybrid synchronization signal C. .

ync This vertical synchronization signal V is given to a first monostable multi-sync ibrator (MMI) 25. The output signal of the monostable multivibrator 25 rises in synchronization with the rise of the vertical synchronizing signal (2), and is held at the H level for a predetermined time T1ync (16 μs in this embodiment). This output signal is applied to the clear terminal of the counter 15 and the second
monostable multivibrator (MM2) 26.

The second monostable multivibrator 2B rises in synchronization with the fall of the output of the first monostable multivibrator 25, and then rises for a predetermined time T2 (3.5 μs in this embodiment).
), and this output signal is applied to the enable terminal of the counter 15. Therefore, the counter 15 operates during this period T2.

The period T2 during which the counter 15 operates is approximately near the center phase ync of the vertical synchronizing pulse portion of the hybrid synchronizing signal C, preferably between the second and third delimiter pulse portions a, or as shown in FIG. It is set to be between the third and fourth delimiter pulse portions a.

This is because although the signal of the sync chip frequency component input to the counter 15 may be disturbed at the edges of the vertical synchronization pulse portion, this disturbance is considered to be less near the center of the vertical synchronization pulse portion. Further, this period T2 is set to be located approximately at the center of the adjacent delimiter pulse portions a. This is also to perform the sync chip frequency measurement operation in a portion where signal disturbance is as small as possible.

As shown by the chain line in FIG. 2, when a synchronization separation circuit is used, which generates a vertical synchronization signal V that rises with almost no delay from the vertical synchronization pulse portion of the hybrid synchronization signal Csync, the first monostable The multivibrator 25 will be one that outputs a one-shot pulse of "12" for a time approximately IH longer than the period T1.

The counter 15 is cleared by the output signal of the first monostable multivibrator 25, and then performs a counting operation in which the output of the second monostable multivibrator 2B is at H level, and is output from the Schmitt inverter 13. In this embodiment, the frequency signal created by the sink chip is divided by 1/IB. As mentioned above, the sync chip frequencies are different between normal band recording and high band recording, so even if frequency division is performed at the same ratio, the frequencies after frequency division will be different. In this embodiment, the counting operation period T2 of the counter 15 is set to 3.5 μs, so as shown in FIG. The output becomes L level, and in the case of a 7.7 MHz signal, becomes H level and is held at that level. Therefore, it is possible to determine whether normal band recording or high band recording is being performed based on the level of the output signal of the counter 15 at the time when one period T2 has elapsed.

The output signal of the counter 15 is applied to a low pass filter 16. The output of the low-pass filter 16 is connected to the inverter 17
The signal appears at the output terminal 18 after passing through.

In the time chart of FIG. 4, when the output of the output terminal 18 is at L level, the recording method is high band;
When the level is H, it is determined that normal band recording is being performed.

In this way, when recording on a magnetic recording medium is determined to be normal band recording or high band recording, reproduction processing according to each recording method, such as switching of the above-mentioned demodulation circuit, etc., is performed.

In this embodiment, the frequency of the generated pulse wave is divided by the counter 15, and normal band recording and high band recording are discriminated based on the level at the end of the operation of counter 5, but the present invention is capable of making such a discrimination. However, other methods may be used, such as counting the sync chip frequency signal for a predetermined period of time by the CPU, and distinguishing between normal band recording and high band recording based on this counted value.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the invention. Figure 2 shows the time diagram showing the main operations of the circuit shown in Figure 1.
The chart, Figure 3 shows the time chart shown in Figure 2 in detail by expanding it, and Figure 4 compresses the time chart shown in Figure 2 and shows the operation in a period of 1V or more. This shows that. FIGS. 5(A) and 5(B) are diagrams showing frequency allocation, where (A) shows normal band recording and (B) shows high band recording, respectively. IO...Magnetic head. 14... Shumi-Soto dispute inverter. 15...Counter. 22...FM demodulation circuit. 24...Synchronization separation circuit. 25, 26... Monostable multivibrator. CL...Clear terminal. ENA...Enable terminal. Patent applicant: Fuji Photo Film Co., Ltd. Agent
Patent attorney Asamichi Maehara (1 other person)

Claims (1)

[Claims] When recording a video signal on a recording medium, there are multiple types of recording methods that perform FM modulation using modulated waves of different frequencies. It is a device for determining whether the FM modulated video signal is a recording medium, and includes a reading head that reads an FM modulated video signal from a recording medium, a demodulation circuit that demodulates the FM modulated video signal read by the reading head, and a video signal demodulated by the demodulation circuit. a synchronization separation circuit for extracting a vertical synchronization signal; a period setting means for setting a predetermined period near the center of the vertical synchronization signal output from the synchronization separation circuit and not affected by pulses related to the horizontal synchronization signal; and the reading head. counting means for counting the signal having the sync chip frequency component in the FM modulated video signal read by the above-mentioned setting means over a predetermined period set by the above-mentioned setting means; and means for determining the recording method based on the counting result by the above-mentioned counting means. , A device for determining a recording method of an FM modulated video signal.