JPH0752942B2 - Mode determination device for recording medium reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mode discriminating apparatus for a recording medium reproducing apparatus, and in particular, a reproducing video signal from a recording medium is recorded in any of a plurality of recording modes. The present invention relates to a mode discriminating apparatus of a recording medium reproducing apparatus for discriminating whether or not.

2. Description of the Related Art In recent years, there has been a demand for a high-resolution, high-quality magnetic recording / reproducing apparatus with improved tape performance and head performance, and a high-quality image in which the carrier frequency has been shifted sufficiently higher than the carrier frequency in the current home VTR. Various modes are considered.

However, since the signals recorded in the recording modes with different carrier frequencies are not completely compatible with each other as described above, the signals recorded in one recording mode cannot be recorded in the other recording mode. However, there is a problem that it cannot be reproduced. In order to solve this, it is conceivable to provide, for example, a changeover switch and the like so that the changeover switch is changed over depending on the recording mode. However, this makes the changeover operation very complicated and the usability is extremely poor. turn into. At this time, at the time of this switching operation, it is judged which recording mode is used for recording, but it is very difficult to make this judgment, and it is necessary to record in different recording modes in the same cassette. Therefore, there is a case where the playback is switched to a different playback mode. Further, there is a problem that the user may mistakenly think that a failure occurs when reproducing in a reproducing mode different from the recording mode.

Therefore, the present invention solves the above-mentioned problems by performing mode discrimination based on both DC levels of the sync tip level transmission section and the pedestal level transmission section of the FM demodulated reproduced video signal, thereby solving the above problems. The purpose is to provide.

Means for Solving the Problems A mode discriminating apparatus for a recording medium reproducing apparatus according to the present invention is a first mode discriminating signal indicating a recording mode of a reproduced video signal based on a DC level in a sync chip level transmission section of a reproduced video signal. And a means for outputting a second mode discriminating signal indicating a recording mode of the reproduced video signal based on the DC level of the pedestal level transmission section in the reproduced video signal, and the first and second mode discriminating signals. When the same recording mode is indicated, a third mode discriminating signal indicating the recording mode is output, and when the first and second mode discriminating signals indicate different recording modes, the first and second preceding modes are output. And a mode discriminating means for directly storing and outputting the third mode discriminating signal when the mode discriminating signals of 1) indicate the same recording mode.

The video signal is pre-recorded on the recording medium reproduced by the device of the present invention in one of a plurality of recording modes in which the carrier frequencies of the frequency-modulated signal video signal are different from each other. The DC levels in the sync tip level transmission section and the pedestal level transmission section in the reproduced video signal obtained by reproduction and demodulation from this recording medium differ depending on the recording mode.

In the device of the present invention, the first and second mode discrimination signals are generated based on the DC levels of the sync tip level and the pedestal level transmission section in the reproduced video signal, respectively.

When the first and second mode discrimination signals indicate the same recording mode, the mode discrimination means outputs the third mode discrimination signal indicating the recording mode, and the first and second modes are outputted.
When the mode discriminating signals of 1 and 2 indicate different recording modes, the third mode discriminating signal when the preceding first and second mode discriminating signals respectively indicate the same recording mode is held and output as it is. .

Embodiment FIG. 1 shows a circuit system diagram of an embodiment of a mode discriminating apparatus for a recording medium reproducing apparatus according to the present invention. Before explaining this embodiment, first, the principle of the device of the present invention will be described with reference to FIGS. 5 and 6.

Frequency modulation (FM modulation) is a modulation method that replaces the amplitude level of a signal with each frequency. For example, this modulation method is generally used for magnetic recording of video signals.

In this case, the frequency spectrum of the frequency-modulated luminance signal (FM luminance signal) is as shown by S _A in FIG. 5 in the standard mode, and as shown by S _B in the same figure in the high image quality mode. The carrier frequency is set higher than that. Frequency spectrum S of FM luminance signal shown in Fig. 5
_{In A} , f _AS , f _AP, and f _AW indicate carrier frequencies at the sync tip level, pedestal level, and white peak level of the luminance signal, respectively, and similarly, frequency spectrum S _B
Among them, f _BS , f _BP, and f _BW indicate carrier frequencies at the sync tip level, pedestal level, and white peak level of the luminance signal, respectively. For example, the carrier frequency f _AS in the standard mode is 3.4 MHz, f _AP is 3.8 MHz, f _AW is 4.4 MHz, and the carrier frequency f _BS 5.0 MHz, f in the high image quality mode is
_BP is 5.6MHz and f _BW is 6.7MHz.

Incidentally, the relationship of proportionality to the general input frequency and the output DC level in FM demodulator, the waveform of the normal mode and the high image quality mode of the demodulated video signal (demodulated luminance signal) to Y _A and Y _B of FIG. 6 It becomes as shown. Therefore, the carrier frequency difference between both modes appears as a DC level difference in the demodulation output. The present invention is characterized in that it is always maintained at a substantially constant level irrespective of the image content, and stable recording mode determination is performed based on both DC levels of the sync tip level and the pedestal level.

Next, the mode discrimination device 1 shown in FIG. 1 will be described. After the FM demodulator 3 demodulates a reproduced frequency-modulated video signal (here, reproduced FM luminance signal) coming in through the input terminal 2, , Figure 2 (A) through LPF4 to remove carrier
The reproduced luminance signal a as shown in (1) is output to the sync signal separation circuit 5 and the sample and hold circuits 6 and 7, respectively.

The sync signal separation circuit 5 separates and extracts the horizontal sync signal from the incoming reproduction luminance signal a, and outputs this as a sampling pulse b as shown in FIG. 2B, as a monostable multivibrator 8, a sample hold circuit 6, and It outputs to one input terminal of the AND circuit 9, respectively.

The sample and hold circuit 6 uses the sampling pulse b
DC level of the horizontal synchronizing signal period of the reproduced luminance signal a supplied from the LPF4 based on V _D1, i.e., a DC level V _D1 of the sync tip level transmission section by sample and hold outputs to the non-inverting input terminal of the comparator 10 .

On the other hand, the reference voltage source 11 is connected to the inverting input terminal of the comparator 10.
The reference voltage V _R1 is supplied from the comparator 10, and the comparator 10 compares the direct current level V _{D1 in} the sync tip level transmission section of the reproduction luminance signal with the reference voltage V _R1 and determines the first mode according to the comparison result. The discrimination signal is output to one input terminal of the coincidence circuit 12 and the D terminal of the D flip-flop 13, respectively.

In this case, the reference voltage V _R1 is set to, for example, an approximately intermediate level between both DC levels in the sync tip level transmission section in the reference mode and the high image quality mode. Therefore, when the recording mode is the high image quality mode, V _D1 > V _R1 and the first
The mode discriminating signal becomes high level, while V _D1 <V _R1 when the recording mode is the standard mode, and the first mode discriminating signal becomes low level.

In this way, the comparator 10 obtains the first mode discrimination signal that switches between the high level and the low level according to the recording mode based on the sync tip level of the reproduction luminance signal a.

On the other hand, the monostable multivibrator 8 delays the incoming sampling pulse b by a predetermined time to generate a sampling pulse c as shown in FIG. 2C, and outputs it to the sampling and holding circuit 7.

The sample hold circuit 7 is configured to perform the sampling pulse c
Based on the above, the DC level V _D2 of the reproduction luminance signal a supplied from the LPF 4 in the pedestal level transmission section is sampled and held and output to the non-inverting input terminal of the comparator 14.

On the other hand, the reference voltage source 15
The reference voltage V _R2 is supplied from the comparator 14, and the comparator 14 compares the direct current level V _{D2 in} the pedestal level transmission section of the reproduction luminance signal a with the reference voltage V _R2, and the second mode corresponding to the comparison result. The discrimination signal is output to the other input terminal of the coincidence circuit 12.

In this case, the reference voltage V _R2 is set to, for example, an approximately intermediate level between both DC levels in the pedestal level transmission section in the standard mode and the high image quality mode. Therefore, when the recording mode is the high image quality mode, V _D2 > V _R2 and the second mode discrimination signal becomes high level. On the other hand, when the recording mode is the standard mode, V _D2 <V _R2 The mode discrimination signal of No. 2 becomes low level.

In this way, the comparator 14 obtains the second mode discrimination signal which switches between the high level and the low level according to the recording mode based on the pedestal level of the reproduction luminance signal a.

The matching circuit (EX-NOR circuit) 12 includes comparators 10 and 14
The output becomes high level only when both levels of the first and second mode discrimination signals supplied respectively match, and the output becomes low level when both levels do not match. The output signal of the coincidence circuit 12 is output to the other input terminal of the AND circuit 9.

The AND circuit 9 outputs the output horizontal synchronizing signal of the synchronizing signal separation circuit 5 as a clock signal to the CK terminal of the D flip-flop 13 only while the output signal of the matching circuit 12 is at a high level.

The D flip-flop 13 outputs the signal obtained by latching the first mode discrimination signal from the comparator 10 according to the clock signal as a mode discrimination signal from its Q terminal.
Output to 16.

Thus, for example, when the recording mode is the high image quality mode, the high-level first mode determination signal is supplied to the D terminal of the D flip-flop 13 and the clock signal is supplied to the CK terminal. A high-level mode discrimination signal is output from the Q terminal. At this time, if the output of one of the comparators 10 and 14 becomes low level due to the influence of noise, etc., the output of the matching circuit 12 becomes low level,
The AND circuit 9 stops outputting the clock signal. Therefore, the output mode discrimination signal of the D flip-flop 13 is held at the high level. After that, the comparator 10,1
When both outputs of 4 become low level, the output of the coincidence circuit 12 returns to high level and a clock signal is output from the AND circuit 9, so that the output mode discrimination signal of the D flip-flop 13 changes from high level to low level. Switch.

In this way, the mode state can be shifted only when the output levels of the comparators 10 and 14 match, and when the output levels are different, the previous mode state is retained.

Next, the recording system and reproducing system of the VTR to which this embodiment is applied will be described with reference to FIGS. 3 and 4. First, the VTR recording system will be described with reference to FIG. 3. The video signal input to the input terminal 17 is supplied to the low-pass filter (LPF), the comb filters 18 and 19, and the band-pass filter (BPF) 20, respectively. .

The BPF 20 correlates the carrier color signal from the incoming video signal and outputs it to the color signal recording processing circuit 21. Color signal recording processing circuit 21
Converts the carrier color signal into a low-frequency converted carrier color signal and outputs it to the adder 22.

On the other hand, LPF and comb filter 18, pre-emphasis circuit
The 23 and FM modulator 24 constitute a standard mode, and the LPF and comb filter 19, the pre-emphasis circuit 25 and the FM modulator 26 constitute a luminance signal recording processing circuit for a high image quality mode. Here, both the luminance signals which are waved from the video signal from the input terminal 17 by the LPF and the comb filters 18 and 19 are respectively given the pre-emphasis characteristics and are frequency-modulated (FM modulated) to be switched by the switch circuit 27. Output to the terminals 27a and 27b.

A mode switching signal corresponding to the recording mode set by a mode selection switch (not shown) or the like is supplied to the switch circuit 27 via a terminal 28. Therefore, when the recording mode is the standard mode, the switch circuit 27 is switched to the terminal 27a side, while when the recording mode is the high image quality mode, the switch circuit 27 is switched to the terminal 27b side.

In this way, the pre-emphasis characteristic according to the recording mode is given, and the frequency-modulated luminance signal (FM luminance signal) FM-modulated at the carrier frequency according to the recording mode is sent from the switch circuit 27 to the adder 22. Is output.

The adder 22 adds the FM luminance signal and the low-frequency conversion carrier color signal and supplies them to the rotary heads H ₁ and H ₂ via the recording amplifier 29 to record them on the magnetic tape T.

Next, regarding the reproduction system of the VTR to which this embodiment is applied,
It will be described with reference to the drawings. Here, the reproduced video signals reproduced from the magnetic tape T by the rotary heads H ₁ and H ₂ are preamplifiers 30 and 31.
To the terminals 32a and 32b of the switch circuit 32, respectively. The switch circuit 32 is switched in response to the head switching pulse coming from the terminal 33, whereby a continuous reproduced video signal is obtained.

The output reproduction video signal of the switch circuit 32 is a low-pass filter (LP
F) 34 and high-pass filter (HPF) 35, respectively. LP
F34 corrugates the low-frequency conversion carrier color signal from the incoming reproduction video signal and outputs it to the color signal reproduction processing circuit 36. The color signal reproduction processing circuit 36 frequency-converts the incoming low-frequency converted carrier color signal into a carrier color signal in the original frequency band and outputs the carrier color signal to the adder 37.

On the other hand, the HPF 35 waves the reproduced FM luminance signal from the incoming reproduced video signal and outputs it to the terminals 40a and 40b of the switch circuit 40 via the equalizer circuits 38 and 39, respectively. The output signal of the switch circuit 40 is supplied to the limiter 42 and the mode discriminating apparatus 1 according to the present embodiment via an automatic gain control circuit (AGC circuit) 41, respectively. The output signal of the limiter 42 is the FM demodulator 43, LPF4.
4, demodulated through the de-emphasis circuit 45, the FM demodulator 46, the LPF 47, and the de-emphasis circuit 48, respectively, and supplied to the terminals 49a and 49b of the switch circuit 49.

The mode discrimination device 1 generates a mode discrimination signal according to the output signal (reproduction FM luminance signal) of the AGC circuit 41 and outputs it to the system controller 50 as described above. The system controller 50 generates a mode switching signal in response to the incoming mode discrimination signal and outputs it to the switch circuits 40 and 49, respectively.
These are switch-controlled.

Here, the equalizer 38, the FM demodulator 43, the LPF 44, and the de-emphasis circuit 45 are provided for the luminance signal reproduction processing in the standard mode, and likewise the equalizer 39 and the FM demodulator 4
6, LPF 47 and de-enhancement circuit 48 are provided for the luminance signal reproduction processing in the high image quality mode. Therefore,
When the mode discriminating apparatus 1 discriminates the recording mode as the standard mode, the switch circuits 40 and 49 are connected to the terminals 40a and 4 respectively.
When the recording mode is determined to be the high image quality mode, the switch circuits 40 and 49 are connected to the terminals 40b and 49b, respectively.
Connected to. As a result, demodulation according to the recording mode and addition of an equalizer characteristic and a de-emphasis characteristic are performed on the reproduced FM luminance signal.

Thereafter, the adder 37 outputs the video signal obtained by adding the output carrier color signal of the color signal reproduction processing circuit 36 and the output luminance signal of the switch circuit 49 to the output terminal 51.

The FM demodulator 3 and the LPF 4 in the mode discriminating apparatus 1 may be omitted and the mode discrimination may be performed based on the output luminance signal of the LPF 47 for the high image quality mode. Further, it goes without saying that the device of the present invention can be applied to a reproducing device for a recording medium other than the magnetic recording medium.

EFFECTS OF THE INVENTION As described above, according to the present invention, the mode discrimination is performed based on both the DC levels of the sync chip level transmission section and the pedestal level transmission section of the FM-demodulated reproduced video signal, so that the influence of noise and the like is exerted. This enables the mode state to be maintained stably even if either the sync tip level or the pedestal level malfunctions, and the mode does not malfunction due to changes in the pattern of the reproduced video signal. The determination can be performed automatically and surely, and therefore, it does not require complicated switching operation of the changeover switch, is very convenient for the user, and is reproduced in a reproduction mode different from the recording mode. Since it can be prevented from being mistaken, it is possible to prevent the user from misunderstanding that it is a failure, and with an extremely simple circuit configuration Having characteristics such as can be achieved over de discriminating device.

[Brief description of drawings]

FIG. 1 is a circuit system diagram showing an embodiment of a mode discriminating apparatus for a recording medium reproducing apparatus according to the present invention, and FIGS. 2 (A) to 2 (C).
1 is a signal waveform diagram for explaining the operation of the circuit system shown in FIG. 1, and FIGS. 3 and 4 are block system diagrams showing an example of a recording system and a reproducing system of a VTR to which the device of the present invention is applied, FIG. FIG. 6 is a diagram for explaining the operation of the device of the present invention. 1 ... Mode discrimination device, 2 ... Playback frequency-modulated luminance signal input terminal, 3 ... FM demodulator, 4 ... Low-pass filter (LP
F), 5 ... Synchronous signal separation circuit, 6, 7 ... Sample and hold circuit, 8 ... Monostable multivibrator, 9 ... AND
Circuit, 10,14 …… Comparator, 11,15 …… Reference voltage source,
12: Matching circuit (EX-NOR circuit), 13: D flip-flop, 16: Mode discrimination signal output terminal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Yamada 3-12 Moriya-cho, Kanagawa-ku, Kanagawa Prefecture Victor Company of Japan, Ltd. (72) Inventor Masahiko Tsuruta 3-12 Moriya-cho, Kanagawa-ku, Yokohama Address within Victor Company of Japan, Ltd. (56) References JP-A-62-223854 (JP, A) SAIKAI-SHO 62-5775 (JP, U)

Claims (1)

[Claims] 1. A signal obtained by reproducing and demodulating a video signal recorded on a recording medium in one of a plurality of recording modes in which carrier frequencies of frequency-modulated signal video signals are different from each other. Means for outputting a first mode discrimination signal indicating the recording mode of the reproduced video signal based on the DC level of the sync tip level transmission section of the reproduced video signal, and based on the DC level of the pedestal level transmission section of the reproduced video signal Means for outputting a second mode discrimination signal indicating the recording mode of the reproduced video signal, and a third mode indicating the recording mode when the first and second mode discrimination signals indicate the same recording mode, respectively. When the discrimination signal is output and the first and second mode discrimination signals indicate different recording modes, the preceding first and second mode discrimination signals are respectively output. Mode determination unit of the recording medium reproducing apparatus characterized by a more structure as it is the mode determination unit for storing and outputting a mode discrimination signal of the third when showed an recording mode.