JPS62291275A - Discriminating device for recording mode of reproducing video signal - Google Patents

Abstract

PURPOSE:To attain the discrimination of a recording mode, by detecting a carrier frequency equivalent to the sync chip level of a reproducing video signal to be frequency-modulated obtained from the reproduction of a recording medium. CONSTITUTION:An FM luminance signal reproduced from a magnetic tape is supplied to BPFs 2 and 3 through an input terminal 1. The BPFs 2 and 3 are filter circuits in which carrier frequencies (fAS, fBS) equivalent to the sync chip levels in a standard mode, and a high picture quality mode, are set as passing center frequencies, and the output of the BPF2 becomes the one having a magnified width in the standard mode, and the output of the BPF3 has a large amplitude in the high picture quality mode. The outputs of the BPFs 2 and 3 are peak-held at peak-holding circuits 4 and 5, and are envelope detected at LPFs 6 and 7. And detected outputs are added on a comparator 8, and the envelope levels of the carrier frequencies (fAS, fBC) are level-compared, then a mode discriminating signal is outputted.

Description

[Detailed Description of the Invention] a. Detailed Description of the Invention Industrial Field of Application The present invention relates to a recording mode discrimination device for a reproduced video signal, and more particularly, to a device for determining a recording mode of a reproduced video signal, and particularly for switching the carrier frequency of a frequency-modulated video signal according to a selected mode. The present invention relates to a device for determining the distribution mode of a reproduced video signal for reproduction of a recorded recording medium.

Conventional technology In home VTRs, the recent improvement in the performance of magnetic tapes and the performance of magnetic heads has combined to make it easier to use frequency-modulated luminance signals than current VTR standards (for example, VH3). By setting the carrier wave frequency to a high value for recording and playback, it is possible to record and play back images with higher resolution and higher quality than images recorded and played back in the current VTR standard mode (hereinafter referred to as standard mode). A high-quality mode recording and reproducing method for obtaining images is being considered.

Problems to be Solved by the Invention However, since there is no complete correspondence between the standard mode and high-quality mode, it is necessary to determine in which of the modes the video signal to be reproduced was recorded. However, it is necessary to play back in the same mode as when recording.

For this reason, for example, F! The VTR is equipped with a changeover switch for switching between the semi-mode playback system and the high-quality mode playback system,
First, the recorded edge signal of the magnetic tape is reproduced in one of the modes, and then, while monitoring the reproduced image, a changeover switch is changed to reproduce the reproduced image in the mode that correctly reproduces the reproduced image.

However, this method is not only extremely inconvenient to use, but also has the problem that when playing in a different mode, the reproduced image quality deteriorates so much that the user may mistake it for a failure.

Therefore, the present invention was created in view of the above points.
An object of the present invention is to provide a recording mode discriminating device for a reproduced video signal that automatically determines in which mode a reproduced signal was recorded out of a plurality of modes.

Means for Solving the Problems The recording mode discriminating device for reproduced video signals according to the present invention has n types of frequency modulated video signals whose carrier frequencies are mutually different (
n is an integer of 2 or more), the carrier wave frequency corresponding to the sync chip level of the reproduced frequency modulated video signal obtained by reproducing the recording medium on which the frequency modulated video signal is recorded in one mode. By detecting this, the recording mode is determined.

Further, the recording mode discrimination device for a reproduced video signal according to the present invention as set forth in claim 2 is characterized in that the carrier wave frequency of the frequency modulated video signal corresponds to each sync chip level of n types of modes in which the carrier wave frequency is different from each other. It is comprised of n filter circuits that pass modulated video signal frequencies separately, n detection circuits, and means for outputting a recording mode discrimination signal of the reproduced frequency-modulated video signal.

In addition, the reproduction video signal recording mode-specific apparatus 1 unit according to the present invention as described in claim 3 is capable of adjusting the frequency-modulated video signal frequency corresponding to the sync chip level of one of the two modes. It is composed of a first filter circuit that allows the signal to pass, a first detection circuit, and a comparator.

In the recording mode discriminating device for reproduced video recited in claim 2, the frequency modulated video signal recorded on the recording medium at an arbitrary speed is reproduced from the recording medium. After that, the frequency components corresponding to the sync depth level of each mode are separately filtered by n filter circuits, and then supplied to the corresponding detection circuits, where they are processed.
fl is detected. The signals respectively taken out from the n detection circuits are compared in level by the discrimination signal output means, and based on the result, a discrimination signal for the recording mode of the reproduced frequency modulated video signal is output.

In addition, in the recording mode discrimination device 2 for reproduced video signals recited in claim 3, the frequency modulated video signal recorded in one of the two modes is reproduced and passed through a single filter circuit. After the frequency component corresponding to the sync tip level of the first mode is divided into 111F waves, it is supplied to a comparator through a detection circuit, where the level is compared with a preset reference level to obtain a recording mode discrimination signal.

Embodiments FIGS. 1 to 4 each show a block system diagram of each embodiment of the 5A neck of the present invention. In each figure, the same components are given the same reference numerals. The device δ of the present invention is a device installed in a VFR video signal reproduction system, and the video signal to be reproduced is e.
Recorded in either standard mode or high quality mode. Here, the video signal, especially the luminance signal, is recorded on a magnetic tape in the form of a frequency-modulated luminance signal (FM luminance signal) obtained by frequency modulating (FM) a carrier wave, and is reproduced. In the standard mode, the frequency spectrum of the signal is as shown by black square in FIG. 6, and in the high image quality mode, the carrier frequency is set higher than in the standard mode, as shown by black square in the same figure.

In the frequency spectrum of the FMtf signal shown in FIG. 6, fAS, fAp, and fAw represent carrier frequencies at the sync level S, pedestal level P, and white peak level W of the FMtf signal shown in FIG. Similarly, in the frequency spectrum ■, ras, fep, and f'8W are the sync tip level S and the pedestal level P of the luminance signal.
and the carrier frequency at the white peak level W.

For example, the carrier frequency fAS in standard mode is 3.
4MH2, fAp is 3.8M1-1z, f' A
W is 4.4MH2, and the carrier frequency TBS in G Nii 'rJ mode is 5.4MH2. OMH2, f e p
is 5.6MH2°fOW is 6.7M)-12.

As can be seen from FIG. 6, at the carrier frequencies fAS and fDS corresponding to the sync level, sideband frequency components of the FM luminance signal of the other mode also exist.
Carrier frequency fAS.

The energy of tas is 4 times higher than that of the sideband component of the same frequency in the other mode. The present invention focuses on this point to perform mode discrimination, and an embodiment will be described below.

In the first embodiment shown in FIG. 1, the F M Yi ff signal reproduced from the magnetic arp is supplied via an input terminal 1 to bandpass filters (hereinafter referred to as BPF) 2 and 3, respectively. BPF2 is a filter circuit with a narrow pass band [characteristic] whose passing center frequency is the carrier wave frequency fAS equivalent to the sync chip level in the standard mode, and BPF3 is a filter circuit whose passing center frequency is the carrier wave frequency f's corresponding to the sync tip level in the high image quality mode. This is a filter circuit that has an autumn passband characteristic fi. Therefore, if the input reproduced FM luminance signal is recorded in standard mode, BPF3 is higher than BPF3.
The output signal of PF2 is extracted with a larger amplitude, and if recording is performed in high-quality mode, the output signal of bBPF3 has a larger amplitude than that of 8PF2.

BPF2.3 Ryogawa power signal is 11'f of the video section signal.
In order to avoid l, it is supplied to a rectification and peak hold circuit 4.5 where it is peak held after rectification. The peak hold has a large time constant and is not affected by the signal in the culm image section, but the FM (H signal) extracted at the same time has a larger amplitude than the actual one due to noise etc., and as a result, Conditions that cause the output to be reversed)
On the other hand, since the time required for recovery becomes longer, an appropriate time constant is selected in consideration of both factors.

Each output signal of the rectifier and peak hold circuits 4 and 5 is supplied to low-pass filters (hereinafter referred to as 1.PF) 6 and 7. This is because the rotating head sequentially scans across multiple tracks during special playback 1, such as in the search section or during still playback. This is to prevent the amplitude of the reproduced FMr4 degree signal from greatly decreasing during the period when the track is scanned, which may cause malfunction.

The LPF 6 and the rectification and peak hold circuit 4 constitute a first detection circuit, and the LPF 7 and the rectification and peak hold circuit 5 constitute a second detection circuit.

Each envelope detection signal taken out from the LPF 6.7 is supplied to a comparator 8, where the levels are compared.

That is, the comparator 8 compares the envelope levels of the image frequency components of the carrier wave frequencies fAs and f'os corresponding to the sync level obtained from the reproduced FM luminance signal, and thereby the reproduced FMIEti intensity signal is recorded in the standard mode. If it has been recorded in high quality mode, it is at the first logic level, and if it has been recorded in high quality mode, it is at the second logic level.

In addition, if the amplitudes of both output FM signals of BPF2 and 3 are approximately equal, and the amplitudes are not stable due to noise etc.,
The output signal of the comparator 8 may rapidly go back and forth between the first logic level and the second logic level, causing so-called chattering, which may result in a screen that is difficult to view. In consideration of such a case, the comparator 8 may be provided with a known hysteresis characteristic by a known means.

Next, a second embodiment of the device of the present invention will be explained together with the second embodiment (3). In the figure, the signal taken out from LPF6.7 is supplied to comparator 11.13, where LttF"
The levels are separately compared with reference pressures at preset levels from the Fjs pressure sources 12 and 14.

As a result, when the input reproduced FM luminance signal is recorded in standard mode, the output signal level of L and PF 6 becomes human level than the output reference voltage If of the reference voltage source 12, so that the comparator 11 The output signal becomes high level,
In addition, since the output signal level of the LPF 7 is lower than the output reference voltage of the reference voltage source 14, the output signal of the comparator 13 is at a low level (hereinafter, such an output state of the comparator 11.13 will be referred to as ), and -1
2.When recording is performed in high-quality mode, the output signal of the comparator 11 is at a low level, and the output signal of the comparator 13 is at a high level (hereinafter, such output states of the comparators 11 and 13) (indicated by "L/1")
becomes.

The discrimination matrix circuit 15 includes comparators 11 and 13
This is an arithmetic circuit that generates a high level signal when the Ryokawa power signal H/L and a low level signal when the L/G power signal is H/L, and outputs it as a hemo power discrimination signal at the output terminal 9. By the way, the 1'' raw FMti degree signal does not always maintain a stable level state, and may become extremely low during special playback or the like.

For this reason, both the power signals of the comparators 11 and 13 may be at the same level (L/L or H/)-1>17. Therefore, when inputs of the same level are received, the discrimination matrix circuit 15 discriminates that it is a high image quality mode and generates a low level signal.

The reason why high-quality mode is given priority in this way is that
If the standard mode is determined, the middle and high frequency components of the FM luminance signal recorded in high-quality mode will be cut by the standard mode playback system, so the video signal recorded in high-quality mode will be played back in standard mode. On the other hand, the reproduction system in high-quality mode has a wide transmission band and can transmit the FM luminance signal recorded in standard Q mode to a certain extent, so it cannot be viewed in standard mode. This is because even when a recorded video signal is played back in a high-quality mode, the quality of the reproduced image does not have to deteriorate so much that it becomes unwatchable.

According to this embodiment, the envelope levels of the two frequency components are compared with the reference voltage, and a discrimination signal is output based on the results. It has the advantage that it has a large amount of information, and from this it can make more stable determinations.

Next, a third embodiment of the present invention will be described with reference to FIG. In the figure, the same components as in Figures 1 and 2 are the same as those in Figures 1 and 2.
I will add a jungo and omit its explanation.

In FIG. 3, each output signal of comparators 8, 11 and 13 is supplied to a discrimination matrix circuit 17. In FIG. This discrimination circuit 17 outputs a predetermined level of () from the combination of the above three instantaneous levels of the human power signals to the output terminal 9 as a discrimination signal.

The output signals of the comparators 11, 13 and 89 discrimination matrix circuit 17 are summarized as shown in the following table.

However, ×: Either H/L2H or [Output As can be seen from the above table, when the output logic levels of comparators 11 and 13 are different from each other, comparator 8
Regardless of the output of the discriminating matrix circuit 17, a signal having the same logic level as the output signal of the comparator 11 is output. On the other hand, when both the power signals of the comparators 11 and 13 are at the same logic level, the discrimination matrix circuit 17 outputs the L signal according to the output signal of the comparator 8.
Outputs a discrimination signal for the higher level mode of the power signals of both PF6 and PF7.

According to this embodiment, the detection of two scales is obtained by comparing the envelope level of two frequency components equal to the frequency corresponding to the sync tip level of the FM luminance signal specified in the two T-modes with the reference voltage. Since the detection information from the comparator 8 that detects the magnitude relationship between the envelope levels of the two frequency components is added to the information, and mode discrimination is performed based on this information, mode discrimination is more stable than in the second embodiment. I can do it.

Incidentally, in each of the above embodiments, two BPFs are used to pass the FMX'i degree signal frequency signal frequency corresponding to each sync chip level of two types of modes.
It can also be configured with just one F. The fourth embodiment of the present invention shown in FIG. 4 is an example of this case, and the output signal of the LPF 6 is supplied to a comparator 20, where the level is compared with a reference voltage from a reference voltage source 21. Input playback FM brightness (
, i If F3 was recorded in standard mode, LP
The reference voltage from the reference voltage source 21 is selected so that the output signal of F6 is higher than the reference voltage, and, on the other hand, is smaller than the reference voltage when recording in high-quality mode.

Therefore, from the comparator 20 to the output terminal T9, PF
A mode determination signal is output by comparing the level of the output signal of 6 and the reference voltage from the reference voltage source 21.

Note that, of course, BPF3 may be used instead of BPF2.

Next, a reproduction system of a two-head helical scan type VTR having the above-mentioned mode discrimination device will be explained with reference to FIG. In the figure, the FM luminance signal recorded in the magnetic arp 25 and the low frequency change l! The frequency-division multiplexed signal with the II carrier color signal is alternately reproduced by rotating heads 26 and 27, and is supplied through preamplifiers 28 and 29 to a switch circuit 30 that is switched by a head switching pulse with a two-field cycle from a terminal 31. Here, the continuous signal is supplied to the Ia band filter (hereinafter referred to as PF) 32 and LPF 48. The reproduced FM luminance signal divided into tliP waves by the HPF 32 is supplied to the switch circuit 35 through the equalizer circuit 33 in the standard mode and the equalizer circuit 34 in the high image quality mode, and further passes through the AGC circuit 36 to the limiter 37. and is supplied to the mode discrimination device 38 according to the present invention.

Reproducing FM with amplitude fluctuation components removed by limiter 37
IIi degree (U degree is standard mode reproduction system FM demodulator 3
9. LPF40 and Dien 7? The signal is supplied to a switch circuit 45 via a cis circuit 41, and an FM demodulator 42 for high image quality mode reproduction. The signal is supplied to a switch circuit 45 via an LPF 43 and a de-emphasis circuit 44.

On the other hand, as described above, the mode discriminating device 38 determines that the playback F
A mode discrimination signal 17 which is automatically determined whether the MRH degree signal was recorded in the standard mode or high image quality mode is supplied to the system controller 46, which then switches the switch circuits 35 and 45. Supplied as a bulse.

As a result, the switch circuits 35 and 45 are connected to the terminal A side when determining the standard mode, and are switched to the terminal B side when determining the high image quality mode.

Furthermore, the reproduced signal taken out from the switch circuit 30 described above is converted into a low frequency carrier color signal by the LPF 48 by 1! I
After being F-waved, O-ma place 1 again! I! A circuit 49 removes jitter using known means and restores the reproduced carrier color signal of the original band. The addition circuit 47 adds and synthesizes this reproduction carrier color signal and the reproduction degree signal taken out from the switch circuit 45 and reproduced and demodulated by the reproduction system in the same mode as that at the time of recording, and outputs the resultant signal as a reproduction color video signal to a terminal. 50
Output to.

Note that the present invention is not limited to the above-described embodiments, and mode discrimination can be performed in the same manner as described above even when there are three or more types of recording/reproducing modes.

Effects of the Invention As described above, according to the present invention, it is possible to automatically determine which mode has been recorded among a plurality of modes based on the reproduced image @ signal, so that it is not necessary to change the manual switch as in the past. There is no need for any operation, which improves usability, and also prevents the user from mistaking it for a malfunction.Furthermore, the signal obtained by detecting the transmission frequency corresponding to the sync chip level in each mode after 111F waves. If the discrimination information is obtained by at least using multiple results of level comparison with the reference voltage, the playback FMIl!
l! Even if the image signal is unstable due to the influence of noise or fluctuations, it is possible to output a stable discrimination signal because there is a large amount of detection information.Furthermore, when configured using a single filter circuit, the circuit configuration is It has a number of advantages, such as being simple, and being advantageous in terms of circuit configuration since the existing synchronous signal separation IC can be used as is in any case.

[Brief explanation of drawings]

1 to 4 are block diagrams showing each embodiment of the device of the present invention, FIG. 5 is a diagram showing video signal reproduction, and FIG. 6 is a diagram showing the frequency spectrum of the FM signal in standard mode and high image quality mode. FIG. 7 is a block system diagram showing an example of video signal reproduction [ff] having the apparatus of the present invention. 1... FMW degree signal input terminal, 2.3... Bandpass filter (BPF), 4.5... Rectification and peak hold circuit, 8, 11.13.20... Comparator, 9.
. . . Discrimination signal output terminal, 12.14.21 . . . Reference voltage source, 15.17 . . . Matrix circuit for discrimination.

Claims (3)

[Claims] (1) Obtained by reproducing a recording medium on which a frequency-modulated video signal is recorded in one of n modes (n is an integer of 2 or more) in which the carrier wave frequency of the frequency-modulated video signal is different from each other. 1. A recording mode discriminating device for a reproduced video signal, characterized in that the recording mode is determined by detecting a carrier wave frequency corresponding to a sync chip level of a reproduced frequency modulated video signal. (2) Obtained by reproducing a recording medium on which a frequency-modulated video signal is recorded in one of n modes (n is an integer of 2 or more) in which the carrier wave frequency of the frequency-modulated video signal is different from each other. n filter circuits to which a reproduced frequency-modulated video signal is supplied and separately pass the frequency-modulated video signal frequencies corresponding to the respective sync chip levels of the n types of modes; and each of the n filter circuits. Output signals are provided separately,
There are a total of n detection circuits that detect the envelope, and the results obtained by comparing the levels of the respective output signals of the n detection circuits, and the preset settings with each output signal of the n detection circuits. recording of a reproduced video signal, comprising: means for outputting a signal for determining the recording mode of the reproduced frequency-modulated video signal based on at least one of the results obtained by comparing the level with a reference level obtained by Mode discriminator. (3) A reproduced frequency-modulated video signal obtained by reproducing a recording medium on which a frequency-modulated video signal is recorded in one of two modes in which the carrier wave frequency of the frequency-modulated video signal is different from each other is supplied. a single filter circuit that passes a frequency-modulated video signal frequency corresponding to the sync chip level of one of the two modes set in advance, and an output signal of the filter circuit is supplied, and its envelope is a detection circuit that detects the line; and a comparator that outputs a signal for determining the recording mode of the reproduced frequency-modulated video signal based on the result obtained by comparing each output signal of the detection circuit with a preset reference level. A recording mode determination device for a reproduced video signal, characterized in that: