JPS62291273A - Discriminating device for recording mode of reproducing video signal - Google Patents

Abstract

PURPOSE:To attain the discrimination of a recording mode, by detecting the carrier frequency of a reproducing video signal to be frequency-modulated obtained by 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 BPF2 is a filter circuit in which the carrier frequency equivalent to a pedestal level in a standard mode is set as a passing center frequency, and the BPF3 is the filter circuit having a narrow band characteristic in which the carrier frequency equivalent to the pedestal level in a high picture quality mode is set as the passing center frequency. Each of the output signals of the BPFs 2 and 3 is supplied to LPFs 6 and 7 respectively through rectifier and peak holding circuits 4 and 5. Envelope detecting signals outputted from the LPFs 6 and 7 are sent to a comparator 8, and are compared with the first logic level at a standard mode time, and with the second logic mode at a high picture quality time, 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 8 when reproducing a recorded recording medium.

Conventional technology In home VTRs, the performance of frequency-modulated luminance signals is higher than that of current VTR standards (e.g. VH8), due to improvements in the performance of magnetic tapes and magnetic heads in recent years. By setting the carrier wave frequency to a higher value for recording and playback, the W? A recording and reproducing method in a high-quality mode that obtains high-quality images with high resolution has been considered.

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

For this reason, for example, a VTR is equipped with a switch for switching between a standard mode playback system and a high-quality mode playback system, and the green signal recorded on the magnetic tape is first played back in either mode, and then the playback image is monitored. Turn the selector switch l/
I decided to play back in the mode that would allow the image to be reproduced correctly.

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

Therefore, the present invention was created in view of the above points.
It is an object of the present invention 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 Recording mode determination of reproduced video signal of the present invention ``''jA Ti
is 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. The recording mode is determined by detecting the carrier frequency of the reproduced frequency-modulated video signal.

Further, the recording mode discrimination device for a reproduced video signal according to the present invention as set forth in claim 3 is characterized in that the frequency modulated video signal corresponds to each pedestal level of n types of modes in which the carrier wave frequency of the frequency modulated video signal is different from each other. It is composed of n filter circuits that pass video signal frequencies separately, n detection circuits, and means for outputting a recording mode discrimination signal of the reproduced frequency modulated video No. 13.

Further, the recording mode discrimination device for a reproduced video signal according to the present invention as set forth in claim 4 passes a frequency-modulated video signal frequency corresponding to the pedestal level of one mode among the 2 GT modes. It consists of a single filter circuit, a single detection circuit, and a comparator.

In the apparatus for determining the recording mode of a reproduced video signal recited in Item 3 of the patent claim σll, the frequency modulated video signal recorded on the recording medium in any one mode is reproduced from the recording medium and then n After the frequency components corresponding to the bed scale level of each mode are separately separated into P waves by the filter circuits, they are supplied to the corresponding detection circuits, where they are envelope-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. □Furthermore, in the recording mode discrimination device for a reproduced video signal according to claim 4, the frequency modulated video signal recorded in one of the two modes is reproduced and processed by a single filter circuit. The frequency component corresponding to the pedestal level of the first mode is divided into
After being converted into an IP wave, the signal 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 present invention. In each figure, the same components are given the same reference numerals. The device of the present invention is a device provided in a video signal reproduction system of a VTR, and the video signal to be reproduced is recorded in either a standard mode or a high-quality mode. Here, the video signal, especially the luminance signal, is recorded on a magnetic tape in the form of a frequency-modulated video signal (FMfli degree signal) obtained by frequency modulating (FM) a carrier wave, and is reproduced. The frequency spectrum of the signal in the above standard mode is as shown in Fig. 6,
In the high image quality mode, the carrier frequency is set higher than in the standard mode, as shown by black in the figure.

In the frequency spectrum I of the FM luminance signal shown in FIG.
fAs, fAp and fAw are the sync tip level S of the wI degree signal shown in FIG. The carrier frequency at the pedestal level P and the white peak level W is shown, and similarly the frequency spectrum ■, res, f'e'p and fs
w indicates the carrier frequency at the sync depth level S, pedestal level P, and white peak level W of the luminance signal. For example, in the standard mode, the carrier frequency fAS is 3.4MH2, fAp is 3.8MH2, f A w 4
．． t 4.4MH2, and the above carrier frequency f's in high image quality mode is 5.0M)-1z, f, P are 5
．． 6MH2°f'ew is 6.7MHZ.

As can be seen from Fig. 6, at the carrier frequencies fAP and f8P corresponding to the pedestal level, there are also sideband frequency components of the FM brightness signal of the other mode, but the energy of the carrier frequencies fAP and fBP is higher. is four times larger than the energy of the sideband component of the same frequency in the other mode. The present invention focuses on this point and performs mode discrimination, and an embodiment will be described below.

In the first embodiment shown in FIG. 1, an FM luminance signal reproduced from a magnetic tape is supplied via an input terminal 1 to band pass filters (hereinafter referred to as BPF) 2 and 3, respectively. Br
F3 is a filter circuit with a narrow pass band characteristic whose pass center frequency is the carrier wave frequency fAP corresponding to the pedestal level in the standard mode, and BrF3 is a filter circuit with a narrow pass band characteristic whose pass center frequency is the carrier wave frequency faρ corresponding to the pedestal level in the high image quality mode. This is a filter circuit with characteristics. Therefore, if the input reproduced FM luminance signal is recorded in standard mode, the output signal of BrF3 will be extracted with a larger amplitude than that of BrF3, and if it is recorded in high quality mode, the output signal of BrF3 will be extracted with a larger amplitude than that of BrF3. The signal has a larger amplitude.

The Ryokawa power signal of BrF3.3 is supplied to a rectification and peak hold circuit 4.5 in order to avoid the influence of signals in the video section, where it is rectified and peak held. The longer the time constant of peak hold, the less it will be affected by the signal in the video section, but the FM signal extracted at the same time will have a larger amplitude than it actually is due to noise, etc., and as a result, the output of comparator 8, which will be described later, will be inverted. On the other hand, under such conditions, the time required for recovery becomes longer, so an appropriate time constant is selected based on the balance between the two conditions.

Each output signal of the rectifier and peak hold circuit 4.5 is supplied to a low pass filter (hereinafter referred to as LPF) 6.7.

This is because during special playback such as serve or still, the rotating head sequentially scans across multiple tracks, so tracks recorded with a rotating head with a different azimuth angle than the rotating head being played back (so-called reverse tracks) ) is scanned, the amplitude of the reproduced FM luminance signal may drop significantly and there is a risk of malfunction, so this is to prevent this.

The PF 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 uses the carrier wave frequencies fAP and t corresponding to the pedestal level obtained from the reproduced FM luminance signal.
The envelope level of the image frequency component of oρ is level-compared, and as a result, if the reproduced FM luminance signal was recorded in standard mode, it will be set to the first logic level, and if it was recorded in high-quality mode, it will be set to the second logic level. A mode discrimination signal having a level is generated and outputted to the output terminal 9.

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 with reference to FIG. In the figure, the signal taken out from LPF6.7 is supplied to comparator 11.13, where reference voltage source 12.
．． The level is compared separately with reference voltages of 14 preset levels.

As a result, if the input reproduction FMR degree signal is recorded as a seed signal, the output signal level of LPF6 will be 1.
Since the level is higher than the output reference voltage of the 3t\ voltage source 12, the output signal of the comparator 11 becomes high level, and the output signal level of the LPF 7 becomes a lower level than the output reference voltage of the reference voltage source 14, so the output signal of the comparator 13 becomes high level. The output signal is low level (hereinafter, such a comparator 1)
1.13 (indicated by H/L), and on the other hand, when recording is in high quality mode, the output signal of comparator 11 is low level, contrary to the above, and comparator 1 is at low level.
The output signal of No. 3 becomes a high level (hereinafter, such an output state of the comparators 11 and 13 will be referred to as L/G1).

The discrimination matrix circuit 15 includes comparators 11 and 13
This is a reproduction circuit which generates a high level signal when the Ryokawa force signal is H/L and a low level signal when the signal is L/H, and outputs it as a hemo-mode discrimination signal at the output terminal 9. By the way, playing FM
The brightness signal does not always maintain a stable level state, and may become extremely low during special playback or the like.

Therefore, both the power signals of the comparators 11 and 13 may be at the same level (L/L or H/H).

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.

Why is the priority given to determining the n-image quality mode in this way? ! If it is determined to be semi-mode, 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. , the image quality is extremely poor and unwatchable, whereas the high-quality mode playback system has a wide transmission band and is recorded in standard mode.
1. This is because signals can also be transmitted over a certain amount of bandwidth, so when a video signal recorded in standard mode is played back in high-quality mode, the quality of the reproduced image does not have to deteriorate so much that it cannot withstand Wffi.

According to this embodiment, the envelope levels of two different frequency components are compared with the reference voltage, and a discrimination signal is output based on their connection, so that the discrimination is more accurate than in the first embodiment. 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 FIGS. 1 and 2 are denoted by the same reference numerals, and their explanations will be omitted.

In FIG. 3, each output signal of the comparators 8, 11 and 13 is supplied to a discrimination matrix circuit 17. The discrimination matrix circuit 17 outputs a signal of a predetermined level from the combination of the logic levels of the three human input signals as a discrimination signal to the output terminal 9.

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

However, ×: Either is acceptable. 1/L: H or L output. As shown in 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 selects 3L according to the output signal of the comparator 8.
The model with the higher level of both river power signals of PF6 and 7
- Outputs a one-mode discrimination signal.

According to this embodiment, FMt! is defined in two modes. A comparator that detects two types of detection information obtained by comparing the envelope level of two frequency components equal to the frequency corresponding to the pedestal level of the i-degree signal with a reference voltage, and further detects the magnitude relationship between the envelope levels of the two frequency components. Since the detection information from 8 is added and mode discrimination is performed based on these, it is possible to perform mode discrimination more stably than in the second embodiment.

Incidentally, in each of the embodiments described above, two BPFs are used to separately pass the FM luminance signal frequencies corresponding to the respective pedestal levels of the two types of modes, but it is also possible to use one BPF.

The fourth embodiment of the present invention shown in FIG. 4 is an example of this case.
The output signal of PF6 is supplied to a comparator 20, where the level is compared with a reference voltage from a reference voltage source 21.

Input playback FM bright f! ! If the signal is recorded in the standard mode, the output signal of the LPF 6 will be higher than the reference voltage, while if it is recorded in the high quality mode, it will be lower than the reference voltage.

Therefore, from the comparator 20 to the output terminal T9, the LPF
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, the first system of the two-head heli-force scan type VTR having the above-mentioned mode discrimination device will be explained with reference to FIG. In the figure, a frequency division multiplexed signal of an FM luminance signal and a low frequency conversion carrier color signal recorded in a magnetic arp 25 is alternately reproduced by rotating heads 26 and 27, and is output from a terminal 31 through a preamplifier 28° 29. The signal is supplied to a switch circuit 30 that is switched by a head switching pulse having a two-field cycle, and is then supplied to a vItr 4-band filter (hereinafter referred to as HPF) 32 and an LPF 48, where it is converted into a continuous signal. 1 minute with HPF32! l
The reproduced FM luminance signal converted into an 1P wave is sent to an equalizer circuit 33 in standard mode and an equalizer circuit 34 in high image quality mode.
are separately supplied to the switch circuit 35, and further supplied from this through the AGC circuit 36 to the limiter 37 and the mode discriminator @38 according to the present invention.

Reproducing FM with amplitude fluctuation components removed by limiter 37
The R degree signal is sent to an FM demodulator 39 of the standard mode reproduction system. LP
The FM signal is supplied to the switch circuit 45 via the F40 and the de-emphasis circuit 41.
Demodulator 42.1PF43 and de-emphasis circuit 44
is supplied to the switch circuit 45 by a shuttle.

On the other hand, as described above, the mode discriminating device 38 determines that the playback F
A mode determination signal obtained by automatically determining whether the M luminance signal was recorded in standard mode or high-quality mode is supplied to the system controller 46, and is further sent to the switch circuits 35 and 45 as a switching pulse. Supplied.

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.
After being waved, jitter is removed by a reproduction chroma processing circuit 49 using known means, and the signal is returned to the reproduction carrier color signal of the original band. The caulking circuit 47 combines this reproduced conveyed color signal with the reproduced luminance 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 it as a reproduced color video signal to the output 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 out of a plurality of modes based on the reproduced video signal. 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 carrier wave frequency corresponding to the pedestal level of each mode after 11 tiF waves and the reference voltage can be used. If discrimination information is obtained by at least using multiple results from level comparisons, even if the reproduced FM video signal is unstable due to the influence of noise or fluctuations,
Since there is a lot of detection information, it is possible to output a stable discrimination signal, and when configured using a single filter circuit,
It has many features such as a simple circuit configuration.

[Brief explanation of the drawing]

1 to 4 are block diagrams showing each embodiment of the device of the present invention, FIG. 5 is a diagram showing the video signal waveform, and FIG. 6 is a diagram showing the frequency spectrum of the FM signal in the standard mode and high image quality mode. The respective figures and FIG. 7 are block diagrams showing an example of a video signal reproducing device having the device of the present invention. 1... FM luminance 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...Discrimination matrix circuit.

Claims (4)

[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. A recording mode discriminating device for a reproduced video signal, characterized in that the recording mode is determined by detecting the carrier wave frequency of the reproduced frequency modulated video signal. (2) Reproduction according to claim 1, wherein the recording mode is determined by detecting a carrier frequency corresponding to a pedestal level among the carrier frequencies of the frequency-modulated video signal to be reproduced. Video signal recording mode discrimination device. (3) 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 the reproduced frequency-modulated video signal is supplied and which separately pass the frequency-modulated video signal frequencies corresponding to the pedestal levels of the n types of modes; and each output of the n filter circuits. signals are supplied separately,
There are a total of n detection circuits that detect the envelope, and the results obtained by comparing the levels of each output signal 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. (4) 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 pedestal level of one of the two modes set in advance, and an output signal of the filter circuit is supplied, and its envelope is 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 level comparing each output signal of the detection circuit with a preset reference level. A recording mode discrimination device for a reproduced video signal, characterized in that: