JPS62291276A - Discriminating device for recording mode of reproducing video signal - Google Patents

Abstract

PURPOSE:To attain the discrimination of a recording mode, by detecting the detection level of a carrier frequency equivalent to a sync chip level in both, or either of interval of a horizontal, and a vertical retrace period, in a reproduc ing video signal to be frequency modulated. CONSTITUTION:An FM luminance signal reproduced from a magnetic tape is supplied to BPFs 2 and 3, and a demodulation circuit 4. The BPFs 2 and 3 are narrow band filter circuits in which the carrier frequencies equivalent to sync chip levels in a standard mode, and a high picture quality mode, are set as center frequencies respectively. The output signals of the BPFs 2 and 3 are envelope-detected at detection circuits 5 and 6, and are sample-held at sample holding S/H circuits 7 and 8. Meanwhile, a reproducing luminance signal is outputted from a demodulation circuit 4, and it is supplied to a sampling pulse generation circuit 10. A sampling pulse generated from the circuit 10 sample-holds the sync chip levels in the horizontal, and the vertical retrace periods, and sends the outputs of the S/H circuits 7 and 8 to a comparator 11.

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 that determines the recording mode of a reproduced video signal when reproducing a recorded recording medium.

Conventional technology In home VTRs, the carrier wave of the frequency-modulated video signal is faster than the current VTR standard (for example, VH8 (registered trademark)) due to the recent improvements in the performance of magnetic tape and the performance of magnetic heads. By setting the frequency high for recording and playback, the current VTRXI! A method of recording and reproducing images in a high-quality mode (hereinafter referred to as standard mode) that produces high-quality images with a higher resolution than images recorded and reproduced in standard mode (hereinafter referred to as standard mode) is being 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 above modes the video signal to be played back was recorded. , it is necessary to play back in the same mode as when recording.

For this reason, for example, a changeover switch for switching between standard q mode playback system and high image quality mode playback system is installed in VTRk:l,
First, the recorded green signal on 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 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 The recording mode discriminating device for reproduced video signals of the present invention has n types of frequency modulated video signals having different carrier frequencies (
The horizontal blanking period and vertical blanking of the reproduced frequency modulated video signal obtained by reproducing the recording medium on which the frequency modulated video signal was recorded in one mode among the modes (n is an integer of 2 or more). The recording mode is determined by comparing and detecting the detection level of the carrier wave frequency corresponding to the sync chip level in both or one of the transmission sections between the line erasure intervals.

Further, the recording mode discriminating 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 is compatible with 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.

Also, special 1. 'F Claim 3: The recording mode discriminating device for a reproduced video signal according to the present invention of ia detects a frequency that transmits a frequency modulated image corresponding to the sync chip level of one of two modes. It is composed of a single filter circuit for passing through, a middle detection circuit, and means for outputting a recording mode discrimination signal.

In the apparatus for determining the recording mode of a reproduced video signal recited in claim 2, 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 sync tip 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 checked by the recording mode discrimination signal output means to compare the signal levels of only the sync chip level transmission section of both or either of the horizontal blanking period and the vertical blanking period. The recording mode of the reproduced frequency modulated video signal is determined based on at least one of the results obtained by level comparison and the results obtained by comparing the signal level of the sync chip level transmission section and a preset reference level, respectively. Output as a discrimination signal.

Furthermore, in the recording mode discriminating device for playback video transmission according to claim 3, the frequency modulated video signal recorded in one of the two modes is reproduced and passed through a single filter circuit. After passing the frequency component corresponding to the sync chip level of the 1st 7th node [F', it is supplied to the output means through the detection circuit, where it is set at a preset reference level, the horizontal blanking period, and the vertical blanking period. The signal level is compared with the signal level of at least one sync tip level transmission section of the erasing period, and based on the result, it is converted into a recording mode determination signal and output.

Embodiments FIGS. 1 to 6 show block diagrams of respective embodiments of the apparatus of the present invention. In each figure, the same components are given the same reference numerals. The present invention \Al is a device installed in a video signal reproduction system of a VTR, and the video signal to be reproduced is recorded in one of the standard mode and 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 (FMii degree signal) obtained by frequency modulating (FM) a carrier wave, and is reproduced. The frequency spectrum of the above &! In the standard mode, it will be as shown by ■ in Figure 8, and the upper &! In the high-quality mode, the carrier frequency is set higher than in the standard mode, as shown by black in the figure.

During the frequency spectrum spectrum analysis of the FM luminance signal shown in FIG.
fAS, fAP and fAW are the sync tip level S of the luminance signal shown in FIG. The carrier wave frequency at the pedestal level P and the white peak level W is shown, and similarly, in the frequency spectrum ■, fos, f'op and fBwG,
The carrier frequency at the sync tip level S, pedestal level P, and white peak level W of the tiii signal is shown. For example, the above carrier frequency fAS in standard mode
is 3.4MH2, f^p is 3.8MHz, f A
W is 4.4 MH2, and the above m transmission frequency f's in high image quality mode is 5.0 M) Iz, fe p is 5.6
MHz.

f'sw is 6.7 MHz.

As can be seen from FIG. 8, at the carrier frequencies fAs and fBs corresponding to the sync tip level, sideband frequency components of the FM luminance signal of the other mode also exist.
Carrier frequency fAS.

The energy of f'os is sufficiently 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.
Examples will be explained 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 bandpass filters (hereinafter referred to as BPF) 2 and 3 and a demodulation circuit 4, respectively. BPF2 is a filter circuit with a narrow passband characteristic whose passing center frequency is the carrier wave frequency fAS corresponding 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'ss corresponding to the sync tip level in the high image quality mode. This is a filter circuit that has narrow cancer band characteristics. Therefore, if the input reproduced FM luminance signal is recorded in standard mode, the output signal of BPF2 will be extracted with a larger amplitude than that of BPF3, and if it is recorded in high quality mode, the output signal of BPF2 will be extracted with a larger amplitude than that of BPF2.
On the output of F3, V) has a larger gain.

The power signals from both BPFs 2 and 3 are separately supplied to detection circuits 5 and 6, where the envelopes are detected, and then supplied to sample and hold circuits (hereinafter referred to as S/H circuits for convenience) 7 and 8.

On the other hand, as shown in FIG. 9, which will be described later, the demodulation circuit 4 consists of an FM demodulation circuit in standard mode, an FM demodulation circuit in high Nl+ quality mode, and a switch circuit for switching the outputs of both FM demodulation circuits. A reproduced luminance signal obtained by demodulating and reproducing the signal in either mode is output to the output terminal 9. This reproduced luminance signal is also supplied to the sampling pulse generation circuit 10 shown in FIG. A sampling pulse having a predetermined level is generated only during the period excluding the section.

These sampling pulses are simultaneously supplied to the S/H circuits 7 and 8, respectively, and the detection signals from the detection circuits 5 and 6 are synchronized signal sections of the horizontal blanking period and the vertical blanking period, respectively. , ripple and hold the signal level during the sync tip level transmission period. Therefore, if the reproduced FM luminance signal was recorded in standard mode,
The output signal of the S/11 circuit 7 has a carrier frequency corresponding to the standard mode sync chip level and is a detection signal of the sync chip level transmission section, so it is at a high level, whereas the output signal of the S/H circuit 8 The signal is a sideband component of the reproduced FM luminance signal in the standard mode, which is equal to the carrier frequency corresponding to the sync chip level in the high-quality mode, and is a detected signal in the sync chip level transmission section, so it has a small level. .

If the reproduced FMtf degree signal is recorded in high-quality mode, the level of the output signal of the S/H circuit 8 will be higher than the level of the output signal of the S/H circuit 7, contrary to the above.

The comparator 11 compares the levels of the Chikara Yamada signals of the S/H circuits 7 and 8, and as a result, if the reproduced FM luminance signal is recorded in the standard mode, it will be recorded at the first logic level, high image quality mode. If so, a mode discrimination signal having a second logic level is generated and outputted to the output terminal 12.

8PF2 and 3 divide the FMOi degree signal frequency corresponding to the respective sync chip levels in the standard mode and high image quality mode into the entire signal interval by 1! Because of the IF wave, the output detection signal levels of the detection circuits 5 and 6 are lower in the video period than in the blanking period. By devising the circuit configuration of the detection circuits 5 and 6, it is possible to reduce the influence of the drop in the detection signal level in this video section, but in this case, for example? !
When mode switching is performed, the switching response speed may be slow due to reasons such as a signal section recorded in standard/[- mode and a signal section recorded in high quality mode being adjacent to each other on the same magnetic tape. Become.

According to this embodiment, since only the detected signal level during the sync chip level transmission period during which the signal is stable is sampled and held for level comparison, clear level comparison results can be obtained. Switching response speed can be increased.

Next, a second embodiment of the device of the present invention will be described with reference to FIG. In the figure, the same components as in FIG. 1 are denoted by the same reference numerals, and their explanations will be omitted. In this embodiment, the levels of both transverse wave signals from the detection circuits 5 and 6 are compared by a comparator 13, and only the signal level during the sync chip level transmission period of the output signal is sampled and held by the S/'H circuit 14. ing.

According to this embodiment, compared to the first embodiment, a mode discrimination operation equivalent to that of the first embodiment can be performed with a configuration having one less S/G1 circuit.

Next, a third embodiment of the device of the present invention will be explained with reference to FIG. In the figure, the same components as in FIG. 1 are denoted by the same reference numerals, and their explanations will be omitted. In FIG. 3, the comparator 15 connects the output signal of the S/)-1 circuit 7 and the reference voltage source
The first criterion from 6? "Comparator 17 is S/1" output signal of circuit 8 and reference voltage source 1
The second base t% lightning voltages from 8 are compared in level. As a result, if the input reproduced FM luminance signal is recorded in the standard mode, the output signal level of the S/T 1 circuit 7 will be higher than the first reference voltage, so the comparator 15
Since the output signal of the S/H circuit 8 becomes a high level and the output signal level of the S/H circuit 8 becomes a level lower than the second reference voltage, the output signal of the comparator 17 becomes a low level (hereinafter, such a comparator 15 .17 output status is indicated by H/L).

On the other hand, when recording is performed in high-quality mode, the output signal of the comparator 15 is at a low level and the output signal of the comparator 17 is at a high level (hereinafter, such an output state of the comparator 15.17 is referred to as a "L"), contrary to the above. / H).

The discrimination matrix circuit 19 includes comparators 15 and 17
This is a performance circuit which generates a high level signal when the Ryogawa force signal is H/L and a low level signal when it is L/H, and outputs it as a hemo-mode discrimination signal to the output terminal 12. By the way, the reproduced FM luminance signal does not always maintain a stable level state, and may become extremely low during special reproduction etc.17. Therefore, it is possible that the Yamada power signals of the comparators 15 and 17 are at the same level (L/L or H/H). Therefore, when the same level of input is received, the discrimination matrix circuit 19 discriminates that the mode is 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 playback system cuts out the middle and high frequency components of the FMTF degree signal recorded in high quality mode, if the standard mode playback system determines that the video signal is When played back in this mode, the image quality is extremely poor (not worthy of an E award), whereas the playback system in high quality mode has a wider transmission band and is 45! FM recorded in semi-mode
Since FIDO Shintan can transmit a certain range of bandwidth, video signals recorded in standard mode can be played back in high quality mode.
: Even in the MA mode, the image quality deterioration of the reproduced image does not have to be so severe that it becomes unwatchable.

According to this embodiment, the envelope levels of two different frequency components in the sync chip level transmission section are compared with the reference voltage respectively, and a discrimination signal is output based on the results. This embodiment has more information for discrimination than the second embodiment, and therefore has the advantage of being able to perform more stable discrimination.

Next, a fourth embodiment of the present invention will be described with reference to FIG. 4. In the figure, the same components as in FIGS. 1 and 3 are designated by the same reference numerals, and their explanations will be omitted.

In FIG. 4, each output signal of comparators 11, 15 and 17 is supplied to a discrimination matrix circuit 20. In FIG. This discrimination matrix circuit 20 outputs a signal of a predetermined level as a discrimination signal to the output terminal 12 from the combination of the logic levels of the three human input signals. The output signals of the comparators 15, 17 and 111 and the discrimination matrix circuit 20 are summarized as shown in the following table.

However, ×: Any H/L, : I-1 or L output As shown in the table above, when the output logic levels of comparators 15 and 17 are different from each other, the output can be used for discrimination regardless of the output of comparator 11. The output signal of the matrix circuit 20 has the same logic level as the output signal of the comparator 15. How to use] When both the power signals of the comparators 15 and 17 are at the same logic level, the discrimination matrix circuit 20 selects the higher level of the power signals of the S/H circuits 7 and 8 according to the output signal of the comparator 11. A signal is output to determine which mode.

According to this embodiment, the reference voltage is compared with the envelope level of two frequency components equal to the frequency corresponding to the sync tip level of the FM luminance transmitter specified in the two modes, and only in the sync tip level transmission section. In addition to the two types of detection information obtained from the above two frequency components, detection information from a comparator 11 that detects the magnitude relationship of the envelope level of the sync chip level transmission section is added, and mode classification is performed from these. Therefore, more stable mode discrimination can be performed than in the third embodiment.

In addition, in each example shown in FIGS. 3 and 4,
S/8 circuit 7 on the input side of comparator 15.17.11
．． Although it has been described that a single S/8 circuit is provided, a single S/8 circuit may be provided on the output side of the discrimination matrix circuits 19 and 20.

Incidentally, in each of the above embodiments, two 3PFs are used in order to pass separately the FM luminance signal frequencies corresponding to the respective sync chip levels of the two types of modes, but the BPF
It can be composed of even one piece. The fifth and sixth embodiments of the present invention shown in FIGS. 5 and 6 are examples of this case.

In FIG. 5, the output signal of the S/8 circuit 7 is supplied to a comparator 21, where the level is compared with a reference voltage from a reference voltage source 22. If the input playback FMffi degree signal was recorded in standard single signal mode, the output signal of the S/8 circuit 7 would be higher than the reference voltage, and on the other hand, if it was recorded in high quality mode, it would be higher than the reference voltage. To be small,
A reference voltage from the reference voltage source 22 is set in advance.

Therefore, from the comparator 21 to the output terminal 12, S
A mode determination signal is output based on a level comparison between the output signal of the /8 circuit 7 and the gtB voltage from the reference voltage source 22.

Next, a sixth embodiment of the device of the present invention will be described with reference to FIG. 6. In FIG. 6, the same components as those in FIG. 2 are denoted by the same reference numerals, and their explanation will be omitted. This embodiment has a configuration in which the positions of the S/1'' circuit 7 and the comparator 21 of the fifth embodiment are swapped, and the output signal of the detection circuit 5 is supplied to the comparator 23, where the preset voltage from the reference voltage source 24 is After comparing the level with the reference voltage obtained, the signal is supplied to the S/8 circuit 14.

Thereby, similarly to the fifth embodiment, it is possible to output the hemo-do discrimination signal from the output terminal 12 with a simple circuit configuration.

In addition, in Figures 5 and 6, BPF2 is replaced by BPF2.
Of course, PF3 may also be used.

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, a frequency division multiplexed signal of an FM luminance signal and a low frequency conversion carrier color signal recorded on a magnetic tape 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 switching circuit 30 that is switched by a head switching pulse with a two-field period, where it is made into a continuous signal, and then passed through a high-pass filter (hereinafter referred to as HPF) 32 and an LP.
Supplied to F48. What is the reproduced FM luminance signal separated and filtered by HPF32? ! Equalizer circuit 3 in quasi mode
3 and the equalizer circuit 34 in high image quality mode separately to the switch circuit 35, and further from this, the AGC
The signal is supplied via a circuit 36 to a limiter 37 and a mode discrimination circuit 38 according to the present invention.

Limiter 3B, FM demodulator 39.42. LPF40.4
3. The de-emphasis circuits 41, 44 and the switch circuit 45 constitute the demodulation circuit 4 shown in FIGS. 1 to 6. In addition, the mode discrimination circuit 38 is the demodulation circuit 4 of the mode discrimination devices of the embodiments shown in FIGS. 1 to 6.
In the circuit excluding , the reproduction FM from the AGC circuit 36
The luminance signal is supplied to the input terminal 1, and the reproduced luminance signal output from the switch circuit 45 is supplied to the internal sampling pulse generation circuit 10.

Playback FM with the shooting width variation component removed by the limiter 37
The luminance signal is FM demodulated m39. of the standard mode reproduction system. LP
F40 and a de-emphasis circuit 41 to a switch circuit 45, while a high-quality mode reproduction system FM demodulator 42. 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 discrimination circuit 38 determines whether the reproduction F
A mode determination signal that automatically determines whether the M luminance signal was recorded in the standard mode or high-quality mode is supplied to the system controller 46, which then sends switching pulses to the switch circuits 35 and 45. Supplied as.

The binding and switching 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 above-mentioned swig circuit 30 is separated into a low frequency conversion 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 adder circuit 47 adds and synthesizes this reproduced carrier color signal and the reproduced video signal taken out from the switch circuit 45 and reproduced and demodulated by the reproduction system in the same mode as at the time of recording, and outputs the resultant signal to the output terminal 50 as a reproduced color video signal. do.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and mode discrimination can be performed in the same manner as described above even when the recording/reproducing mode is three or more scales. In addition, the upper arch section for sample and hold has been explained as a sync tip level transmission section excluding the same tt'+ signal section within both the horizontal and vertical blanking periods; Of course, only one of the sync chip level transmission sections may be used.

Effects of the Invention As described above, according to the present invention, it is possible to automatically determine in which mode of a plurality of modes recording was made based on the reproduced video signal, and therefore it is not necessary to change the manual switch as in the conventional method. This operation is completely unnecessary, improving usability and eliminating the possibility that the user will mistake it for a malfunction.Furthermore, the carrier frequency corresponding to the sync chip level of each mode is detected after the IF' wave, and the sync chip level is detected. Since the discrimination information is obtained by using the signal obtained by sample-holding the detection signal level in the transmission section, it is possible to obtain a sample-and-hold circuit output that can clearly identify the mode, and it is possible to obtain a sample-and-hold circuit output that can clearly identify the mode. Compared to the case where a detection circuit configured to compensate for the drop is used, it is possible to quickly output an accurate mode discrimination signal without impairing the response speed when switching modes, and the sampling pulse generation circuit is integrated. It has many features such as being able to be incorporated into the circuit and using an existing synchronous signal separation IC in the sampling pulse generation circuit, which is advantageous in terms of cost and circuitry. .

[Brief explanation of the drawing]

1 to 6 are block diagrams showing respective embodiments of the apparatus of the present invention, FIG. 7 is a diagram showing video signal waveforms, and FIG. 8 is a diagram showing the frequency of the FM signal in standard mode and high-quality mode FIG. 9 is a block system diagram showing an example of a video topography reproducing device having the device of the present invention. 1... Reproduction FM volatility signal input terminal -12, 3... Bandpass filter (BPF), 4... Demodulation circuit, 5, 6...
・Sample hold circuit (S/8 circuit), 10... Limbling pulse generation circuit, 11.13.15°17.
...Comparator, 12...Discrimination signal output terminal, 16
．． 18... Reference voltage source, 19.20... Matrix circuit for discrimination, 38... Mode discrimination circuit. Figure 1 Figure 2

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. By comparing and detecting the detection level of the carrier wave frequency corresponding to the sync chip level in the transmission section of both or either of the horizontal blanking period and the vertical blanking period of the reproduced frequency-modulated video signal, the recording mode is determined. What is claimed is: 1. A recording mode discriminating device for a reproduced video signal. (2) Reproduction 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 signal is different from each other. A frequency modulated video signal is supplied, and the n
n filter circuits that separately pass frequency-modulated video signal frequencies corresponding to respective sync chip levels of different modes; each output signal of the n filter circuits is separately supplied;
A total of n detection circuits that detect the envelope, and a sync chip level transmission section of both or either of the horizontal blanking period and the vertical blanking period of each output signal of the n detection circuits. The above-mentioned method is based on at least one of the results obtained by comparing the signal levels of the sync chip level transmission period and the preset reference level. 1. A recording mode determination device for a reproduced video signal, comprising means for outputting a recording mode determination signal for a reproduced frequency modulated video signal. (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 each sync chip level of one of the two modes set in advance, and an output signal of the filter circuit is supplied; A detection circuit that detects the envelope, and a signal level of only the sync chip level transmission section of both or either of the horizontal blanking period and the vertical blanking period among the output signals of the detection circuit and a preset reference level. An apparatus for discriminating a recording mode of a reproduced video signal, comprising means for outputting a discriminating signal for determining the recording mode of the reproduced frequency modulated video signal based on the results obtained by comparing the levels of the reproduced video signal.