JPS63146586A - Video signal reproducing device - Google Patents

Abstract

PURPOSE:To surely prevent a malfunction and to attain stable mode discrimination even at special reproduction by providing a means fixing a discrimination mode of a mode discrimination means to the discrimination mode at the preceding reproduction. CONSTITUTION:At the special reproduction, a normal reproduction flag coming to an input terminal 18 goes to a low level. Thus, an AND circuit 17 is closed to block the passing of an edge detection pulse from a monostable multivibrator 16. Since no clock pulse comes to the clock terminal of a D flip-flop 11 during the special reproduction, the D flip-flop 11 holes the mode discrimination signal at the preceding normal reproduction. Thus, a switch circuit 21 is fixed to the connection mode at the mode discrimination at the normal reproduction just before the special reproduction. Thus, the mode discrimination is not malfunctioned even at the special reproduction.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video signal reproducing device, and more particularly to a video signal reproducing device for reproducing recorded edge video on a recording medium recorded by switching the carrier frequency of a frequency modulated video signal according to a selected mode. The present invention relates to a playback device that plays back signals.

Conventional technology In home VTRs, the current 171VT
By setting the carrier frequency of the frequency-modulated luminance signal higher than the RwA rating (for example, VH8 (registered trademark)) and recording and reproducing, the current ■Tl1l rating mode (hereinafter referred to as
A recording and reproducing method in a high-quality mode is being considered, which produces images of higher resolution and higher quality than images recorded and reproduced in the standard mode (this mode is referred to as the standard mode).

Problems to be Solved by the Invention However, the difference between the above standard mode and high quality mode is
- Since there is no complete compatibility between the two, it is necessary to determine in which of the above modes the video signal to be reproduced was recorded, and to reproduce it in the same mode in which it was recorded.

For this reason, for example, a VTR is equipped with a changeover switch for switching between a standard mode playback system and a high-quality mode playback system, so that the previously recorded signal on the magnetic tape is first played back in either mode, and then the playback image is monitored. By changing the changeover switch, the reproduced image is reproduced in the t-mode which reproduces it correctly.

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

Therefore, the present applicant first compares the envelopes of the different Cytosyrian frequencies depending on the mode of the reproduced frequency modulated video signal to determine the recording mode (for example, Japanese Patent Application No. 61-135609), or An apparatus has been proposed that determines the recording mode by comparing and detecting DC level differences that differ depending on the mode of the demodulated video signal (for example, Japanese Patent Application No. 135613/1982).

However, for example, search (forward, backward), 1/
During double-speed, double-speed, and other various special playbacks, the envelope of the reproduced frequency-modulated video signal becomes unstable, and the DC level of the demodulated video signal also becomes unstable. There is a problem in that malfunctions may occur during playback.

The present invention was created in view of the above points, and an object of the present invention is to provide a video signal reproducing device that prevents malfunctions during special reproduction.

Means for Solving the Problems The video signal reproducing apparatus of the present invention reproduces a frequency modulated video signal recorded on a recording medium in any one mode, and includes mode determining means for determining the recording mode, and a flag. It consists of a generating means, and a means for fixing the discrimination mode only during special reproduction to the discrimination mode during the immediately preceding reproduction.

The carrier wave frequencies of the frequency-modulated video signals are different from each other.
A reproduced frequency modulated video signal obtained by reproducing a recorded signal of a recording medium on which a frequency modulated video signal is recorded in any one of the following modes (where n is an integer of 2 or more) The recording mode is determined by the mode determining means, and a demodulated video signal demodulated by a predetermined demodulation system based on the determined mode is switched and output.

On the other hand, during special reproduction, the discrimination mode fixing means fixes the discrimination mode of the mode discrimination means to the discrimination mode during the immediately preceding reproduction based on the flag generated by the flag generation means. Therefore, during special playback, the mode discrimination means does not discriminate the mode based on the reproduced frequency modulated video signal, but maintains the mode determined during the immediately preceding reproduction.

Embodiment FIG. 1 shows a block system diagram of a first embodiment of the apparatus of the present invention. In the figure, 1 is recorded! ! The magnetic tape and its recorded edge video signals are recorded in either a standard mode or a high quality required 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 is as shown in Figure 2, and in the high-quality mode, as shown in the figure,
The carrier frequency is set higher than in standard mode.

In the frequency spectrum of the FM luminance signal shown in Figure 2,
fAs, fAP, and f'AW indicate carrier frequencies at the sync tip level, pedestal level, and white peak level of the luminance signal, and similarly, the frequency spectrum ■
In the figure, fBs, fBP, and f'ew indicate carrier frequencies at the sync tip level, pedestal level, and white peak level of the luminance signal. For example, in the standard mode, the carrier frequency fAS is 3.4MH2, and fAP is 3.
, 8MH2, fAw is 4.4MH7, and the carrier frequency fBs in high image quality mode is 5.4MH2°fBP.
is 5.9MHz, fa w is 7. OM HZ.

As can be seen from FIG. 2, at the carrier wave frequencies fAs and fBs corresponding to the sync level, there are also sideband frequency components of the FMIIi degree signal of the other mode, but the carrier wave frequency fAS.

The energy of f8S is sufficiently larger than the energy of the sideband component of the same frequency in the other mode. This embodiment focuses on this point and performs mode discrimination.

In addition, the carrier wave frequency f^ρ corresponding to the pedestal level
, f'ep may be used to determine the mode.

In the first embodiment shown in FIG.
The FM luminance signal reproduced by the rotary head 2 is passed through a preamplifier 3 and an AGC circuit 4, respectively, to a bandpass filter (
(hereinafter referred to as BPF) 5 and an FM demodulating crystal 6, respectively. The BPF 5 is, for example, a filter circuit with a narrow pass band characteristic whose pass center frequency is a carrier frequency fAS corresponding to the sync chip level described in the standard mode. Therefore, when the input reproduced FM luminance signal is recorded in the standard mode, the output FMtii degree signal of the BPF 5 is extracted as a large signal, and when it is recorded in the high quality mode, it is extracted with extremely small amplitude.

The output FM luminance signal of the BPF 5 is envelope-detected by the detection circuit 7, smoothed by a low-pass filter (hereinafter referred to as LPF) 8, and then applied to the non-inverting input terminal of the comparator 9, where the signal from the input terminal 10 is The level is compared with the reference voltage.

This reference voltage is smaller than the output signal level of LPF8 when reproducing the FM luminance signal recorded in standard mode, and
L when playing back FM brightness signal recorded in high image quality mode
A predetermined value higher than the output signal level of PF8 is selected.

As a result, comparator 9 outputs FMI! recorded in standard mode! The reproduction signal of the ii degree signal is high level,
? When reproducing the FM luminance signal recorded in the 3-picture quality mode, a low-level mode discrimination signal is extracted. Such a mode discrimination means has already been proposed by the present applicant, for example, in Japanese Patent Application No. 61-1.
It is proposed in No. 35611, etc. The output mode determination signal of the comparator 9 is applied to the data input terminal of the D-type flip-flop 11.

Note that the rotary head 2 actually consists of two rotary heads mounted 180 degrees facing each other on the rotating surface of a rotary cylinder, and as is well known, these rotate the recording tracks on the recorded magnetic tape 1 one by one. The reproduced signal obtained by sequential scanning is switched field by field by a switcher (not shown) and output as a continuous signal to the AGC circuit 4.
A switching pulse (so-called drum flip-flop) for switching the switcher for each field is also supplied to the input terminal 12.

The switching pulse as shown in FIG. 3(B), which is inverted every field, is delayed for a certain period of time by an integrating circuit consisting of a resistor 13 and a capacitor 14, and then is supplied to an exclusive OR circuit 15 while being delayed. The signal is directly supplied to the exclusive OR circuit 15 without any processing. As a result, an edge detection pulse of a constant width as shown in FIG. 3(C) is taken out from the exclusive OR circuit 15 and is phase synchronized with both the rising edge and the falling edge of the input switching pulse. The pulse width of this edge detection pulse is selected to avoid unstable parts of the reproduced FM luminance signal level near the switching point. Note that FIG. 3(A) shows the output demodulated luminance signal of the FM demodulator 6, and the numerical value above the waveform indicates the horizontal scanning line number. That is, since FIG. 3 shows the timing beat of the demodulated luminance signal near the vertical blanking period, although not shown, the input switching pulse of the input terminal 12 is inverted every field. The period of the edge detection pulse shown in FIG. 3(C) is one field.

This edge detection pulse is supplied to a monostable multivibrator (monomulti) 16, where it is converted into a pulse as shown in FIG.

On the other hand, a normal playback flag is input to the input terminal 18, which is at a high level during normal playback and at a low level during special playback.
It is applied to the other input terminal of the ND circuit 17. The normal playback flag is generated by a system controller (not shown) that is supplied with the mode operation inputs of the user of the device. Since the gate of the AND circuit 17 is closed during normal reproduction by the normal reproduction flag, the edge detection pulse from the monomulti 16 is applied as a clock pulse to the D-type flip-flop 11 through the AND circuit 17.

Therefore, during normal reproduction, the D-type flip-flop 11 outputs a pulse obtained by sampling the mode discrimination signal from the comparator 9 using the edge detection pulse from its Q output terminal, and supplies it to the switch circuit 21 as a switching pulse. . When the switching pulse is at a high level, the input signal of the terminal 21a is selectively output, and when it is low level, the input signal of the terminal 21b is selectively output.

The switch circuit 21 has its terminal 21a inputted with a luminance signal obtained by subjecting the demodulated luminance signal output from the FM demodulator 6 to predetermined signal processing in the standard mode by the standard mode reproducing circuit 19, and its terminal 21t) A luminance signal obtained by subjecting the demodulated luminance signal to predetermined signal processing in the high-picture-quality mode by a high-picture-quality mode reproducing circuit 20 is input. Therefore, the switch circuit 21 selects and outputs the output demodulated luminance signal of the standard mode reproduction circuit 19 to the output terminal 22 when reproducing the FM luminance signal recorded in the standard mode, based on the Q output signal of the 0 type flip 70 knob 11. When reproducing the FM luminance signal recorded in the high-quality mode, the output demodulated video signal of the high-quality mode reproduction circuit 20 is selectively outputted to the output terminal 22.

Note that the standard mode reproducing circuit 19 and the high-quality mode reproducing circuit 20 pass the input luminance signal through a low-pass filter having a cutoff frequency unique to that mode, and then impart de-emphasis characteristics unique to that mode. This is a circuit that performs noise cancellation. In this manner, during normal reproduction, the recording mode is determined from the reproduced FM luminance signal, and the luminance signal that has passed through the reproduction system of the determined mode is extracted.

On the other hand, during special playback, the normal playback flag input to the input terminal 18 becomes low level, so the AND circuit 1
Gate 7 is closed to prevent the edge detection pulse from monomulti 16 from passing through.

As a result, no clock pulse enters the clock terminal of the D-type flip-flop 11 during the special reproduction 11, so the D-type flip-flop 11 continues to hold the mode discrimination signal from the immediately preceding normal reproduction.

Therefore, the switch circuit 21 is fixed to the connection 1m at the time of mode discrimination during normal playback immediately before special playback. Normally, the same recorded magnetic tape is often recorded in the same mode, which eliminates mode discrimination errors even during special playback.

Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 4, the same components as those in FIG. 1 are designated by the same reference numerals, and their explanations will be omitted. In this embodiment, mode discrimination is performed based on the DC level of the demodulated luminance signal. Fourth
In the figure, the DC component of the demodulated luminance signal output from the FM demodulator 6 is extracted by a low-pass filter (PF) 24 and applied to an inverting input terminal of a comparator 25. Here, as shown in Figure 2 in the standard mode and high image quality mode, the carrier frequency of the FM brightness signal is higher in the high image quality mode, so the DC level of the demodulated brightness signal is also higher in the high image quality mode. It's more expensive.

The reference voltage applied to the non-inverting input terminal of the comparator 25 via the input terminal 26 is the output DC level of the PF 24 during reproduction of the FM luminance signal recorded in the standard mode and the output DC level recorded in the high image quality mode. It is set in advance to a value intermediate between the output DC level of the LPF 24 when reproducing the FMB degree signal.

As a result, the comparator 25 outputs a high level when reproducing the FM luminance signal recorded in the standard -[- mode,
! When reproducing the FM luminance signal recorded in the J quality mode, the low level output mode discrimination signal of the comparator 9 and the question and answer mode discrimination signal are taken out and applied to the data input terminal of the D-type flip-flop 11.

In the case of this embodiment, as in the first embodiment, during special playback, the mode determination made during normal playback immediately before is retained, and playback is performed based on the mode determination.

It should be noted that the present invention is not limited to the above-described embodiments, and it goes without saying that the recording medium may be other than tape, such as a disk. Furthermore, during special playback, in devices that can play high-quality still motion with very few noise bars, mode discrimination may not be fixed during still motion playback, and mode discrimination may be performed in the same way as during normal playback. . Furthermore, the number of recording and playback modes is 3.
The above is fine.

Effects of the Invention As described above, according to the present invention, during special playback, the discrimination code from the previous playback is retained, so stable mode discrimination is possible even during special playback, and malfunctions are reliably prevented. It also has the advantage of being able to be constructed at low cost by simply adding an extremely simple circuit.

4. f of the drawing! ! III. Explanation FIG. 1 is a block system diagram showing a first embodiment of the device of the present invention, FIG. 2 is a diagram showing frequency spectra in each mode of the frequency modulated video signal reproduced by the device of the present invention, and FIG. 1 is a signal waveform diagram for explaining the operation of the block system shown in FIG. 1, and FIG. 4 is a block system diagram showing a second embodiment of the apparatus of the present invention.

1... Recorded magnetic tape, 2... Rotating head, 5...
... Bandpass filter (BPF), 6... FM demodulator, 7
...Envelope detection circuit, 9,25...Comparator, 10.26...Reference voltage input terminal, 11...
D-type flip-flop, 12... switching pulse input terminal, 17... AND circuit, 18... normal flag input terminal, 19... standard mode regeneration circuit, 20...
・High-quality mode reproduction circuit, 21... switch circuit, 2
2...Output terminal, 24...Low pass filter (LPF)
.

Claims (1)

[Claims] Frequency modulated video signals have different carrier frequencies n
A video signal in which a reproduced video signal is obtained by reproducing and demodulating a recorded signal of a recording medium on which a frequency modulated video signal is recorded in any one of the following modes (where n is an integer of 2 or more) A playback device, comprising: mode discrimination means for determining a recording mode of a reproduced frequency modulated video signal and switching output of a demodulated video signal demodulated by a predetermined demodulation system based on the recording mode; and during special playback and normal playback. The present invention comprises a flag generating means for generating a flag having a different logical value depending on the time, and a means for fixing the discrimination mode of the mode discrimination means only during special playback based on the flag to the discrimination mode during the immediately preceding playback. A video signal reproducing device characterized by: