JP2982242B2 - Video recording and playback device - Google Patents

Description

The present invention relates to a video tape recorder for dubbing (hereinafter referred to as VTR).
(Hereinafter referred to as “video recording / reproducing device”).

2. Description of the Related Art In recent years, as home-use VTRs have become widespread, the demand for soft tapes has been increasing. The most common method for duplicating a large number of soft tapes is dubbing, and a dubbing company combines one master unit and many slave units to duplicate many soft tapes at the same time. General household use
Even in VTRs, dubbing can be easily performed, so measures are considered from the standpoint of copyright protection, and some measures are being implemented. As an example, a copy guard signal (a signal in which a pulse signal is irregularly present in a portion where there is essentially no video information after several hours of an equivalent pulse signal after a vertical synchronization signal of a video signal (H is a horizontal scanning period)). ) Is inserted into the soft tape. This soft tape can be used for recording
The AGC circuit of the VTR malfunctions to prevent dubbing. When dubbing companies create such soft tapes,
After inserting the copy guard signal into the video signal output of the VTR of the master unit, dubbing is performed by the VTRs of a plurality of slave units. In this case, the switch is manually operated so as not to pass through the AGC circuit.

Hereinafter, an example of the above-described conventional video recording / reproducing apparatus will be described with reference to FIGS. 3 to 5. FIG. 3 is a block diagram of a conventional video recording / reproducing apparatus. In FIG. 3, 21 is an AGC circuit, 22 is a switch, and 23 is a luminance signal processing circuit.

The operation of the conventional video recording / reproducing apparatus thus configured will be described below. FIG. 4 shows waveforms at points 1 to n in FIG. 3 when a normal video signal is input, and FIG. 5 when a video signal to which a copy guard signal is added is input.

When a normal video signal is input, the video signal l (fourth
(FIG. 4) passes through the AGC circuit 21 and the video signal level is automatically adjusted to an appropriate value (FIG. 4m). The AGC circuit 21 mixes a keyed pulse (a) immediately after the trailing edge of the horizontal synchronizing signal of the input video signal 1 (shown by a broken line in FIG. 4l), compares this pulse with a reference voltage, and adjusts the level. switch
22 is normally on the A side, so the output m of the AGC circuit 21 is
(FIG. 4n), the luminance signal processing is performed in the luminance signal processing circuit 23.

Next, an operation when a video signal to which a copy guard signal is added is input will be described. The copy guard signal is inserted in a portion of the H which has no video information after the equivalent pulse after the vertical synchronizing signal, and the signal waveform is a pulse signal (b) and a pseudo synchronizing signal (b) as shown in FIG. C). When the switch 22 is on the A side, the input video signal l passes through the AGC circuit 21, but the keyed pulse (d) is also mixed immediately after the trailing edge of the pseudo sync signal (c). AGC circuit 2
1 compares the reference signal with the reference voltage at the level obtained by adding the pulse signal (b) and the keyed pulse (d). Therefore, the AGC circuit 21 determines that the input is excessive, lowers the gain, and the output level becomes lower than an appropriate value ( (Fig. 5m). In order to avoid such a malfunction, when such a video signal is input, the switch 22 is switched to the B side to return to a normal signal level (n in FIG. 5), and is input to the luminance signal processing circuit 23. Done.

In such a conventional configuration, when dubbing a normal video signal from the VTR of the master unit by the VTR of the slave unit, the video signal with the copy guard signal inserted is passed through the AGC circuit 21. When dubbing by the VTR of the slave units, it is necessary to manually switch the switch 22 so as to bypass the AGC circuit 21, so that in the dubbing step of dubbing by operating the VTRs of many slave units in parallel, the amount of work increases. There was a problem that.

If the switch 22 is always set to the B side and the AGC circuit 21 is bypassed, the recording video signal level becomes abnormal when the termination condition of the input / output terminals of the VTRs is incorrect,
The AGC circuit 21 is indispensable because a monitor of the video signal level of the sending system is always required.

SUMMARY OF THE INVENTION The present invention solves the above-described problem, and eliminates a step of manually switching a switch by bypassing an AGC circuit when detecting an irregularly existing pulse signal in a copy guard signal added to a video signal. It is another object of the present invention to provide a video recording / reproducing apparatus which reduces dubbing work steps using a large number of slave VTRs.

Means for Solving the Problems In order to achieve the above object, the present invention provides an AGC circuit for adjusting an input video signal level to a predetermined value, and a pulse signal for separating a pulse signal below a blanking level from the input video signal. A separation circuit, and a first signal for generating a pulse signal having a time width from a trailing edge of the horizontal synchronization signal included in the output of the pulse signal separation circuit to near a leading edge of the next horizontal synchronization signal
A monostable multivibrator (hereinafter referred to as MM), and a first output of the pulse signal separation circuit output and the first MM output.
An AND gate circuit, a vertical synchronizing separation circuit for separating a vertical synchronizing signal from the output of the pulse signal separating circuit, and a pulse signal triggered by the vertical synchronizing signal to generate a pulse signal having a time width up to near the start point of the copy guard signal. 2 MM,
A third MM that is triggered by a trailing edge of the second MM output pulse signal and generates a pulse signal having a time width corresponding to a copy guard signal period; the first AND gate circuit output and the third MM output A second AND gate circuit, and the second AND gate
It has an integrating circuit for integrating the output of the gate circuit, and a switch circuit controlled by the output of the integrating circuit.

Operation According to the present invention, the input video signal can bypass the AGC circuit when the irregularly-existing pulse signal in the copy guard signal is detected.

Embodiment Hereinafter, a video recording / reproducing apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. FIG. 1 is a block diagram of one embodiment of the present invention. In the figure,
1 is an AGC circuit, 2 is a pulse signal separation circuit, 3 is a MM (monostable multivibrator), 4 is an AND gate circuit, 5 is a vertical synchronization separation circuit, 6, 7 are MM, 8 is an AND gate circuit, and 9 is integration. A circuit, 10 is a switch circuit, and 11 is a luminance signal processing circuit.

 FIG. 2 shows waveforms at points a to k in FIG.

When the video signal a to which the copy guard signal is added is input, the AGC circuit 1 malfunctions, and the amplitude of the video signal a decreases like the waveform b.

On the other hand, the pulse signal c which is lower than the blanking level of the video signal a is taken out by the pulse signal separation circuit 2,
MM3 generates a pulse signal d having a time width from the trailing edge of the horizontal synchronization signal to the vicinity of the leading edge of the next horizontal synchronization signal. The AND gate circuit 4 performs an AND operation between the pulse signal c and the pulse signal d, and extracts a pulse signal e other than the horizontal synchronizing signal arranged at 1H intervals. The vertical synchronizing signal f is extracted from the pulse signal c by the vertical synchronizing separation circuit 5, and the falling edge of the vertical synchronizing signal f triggers the MM6. MM6 generates a pulse signal g having a time width immediately before the start point of the copy guard signal after the trigger. MM7 is triggered by the falling of this pulse signal g,
A pulse signal h having a time width corresponding to the copy guard signal period
Occurs. The AND gate circuit 8 performs an AND operation on the pulse signal h and the output pulse signal e from the AND gate circuit 4 to detect a pseudo synchronization signal i in the copy guard signal.
The integrating circuit 9 integrates the pseudo synchronizing signal i, outputs an H level signal (FIG. 2j), switches the switch circuit 10 from the A contact to the B contact, and uses the input video signal a as it is without passing through the AGC circuit 1. The signal is supplied to the signal processing circuit 11 (FIG. 2, k).

When a normal video signal without a copy guard signal is input, the output of the integration circuit 9 becomes L level, the switch circuit 10 is switched to the A contact, and the video signal a passes through the AGC circuit 1.

As described above, according to the video signal recording / reproducing apparatus of the embodiment of the present invention, the AGC circuit 1, the pulse signal separation circuit 2, the MM3,
By providing the gate circuit 4, the vertical sync separation circuit 5, MM6 and MM7, the AND gate circuit 8, the integration circuit 9, and the switch circuit 10, when dubbing the video signal to which the copy guard signal is added, Since the switch circuit 10 is automatically switched so as to detect the pseudo synchronization signal and to bypass the AGC circuit 1, the dubbing operation can be saved.

Note that the MM 6 may be triggered when the vertical synchronization signal rises (leading edge).

As is clear from the above embodiments, according to the present invention, since the pseudo synchronization signal in the copy guard signal added to the video signal is detected and the AGC circuit is bypassed, dubbing is performed. In this case, the step of manually switching the switch can be omitted, and a video symbol recording / reproducing apparatus with a small number of work steps can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a video recording / reproducing apparatus according to one embodiment of the present invention, FIG. 2 is a signal waveform diagram of a main part of the video recording / reproducing apparatus according to one embodiment of the present invention, and FIG. FIG. 4 is a block diagram of a reproducing apparatus, FIG. 4 is a signal waveform diagram of a main part of the conventional video recording / reproducing apparatus when a normal video signal is input, and FIG. 5 is a video to which a copy guard signal of the conventional video recording / reproducing apparatus is added. FIG. 4 is a waveform diagram of a main part when a signal is input. 1 ... AGC circuit, 2 ... Pulse signal separation circuit, 3 ... Monostable multivibrator, 4 ... AND gate circuit, 5 ...
... Vertical sync separation circuit, 6 monostable multivibrator, 7 monostable multivibrator, 8 AND gate circuit, 9 integrating circuit, 10 switching circuit.

Claims (1)

(57) [Claims] An AG for adjusting an input video signal level to a predetermined value.
C circuit, a pulse signal separation circuit that separates a pulse signal below a blanking level from the input video signal,
A first monostable multivibrator for generating a pulse signal having a time width from the trailing edge of the horizontal synchronization signal included in the output of the pulse signal separation circuit to the vicinity of the leading edge of the next horizontal synchronization signal; A first AND gate circuit of a circuit output and the output of the first monostable multivibrator;
A vertical synchronizing separation circuit for separating a vertical synchronizing signal from an output of the pulse signal separating circuit, and a second monostable multivibrator for generating a pulse signal triggered by the vertical synchronizing signal and having a time width up to near a start point of a copy guard signal A third monostable multivibrator triggered by a trailing edge of the second monostable multivibrator output pulse signal to generate a pulse signal having a time width corresponding to a copy guard signal period; and the first AND gate circuit Output and the third
A second AND gate circuit with the output of the monostable multivibrator, an integration circuit for integrating the output of the second AND gate circuit, and a switch circuit controlled by the output of the integration circuit. A video recording / reproducing apparatus arranged to select the input video signal bypassing the AGC circuit and the signal passed through the AGC circuit in accordance with the presence or absence of a copy guard signal.