JPH0396090A - Signal substitution circuit for recording and reproducing device - Google Patents

Abstract

PURPOSE:To substitute part of a video signal for a character, etc., even in reproduction by sharing a clamping circuit and a signal substitution circuit required for the substitution of part of the video signal for the character, etc., in recording with in the reproduction. CONSTITUTION:The clamping circuit 4 to set a reference voltage and the substitution circuit 5 to substitute the signal clamped with the clamping circuit 4 for the character, etc., required for the substitution of a signal are provided. And a video signal to be recorded and a reproduced video signal can be selected by switching a switch 3 provided at the preceding stage of the clamping circuit 4 so as to share the clamping circuit 4 in the recording with in the reproduction. In such a way, it is possible to substitute the video signal to be recorded and the video signal in the reproduction for the character, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to signal replacement such as superimposition of video signals used in video tape recorders and the like. [Prior Art] Conventionally, in a video tape recorder, as a method of replacing characters etc. in a video signal, for example, Japanese Patent Laid-Open No. 1725-1983
As described in Publication No. 77, the video signal recorded from the video camera is replaced with characters, etc., and then supplied to a video signal recording/reproducing device. [Problems to be Solved by the Invention] The above-mentioned prior art is not suitable for replacing characters, etc. with signals other than video signals from a video camera (for example, video signals input from the outside and video signals during playback). No consideration was given to this, and in order to deal with these issues, it was necessary to provide a new circuit for replacing characters, etc.

An object of the present invention is to provide a configuration in which characters and the like can be replaced in a video signal recorded and a video signal during playback using a simple W1 configuration.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a clamp circuit that sets a reference voltage necessary for replacing a signal in a recording/reproducing device, and a replacement circuit that replaces characters, etc. with respect to the signal clamped by the clamp circuit. A means for selecting a video signal to be recorded and a video signal to be reproduced is provided before the clamp circuit so that the clamp circuit can be used in both recording and reproduction.

[Effect]

The signal replacement circuit of the recording and reproducing apparatus of the present invention supplies the video signal during recording and the video signal during playback to the clamp circuit and the signal replacement circuit according to the recording and playback modes. It is possible to replace characters etc. in a part of .

〔Example〕

An embodiment of the present invention will be explained below with reference to FIG. First, the operation during recording will be explained.

The video signal supplied to input terminal 1 is . After the level fluctuation is removed by the AGC circuit 2, the switch 3 connected to the A side
It is supplied to the clamp circuit 4 via. The video signal clamped to the reference voltage by the clamp circuit 4 is sent to the signal replacement circuit 5.
part of the video signal is replaced with another signal (date, title, etc.).

The video signal output from the signal replacement circuit 5 is output to an output terminal 7 for monitoring the signal to be recorded. On the other hand, it is supplied to the Y/C separation circuit 8 as a signal to be recorded. Y/C
A separation circuit 8 separates the video signal into a luminance signal and a chroma signal. The luminance signal separated by the Y/C separation circuit 8 is band-limited by an LPF 9 provided as necessary, and after the Takagi component is emphasized by an emphasis circuit 10, the luminance signal is sent to the FM modulation circuit 1.
1. The FM modulated FM luminance signal is
Unnecessary components are removed at F12 and the resultant signal is supplied to the adder 13.

The chroma signal separated by the Y/C separation circuit 8 has level fluctuations removed by the ACC circuit 14, and is sent to the recording chroma processing circuit 1.
After the necessary chroma processing is performed in step 5, the frequency conversion circuit 16
The signal is frequency-converted to the lower frequency side of the FM luminance signal, and the unnecessary components generated at this time are removed by the LPF 17, and the signal is supplied to the adder l3. The previous FM luminance signal and the low frequency converted chroma signal are frequency multiplexed by the adder l3, and then sent to the recording amplifier circuit 18. It is recorded on the magnetic tape 20 via the video head 19.

Next, the operation during playback will be explained.

During reproduction, signals reproduced from the magnetic tape 20 via the video head 21 are amplified by the reproduction amplification circuit 22. H
The PF 23 extracts an FM luminance signal from the reproduced signal and supplies it to the FM demodulation circuit 24. After being demodulated into a baseband luminance signal by the FM demodulation circuit 24, unnecessary components are removed by the LPF 25, de-emphasis is performed by the de-emphasis circuit 26, and noise removal processing such as noise clipping and noise cancellation is performed by the noise processing circuit 27. , are supplied to the adder circuit 28.

On the other hand, the LPF 29 extracts a low frequency converted chroma signal from the reproduced signal, the ACC circuit 30 removes level fluctuations, and the frequency conversion circuit 31 restores the original carrier chroma signal. After that, the unnecessary part is removed by the BPF 32, and the desired chroma processing is performed by the reproduction chroma processing, and then the adder 28 adds it to the previous luminance signal to become a reproduced video signal, and the switch 3 connected to the mouth side is The signal is supplied to the clamp circuit 4 via the clamp circuit 4. The reproduced video signal clamped to the reference voltage by the clamp circuit 4 is output to the output terminal 7 after part of the video signal is replaced by another signal (such as a title) in the signal replacement circuit 5. In this way, it is possible to partially replace characters or the like in the video signal even during playback, and the processing means for this also serves as the processing means during recording.

In addition, by providing a configuration that replaces a part of the video signal with characters, etc. during recording, and by providing it after the AGC circuit 2 during recording, level fluctuations in the input video signal can be removed, allowing highly accurate signal replacement. can be done.

FIG. 2 shows a specific example of the clamp circuit 4 and signal replacement circuit 5 in FIG. 1, and the operation will be explained together with FIG. 3. In FIG. 2, reference numeral 4 denotes a clamp circuit, which is composed of a capacitor 51, a diode 52, and a reference voltage source 53 for bias. Reference numeral 5 denotes a signal replacement circuit, which is composed of a switch 54, a diode 57, and a voltage source 55. Since the video signal input to the clamp circuit 4 charges the capacitor 51 at the lowest voltage portion of the synchronizing signal as shown in FIG. 3(A), the lowest voltage portion of the synchronizing signal is
The difference between the voltage VA of the reference voltage source 53 and the forward falling voltage vF of the diode 52, ie, VF, causes the signal shown in FIG. 3(A) to be supplied to the C side of the switch 54 of the signal replacement circuit 5. ．． This switch 54 is controlled by a signal input from a control signal input terminal 56, and when the signal from the control signal input terminal 56 is (Low), it is switched to the C side, and when it is (High), it is switched to the 2 side. connected to. At this control signal input terminal 56, Ta as shown in FIG. 3(B),
When a signal for the period Tb, Tc (High) is supplied, the switch 54 for the period Ta, Tb, Tc is connected to the two sides, and the voltage v3 of the voltage source 55 and the forward drop voltage 2 of the diode 57 are Since the difference between Vs and Vv is output, the output signal of the signal replacement circuit 5 becomes the signal shown in FIG. 3(C), which can replace the period signals of Ta, Tb, and Tc. In this way, the control signal input terminal 56
It is possible to replace the input signal from the video signal with the video signal. In the embodiment shown in FIG. 2, the voltage source 55 was used as the signal to be replaced, but the signal to be replaced may be a video signal obtained by another means, and the same effect as in the above embodiment can be obtained.

FIG. 4 shows another specific example of the clamp circuit 4 and signal replacement circuit 5 in FIG. Missing during special playback such as or stills (S/N deteriorates due to noise)
This shows a configuration in which the vertical synchronization signal used in the system is replaced with a pseudo vertical synchronization signal. In FIG. 4, 61 is a mode switching control signal input terminal, and according to the control signal input from 61, switches 3, 62, and 65 are connected to the A side during recording.
During playback, it is controlled so that it is connected to the mouth side. First, during recording, the switches 3, 62, and 65 are connected to the A side, and a voltage constituted by the voltage source 55 and the diode 57 is supplied to the two sides of the switch 54. The switch circuit 54 is controlled by a signal input to a control signal input terminal 56. Therefore, the structure during recording is the same as the embodiment shown in FIG. 2, and as explained using FIGS. 2 and 3, a part of the video signal is
etc. can be replaced.

Next, the operation during reproduction of the embodiment shown in FIG. 4 will be explained with reference to FIG. 5.

In FIG. 4, during playback, the switches 3, 62, and 65 are connected to the opening side, and the voltage source 64 is connected to the second side of the switch 54.
A voltage formed by a diode 63 is supplied. Now, let us consider a case where the recording and reproducing apparatus is in the reproducing mode and is in search mode. It is well known that in the case of a two-head helical scan type recording/reproducing apparatus, the signal reproduced from the magnetic tape is as shown in FIG. ) The head for reproduction is switched every other field by a head switching pulse as shown in FIG. In addition, in the part where the reproduced signal is minimum, the signal is not reproduced and becomes noise, but in order to minimize the output of noise to a monitor etc.,
), as shown in (E), the vicinity of the field switching point (
The recording and reproducing apparatus is controlled so that the reproduction signal reaches the minimum portion (indicated by α and β in FIG. 5) during the vertical blanking period). Therefore, the reproduced video signal contains a certain amount of noise, and the S/N ratio of the vertical synchronization signal deteriorates significantly. This reproduced video signal is passed through a clamp circuit 4 composed of a capacitor 51, a diode 52, and a reference voltage source 53 for bias. The signal shown in FIG. 5(F) is clamped by the difference with the directional drop voltage V2, that is, VA VF, and is supplied to the C side of the switch 54 of the signal replacement circuit 5. This switch circuit 54
is the signal input from the control signal input terminal 66 in FIG.
If the pseudo vertical synchronizing signal pulse inputted from the control signal input terminal 66 is (Low), it is connected to the C side, and if it is (High), it is connected to the 2 side. . Therefore, as shown in FIG. 5(G), when the pseudo vertical synchronization signal is
The pulse of the period (High) of Te is sent to the control signal input terminal 6.
6, the Td, Te period switch 54 is connected to the two sides of the voltage source 64 voltage ■. and diode 6
3 and the forward drop voltage V2, that is, VC VF
is output. Therefore, the voltage vA of the reference voltage source 53 provided in the clamp circuit 4 and the voltage Vc of the voltage source 64 provided in the signal replacement circuit 5. V A =
By setting it to be Vc, the video signal output from the signal replacement circuit 5 replaces the pseudo vertical synchronization signal with the lowest voltage of the synchronization signal of the reproduced video signal, as shown in FIG. 5(H). be able to. FIG. 6 shows yet another specific example of the clamp circuit 4 and signal replacement circuit 5 in FIG. 1, and the same parts as in FIGS. 2 and 4 are designated by the same reference numerals and explanations are omitted. do. In the embodiment shown in FIG. 6, the signal replacement circuit 5 includes means for replacing a part of the video signal with characters, etc., consisting of a switch 54, a voltage source 55, and a diode 57, and a switch 71,
The apparatus is equipped with a means for substituting a part of the video signal composed of a voltage source 64 and a diode 63 with the lowest potential of the synchronizing signal, and is designed so that the above two means can be used simultaneously during reproduction. Next, a second embodiment of the present invention will be described with reference to FIG.

In FIG. 7, parts that are the same as those in the embodiment shown in FIG. 1 are given the same reference numerals, and have the same functions as those shown in the embodiment shown in FIG. In the second embodiment shown in FIG. 7, a signal replacement circuit 34 is provided before the output terminal 7, and a part of the video signal outputted to a monitor etc. is replaced with another signal. The configuration is as follows. By doing this, signals such as tape power counters that are not recorded on the recording/playback device can be removed without adding a clamp circuit to set the reference voltage required to replace the signal.
It can be replaced with a part of the video signal output to a monitor or the like.

〔Effect of the invention〕

As explained above, according to the present invention, the clamp circuit and signal replacement circuit necessary for replacing characters etc. in a part of the video signal can be used in common during recording and playback. The configuration allows characters, etc. to be replaced with part of the video signal during playback. In addition, by providing a configuration that replaces a part of the video signal with characters, etc. during recording, and by providing it after the AGC circuit during recording, level fluctuations in the input video signal can be removed, resulting in highly accurate signal replacement. be able to.

Furthermore, with a simple structure, it is also possible to replace signals from a tape counter, etc., which are not desired to be recorded in the recording/reproducing device, only with video signals to be output to a monitor or the like.

Furthermore, as described above, since one clamp circuit can be used for multiple signal replacements, the number of capacitor pins required for the clamp circuit can be minimized even when integrated into an IC.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of a signal replacement circuit of a recording/reproducing apparatus according to the present invention, FIG. 2 is a diagram showing a specific example of the main part of the present invention, and FIG. 3 is a waveform diagram showing its operation. , FIG. 4 is a diagram showing another specific example of the essential part of the present invention, FIG. 5 is a waveform diagram showing its operation, and FIG. 6 is a diagram showing still another specific example of the essential part of the present invention. , FIG. 7 is a block diagram showing another embodiment of the signal replacement circuit of the recording/reproducing apparatus according to the present invention. 2... AGC circuit, 3... Switch, 4... Clamp circuit, 5, 34... Signal replacement circuit.

Claims (1)

[Claims] 1. A device for recording and reproducing a video signal from a video camera or a video signal input from the outside, comprising: a clamp circuit that clamps the video signal to a reference voltage; and a video clamped by the clamp circuit. and means for replacing part of the signal with another signal, and a switch (3) for making the clamp circuit and the means for replacing the signal (5) common during recording and reproduction. A signal replacement circuit for a recording/reproducing device, characterized in that the signal replacement circuit is provided at a front stage of a recording/reproducing device. 2. In a device that records and plays video signals from a video camera or externally input video signals, a clamp circuit that clamps the video signal to a reference voltage and a part of the video signal clamped by the clamp circuit are separated. and means for replacing a part of the video signal clamped by the clamp circuit with the lowest potential of the synchronization signal of the video signal, and recording the means for replacing the signal with the clamp circuit. 1. A signal replacement circuit for a recording/reproducing device, characterized in that a switch for common use during both time and playback is provided in a preceding stage of a clamp circuit. 3. In a device that records and plays back a video signal from a video camera or a video signal input from the outside, an AG that removes level fluctuations in the input video signal during recording.
C circuit, a clamp circuit for clamping the video signal output from the AGC circuit to a reference voltage, and means for replacing a part of the video signal clamped by the clamp circuit with another signal, A video signal in which a part of the signal is replaced with another signal is output as an output signal to a monitor etc. and a recording signal to a recording medium, and during playback, a part of the reproduced video signal is replaced with another signal. 1. A signal replacement circuit for a recording and reproducing apparatus, characterized in that a switch is provided at the front stage of the clamp circuit so that the replacement means and the clamp circuit provided at the front stage thereof can be used during recording.