JPH04336785A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To realize high sound quality by detecting the recording state of a sound signal and controlling the band of a video signal interfering with the sound signal and to prevent the resolution of the video signal from being deteriorated by optimizing the band of the video signal when the sound signal is recorded in monoral at the same time. CONSTITUTION:A detection circuit 9 detecting the state of a sound input terminal is provided, and an FM signal band control circuit 2 controlling the recording band of the video signal according to the output of the circuit 9 and traps 5 and 6 removing the signal in the band of the FM sound are provided, and the trap 6 is controlled with the output of the detection circuit 9. At the same time in a sound signal processing circuit 7, a stereo/monoral recording is realized corresponding to the output of the detection circuit 9 and at the time of stereo recording, the sound quality can be prevented from being deteriorated by suppressing the band of the video signal with the trap 6. At the time of monoral recording, the band of the video signal is expanded without actuating the trap 6 and the resolution can be prevented from being deteriorated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording and reproducing apparatus that is effective for use in an 8 mm video tape recorder that simultaneously records and reproduces stereo audio signals and video signals.

0002

[Prior Art] In recent years, in order to achieve high sound quality in 8mm video tape recorders (hereinafter referred to as 8mm VTR), a method for recording and playing back stereo audio signals by FM modulation has been newly standardized and is attracting attention. . The 8mm stereo recording system uses two FM modulation carrier frequencies of 1.5MH
This is achieved by setting the frequency to 1.7MHz. However, in this case, since a 1.7 MHz audio FM modulation signal is added compared to when recording a conventional monaural audio signal, the FM modulated video signal is mixed into the FM audio signal in the 1.7 MHz band. That has become a problem. Therefore, in order to prevent the video FM modulation signal from being mixed into the 1.7 MHz audio FM modulation band, the band of the video FM modulation signal is limited using a trap or the like to prevent deterioration in sound quality.

[0003] The conventional stereo recording system will be explained below. FIG. 3 is a block diagram showing a conventional stereo recording method. In FIG. 3, 1 is a video signal processing circuit;
1 is an FM signal band limiting circuit, 3 is an adder, 4 is a recording amplifier, 5 is a 1.5 MHz trap, 6 is a 1.7 MHz trap, 7 is a stereo audio signal processing circuit, and 8 is an adder. Here, the video signal is processed by the video signal processing circuit 1 at 8 mm.
After being subjected to format signal processing and FM modulation, it is supplied to the FM signal band limiting circuit 2. In the FM signal band limiting circuit 2, a signal of 1.5 that interferes with the FM modulated audio signal is supplied.
The MHz signal and the 1.7 MHz signal are each removed by a trap 5.6 and supplied to the adder 3. Adder 3
Then, the audio signal is added to the FM modulated audio signal in the audio signal processing circuit 7, and is supplied from the recording amplifier 4 to the magnetic head.
It will be recorded on magnetic tape.

0004

[Problem to be Solved by the Invention] However, with the above conventional configuration, even when recording audio signals in stereo,
In both cases, when recording in monaural, the recording band of the video signal is degraded by 0.2 MHz compared to the conventional monaural recording only device, that is, the resolution of the video signal is degraded by about 20 TV lines. There was a problem with this.

[0005] The present invention solves the above-mentioned conventional problems, and uses a simple method to detect whether an audio signal is recorded in monaural or stereo, and automatically changes the recording band of a video signal. The purpose of this optimization is to prevent resolution degradation when recording monaural audio.

[0006]

[Means for Solving the Problem] In order to achieve this object, the present invention detects the presence or absence of an audio input terminal, determines whether it is monaural recording or stereo recording, and uses the detected output to determine whether monaural recording is possible. , a control circuit that does not activate the 1.7 MHz trap is provided to prevent deterioration of the video signal band. Furthermore, based on the detection output, a 1.7 MHz trap is applied during stereo recording to eliminate interference with the video signal to the audio signal, thereby ensuring a good audio recording state.

[0007]

[Operation] With this configuration, it is possible to optimize the recording band of the video signal according to the state of the audio input signal, and when recording monaural audio signals, it prevents deterioration of the resolution of the video signal and records stereo audio. At the same time, you can enjoy high-quality stereo audio.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a video signal processing circuit; 2 is a video signal processing circuit;
is an FM signal band limiting circuit, 3 is an adder, 4 is a recording amplifier, 5 is a 1.5 MHz trap, 6 is a 1.7 MHz trap, 7 is an audio signal processing circuit, 8 is an adder, 9 is an audio input terminal presence/absence detection 10 is a switch circuit, 11 is a detection signal from the audio input terminal detection circuit 9, 12 is a video input terminal, and 13 and 14 are audio input terminals.

FIG. 2 shows an example of the audio input terminal presence/absence detection circuit 9 of FIG. In Figure 2, 15, 16, 17, 1
8 is a resistor, 19 is a transistor, 20 is an input terminal to the audio signal processing circuit 7, 21, 22, 23 are an example of the audio input terminal 14 and are RCA terminals, audio signal conduction terminal 21, switch terminal 22, A ground terminal 23 is shown.

An embodiment of the present invention constructed as described above will be explained. First, the operation of the audio input terminal presence/absence detection circuit 9 will be explained using FIG. First, when an RCA pin is inserted to supply an audio signal to the audio input terminal 14, the audio signal is transmitted through the audio signal conduction terminal 21.
After being attenuated to an appropriate level by resistors 15 and 16, the signal is supplied to the audio signal processing circuit 17 through an input terminal 20. At that time, the contact between the audio signal continuity terminal 21 of the audio input terminal 14 and the switch terminal 22 is open, so the transistor 19 is turned off and the detection signal 11 is 0V (L
o-level). That is, when an audio signal is input from the input terminal 14, the detection signal 11 of the audio input terminal presence/absence detection circuit 9 becomes 0V. Next, connect the RCA to the input terminal 14.
If the pin is not inserted, the audio signal continuity terminal 21
Since the contacts of the switch terminal 22 and the switch terminal 22 are in a closed state, the base potential of the transistor 19 is lowered by the resistors 17, 15, and 16, so the transistor 19 is turned on, and the detection signal 11 becomes approximately VccV (Hi- level). That is, when no audio signal is input from the input terminal 14, the detection signal of the audio input terminal presence/absence detection circuit 9 is approximately V.
It becomes cc (Hi). Therefore, when the input terminal 14 is configured as a sub audio input terminal, the detection signal 11 becomes 0 (Lo) when recording a stereo signal, and when recording a monaural signal, the RCA pin is connected to the input terminal 14. is not inserted, the detection signal 11 is Vcc (Hi)
Therefore, it is possible to distinguish between stereo/monaural recording with a simple configuration.

Next, FIG. 1 shows an overall embodiment of the present invention.
Explain using. First, the video signal is supplied from the input terminal 13 to the video signal processing circuit 1, undergoes 8mm signal processing, is FM modulated, and is FM signal band limiting circuit 2.
supplied to In the FM signal band limiting circuit 2, F
The 1.5 MHz trap 5 removes signals that interfere with the audio from the M-modulated video signal, and when recording a stereo audio signal, the detection signal 11 causes the switch 10 to be removed.
is turned on, the 1.7 MHz trap 6 operates, and the 1.7 MHz signal component is removed and supplied to the adder 3. Further, audio signals are inputted from input terminals 13 and 14, subjected to FM modulation in an audio signal processing circuit 7, mixed in an adder 8, and then supplied to an adder 3. When recording a monaural audio signal here, the audio signal processing circuit 7 performs monaural signal processing based on the detection signal 11 from the audio input terminal presence/absence detection circuit 9, and outputs a 1.5 MHz signal as an FM audio recording signal. only is supplied to the adder 8. In this way, the adder 3 mixes the FM-modulated video signal and the FM-modulated audio signal, which is supplied from the recording amplifier 4 to the magnetic head and recorded on the magnetic tape.

As described above, according to this embodiment, the input state of the audio signal can be detected with a simple configuration, and the recording band of the video signal can be optimally controlled in accordance with the detection.

[0014] In the embodiment of the present invention, the system automatically detects the monaural recording/stereo recording decision, but instead of the audio input terminal detection circuit 9, a dedicated switch is provided to allow the user to Needless to say, the same effect can be obtained even if selected.

[0015] Furthermore, in the case of a camera-integrated VTR, the video signal band is often quite narrow;
In that case, the present invention can easily realize controlling the switch 10 to keep it in the OFF state when recording camera signals.

[0016]

As described above, the present invention provides a magnetic recording and reproducing device that can optimally control the recording band of a video signal depending on whether an audio signal is recorded in stereo or monaural. It is possible to realize this.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a video signal band control circuit in an embodiment of the present invention.

[Fig. 2] A circuit diagram showing the configuration of an input terminal presence/absence detection circuit in an embodiment of the present invention.

[Figure 3] Block diagram showing the configuration of a conventional stereo recording system

[Explanation of symbols]

1 Video signal processing circuit 2 FM signal band limiting circuit 3 Adder 4 Recording amplifier 5 1.5MHz trap 6 1.7MHz trap 7 Audio signal processing circuit 8 Adder 9 Audio signal input terminal presence/absence detection circuit 10
Switch circuit 11 Detection signal 12 Video input terminal 13 Audio input terminal 14 Audio input terminal 15 Resistor 16 Resistor 17 Resistor 18 Resistor 19 Transistor

Claims (1)

[Claims] 1. A magnetic recording and reproducing device comprising a circuit for FM modulating and recording two independent audio signals such as a stereo audio signal or an audio multiplex signal, and a circuit for FM modulating and recording a video signal. The apparatus is characterized by comprising an input state detection circuit for detecting an input state of an audio signal, and a circuit for changing a recording band of a video signal to an optimal state in accordance with an output from the input state detection circuit. Magnetic recording and reproducing device.