JPH0723417A - Recording current correction device - Google Patents

Abstract

PURPOSE:To keep the C/N of a recorded FM audio signal constant without being affected by a luminance signal. CONSTITUTION:The device is provided with a Y/C separation circuit 1, a recording color signal processing circuit 2 to convert a fed color signal frequency into 743kHz, a recording equalizer 3 making the amplitude characteristic flat, a recording luminance signal processing circuit 4 FM-modulating a luminance signal, a recording equalizer 5 to make the amplitude characteristic flat, a band pass filter 6 extracting the same band as that of the FM audio signal from the luminance signal, an envelope detector 7 converting a luminance signal fed from the band pass filter 6 into a DC voltage, an amplifier 8 amplifying a DC voltage outputted from the envelope detector 7, a voltage controlled amplifier 10 controlling a recording level of the audio signal with the signal outputted from the amplifier 8, a recording audio processing circuit 9 frequency-modulating the inputted audio signal, a recording pilot signal generating means 11 generating a recording pilot signal, and a mix amplifier 12 mixing received each inputted signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording current correction device used in a magnetic recording / reproducing device of a multiple recording system for recording three or more kinds of signals on the same recording track.

[0002]

2. Description of the Related Art Recording and reproduction of television and image information
It is used in a wide range of fields from broadcasting and production to homes and plays a part in the advanced information society. In addition, a high-definition method that can be used for movie production and publishing has also been developed, and its importance is increasing.

The VHS system, β system and 8 mm system are known as recording / reproducing formats used in general households. In these systems except the VHS system, three or more kinds of signals are recorded on the same recording track. The multiple recording method is adopted.

Among them, FIG. 3 shows a block diagram of a conventional 8 mm format recording system circuit.

The recording system circuit is a Y / C separation circuit 31 for separating a luminance signal and a color signal from an input video signal.
A recording color signal processing circuit 32 for frequency-converting the supplied color signal to 743 KHz, and an FM audio signal (AF
M) A recording equalizer 33 having a trap or the like for flattening the amplitude characteristic of the color signal, a recording luminance signal processing circuit 34 for FM-modulating the luminance signal, and an amplitude characteristic of the luminance signal having a low-frequency chromatolap. Recording equalizer 35 for flattening the input signal, a recording audio processing circuit 39 for FM-modulating the input audio signal, and a recording pilot signal generation circuit 41 for generating a recording pilot signal.
A mix amplifier 42 for mixing the frequency-converted color signal, the FM-modulated luminance signal, the FM-modulated audio signal, and the recording pilot signal, and for amplifying the signal supplied from the mix amplifier 42. Recording amplifier 43 and a head 44 for writing a signal supplied from the recording amplifier 43 onto a magnetic tape.

The operation of each section will be described in detail below.

The input recording video signal is separated into a luminance signal and a chrominance signal by the Y / C separation circuit 31.

The separated color signals are low-frequency converted to 743 KHz (in the case of NTSC) by the recording color signal processing circuit 32 in the next stage, and then are composed of an AFM trap or the like for removing the recording FM audio signal (AFM). Recorded equalizer 3
3 is supplied.

On the other hand, the separated luminance signal is FM-modulated by the recording luminance signal processing circuit 34 at the next stage, and then supplied to a recording equalizer 35 having an AFM trap, a low frequency chromatolap, and the like.

Here, the luminance signal is set so as to have a predetermined recording current (a point where C / N becomes maximum by self recording / reproducing) and is input to the mix amplifier 42.

In the recording equalizer 33, the color signal is set so as to have a predetermined recording current (self-recording / reproducing luminance FM = f
When Y and low-pass color = fC, a reproduction spurious of fY-2fC = -22 dB (as fY = 0 dB)), and then input to the mix amplifier 42.

Similarly, the recording audio signal is modulated into an FM signal by the recording audio signal processing circuit 39, and then set to a point where the color signal recording current becomes -13 dB and is input to the mix amplifier 42.

Further, the recording pilot signal output from the recording pilot signal generation circuit 41 is set at a point where the recording signal current becomes -14 dB from the color signal recording current, and the mix amplifier 4 is set.
Entered in 2.

The recording signals set at the respective setting points as described above are added by the mix amplifier 42, and the recording amplifier 43 drives the head 44 to record four recording signals on the same track. It will be possible.

FIG. 2 shows the frequency allocation at the output of the head amplifier when recording / reproducing in this way.

The recording FM luminance signal is sync tip = 4.2.
MHz, 100% white = 5.4 MHz, and FIG. 2 shows the state of the sideband component that appears when the luminance level is 50%.

If, for example, a video signal having a horizontal resolution of 320 lines is recorded, an FM frequency of 50% luminance and an FM frequency of 5M are used.
For the FM luminance signal of Hz, the lower side is approximately 5-320 / 80 =
There is sideband energy up to 1.0 MHz and about 5 + 320/80 = 9 MHz on the upper side.

Therefore, at this time, the FM audio signal (1.5M
Since the sideband component of the luminance signal enters into the (Hz), the C / N is deteriorated for the FM audio signal.

[0019]

In the magnetic recording / reproducing apparatus of the VTR format which employs the multiplex recording method for recording three or more kinds of signals on the same recording track including the 8 mm format, in order to increase the recording density. Since the frequency relationships of the recording signals are close to each other, other recording signals are affected by the luminance FM signal having a large change amount.

Therefore, in the case of the above-mentioned example, the C / N of the FM audio signal is lowered due to the side band component and is recorded, and when that part is reproduced, S is output as audio.
/ N appears as noise. The following two methods can be considered as simple methods for always recording the recorded FM audio signal with a stable C / N.

The first method is based on the assumption that the lower sideband of the luminance FM signal extends to the FM voice band, and has a sufficient recording level for noise (C / N) in the bad state. Is the method of setting.

The second method is to limit the lower sideband of the FM luminance signal so that the sideband does not reach the FM audio signal band.

However, both of the above two methods have an adverse effect, and in the former case, as described above, the recording current deviated from the 8 mm standard.

In the latter case, when the side band energy is limited, demodulation results in an image with a small horizontal resolution (the upper side band remains at the recording current, but falls into a wide range component due to electromagnetic conversion characteristics. Because).

Therefore, the present invention is a recording current correction apparatus used in a magnetic recording / reproducing apparatus for storing three or more kinds of signals in the same recording track such as the 8 mm format, and the horizontal resolution of a recorded luminance signal is high. In this case, the purpose is not to deteriorate the C / N of the recorded voice signal.

[0026]

A recording current correction apparatus according to the present invention is divided into a detection means for detecting a side band component of an FM luminance signal, which is one of the recording signals, and a detection signal output from the detection means. FM which is one of the recording signals of
And a control means for controlling the recording level of the audio signal.

[0027]

The detecting means extracts the lower sideband component of the luminance FM signal that enters the FM audio signal band and detects its level. The control means controls by controlling the amplification degree by a voltage control amplifier that amplifies the FM audio signal according to the detection result output by the detection means. Therefore, when the horizontal resolution becomes high and the lower sideband of the luminance signal extends to affect the FM voice band, the F
By increasing the recording level of the M audio signal, F of the same level is always achieved.
The C / N of the M audio signal is obtained.

[0028]

FIG. 1 shows an embodiment of a recording current correction device according to the present invention.

The recording system circuit according to the present invention is a Y / C circuit for separating a luminance signal and a chrominance signal from an input video signal.
A separation circuit 1, a recording color signal processing circuit 2 for frequency-converting the supplied color signal to 743 KHz, a recording equalizer 3 having an AFM trap or the like for flattening the amplitude characteristic, and a luminance signal for FM modulation. For recording luminance signal processing circuit 4, a recording equalizer 5 having a low-frequency chromatolap for flattening the amplitude characteristic, and a bandpass filter (BPF) 6 for extracting the same band as the FM audio signal from the luminance signal. And the bandpass filter 6
Envelope detector 7 for converting the luminance signal supplied from the device into a DC voltage, and D output from the envelope detector 7.
An amplifier 8 for amplifying the C voltage, a voltage control amplifier (VCA) 8 for controlling the recording level of the audio signal by the signal output from the amplifier 8, and an FM modulation of the input audio signal. Recording audio processing circuit 9, a recording pilot signal generating circuit 11 for generating a recording pilot signal, and a mix amplifier 12 for mixing a frequency-converted color signal, an FM-modulated luminance signal, and a recording pilot signal. And a recording amplifier 13 for amplifying the signal supplied from the mix amplifier 12, and a head 14 for writing the signal supplied from the recording amplifier 13 onto a magnetic tape.

The present embodiment will be described in detail below.

The input recording video signal is separated by the Y / C separation circuit 1 into a luminance signal and a color signal.

The separated color signal is low-pass converted to 743 KHz (in the case of NTSC) by the recording color signal processing circuit 2 in the next stage, and then the recording equalizer 3 having an AFM trap or the like for removing the recording FM audio signal. Is supplied to.

Here, the color signal is set to have a predetermined recording current (luminance FM = fY, low-pass color = fC, FY-2fC reproduction spurious = -22 dB (Y = 0).
point (in dB)), and then input to the mix amplifier 12.

On the other hand, the separated luminance signal is FM-modulated by the recording luminance signal processing circuit 4 at the next stage, and then the recording equalizer 5 having an AFM trap, low-pass chromatolap, etc.
And to the bandpass filter 6.

The luminance signal is set by the recording equalizer 5 so as to have a predetermined recording current (a point at which C / N becomes maximum by self recording / reproducing) and is input to the mix amplifier 12.

The band-pass filter 6 is set so that the band of the FM audio signal is usually ± 60 KHz and maximum ± 100 KHz (center frequency 743 kHz ... In the case of NTSC) so that the band matches the band.

The output of the bandpass filter 6 is input to the envelope detector 7 in the next stage, where it is converted into a DC voltage.

The DC voltage output from the envelope detector 7 is very small (when the brightness level is 0%, the horizontal resolution is 24).
In the vicinity of 0, 50% → 280 and 100
% → 310 lines, which is a fine signal corresponding to a high resolution component as a video signal component), and thus cannot be used as the control voltage of the voltage control amplifier 10 as it is.
Therefore, after being amplified by the amplifier 8 to a voltage level suitable for the voltage control amplifier 10, the voltage is input to the voltage control amplifier 10.

The recorded voice signal is F by the recorded voice processing circuit 9.
After being modulated into the M signal, it is input to the input terminal of the voltage control amplifier 10.

Since the control voltage of the voltage control amplifier changes according to the sideband level of the luminance FM signal, an FM audio signal whose output also changes according to the sideband level can be obtained. (Dotted line part of REC AFM carrier in FIG. 2) This FM audio signal sets the recording current value to a predetermined level based on the level when the voltage control amplifier gain is minimum, that is, when there is no sideband component in the bandpass filter 6 output. Then, it is input to the mix amplifier 10.

(In the case of operating the circuit of the present invention, when recording a video signal having a high horizontal resolution, the recording current of the FM audio signal becomes larger than the 8 mm standard. Further, the recording pilot signal output from the recording pilot signal generating circuit 11 is set at a point where the color signal recording current becomes −14 dB and is input to the mix amplifier 12.

The recording signals set at the respective set points as described above are added by the mix amplifier 12, and the recording amplifier 13 drives the head 14 to record four recording signals on the same track. It will be possible. When the horizontal resolution of the recorded luminance signal is high, the side band is extended and the C / N of the recorded voice signal is deteriorated when FM-modulated. However, by adopting the above configuration, the C / N of the recorded voice signal is reduced.
N stabilizes.

[0043]

As described above in detail, according to the present invention, since the C / N of the recorded FM audio signal is not affected by the sideband component of the luminance signal and a stable level is always obtained, it is recorded. When the recording tape is reproduced, a clear audio signal is always obtained.

[Brief description of drawings]

FIG. 1 shows a block diagram of an embodiment according to the present invention.

FIG. 2 shows frequency allocation of a recording signal.

FIG. 3 shows a conventional example.

[Explanation of symbols]

 1 Y / C separation circuit 2 Recording color signal processing circuit 3 Recording equalizer 4 Recording luminance signal processing circuit 5 Recording equalizer 6 Band pass filter (BPF) 7 Envelope detector 8 DC amplifier 9 Recording audio signal processing circuit 10 Voltage control amplifier ( VCA) 11 recording pilot signal generation circuit 12 mix amplifier 13 recording amplifier 14 head

Claims (1)

[Claims] 1. A storage current correction device used in a magnetic recording / reproducing device of a multiple recording system for recording three or more kinds of signals on the same recording track, which is one of recording signals.
Recording current correction comprising detection means for detecting a sideband component of a luminance signal and control means for controlling a recording level of an FM audio signal, which is one of other recording signals, according to the detection signal output from the detection means. apparatus.