JPH0334149B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a magnetic recording and reproducing device, which records an FM modulated signal on a magnetic tape and FM demodulates the reproduced signal to obtain the original signal. Regarding a playback device.

Conventional technology When recording, a conventional magnetic recording/reproducing device pre-emphasizes a luminance signal, clamps the obtained signal, and uses a clip circuit to eliminate overshoot above a specified level, undershoot below a specified level, etc. After that, the luminance signal is FM-modulated, a low-frequency converted carrier color signal is mixed therein, and the signal is recorded on a magnetic tape. Also, during playback, the FM brightness signal extracted from the playback signal is
The luminance signal is extracted by demodulating and de-emphasizing the obtained signal. In this conventional device, an overshoot occurs immediately after the rising edge of a brightness signal such as that shown in FIG. 4A, which has a sharp rise, when pre-emphasis is performed, and this overshoot is removed by the clip circuit. As a result, information on the rising edge of the luminance signal is lost, and the luminance signal obtained by demodulating the reproduced signal and performing de-emphasis lacks the rising edge as shown in Figure 4B. The signal waveform before recording cannot be faithfully reproduced.
Since the waveform at such a sharp rise portion is blunted, there are problems such as smearing in the reproduced image.

Therefore, the applicant of the present invention previously disclosed in Japanese Patent Application No. 59-116183, entitled "Magnetic Recording and Reproducing Apparatus," by extracting and inverting the portion that would be removed due to the overshoot level limit, and inverting the portion immediately before the edge of the signal from the clip circuit. Magnetic recording configured to perform additional recording, extract the added part immediately before the edge from the demodulated signal obtained by FM demodulating the reproduced signal, invert it, and add it to the added part of the demodulated signal and the part from which the overshoot has been removed. We proposed a playback device.

Problems to be Solved by the Invention The magnetic tape recorded by the above-mentioned apparatus proposed by the applicant is capable of reversing the portion that is removed due to the overshoot level limit, so that the portion immediately before the edge of the signal from the clip circuit is inverted. Therefore, when this magnetic tape is played back by a normal magnetic recording/reproducing device other than the above-mentioned device, there is a problem that it is not compatible with the normal magnetic recording/reproducing device.

Therefore, the present invention solves the above problems by extracting the portion from which the overshoot is removed, attenuating it, inverting it, and adding it just before the edge of the signal from the clip circuit for recording. The purpose is to provide equipment.

Means for Solving the Problems In the present invention, the portion removed due to the overshoot level limit is taken out, after attenuation, added just before the edge of the signal from the clip circuit, and recorded. Further, the added portion immediately before the edge of the reproduced and demodulated signal is extracted, inverted, and added to the added portion of the demodulated signal and the portion from which the overshoot has been removed.

Further, in the second invention, the additional portion extracted from the demodulated signal is amplified and inverted and added to the additional portion of the demodulated signal, and this additional portion is inverted and added to the portion from which overshoot has been removed.

Function: In the present invention, the clip circuit of the recording system extracts the portion from which overshoot is removed, attenuates it, and adds it to the signal from the clip circuit immediately before the edge. In the reproduction system, the added portion immediately before the edge is extracted from the demodulated signal, amplified and inverted (or inverted), and added to the added portion of the demodulated signal, and the added portion is added to the portion from which the overshoot has been removed. Therefore, the level of the added portion immediately before the edge of the recorded signal is low, and even when reproduced by a normal device, the influence of the added portion is small and does not interfere with reproduction.

Embodiment FIGS. 1A and 1B show block diagrams of a first embodiment of the recording system and reproduction system of the apparatus of the present invention, respectively.

In FIG. 1A, reference numeral 1 denotes a terminal to which a luminance signal separated from a video signal is input, and the luminance signal input here is supplied to an emphasis circuit 2.
The emphasis circuit 2 has a predetermined frequency characteristic in which the amplification degree of the high frequency range is, for example, about five times the amplification degree of the low frequency range, and the high frequency component of the luminance signal is enhanced here, as shown in FIG. 2A. The signal a is supplied to the clip circuit 3 and the lower limiter circuit 4. In this signal a, the fall timing of the horizontal synchronization signal is defined as time t ₀ . The clip circuit 3 detects the portion where the level difference from the sync chip to the white peak exceeds, for example, 160%, as shown by the broken line in FIG. A portion of the difference below -40%, for example, is level limited to obtain signal b shown in FIG. 2B. This signal b
is delayed by a certain time τ (τ is, for example, several tens to hundreds of nanoseconds) in the delay circuit 5, and the signal c shown in FIG. 2C is supplied to the mixer 6.

Further, the lower limit limiter circuit 4 limits the signal a to the level shown by the broken line, sets the DC component to 0V, and generates a signal d having the waveform shown in FIG.
supply to. The attenuator 7 attenuates the level of the signal d to about 1/10, for example, to produce a signal e shown in FIG. 2E, and supplies this to the mixer 6. The mixer 6 subtracts and mixes the signal e with the signal c to produce a signal f shown in FIG. 2F.
get. After this signal f is clamped at the sync chip level by the clamp circuit 8, it is sent to the FM modulator 9.
The FM modulated wave obtained by FM modulating the carrier wave with the signal f is output from the terminal 9, and after subsequent processing is recorded on a magnetic tape by, for example, a rotating head. In other words, the overshoot of the rising edge of the signal a that is removed by the clip circuit 3 is taken out as the signal d, and the signal f, which is attenuated from the signal d, is inverted and output from the clip circuit 3, and the signal c is further delayed. is added just before the edge of , to obtain the signal e.

A reproduced signal reproduced from the magnetic tape by the rotary head enters the terminal 11 in FIG. 1B and is supplied to the FM demodulator 12. The signal demodulated by the FM demodulator 12 is taken out by the low-pass filter 13.
The signal g shown in FIG.
It is supplied to each of the mixers 16. In this signal g, the fall timing of the horizontal synchronization signal is defined as time _t1 . The delay circuit 14 has the same delay time τ as the delay circuit 5, and delays the signal g and supplies it to the sampling circuit 17 as a signal h shown in FIG. 2H. Further, the clamp circuit 15 clamps the sync chip level of the signal g and supplies it to the comparator 18. The comparator 18 has a reference level slightly lower than the 160% level of the white peak of the signal g, as shown by the broken line in FIG. 2 Generating and extracting the signal i shown in FIG. 1 17
supply to.

The sampling circuit 17 extracts the signal h supplied from the delay circuit 14 during the H level period of the signal i,
Signal j shown in Figure 2 J assuming that the DC component is 0V
is generated and supplied to the amplifier 19 and mixer 20, respectively. The amplifier 19 has an amplification factor of 10, for example, and amplifies the signal j to obtain a signal k as shown in FIG. 2K. This signal k is substantially the same as the inverted signal d. Signal k is low pass filter 2
1. The low-pass filter 21 has a cutoff frequency of, for example, 1 MHz, and the signal k is supplied to the mixer 16 after high-frequency noise components are removed therefrom. The mixer 16 mixes the demodulated signal g with the signal k
The signal l shown in FIG. Delay circuit 2
2 has the same delay time τ as the delay circuits 5 and 14, and delays the signal l to produce the signal m shown in FIG.
and supplied to the mixer 20. This signal m is delayed by a time τ compared to the signal g. mixer 20
subtracts and mixes the signal j with the signal m to generate the signal n shown in FIG. 2N. This signal n is supplied to the de-emphasis circuit 23, where the high frequency enhancement performed by the emphasis circuit 2 during recording is restored to its original characteristics, and the signal from the de-emphasis circuit 23 is sent to the terminal 2.
4. That is, the extraction circuit 17 extracts the added portion immediately before the edge from the demodulated signal g, and this extracted signal j is amplified and inverted and added to the portion of the signal g from which the overshoot has been removed. Signal j is inverted and added to the additional portion of signal g, resulting in a signal n that is substantially the same as the original signal a.

In this way, a portion of the overshoot removed by the clip circuit 3 is completely restored. Therefore, the edge of the rising edge of the signal after de-emphasizing the signal n is not blunted, and as shown in FIG. 4A, for example.
When the signal shown in FIG. 4 is recorded and reproduced, a signal as shown in FIG.

Also, the signals recorded on the magnetic tape are shown in Figure 2F.
As shown in Figure 1A, since the level of the portion delayed immediately before the edge is small, the magnetic tape recorded through the circuit of Figure 1A is
When the data is reproduced using the delay circuits 14 to 22 shown in FIG. Note that the low-pass filter 21 is connected to the sampling circuit 17 and the amplifier 1.
9, etc., and if these effects are small, there is no need to provide the low-pass filter 21.

FIGS. 3A and 3B show block diagrams of a second embodiment of the recording system and reproducing system of the apparatus of the present invention, respectively. In this figure, the same parts as in FIGS. 1A and 1B are given the same reference numerals, and their explanations will be omitted. In the reproduction system of FIG. 3B, the amplifier 19 and low-pass filter 21 are not provided, and the signal j from the sampling circuit 17 is supplied to mixers 16 and 20, respectively. The mixer 16 subtracts and mixes the signal j with the signal g to generate the signal o shown in FIG. 2O. After the signal o is delayed by a time τ in the delay circuit 22, it is subtractively mixed with the signal j in the mixer 20 to produce the signal p shown in FIG. 2P.

In this circuit, a portion of the overshoot removed by the clip circuit 3 is restored to some extent. As a result, the edge of the rising edge of the signal after de-emphasizing the signal p is not so dull.
When the signal shown in FIG. 4A is recorded and reproduced, a signal substantially equal to the signal shown in FIG. 4C is obtained, and the occurrence of smear in the reproduced image can be suppressed.

The first point is that the magnetic tape recorded through the circuit shown in Figure 3A can be played back without any problems using ordinary equipment.
This is similar to the case where the apparatuses shown in Figures A and B are used.

Effects of the Invention As mentioned above, the magnetic recording and reproducing apparatus according to the present invention has the following effects:
The part from which the overshoot has been removed is taken out, attenuated, and added to the signal from the clip circuit just before the edge, and the added part is extracted from the demodulated signal and inverted to produce the added part of the demodulated signal and the part from which the overshoot has been removed. Because the level of the added part immediately before the edge is small, it does not interfere with playback even when played back with normal equipment, making it compatible with normal equipment, and the edges of the reproduced signal will not be too dull. It has characteristics such as being able to suppress the occurrence of smear.

In addition, by amplifying and inverting the additional part extracted from the demodulated signal and adding it to the additional part of the demodulated signal, it is possible to completely reproduce the overshoot that is removed during recording, and the edges of the reproduced signal are dulled. It has the advantage of being able to prevent the occurrence of smear.

[Brief explanation of drawings]

1 and 3 are block system diagrams of each embodiment of the device of the present invention, FIG. 2 is a waveform diagram of each part of the device shown in FIGS. 1 and 3, respectively, and FIG. 4 is a diagram of the conventional device and the device of the present invention. FIG. 3 is a waveform diagram of an example of a signal recorded and reproduced in the apparatus. 1, 10, 11, 24... terminal, 2... emphasis circuit, 3... clip circuit, 4... lower limit limiter circuit, 5, 14, 22... delay circuit, 6, 16, 20
... Mixer, 7... Attenuator, 8, 15... Clamp circuit, 9... FM modulator, 12... FM demodulator, 13,
21...Low pass filter, 17...Sampling circuit, 18...Comparator, 19...Amplifier, 23...De-emphasis circuit.

Claims (1)

[Claims] 1. After level-limiting the overshoot of the rising edge of the signal using a clip circuit, the signal is FM modulated and recorded on a magnetic recording medium, and the reproduced signal from the recording medium is FM demodulated to recover the original signal. In a magnetic recording/reproducing device for obtaining a signal, the portion removed due to the level limit of the overshoot is extracted, attenuated, inverted, and added immediately before the edge of the signal from the clip circuit, and the reproduced signal is Magnetic recording characterized in that the added portion immediately before the edge is extracted from the demodulated signal obtained by FM demodulation, inverted, and added to the added portion of the demodulated signal and the portion from which the overshoot has been removed. playback device. 2. Magnetic recording and reproducing that limits the level of the overshoot of the rising edge of the signal using a clip circuit, then performs FM modulation and records on a magnetic recording medium, and then FM demodulates the reproduced signal from the recording medium to obtain the original signal. In the device, the portion removed due to the level limit of the overshoot is taken out, attenuated, inverted, and added just before the edge of the signal from the clip circuit, and the reproduced signal is FM demodulated to obtain demodulation. The additional portion immediately before the edge is extracted from the signal, inverted, and added to the additional portion of the demodulated signal, and the extracted additional portion is amplified and inverted and added to the removed portion of the overshoot. A magnetic recording/reproducing device characterized by: