JPH0449786A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a reproduced picture faithful to an original signal at the time of variable-speed reproduction by enabling to switch the amplifying ratio of an amplifier provided on the post stage of an FM demodulator corresponding to the speed of the variable-speed reproducing. CONSTITUTION:An inputted video signal is recorded on a magnetic tape 5 through a preemphasis circuit 1, an FM modulator 2, a recording amplifier 3 and video head 4. A regenerative FM signal is read by a video head from the magnetic tape 5 at reproducing and the regenerative video signal with the reduced noise of high frequency is obtained through a head amplifier 7, a reproducing equalizer circuit 8, an FM demodulator 9 and a deemphasis circuit 12. The regenerative video signal is converted into an analog signal through a clamping circuit 13, an A/D converter 14, a regenerative signal processing circuit 15 and a D/A converter 16 and is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetic recording and reproducing apparatus that can obtain a reproduced image faithful to an original signal during variable speed reproduction.

[Conventional technology]

FIG. 7 is a block diagram showing an example of the configuration of a VTR, which is one of the conventional magnetic recording and reproducing devices. In FIG. 3 is the recording amplifier, 4.6 is the video head,
5 is a magnetic tape. In addition, 7 is a head amplifier, 8 is a reproduction equalizer circuit that compensates for the frequency characteristics of the reproduced FM signal, 9 is an FM demodulator, 12 is a de-emphasis circuit with characteristics opposite to that of pre-emphasis circuit 1, and 13 is an A/D converter. 14 is an A/D converter that converts the reproduced video signal from an analog signal to a digital signal; 15 is a time base converter that removes time axis fluctuations of the reproduced video signal; A digital reproduction signal processing circuit consisting of a collector, etc., 16 is a D/A
It is a converter.

Next, the operation will be explained.

In the block diagram of FIG. 7, a pre-emphasis circuit 1 emphasizes high-frequency components of an input video signal, and an FM modulator 2 performs FM modulation. Thereafter, the signal is amplified by a recording amplifier 3 and recorded on a magnetic tape 5 by a video head 4.

During reproduction, a reproduced FM signal is read from the magnetic tape 5 by a video head 6 and amplified by a head amplifier 7. This amplified reproduction FM signal is transmitted to a reproduction equalizer circuit 80.
The amplitude fluctuation of the reproduced FM signal is reduced by suppressing the lower sideband and emphasizing the upper sideband using the frequency characteristics. Then, this reproduced FM signal is FM demodulated by the FM demodulator 9, and the de-emphasis circuit 12 attenuates the high-frequency components emphasized during recording, thereby obtaining a reproduced video signal in which high-frequency noise is simultaneously reduced. . The recurrent video signal output from the de-emphasis circuit 12 is A/
The signal is clamped to have a DC level that falls within the input voltage range of the D converter 14, and is input to the A/D converter 14. The analog video signal is converted into a digital signal by the A/D converter 14. This digital signal undergoes processing such as removing time axis fluctuations of the reproduced video signal by a time base collector constituting the digital reproduced signal processing circuit 15, and is converted into an analog signal by a D/A converter 16 and output.

Incidentally, among professional equipment such as high-definition VTRs, there are devices that are designed to transmit digital video signals between a plurality of devices, and devices that process digital video signals within each device. When connecting such devices, the video signal transmitted between the devices must be a signal that conforms to the video signal standard.
These are the frame, field frequency, horizontal frequency, etc. of the TR output video signal. To achieve this, reproduction signal processing inside the VTR is required to be performed in units of fields or frames. Generally, a rotating head is used, in which a video head is attached to a VTR rotating drum, and the device is configured to have a high relative speed with respect to the magnetic tape.

In order to process reciprocating signals within the VTR in units of fields and frames with such a configuration, the number of revolutions of the rotary drum is kept constant. In other words, it is desirable to keep the speed of the video head constant.

Next, the operation of the above-mentioned conventional example during forward high-speed playback and reverse high-speed playback when the rotational speed of the rotating drum is always constant will be described below.

If the rotational speed of the rotary drum is always constant, the relative speed between the video head 6 and the magnetic tape 5 will change as the speed and traveling direction of the magnetic tape 5 changes during special playback. FIG. 8 shows the trajectory of the video head 6 scanning over the magnetic tape 5 during normal playback, forward high speed playback, and reverse high speed playback. During normal playback, the video head 6 is connected to the magnetic tape 5 as shown in FIG.
Since the same trajectory is drawn during recording and reproduction, the relative speed between the video head 6 and the magnetic tape 5 is equal to the relative speed during recording. Therefore, the amplitude level of the reproduced video signal output from the FM demodulator 9 is equal to the amplitude level at the time of recording. FIG. 9(a) shows a reproduced video signal and its amplitude level during normal reproduction.

During high-speed playback in the forward direction, the trajectory of the video head 6 becomes as shown in FIG. 8, and the relative speed during playback is smaller than the relative speed during recording. In other words, the frequency of the reciprocating FM signal read by the RAD 6 from the magnetic tape 5 to the video becomes lower. Therefore, since the frequency deviation of the reproduced FM signal becomes small, the amplitude level of the reproduced video signal that has been FM demodulated and de-emphasized by the FM demodulator 9 is as shown in FIG.
)), the amplitude level is smaller by (A) than the normal amplitude level at the time of re-excursion.

Similarly, during high-speed reproduction in the reverse direction, the trajectory of the video paddle 1'6 becomes as shown in FIG. 8, and the relative speed during reproduction is greater than the relative speed during recording. Therefore, the frequency shift of the reproduced FM signal becomes large, so that the amplitude level becomes larger by CB) than the amplitude level during normal reproduction, as shown in FIG. 9(C).

[Problem to be solved by the invention]

Since the conventional magnetic recording and reproducing apparatus is configured as described above, the amplitude level of the reproduced video signal output from the FM demodulator changes in accordance with changes in the relative speed between the video head and the magnetic tape. Therefore, a method of recording a luminance signal and a color signal as a composite causes a change in contrast in the reproduced video, and a method of recording the signal as a component also causes a change in color tone.

This invention was made to solve the above-mentioned problems, and it is possible to obtain a good reproduced video signal output even if a relative speed change occurs between the video rad and the magnetic tape during high-speed reproduction. The purpose is to obtain a magnetic recording/reproducing device.

[Failure to solve the problem]

The magnetic recording and reproducing apparatus according to the present invention includes a reproduction mode signal generator that generates a reproduction mode signal based on the reproduction mode, and switches the amplification factor of the amplifier downstream of the FM demodulator according to the reproduction mode signal. Since a video signal having the same amplitude level as the video signal during recording is obtained even during high-speed reproduction, it is possible to obtain a reproduced video signal that is faithful to the original signal.

Further, the magnetic recording and reproducing apparatus according to the present invention is provided with a reproduction mode signal generator that generates a reproduction mode signal based on the reproduction mode, and a reproduction system A/D according to the reproduction mode signal.
By switching the multiplication value for the digital playback video signal after A/D conversion by the digital multiplier provided in the digital signal processing circuit system after conversion, the amplitude level remains the same as the video signal during recording even during high-speed playback. This makes it possible to obtain a reproduced video signal that is faithful to the original signal.

[Effect]

The magnetic recording/reproducing apparatus according to the present invention is capable of switching the amplification factor at the latter stage of the FM demodulator based on the reproduction mode signal, so that even if the relative speed changes due to high-speed reproduction, the video signal has the same amplitude level as when recording. Obtainable.

Further, in the magnetic recording and reproducing apparatus of the present invention, the multiplication value of the reproduced video signal after A/D conversion by the digital multiplier provided in the digital signal processing circuit system after A/D conversion is switched based on the reproduction mode signal. Therefore, even if the relative speed changes due to high-speed reproduction, it is possible to obtain a reproduced video signal having the same amplitude level as when recording.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a magnetic recording/reproducing apparatus according to a first embodiment of the present invention, and in the figure, recording systems 1 to 5. Regeneration system 6-9.1
2 to 16 are exactly the same as the conventional device shown in FIG.

10 is a reproduction mode signal generator that generates a reproduction mode signal based on the reproduction mode, and 11 is an amplification factor switchable for making the amplitude level of the reproduced video signal equal to the amplitude level of the video signal at the time of recording based on the reproduction mode signal. It is a powerful amplifier.

Next, the operation will be explained. A reproduced FM signal read out from the video head 6 during reproduction is amplified by a head amplifier 7 and then sent to a reproduction equalizer circuit 8. The reproduction equalizer circuit 8 compensates the frequency characteristics of the reproduction FM signal, and
The M demodulator 9 performs FM demodulation to obtain a reproduced video signal.

The signal processing up to this point is the same as in the conventional example. Here, a description will be given of fluctuations in the amplitude level of the reproduced video signal when the reproduction mode changes to high-speed reproduction.

During normal playback, the relative speed between the video head 6 and the magnetic tape 5 is equal to the relative speed between the video head 4 and the magnetic tape 5 during recording, so the amplitude level of the playback video signal output from the FM demodulator 9 is It becomes equal to the amplitude level of the video signal at the time of recording. Incidentally, when performing high-speed forward playback or high-speed reverse playback, the relative speed between the video head 6 and the magnetic tape 5 changes with respect to the relative speed during normal playback.

In other words, the frequency shift of the reproduced FM signal read by the video head 6 from the magnetic tape 5 changes, so the FM
The amplitude level of the reproduced video signal FM demodulated by the S modulator 9 changes. Therefore, the reproduced video signal output from the FM demodulator 9 is input to an amplifier 11 that can be controlled by a reproduction mode signal. The amplifier 11 includes a reproduction mode signal generator 10.
The playback mode signal generated in By switching the amplification factor of the amplifier 11 using this reproduction mode signal, the amplitude level of the reproduced video signal can be made equal to the amplitude level of the video signal at the time of recording. During forward high-speed reproduction, the amplitude level (A) during normal reproduction is reduced as shown in FIG. 9(b), so the amplification factor of the amplifier 11 is increased by the amount of the decrease. Further, during reverse high-speed reproduction, the amplitude level becomes larger by CB) than during normal reproduction, as shown in FIG. 9(e), so the amplification factor of the amplifier 11 is reduced by the amount of increase.

The subsequent processing is the same as in the conventional example.

An example of the configuration of the amplifier used in the above embodiment will be described below with reference to FIG. 2.

In the circuit configuration example shown in FIG. 2, the amplification factor of the non-inverting amplifier constituted by the operational amplifier 21 is changed by switching the contacts (a), (b), and (e) of the switch 22 in response to the reproduction mode signal. . Here, the contact (a) is used during forward high-speed playback, and the contact (C) is used during normal playback.
) is connected during reverse high-speed playback. Contact (a).

Resistors R, ,R, ,R, are connected to (b) and (C), respectively, and the relationship between them is R,<R,<Rc. The amplification factor of this amplifier is the feedback resistor R1 and R,
, R, , Re, the amplification factor during forward high speed playback is (R, +R,)/R1, and during normal playback (R
t +Rh, ) /Rb, (R
f+Rc)/Rc. Therefore, the amplification factor during high-speed playback is larger during forward high-speed playback and smaller during reverse high-speed playback than the amplification factor during normal playback. As described above, it is possible to change the amplification factor of the amplifier depending on the reproduction mode signal.

In addition, in the above embodiment, explanation was given for high-speed playback, but
It may be possible to perform low-speed reproduction (slow reproduction), and the same effect as in the above embodiment can be achieved.

Further, FIG. 3 shows a magnetic recording/reproducing apparatus according to a second embodiment of the present invention, and in the figure, recording systems 1 to 5. Regeneration system 6
~9.12 to 16 are exactly the same as the conventional bag W shown in FIG. 17 is a reproduction mode signal generator that generates a reproduction mode signal based on the reproduction mode, and 18 is a multiplication value switchable for making the amplitude level of the reproduced video signal equal to the amplitude level of the video signal at the time of recording based on the reproduction mode signal. It is a digital multiplier.

Next, the operation will be explained. The reproduced FM signal read out from the video rad 6 during reproduction is amplified by the head amplifier 7 and then sent to the reproduction equalizer circuit 8. The reproduction equalizer circuit 8 compensates the frequency characteristics of the reproduction FM signal, and
The MI modulator 9 performs FM demodulation to obtain a reproduced video signal.

The signal processing up to this point is the same as in the conventional example. Here, a description will be given of fluctuations in the amplitude level of the reproduced video signal when the reproduction mode changes to high-speed reproduction.

During normal playback, the relative speed between the video head 6 and the magnetic tape 5 is equal to the relative speed between the video head 4 and the magnetic tape 5 during recording, so the amplitude level of the playback video signal output from the FM demodulator 9 is It becomes equal to the amplitude level of the video signal at the time of recording. Incidentally, when performing high-speed playback in the forward direction or high-speed redirection in the reverse direction, the relative speed between the video head 6 and the magnetic tape 5 changes with respect to the relative speed during normal playback.

In other words, the frequency shift of the reproduced FM signal read by the video head 6 from the magnetic tape 5 changes, so the FM
The amplitude level of the reproduced video signal FM demodulated by the demodulator 9 changes.

The reproduced video signal output from the FM demodulator 9 is processed by a de-emphasis circuit 1o, which attenuates the high-frequency components emphasized by the pre-emphasis circuit 1 in the recording system circuit, thereby producing a reproduced video signal with reduced high-frequency noise. obtain. De-emphasis circuit 1
The reproduced video signal outputted from the sync chip is clamped by a zinc chip by the clamp circuit 11, and the analog video signal is converted by the A/D converter 14 into a digital signal such that the digital data at the sync chip level becomes rQ. be done. This digital signal is input to a digital multiplier 18 which can be switched by a reproduction mode signal. This digital multiplier 18 multiplies the digital playback video signal after A/D 5E conversion by X(a) depending on the content of the playback mode signal generated by the playback mode signal generator 17. In other words,
During forward high-speed playback, as shown in Figure 9 0)), the amplitude level of the reproduced video signal is smaller than the amplitude level of the reproduced video signal during normal reproduction by (A), so the amplitude level increases by the amount equivalent to (A) in the digital reproduced video signal. Multiply by a constant like Also, during reverse high-speed playback, as shown in Figure 9(C), the amplitude level of the reproduced video signal is greater than the amplitude level of the reproduced video signal during normal playback by (B), so the amplitude level of the digital reproduced video signal is increased by an amount corresponding to (B). Multiply by a constant that makes it smaller.

As described above, by switching the multiplication value to the digital playback video signal after A/D/conversion, even during high-speed playback, the amplitude level of the repeat video signal is the same as that during normal repeat playback, and the digital playback signal processing It is input to the circuit 15. The subsequent processing is the same as in the conventional example.

An example of the configuration of the digital multiplier 14 used in the above embodiment will be described below with reference to FIGS. 4 and 5.

In the configuration example shown in FIG. 4, as an address input to the ROM 22,
The digital video signal whose amplitude direction has been quantized into n bits is sent to addresses A0 to AI1. l, and when in playback mode, normal playback mode, forward high speed playback mode,
Three types of reverse high-speed playback modes are stored as 2-bit data and input to addresses A7°A, , *l.

Then, the data stored in the ROM 22 is outputted from 0° to 0,1 corresponding to each address input.

FIG. 5 explains the data inside the ROM 22.8 During normal playback, as shown by 221 in FIG.
22 address input ([xa and ROM22 output (!I
Iy + becomes equal. In other words, X.

=y. During the forward high-speed forward movement, as shown at 222 in FIG. 5, the output y! of the ROM 22 is larger than the address input value x0 of the ROM 22 by a predetermined constant multiple. The data is stored as follows. Similarly, during reverse high-speed playback, as shown at 223 in FIG.
Data is stored so as to be the output y3 of M22.

Note that the internal data of the ROM 22 shown in FIG. 5 is clamped by the clamp circuit 13 at the front stage of the reproduction system A/D converter 14 at the sync chip of the reproduced video signal, and is also digital data after A/D conversion. This is an example when A/D conversion is performed to represent the sync chip level when is "0". With the configuration described above, the digital multiplier 14 can be realized.

In the above embodiment, the clamp circuit 13 clamps the reproduced video signal at the sync chip level, and the A/D converter 14 at the subsequent stage sets the sync chip level of the reproduced video signal to correspond to "0" in digital data. Since we have shown an example of A/D conversion, digital multiplier 1
8, but even if the clamp circuit 11 clamps the reproduced video signal at another level or clamps the sync depth, if the digital data corresponding to the sync chip level does not become r□, Alternatively, a digital data converter may be used instead of the digital multiplier 18.

FIG. 6 shows ROM table data when a ROM is used as an example of the configuration of a digital data converter when the reproduced video signal is clamped at the pedestal level and the digital data at the pedestal level corresponds to "α".

Note that the circuit configuration is the same as that shown in FIG.

In addition, in the above embodiment, explanation was given for high-speed playback, but
This may be performed during low-speed playback (slow playback), and the same effects as in the above embodiment can be achieved.

〔Effect of the invention〕

As described above, according to the present invention, in the reproduction signal processing circuit of the magnetic recording and reproduction apparatus, the amplification factor of the amplifier provided after the FM demodulator is configured to be controllable based on the reciprocating mode signal, or Since the multiplication value of the digital playback video signal after A/D conversion by the digital multiplier provided in the digital signal processing circuit system after A/D conversion can be controlled based on the playback mode signal, playback mode change is possible. Despite changes in the relative speed between the video head and the magnetic tape due to this, the amplitude level of the reproduced video signal is equal to the amplitude level of the video signal during recording, so it is possible to obtain a reproduced signal that is faithful to the original signal. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a magnetic recording/reproducing apparatus according to a first embodiment of the invention, FIG. 2 is a circuit diagram showing an example of the configuration of an amplifier used in the first embodiment of the invention, and FIG. A block diagram showing a magnetic recording/reproducing apparatus according to a second embodiment of the present invention, FIGS. 4 and 5 are diagrams illustrating an example of the configuration of a multiplier used in the second embodiment of the present invention, and FIG. 7 is a circuit diagram illustrating an example of a conventional magnetic recording/reproducing device; FIG. 8 is a diagram illustrating the trajectory of a video head during high-speed reproduction; and FIG. 9 is a diagram illustrating a configuration example of a digital data converter.
The figure is a diagram illustrating changes in the amplitude level of a reproduced video signal during high-speed reproduction. In the figure, 4.6 is a video head, 9 is an FM demodulator,
10 is a reproduction mode signal generator, 11 is an amplifier controllable by the reproduction mode signal, 14 is an A/D converter, 15 is a digital reproduction signal processing circuit, 16 is a D/A converter, 1
7 is a reproduction mode signal generator, and 18 is a digital multiplier. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (2)

[Claims] (1) FM modulating the video signal, recording and reproducing it with a magnetic head mounted on a rotating drum, and converting the FM demodulated video signal into digital data A.
In a magnetic recording and reproducing device equipped with a /D converter, the rotational speed of the rotating drum during variable speed reproduction is the same as that during recording, and the amplification factor of the amplifier provided after the FM demodulator is adjusted according to the speed of variable speed reproduction. A magnetic recording/reproducing device characterized by switching. (2) FM modulating the video signal, recording and reproducing it with a magnetic head mounted on a rotating drum, and converting the FM demodulated video signal into digital data A.
In a magnetic recording/reproducing device equipped with an A/D converter, the rotational speed of the rotating drum during variable speed playback is the same as that during recording, and the A/D conversion is performed by a digital data converter provided in a digital signal processing circuit system after A/D conversion. A magnetic recording and reproducing device characterized in that conversion characteristics to a digital reproduced video signal after D conversion are switched according to the speed of variable speed reproduction.