JPH0589593A - Magnetic recording / reproducing device - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce variations in characteristics between channels. In a magnetic recording / reproducing apparatus in which a luminance signal Y and color signals BY and RY are digitally time-division multiplexed to perform multi-channel recording, a horizontal linear emphasis circuit 20, a horizontal linear emphasis circuit 20, is used as a horizontal emphasis circuit. Two
1 and the horizontal non-linear emphasis circuits 16 and 17 are used. In the horizontal non-linear emphasis circuits 16 and 17, the amount of emphasis is set to be large for a small amplitude signal, and a large amplitude signal is limited. Emphasis processing is performed. The horizontal non-linear emphasis circuits 16 and 17 are configured as digital circuits. The horizontal non-linear de-emphasis circuits 38 and 39 are also configured as digital circuits.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus such as a high-definition analog VTR, and more particularly to a magnetic recording / reproducing apparatus in which variations in characteristics of a horizontal emphasis circuit or a horizontal de-emphasis circuit are improved.

[0002]

2. Description of the Related Art Since a magnetic recording / reproducing apparatus such as an analog VTR for high definition uses a multi-channel recording system, the number of circuit systems used increases in proportion to the number of channels. FIG. 8 is a system diagram showing an example of an analog VTR for high-definition. In the figure, a 2-channel recording system is adopted. In the figure, 10R indicates the recording system and 10P indicates the reproducing system. The recording system 10R will be described.

A luminance signal Y and a pair of color difference signals BY,
RY is band-limited by low-pass filters 1, 2 and 3, respectively, and then converted into digital signals by A / D converters 4, 5 and 6. The digitized luminance signal Y and the pair of color difference signals B-Y and R-Y are subjected to time division compression multiplexing processing and shuffling processing in a time division multiplexing circuit (TDM circuit) 11 having a shuffling function. That is, the color difference signals are compressed, and a pair of color difference signals are line-sequentially multiplexed with the luminance signal Y.

When two channels of video signals are recorded,
For example, in the A channel, the color difference signal BY is time-axis compressed to form a compressed color difference signal, and this and the luminance signal Y are time-division multiplexed in this order to generate a video signal. In the B channel, the color difference signal R-Y is time-axis compressed to form a compressed color difference signal, and this and the luminance signal Y are time-axis multiplexed in this order to generate a video signal. afterwards,
Shuffling processing is performed on each channel. 12
Is a clock generation circuit for generating various clocks used in the recording system 10R.

The video signals SA and SB which have been subjected to the time division multiplexing process and the shuffling process are added with the synchronizing signal and the burst signal output from the signal generating circuit 13, and in that state, the D / A converter 14, At 15, it is converted to an analog signal. After that, they are supplied to the horizontal non-linear emphasis circuits 16 and 17, respectively, and this time, non-linear emphasis processing in the horizontal direction is performed.

The analogized video signals SA and SB are band-limited by the low-pass filters 18 and 19, and then supplied to the FM modulators 22 and 23 via the linear horizontal emphasis circuits 20 and 21 composed of CR circuits. FM modulation is performed so as to be suitable for recording. Then, after that, two channels are recorded via the recording amplifiers 24 and 25 by using a dedicated magnetic head (not shown).

As the horizontal emphasis circuits, the horizontal non-linear emphasis circuits 16 and 17 and the linear horizontal emphasis circuits 20 and 21 are provided because only the linear horizontal emphasis circuits 20 and 21 provide a flat screen (screen at a small amplitude). This is because the noise reduction effect in () is small, so that the horizontal non-linear emphasis circuits 16 and 17 are provided to increase the emphasis amount on a particularly flat screen, that is, when the amplitude is small to increase the noise reduction effect.

When a signal with a large amplitude is input, the amplitude of the signal is limited by the horizontal nonlinear emphasis circuits 16 and 17, so that there is no noise reduction effect for a signal with a large amplitude. However, since the noise at that level is reduced by the horizontal linear emphasis circuits 20 and 21 in the subsequent stage, a noise suppressing effect is produced as a whole.

In the reproducing system 10P, first, the video signal reproduced by the magnetic head described above is transferred to the head amplifier 3
The video signal is supplied to the FM demodulators 32 and 33 via 0 and 31 to be FM-demodulated, and also to the horizontal non-linear de-emphasis circuits 38 and 39 via the horizontal de-emphasis circuits 34 and 35 and the low pass filters 36 and 37. It is supplied and subjected to de-emphasis processing in the horizontal direction.

The outputs of the low-pass filters 36 and 37 are also supplied to clock generation circuits 40 and 41 corresponding to the respective channels in order to generate a clock used in the digital signal processing of the reproduction system 10P.

The de-emphasis processed emphasis is supplied to A / D converters 42 and 43 to be converted into digital signals, and then supplied to a time division separation circuit 44 having a deshuffling function.

In the time division separation circuit 44, the time axis is first corrected (TBC processing), and the deshuffling processing for the time axis compressed video signals SA and SB and the time axis expansion of the color difference signals BY and RY are performed. The separation processing is performed, and the luminance signal Y and the pair of color difference signals BY and R- whose time axes are aligned are provided.
Returned to Y.

The luminance signal Y and a pair of color difference signals B-
Thereafter, Y and RY are D / A converters 48, 49 and 50.
After being converted into an analog signal by the low-pass filter 51,
Band limitation processing is performed at 52 and 53 to form a final high-definition luminance signal Y and a pair of color difference signals BY and RY.

[0014]

By the way, in the VTR 10 adopting the multi-channel recording system as described above, it is necessary to perform emphasis processing for edge enhancement in the horizontal direction for each channel, and for that purpose, each channel is processed. On the other hand, it is necessary to provide a horizontal emphasis circuit and a horizontal de-emphasis circuit having the same structure.

A problem in such a case is variation in characteristics between channels. As described above, as the horizontal emphasis circuit, since the horizontal non-linear emphasis circuits 16 and 17 and the horizontal linear emphasis circuits 20 and 21 are provided in each channel, the variation between the horizontal non-linear emphasis circuits 16 and 17 may be reduced. If there is a variation between the horizontal linear emphasis circuits 20 and 21, it is necessary to adjust the level between the channels, which makes the adjustment work troublesome. In particular, the variation between the horizontal non-linear emphasis circuits 16 and 17 remarkably appears as a level difference between channels, and therefore the maximum adjustment target is to eliminate the variation.

Horizontal linear de-emphasis circuits 34, 3
Similarly, the variation between channels 5 and the variation between the horizontal non-linear de-emphasis circuits 38 and 39 also result in variation in characteristics between channels.

When a non-linear emphasis characteristic is imparted also to the vertical direction to emphasize the edge in the vertical direction, the analog processing of this vertical non-linear emphasis circuit is the same as described above. Problem occurs.

In view of the above, the present invention has solved such a conventional problem, and can reduce variations in emphasis and de-emphasis characteristics between channels at least in the horizontal direction when the multi-channel recording method is used. The present invention proposes a magnetic recording / reproducing device that can be used.

[0019]

In order to solve the above-mentioned problems, according to the present invention, a magnetic recording / reproducing apparatus for digitally performing time-division multiplexing processing on a luminance signal and a chrominance signal to perform multi-channel recording is provided. At least a horizontal linear emphasis circuit and a horizontal non-linear emphasis circuit are used as the horizontal emphasis circuit. In the above-mentioned horizontal non-linear emphasis circuit, the amount of emphasis is large with respect to a small amplitude signal, and a large amplitude signal is limited to a non-linear one. The horizontal non-linear emphasis circuit is configured as a digital circuit while being subjected to various emphasis processes. The horizontal non-linear de-emphasis circuit is also digitally processed.

[0020]

As shown in FIG. 1, in the recording system 10R, time-division multiplexed digital video signal S for each channel is used.
A and SB are horizontal non-linear emphasis circuits 16 and 17, respectively.
Digitally emphasis processed by D / A
It is supplied to the converters 14 and 15 and converted into analog signals. After that, the horizontal linear emphasis circuits 20 and 21 perform emphasis processing in an analog manner.

In the figure, non-linear emphasis circuits 7, 8 and 9 in the vertical direction are further provided, and the non-linear emphasis processing is also digitally processed.

In the reproducing system 10P, the horizontal linear de-emphasis circuits 34 and 35 perform analog de-emphasis processing, and after A / D conversion, they are supplied to the horizontal non-linear de-emphasis circuits 38 and 39 to be digitalized. Is de-emphasis processed. Also in the vertical direction, digital non-linear de-emphasis processing is performed by the non-linear de-emphasis circuits 45, 46 and 47.

As described above, as the horizontal emphasis circuit and the horizontal de-emphasis circuit, the non-linear emphasis circuits 16 and 17 and the non-linear de-emphasis circuit 3 are used.
By configuring both 8 and 39 so that they can be digitally processed, it is possible to reduce variations in their characteristics. Since it is a digital circuit, the setting of the delay time and the coefficient is unique and the variation can be suppressed.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an example of a magnetic recording / reproducing apparatus according to the present invention will be described in detail with reference to the drawings when applied to a high-definition analog VTR adopting the above-mentioned two-channel recording system. Description of parts having the same configuration as in FIG. 8 will be omitted.

In the present invention, as shown in FIG. 1, the A / D converted luminance signal Y and the pair of color difference signals BY, R- are used.
Y is the vertical non-linear emphasis circuit 7,
8 and 9, the edges in the vertical direction are emphasized, and the non-linear characteristics are set so that the edges having a high luminance level are not emphasized too much.

The luminance signal and the pair of chrominance signals BY and RY which have been subjected to vertical emphasis are supplied to the time division multiplexing circuit 11 and subjected to time division compression multiplexing processing.
The time-division-compression-multiplexed digital video signals SA and SB obtained from the time-division multiplexing circuit 11 are supplied to the horizontal non-linear emphasis circuits 16 and 17 as digital signals and subjected to digital emphasis processing.

D / A converters 14 and 15 are provided after digitally adding a synchronizing signal and a burst signal to the emphasis-processed video signals SA and SB of the respective channels.
Is supplied to and converted to analog. After that, it is supplied to the horizontal linear emphasis circuits 20 and 21 via the low-pass filters 18 and 19 and subjected to analog emphasis processing as in the conventional case.

By performing the emphasis processing as described above, the amplitude characteristic as shown in FIG. 2 can be obtained. The figure shows the characteristic diagram in the horizontal direction when a stepped video signal is input.The solid line shows the waveform of the original signal with a relatively large level, and the broken line shows the waveform when non-linear emphasis is applied in the vertical direction. Yes, the one-dot chain line is the waveform when horizontal non-linear emphasis is applied.
It can be seen that the amount of emphasis at the rising edge of the signal is limited by the non-linear emphasis.

Also in the reproducing system 10P, the A / D converter 4
Video signals SA digitally converted by 2, 43,
SB is a horizontal non-linear de-emphasis circuit 38, 39
To be digitally processed. The de-emphasis-processed video signals SA and SB are supplied to a time division separation circuit 44, and an original luminance signal Y and a pair of color difference signals BY,
Converted to RY.

The luminance signal Y and a pair of color difference signals B-
Y and R-Y are subjected to vertical de-emphasis processing by vertical non-linear de-emphasis circuits 45, 46 and 47 to be returned to the original amplitude characteristics, and then D / A converters 48, 49 and 50. Will be analogized in.

When at least the horizontal non-linear emphasis circuits 16 and 17 and the horizontal non-linear de-emphasis circuits 38 and 39 are configured as digital circuits in this way, the delay times and the coefficients of the delay elements that configure the digital circuits will be described later. Since the coefficients of the multipliers and the like can all be set exactly as designed, the amplitude characteristics and frequency characteristics do not differ from each other, and if any, they are very small. Therefore, there is no variation in the characteristics between the horizontal non-linear emphasis circuits 16 and 17, and there is no variation in the characteristics between the horizontal non-linear de-emphasis circuits 38 and 39.

Since these digital circuits have non-linear characteristics, the emphasis amount for a large amplitude signal is smaller than the emphasis amount for a small amplitude signal, and the amplitude difference from the signal before the emphasis is small.
This means that the increase in word length, which is a problem in digital processing, is small. In the case of the present example, when the original signal is a digital signal of 8 bits, the error length is increased by 1 bit to a total of 9 bits by this emphasis processing. The small increase in error length also means that the number of elements used in the digital circuit is reduced and the increase in the circuit scale can be suppressed.

As shown in FIG. 1, when the non-linear emphasis circuits 7, 8 and 9 and the non-linear de-emphasis circuits 45, 46 and 47 in the vertical direction as well as in the horizontal direction are configured to be digitally processed, The variation between them can be further reduced. The non-linear characteristic enables processing without increasing the error length of the digital processing system.Therefore, when performing non-linear emphasis processing in the vertical direction, the non-linear emphasis circuit or non-linear It is preferable that the emphasis circuit is also digitally processed at the same time. Of course, analog processing may be performed as it is as in the conventional case.

The horizontal non-linear emphasis circuit 1
6, 17 and horizontal non-linear de-emphasis circuit 38,
39, as well as horizontal linear emphasis circuits 20, 2
1 and the horizontal linear de-emphasis circuits 34 and 35 may also be configured as digital processing. In this case, however, the emphasis processing is linear processing, so the error length increases accordingly and the circuit scale of the digital circuit increases. It is hard to say that it is a very good solution because it will increase Therefore, in the present invention, the linear emphasis processing system is analog processing.

3 and the following are specific examples of the emphasis circuit and the like. Since all the emphasis circuits provided in the respective signal systems have the same configuration, one specific example will be shown.

FIG. 3 shows a specific example of the vertical non-linear emphasis circuit 7. 7a is an input terminal and 7b is an output terminal. In this example, 1H (H
Is a horizontal period) and the current signal is 1H.
While being delayed, the delayed signal and the current signal are subtracted by the subtractor 6
Subtraction processing is performed in 3. The subtraction signal subjected to the subtraction processing in the line direction is supplied to the limiter 65 via the coefficient multiplier 64 of the coefficient K, and the subtraction signal having a predetermined level or higher is limited. The limiter output is supplied to the adder 66 together with the current signal, and the limiter output which is a high frequency component of the current signal is added to the current signal. As a result, the current signal supplied to the terminal 7a is subjected to non-linear emphasis processing in the vertical direction.

In FIG. 3, if the output of the limiter 65 supplied to the adder 66 is inverted and added, or a subtracter is used instead of the adder 66 and the limiter output is subtracted from the current signal. The emphasis circuit 7 is a de-emphasis circuit. A further detailed description of the de-emphasis circuit will be omitted.

FIG. 4 shows a horizontal nonlinear emphasis circuit 1
16 is an input terminal and 16b is an output terminal. The emphasis circuit 16 has a digital high-pass filter 71, and its transfer function H1 (z) shown in (Equation 1) is used.

[0039]

[Equation 1]

An IIR type (Infinite Impluse R) is used as a high-pass filter having such a transfer function H1 (z).
esponse) digital high-pass filter.

The high-pass output of the high-pass filter 71 is supplied to a limiter 73 via a coefficient multiplier 72 having a coefficient of K2, and the limiter output is added to the current signal by an adder 74. By using the high-pass filter 71 having such a transfer function H1 (z), an emphasis circuit having a non-linear characteristic can be realized.

In FIG. 4, if the output of the limiter 73 supplied to the adder 74 is inverted and added, or a subtracter is used instead of the adder 74 and the limiter output is subtracted from the current signal. The emphasis circuit 16 has a configuration of a de-emphasis circuit. A further detailed description of the de-emphasis circuit will be omitted.

The horizontal non-linear emphasis circuit 16 shown in FIG. 5 is a second example and has the same configuration as that of FIG. 4, but the transfer function H2 (z) of the high pass filter 75 used is as follows. Use one.

[0044]

[Equation 2]

As a high-pass filter having such a transfer function H2 (z), a FIR type (Finite Impluse Res)
ponse) digital high-pass filter.

The horizontal non-linear emphasis circuit 16 of the third example shown in FIG. 6 has the same configuration as that of FIG. 4, but the high-pass filter 76 used has a linear phase and its transfer function H3 (z) is as follows. Used by filters that satisfy the formula.

[0047]

[Equation 3]

As the high-pass filter having such a transfer function H3 (z), an IIR type digital high-pass filter and an FIR type digital high-pass filter (for example, a transversal filter having an asymmetric structure) are used.
Can be connected in cascade. This configuration has a linear phase characteristic.

In the embodiment shown in FIG. 1, the recording system 10R is provided with horizontal non-linear emphasis circuits 16 and 17 composed of digital circuits in the subsequent stage of the time division multiplexing circuit 11 and its reproducing system. In the 10P, the horizontal non-linear de-emphasis circuits 38 and 39 are provided in the preceding stage of the time division separation circuit 44, but this can be modified as shown in FIG.

As shown in the figure, in the recording system 10R, digital conversion is performed, and vertical non-linear emphasis circuits 7, 8 and 9 perform vertical emphasis processing, and immediately thereafter, horizontal direction. Emphasis processing is performed. Therefore, between the vertical non-linear emphasis circuits 7, 8 and 9 and the time division multiplexing circuit 11, three non-linear emphasis circuits 16, 17, and 26 in the horizontal direction are provided.

In the reproducing system 10P, the time division separation circuit 44 and the vertical non-linear de-emphasis circuits 45 and 4 are provided.
Similarly, three horizontal non-linear de-emphasis circuits 38, 39 and 54 are provided between the terminals 6 and 47.

Even with such a configuration, both the horizontal non-linear emphasis circuit and the horizontal non-linear de-emphasis circuit can be processed digitally.
It has the same function as.

[0053]

As described above, according to the present invention, both the horizontal non-linear emphasis circuit and the horizontal non-linear de-emphasis circuit are configured as digital circuits. Therefore, even in a multi-channel configuration, variations in characteristics between channels can be effectively suppressed. It has the features that can. In particular, when giving a non-linear emphasis characteristic in the vertical direction as well, the non-linear emphasis circuit and the non-linear de-emphasis circuit can be digitally processed to further suppress the variation between channels in combination with the above configuration. Have.

Therefore, the present invention is extremely suitable when applied to a magnetic recording / reproducing apparatus which employs a multi-channel recording system such as an analog VTR for high definition.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example in which a magnetic recording / reproducing apparatus according to the present invention is applied to a high-definition analog VTR.

FIG. 2 is a waveform diagram showing an emphasis characteristic at that time.

FIG. 3 is a system diagram of a vertical non-linear emphasis circuit.

FIG. 4 is a system diagram showing a first example of a horizontal nonlinear emphasis circuit.

FIG. 5 is a system diagram showing a second example of a horizontal nonlinear emphasis circuit.

FIG. 6 is a system diagram showing a third example of a horizontal nonlinear emphasis circuit.

FIG. 7 is a system diagram showing another example of FIG.

FIG. 8 is a system diagram showing an example of a conventional high definition analog VTR to which the present invention can be applied.

[Explanation of symbols]

10 High-definition analog VTR 10R Recording system 10P Playback system 7, 8, 9 Vertical non-linear emphasis circuit 11 Time axis multiplex circuit 16, 17, 26 Horizontal non-linear emphasis circuit 38, 39, 54 Horizontal non-linear de-emphasis circuit 44 Time axis separation circuit 45,46,47 Vertical non-linear de-emphasis circuit 73 Limiter 71,75,76 Digital high pass filter

Claims (2)

[Claims] 1. A magnetic recording / reproducing apparatus for digitally time-division-multiplexing a luminance signal and a chrominance signal to perform multi-channel recording, wherein at least a horizontal linear emphasis circuit and a horizontal non-linear emphasis circuit are provided as horizontal emphasis circuits. The horizontal non-linear emphasis circuit is used to perform non-linear emphasis processing such that the amount of emphasis is large for a small amplitude signal and the large amplitude signal is limited. A magnetic recording / reproducing apparatus characterized in that the circuit is configured as a digital circuit. 2. A magnetic recording / reproducing apparatus for digitally performing time-division multiplex processing on a luminance signal and a chrominance signal for multi-channel recording, wherein at least a horizontal de-emphasis circuit includes a horizontal linear de-emphasis circuit and a horizontal non-linear circuit. A de-emphasis circuit is used, and in the above-mentioned horizontal non-linear de-emphasis circuit, the de-emphasis amount is set to be large for small-amplitude signals, and non-linear de-emphasis processing is performed to limit large-amplitude signals. A magnetic recording / reproducing apparatus characterized in that the horizontal non-linear de-emphasis circuit is configured as a digital circuit.