JPH09312856A - Magnetic recording reproducing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correspond to plural different broadcast systems by adding relatively few circuits and to obtain a low-cost digital chroma emphasis circuit by processing image signal processing in a digital circuit and processing the chroma emphasis circuit in base band. SOLUTION: At the time of recording, a video signal inputted from an input terminal 1 is separated into a luminance signal Y and a chroma signal C in a Y/C separation circuit 3 after the video signal is converted into a digital signal in an A/D converter 2. The luminance signal Y is inputted to a luminance signal processing circuit 4, while the chroma signal is inputted to a switch circuit 5. Switch circuits 5, 10, 11, 18, 19, 24 and 25 respectively select a black circle at the time of recording and a white one at the time of reproducing. Output of the switch 5 is demodulated into a base band signals (R-Y), and (B-Y) in demodulators 6 and 7. Using digital circuits facilitate integration, and action clock frequency is reduced by means of base band processing. Thereby, it becomes possible to save electric consumption.

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 capable of recording / reproducing a composite video signal, and more particularly to a magnetic recording / reproducing apparatus in which video signal processing is realized by a digital signal processing circuit.

[0002]

2. Description of the Related Art Most video signal processing circuits in home video tape recorders (hereinafter abbreviated as VTRs) to date have been mostly composed of analog signal processing circuits. VH
In the S-standard VTR, an FM-modulated luminance signal and a low-frequency converted chroma signal are frequency-multiplexed and recorded on a magnetic tape. On the other hand, in the 8 mm standard, in addition to the FM-modulated luminance signal and the low-frequency-converted chroma signal, F is added to the high-frequency side of the low-frequency converted signal.
An M-modulated audio signal and a pilot signal for tracking are frequency-multiplexed and recorded on the low frequency side. For this reason, the voice signal and the pilot signal interfere with both sidebands of the chroma signal. In order to reduce this interference, a method of emphasizing during recording and suppressing (de-emphasis) during reproduction is standardized. This standard is called chroma emphasis, and as a conventional example, JP-A-59-10.
As disclosed in Japanese Patent No. 4885, fsc (about 3.58 MHz at the color subcarrier frequency NTSC, about 4.4 at PAL).
Signal processing is performed in the (3 MHz) band, and it is composed of a trap circuit having a resonance frequency in fsc and a limiter circuit.

Further, one circuit can be used for both chroma emphasis during recording and chroma deemphasis during reproduction, and it is devised to reduce adjustment variations and costs. Further, generally, for signal processing of chroma signals, input signals are color difference signals (RY, BY).
There is also a system for demodulating and signal processing (hereinafter referred to as a baseband chroma system), and it may be applied to a signal processing circuit such as a television or a VTR.

[0004]

Since the chroma emphasis circuit in the above-mentioned analog signal processing uses the fsc trap circuit for the chroma signal processing, when fsc is different as in the NTSC system / PAL system, the resonance of the trap circuit occurs. It is necessary to switch the frequency, which increases the number of elements. Further, since the resonance frequency is high, it is difficult to integrate it into an IC, and an external block filter is required to ensure accuracy, resulting in an increase in cost. In the case where the circuit is digitized (C-MOS process), when the process is performed in the fsc band, the operating frequency is high and the power consumption is large.

Further, when an attempt is made to use a common video signal processing circuit for VHS / 8 mm, the chroma emphasis circuit required for the 8 mm standard VTR is not necessary for the VHS standard VTR, resulting in a wasteful circuit, leading to an increase in cost. There is also the problem of being lost. In analog processing, standardization of VHS / 8 mm was a difficult problem in the standard.

An object of the present invention is to support a VTR of a different system (for example, NTSC / PAL) without switching the characteristics by forming a chroma emphasis circuit with a digital signal processing circuit and performing processing in the base band. Another object of the present invention is to provide a magnetic recording / reproducing apparatus having a low-cost and highly accurate chroma emphasis circuit.

[0007]

In order to solve the above-mentioned problems of the prior art and achieve the above object, the present invention provides a VTR.
The video signal processing circuit of is composed of a digital circuit, and the chroma signal is further composed of a baseband chroma signal processing circuit,
By installing the chroma emphasis circuit in the baseband chroma signal processing circuit using the first-order IIR digital filter, the circuit is made common and different broadcasting systems (for example, NTS) are used.
(EN) Provided is a magnetic recording / reproducing device which is compatible with C / PAL) and consumes less power.

Further, the chroma emphasis circuit has a primary I
While it is composed of an IR digital filter, the first-order II
Provided is a magnetic recording / reproducing apparatus with high performance and low cost in a chroma emphasis circuit by switching the tap coefficient of the R digital filter according to the input level.

Further, when changing the tap coefficient of the IIR digital filter, a microcomputer (hereinafter abbreviated as "microcomputer") and a read-only memory (Rea controlled by the microcomputer) are used.
d Only Memory (hereinafter abbreviated as ROM), and by providing a configuration in which data is transferred from the ROM to a storage element, a magnetic recording / reproducing device having a low-cost chroma emphasis circuit is provided to support a plurality of different recording methods. be able to.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows the system configuration of a VTR, which includes an input terminal 1, analog / digital converters (hereinafter abbreviated as A / D converters) 2, 36, a luminance signal / chroma signal separation circuit (hereinafter Y / C separation). (Abbreviated as circuit) 3, luminance signal processing circuit 4, switch circuits 5, 10, 11, 18, 19,
24, 25, demodulators (decoders) 6, 7, color subcarrier frequency carrier generation circuit (hereinafter abbreviated as fsc carrier generation circuit) 8, low frequency subcarrier frequency carrier generation circuit (hereinafter abbreviated as flsc carrier generation circuit) 9 , Low-pass filter (hereinafter abbreviated as LPF) 12, 13, 28, 37, auto color control circuit (hereinafter abbreviated as ACC) 1
4, 15, chroma signal comb filters (hereinafter abbreviated as C comb filters) 16, 17, chroma emphasis 20, 21
Modulators (encoders) 22, 23, adder circuit 26, bandpass filters (hereinafter abbreviated as BPF) 27, 38, digital / analog converters (hereinafter abbreviated as D / A converter) 2
9, 39, 41, luminance signal / chroma signal mix circuit (hereinafter abbreviated as Y / C mix circuit) 30, 40, rotary drum 32, magnetic heads 33, 34, reproduction preamplifier 3
5, output terminal 42.

At the time of recording, a video signal input from the input terminal 1 is converted into a digital signal by the A / D converter 2 and then Y
The / C separation circuit 3 separates the luminance signal Y and the chroma signal C. The luminance signal Y is input to the luminance signal processing circuit 4, and the chroma signal C is input to the switch circuit 5. Here, the switch circuits 5, 10, 11, 18, 19, 24, and 25 select the black circle side during recording and the white circle side during reproduction, respectively. The output of the switch circuit 5 is a demodulator (decoder) 6,
7 demodulates into (RY) and (BY) baseband signals. The converted carrier signal at the time of demodulation is generated by the fsc (about 3.58 MHz at the color subcarrier frequency NTSC, about 4.43 MHz at the PAL) carrier generation circuit 8 and is sent to the demodulators 6 and 7 via the switch circuits 10 and 11. Sent.
Baseband demodulated signals (RY) and (BY)
Is input to the LPFs 12 and 13, respectively, and the 2fsc component generated during baseband demodulation is removed. Then A
After being suppressed to a constant amplitude by CCs 14 and 15, it is input to the chroma emphasis 20 and 21 via the switch circuits 18 and 19. When the recording method is 8 mm, it operates so as to emphasize the side band of the signal, and the recording method is VHS.
In the case of, it operates so as to output the signal without doing anything.
In the case of the 8 mm system, the flat frequency characteristics such as the straight line 71 shown in FIG.
Then, the curves 72, 73, and 74 shown in FIG. The signal 72 having a large amplitude operates so as to have a small enhancement amount, and the signal 74 having a small amplitude operates so as to have a large enhancement amount. VH
In the case of S, nothing is done, so the output is as it is in FIG.
The outputs of the chroma emphasis 20 and 21 are converted into low-pass conversion color signals by modulators (encoders) 22 and 23. The converted carrier signal for modulation is generated by the flsc carrier generation circuit 9 and sent to the modulators 22 and 23 via the switch circuits 24 and 25. Here, flsc is the low frequency conversion color subcarrier frequency. 8 mm standard VTR, NT
47.25 fH = 743 kHz (SC is a horizontal scanning frequency) in SC, 40 fH in NTSC in VHS standard VTR
= 629 kHz. At this time, the frequency characteristic in the case of 8 mm is as shown by the curves 75, 76, and 77 in FIG. 2C, and has a line-symmetrical characteristic about flsc. Modulator 2
The outputs of 2 and 23 are added by the adder 26, and the LPF 28
The 2flsc component generated at the time of modulation is removed by. After that, it is converted into an analog signal by the D / A converter 29 and input to the Y / C mix circuit 30. On the other hand, the luminance signal processing circuit 4
The luminance signal Y input to is processed into an FM luminance signal, and D
The analog signal is converted by the / A converter 41 and input to the Y / C mix circuit 30. After the FM luminance signal and the low frequency conversion color signal are added by the Y / C mix circuit 30, it is sent to the rotary drum 32, and the signal is transmitted to the magnetic heads 33 and 34.

During reproduction, the signals reproduced from the magnetic heads 33 and 34 are sufficiently amplified by the reproduction preamplifier 35 and then converted into digital signals by the A / D converter 36, and the LPF 3
7 and the BPF 38. Only the chroma signal component is extracted by the LPF 37, and is demodulated into the (RY) and (BY) baseband signals by the demodulators 6 and 7 via the switch circuit 5. The clock can be operated at a low frequency by performing the processing in the baseband. That is, C-MO
In the case of the S process, it can be operated with a small amount of power, and power can be saved. The exchange carrier signal for demodulation is generated by the flsc carrier generation circuit 9 and sent to the demodulators 6 and 7 via the switch circuits 10 and 11. The signals (R-Y) and (B-Y) demodulated to the base band are input to LPFs 12 and 13, respectively, and the 2flsc component generated during the base band demodulation is removed. Then ACC
After being suppressed to a constant amplitude by 14 and 15, they are input to C comb filters 16 and 17 to remove adjacent crosstalk components and noise, and are input to chroma emphasis 20 and 21 via switch circuits 18 and 19. Here the recording method is 8
In the case of millimeters, the sideband emphasized at the time of recording is suppressed so as to be restored, and when the recording method is VHS, it operates as a noise reducer. In the case of 8 mm, the flat frequency characteristic like the straight line 78 shown in FIG. 2D has the chroma emphasis 20 and 21 and the curves 79 and 80 shown in FIG.
It becomes like 81. At this time, the frequency characteristics emphasized during recording are restored. In the case of VHS, since nothing is processed during recording, it simply operates to remove noise and outputs it to the modulators 22 and 23. Modulator (encoder) 2
At 2, 23, it is converted into a reproduction chroma signal. The converted carrier signal at the time of modulation is generated by the fsc carrier generation circuit 8 and is transmitted through the switch circuits 24 and 25 to the modulators 22 and 23.
Sent to The frequency characteristic at this time is as shown by curves 82, 83, and 84 in FIG. 2F, and has a characteristic line-symmetrical about fsc. The outputs of the modulators 22 and 23 are added by the adder 26.
Is added and input to the BPF 27. The BPF 27 removes the 2fsc component generated at the time of modulation, and extracts only the chroma signal component. After that, it is converted into an analog signal by the D / A converter 39 and input to the Y / C mix circuit 40.
On the other hand, the BPF 38 extracts only the luminance signal component from the input signal and outputs it to the luminance signal processing circuit 4. After being reproduced by the luminance signal processing circuit 4, it is converted into an analog signal by the D / A converter 41 and input to the Y / C mix circuit 40. The luminance signal and the chroma signal are added by the Y / C mix circuit 40 and output from the output terminal 42.

By using the digital circuit as described above, the integration is facilitated, and the frequency of the operation clock can be lowered by adopting the configuration in which the processing is performed in the base band, so that the power saving can be achieved, and the fsc carrier generation circuit, Both the NTSC / PAL can be easily supported by changing the frequency of the carrier generated by the flsc carrier generation circuit. Further, the chroma emphasis circuit is 8 mm for chroma emphasis, and VHS is a noise reducer, so that the circuit can be used in common and the cost can be reduced.

Next, a specific structure of the chroma emphasis circuit will be described. FIG. 3 is a diagram showing a specific embodiment of the chroma emphasis circuit constituted by a first-order IIR digital filter, which includes an input terminal 101 and a subtraction circuit 10.
2, 104, flip-flop 103, tap coefficient unit 1
05, 107, ROM 106, addition circuit 108, output terminal 109, comparison circuit 110, threshold value 111, coefficient unit 1
12, 113, 115, selection circuits 114, 116, and a control signal 117. The tap coefficient unit 105 is for changing the feedback amount of the feedback loop, and the tap coefficient unit 107 is for changing the addition amount. These are for setting constants of the coefficients K1 and K2, each of which comprises a coefficient unit and a selection circuit. Here, the tap coefficient unit 105 has a positive constant for both the chroma emphasis during recording and the chroma deemphasis during reproduction, but the tap coefficient unit 107 has a positive number during chroma emphasis and a negative number for the chroma de-emphasis circuit. The baseband chroma signal coming from the input terminal 101 is input to the subtraction circuit 102, the output of the feedback loop is subtracted, and the baseband chroma signal is input to the subtraction circuit 104 via the flip-flop 103. The subtraction circuit 104 subtracts the output of the flip-flop 103 from the baseband chroma signal, and tap coefficient unit 105, ROM1
06. The tap coefficient unit 105 is the coefficient unit 11
2 and 113, and the straight lines 151 and 15 shown in FIG.
It has input / output characteristics such as 2. The selection circuit 114 selects one of the coefficient multipliers 112 and 113, and the subtraction circuit 10
Output to 2. The switching method of the selection circuit 114 is that the comparison circuit 110 compares the level of the baseband chroma signal with the threshold value 111 set to a certain value, and when the level of the baseband chroma signal is lower than the threshold value, The selection circuit 114 is controlled to select the coefficient unit 112 side,
When it is higher, the coefficient unit 113 is controlled to be selected. That is, when the baseband chroma signal is lower than the threshold value shown at point a in FIG. 4, the characteristic is shown by the straight line 151, and when it is high, the characteristic is shown by the straight line 152. On the other hand, ROM10
6 is the ROM 10 depending on the output level of the subtraction circuit 104.
The address 6 is read out and input to the tap coefficient unit 107. The tap coefficient unit 107 includes a coefficient unit 115 and a selection circuit 116, and is controlled by a REC / PB control signal 117. The selection circuit 116 operates so as to select the ROM 106 side at the time of recording and operates the coefficient unit 115 side at the time of reproduction. The value of the coefficient unit 115 is -1, and R
The value of OM106 is made negative. By doing so, the emphasis is performed during recording and the de-emphasis is performed during reproduction, and recording / reproduction can be performed by one circuit. After that, the output of the tap coefficient unit 107 is sent to the adding circuit 108, is added to the baseband chroma signal, and is output from the output terminal 109.

As described above, unless the value of the tap coefficient unit 105 is of a switching type, the 8 mm chroma emphasis standard cannot be satisfied. As shown in FIG. 5A, in order to match the chroma emphasis standard of the curves 161, 162, 163, when the tap coefficient is constant, it can be adjusted when the large amplitude signals 164, 165 are input. In the case of the amplitude signal 166, the standard value cannot be adjusted. In the case of the switching type circuit configuration described above, the curves 167 and 16 of FIG.
The characteristics shown in Nos. 8 and 169 are obtained, and the characteristics can be adjusted to the chroma emphasis standards 161, 162 and 163. When used as a VHS noise reducer, it can be easily handled by changing the value of the tap coefficient unit and the threshold value of the comparison circuit. If you want to set the characteristics more precisely, you can add a coefficient unit and a threshold. As explained above, IIR1
Configure a chroma emphasis circuit using the next filter,
By switching the tap coefficient according to the input level of the baseband chroma signal, one circuit can be used for both recording and reproduction, and a characteristic satisfying the chroma emphasis standard can be obtained. Further, by changing the tap coefficient unit and the threshold value, it can be used as a noise reducer in different standards such as VHS.

Another embodiment of the chroma emphasis circuit is shown in FIG. 6, those parts which are the same as those corresponding parts in FIG. 3 are designated by the same reference numerals, and a description thereof will be omitted. 3 is different from that of FIG. 3 in that the tap coefficient unit is composed of a storage circuit that stores data sent by a bus line by controlling a ROM with a multiplication circuit and a microcomputer. These are control signal 200, microcomputer 201, bus line 2
02, 204, ROM 203, storage element (register) 2
05 and 207 and multiplication circuits 206 and 208. The output of the comparison circuit 110 and the control signal 200 are input to the microcomputer 201. Control signal 200 is REC / PB, 8 mm / V
The microcomputer 201 has information such as HS. Using this signal, the microcomputer 201 determines which mode the current state is, and controls the read address of the ROM 203 through the bus line 202. The bus lines 202 and 203 are configured to be able to transmit data serially or in parallel. R
The output of the OM 203 passes through the bus line 204 to rewrite the contents of the storage elements 205 and 207. Storage element 205,
The output of 207 is sent to multiplication circuits 206 and 207, respectively. The multiplication circuit 206 is for changing the feedback amount of the feedback loop, and the multiplication circuit 208 is for changing the addition amount. The multiplication circuit 206 is the subtraction circuit 1
By multiplying the output of 04, the feedback amount of the feedback loop can be changed.
The amount of addition can be changed by multiplying the output of 6. With this configuration, when changing the chroma emphasis characteristics such as another standard, broadcasting system, recording speed, etc., it is possible to easily cope with the change of the software of the microcomputer 201 and the contents of the ROM 203, and only one circuit is required. Therefore, advantages such as power saving and cost reduction can be obtained.

[0017]

According to the present invention, the video signal processing circuit of the VTR is composed of a digital circuit, and the chroma emphasis circuit is processed in the base band, so that a relatively small number of circuits are added, and a plurality of different broadcasting systems ( For example NTSC / PA
It is possible to realize a low cost digital chroma emphasis circuit that is compatible with L).

Further, since the chroma emphasis circuit can be processed at a low frequency by performing the baseband processing, the operating frequency of the digital signal processing can be lowered and the merit of power saving can be obtained.

Further, the chroma emphasis circuit has a primary I
By using an IR digital filter and switching its tap coefficient, the circuit can be shared for circuits that require reverse characteristics for recording and playback, and high-performance chroma emphasis characteristics can be obtained with almost no increase in cost. There is also.

Further, the characteristics can be set through the ROM and the register, so that the recording / reproducing and broadcasting system (NTSC
/ PAL), chroma emphasis / noise reducer, etc. One video signal processing circuit has the merit of being able to support various modes and different standards by changing the software of the microcomputer.

[Brief description of drawings]

FIG. 1 is a signal processing circuit of a VTR showing an embodiment of the present invention.

FIG. 2 is a frequency characteristic diagram of a signal processing circuit of a VTR.

FIG. 3 is a block diagram of a chroma emphasis circuit of a VTR showing an embodiment of the present invention.

FIG. 4 is an input / output characteristic diagram of a tap coefficient unit.

FIG. 5 is a frequency characteristic diagram of a chroma emphasis circuit.

FIG. 6 is a block diagram of a chroma emphasis circuit of a VTR showing an embodiment of the present invention.

[Explanation of symbols]

 2, 36 ... A / D converter, 3 ... Y / C separation circuit, 4 ... Luminance signal processing circuit, 6, 7 ... Demodulator, 8 ... fsc carrier generation circuit, 9 ... Flsc carrier generation circuit, 12, 13, 28, 37 ... LPF, 14, 15 ... ACC, 16, 17 ... C comb filter, 20, 21 ... Chroma emphasis circuit, 22, 23 ... Modulator, 27, 38 ... BPF, 29, 39, 41 ... D / A Converter, 30, 42 ... Y / C mix circuit, 32 ... Rotating drum, 33, 34 ... Magnetic head, 35 ... Preamplifier, 103 ... Flip-flop, 105, 107 ... Tap coefficient unit, 106, 203 ... ROM, 110 ... Comparing circuit, 112, 113, 115, 116 ... Coefficient unit, 114, 117 ... Selection circuit, 201 ... Microcomputer, 202, 204 ... Bus line, 205, 207 ... Storage Element, 206, 208 ... Multiplier circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuyuki Watanabe 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd. Hitachi, Ltd. multimedia system development headquarters (72) Inventor Akifumi Tabata Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa No. 292 Stock Company Hitachi Image Information System

Claims (5)

[Claims] 1. At least two magnetic heads are mounted on a rotating drum to record / reproduce an FM-modulated luminance signal and a low-frequency converted chroma signal, and to record side data according to the signal level of the chroma signal. In a helical scan type magnetic recording / reproducing apparatus that has a chroma emphasis circuit that emphasizes band components and suppresses them during playback, a video signal processing is configured with a digital signal processing circuit, and a baseband signal that processes the chroma signal by converting it to a color difference signal. A magnetic recording / reproducing apparatus having a processing circuit, wherein the chroma emphasis circuit is arranged in a baseband signal processing circuit. 2. The magnetic recording / reproducing apparatus according to claim 1, wherein the chroma emphasis circuit is used as a noise removing circuit for suppressing a sideband component only during reproduction. 3. The magnetic recording / reproducing apparatus according to claim 1, wherein the chroma emphasis circuit arranged in the baseband signal processing circuit is constituted by a first-order IIR (infinite tone impulse response) digital filter. . 4. A comparison circuit for comparing the input level with at least one threshold value set to a certain value, wherein the first-order IIR digital filter has two tap coefficients, and the comparison circuit. 4. The magnetic recording / reproducing apparatus according to claim 3, further comprising switching means for switching the values of the two tap coefficients by using the output of the above. 5. A microcomputer for receiving the output of the comparison circuit and outputting a control signal, a read-only memory controlled by the output of the microcomputer, and a bus line for transmitting the output of the read-only memory to each circuit. When,
5. The value of the two tap coefficients can be changed by having a storage element for storing information from the bus line, and controlling the read-only memory by the microcomputer. Magnetic recording and reproducing device.