JP2585806B2 - Magnetic tape recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is configured to record and reproduce a video signal, a frequency-converted FM audio signal, and a PCM audio signal that has been converted into digital data and phase-modulated on a magnetic tape. More specifically, the present invention relates to control of the above three recording signal levels.

[Prior Art] FIG. 4 is a block diagram showing a configuration of a conventional magnetic tape recording / reproducing apparatus disclosed in, for example, Japanese Patent Application Laid-Open No. 63-288402. −VH
S-type magnetic tape recording / reproducing device (hereinafter S-VHS type VTR)
The PCM signal is recorded and reproduced in the same manner as that described above, and a PCM signal of about 2.6 Mbps is offset, for example, as shown in the 1986 ICASSP draft "Study on Digitalization of Audio Signal in Video Tape Recorder". In this case, the data is recorded and reproduced after being subjected to type 4 phase differential phase modulation (hereinafter referred to as O-QDPSK).

In FIG. 4, (1) is a video signal recording processing circuit,
(2) is a video signal recording amplifier, (3) is a rotating drum,
(4) is a magnetic head for video signals (hereinafter referred to as video head), (5) is a magnetic tape, (6) is a video signal reproduction amplifier, and (7) is a video signal reproduction processing circuit.

(8) is an FM audio signal recording processing circuit, (9) is an L / R channel FM audio signal addition circuit, (10) is an FM audio signal recording amplifier, and (11) is a magnetic head for FM audio signals (hereinafter referred to as a magnetic head). ,
FMA head), (12) FM audio signal reproduction amplifier,
(13a) is a bandpass filter (hereinafter, referred to as BPF-L) for separating the L-channel component of the FM audio signal, and (13b) is
A bandpass filter (hereinafter referred to as BPF-R) for separating the R-channel component of the FM audio signal, and (14) is an FM audio signal reproduction processing circuit.

(15) is an analog-to-digital converter (hereinafter referred to as ADC), (16) is a digital audio recording processing circuit, (17)
Is an offset type four-phase differential phase modulation circuit (hereinafter referred to as a four-phase phase modulation circuit), (18) is a PCM audio signal recording amplifier,
(19) is a magnetic head for PCM audio signal (hereinafter, referred to as PCM head), (20) is a PCM audio signal reproduction amplifier, (21) is an offset type four-phase differential phase modulation signal demodulation circuit (hereinafter, four-phase demodulation). (22) is a digital audio reproduction processing circuit, (23) is a digital-analog converter (hereinafter, referred to as a circuit).
DAC).

FIG. 5 is a diagram showing spectra of a video signal, an FM audio signal and a PCM audio signal of the conventional magnetic tape recording / reproducing apparatus having the above-mentioned configuration. In FIG. Y-FM signal) spectrum,
(31) is a spectrum of a low-frequency-converted color signal (hereinafter, referred to as a C (L) signal), and (32) is an FM-modulated L-channel audio signal (hereinafter, referred to as an FMA-L signal). (33) is a spectrum of an FM-modulated R-channel audio signal (hereinafter referred to as an FMA-R signal), (3)
4) is a spectrum of a PCM audio signal (hereinafter referred to as a QDPSK signal) subjected to four-phase modulation.

FIG. 6 is a magnetic tape (5) for explaining two-layer recording.
In this figure, (35) is the base film of the magnetic tape (5), (36) is the magnetic layer of the magnetic tape (5), and (37) and (38) are the above magnetic layers (3).
This is the recording layer for the FM audio signal and video signal recorded in 6).

 Next, the operation of the above configuration will be described.

In FIG. 4, a baseband video signal is input to a video signal recording processing circuit (1), and a luminance signal component of the baseband video signal has a synchronization front level of 5.4 MHz and a white peak level of 7.0 MHz. After being FM-modulated into a Y-FM signal (30), the chrominance signal component is converted to a C (L) signal (31) by low-frequency conversion so that the carrier frequency becomes about 629 KHz, and then converted into the Y-FM signal (31). The signal (30) and the C (L) signal (31) are added to produce a video signal recording amplifier (2) and a rotating drum (3) as an RF video signal having the spectrum shown in FIG.
The data is recorded on a magnetic tape (5) via a rotary transformer (not shown) incorporated in the video recorder and a video head (4).

The RF video signal reproduced by the video head (4) is amplified by a video signal reproduction amplifier (6), restored to a baseband video signal by a video signal reproduction processing circuit (7), and output.

The FM audio signal is input to the FM audio signal recording processing circuit (8), and after noise reduction processing, the L channel is set to 1.
The 3 MHz and R channels are frequency-modulated with a 1.7 MHz carrier and converted into an FMA-L signal (32) and an FMA-R signal (33) having the spectrum shown in FIG. And recorded as an FMA signal on a magnetic tape (5) via an FM audio signal recording amplifier (10), a rotary transformer (not shown) built in the rotating drum (3), and an FMA head (11). .

The FMA signal reproduced by the FMA head (11) is amplified by an FM audio signal reproduction amplifier (12),
The FMA-L signal (32) and the FMA-R signal (33) are separated by the BPF-L (13a) and BPF-R (13b), and frequency demodulation and noise reduction processing are performed by the FM audio signal reproduction processing circuit (14). After that, the audio signal is restored and output.

In recording on the magnetic tape (5), as shown in FIG. 6, the FMA is applied to the magnetic layer (36) of the magnetic tape (5).
Since the signal is recorded to form an FM audio signal recording layer (37), and then the RF video signal is recorded on the magnetic layer (36), the video signal recording layer (37) is formed on the surface layer side of the FM audio signal recording layer (37). 38) is formed. That is, the magnetic layer (36) of the magnetic tape (5)
The RF video signal is recorded on the surface layer and the FM audio signal is recorded on the deep layer,
This is called a two-layer recording method.

In such a two-layer recording system, since two types of signals are recorded in substantially the same recording track, the video head (4) uses the FMA signal as the noise, and the FMA head (11) uses the RF video signal as the noise component. Reproduce. Therefore, the azimuth angle of the FMA head (11) is set to ± 30 ° while the azimuth angle of the video head (4) is set to ± 6 °. The combination of the azimuth angles is, as shown in FIG. 7, a tape speed standard mode (hereinafter referred to as SP mode) and a 1/3 mode (hereinafter referred to as E mode).
P mode). The above operation is S-VHS
It is the same as the system VTR.

On the other hand, the PCM audio signal is converted into a digital signal by the ADC (15), and then converted to a digital audio recording processing circuit (1).
An error correction code and the like are added by 6), pulse code modulated, converted into a PCM signal of about 2.6 Mbps, and subjected to offset type four-phase differential phase modulation in a four-phase modulation circuit (17), and FIG. As shown in the figure, ±
It is converted to a QDPSK signal (34) with a bandwidth of 0.65 MHz.
Considering the interference with the RF video signal, the carrier frequency of the QDPSK signal (34) is around 2.0 to 2.5 MHz,
Considering interference with the MA signal, 2.8 MHz or more is desirable.

On the other hand, when the QDPSK signal (34) is recorded in a deeper layer than the RF video signal, the high-frequency signal component is easily partially erased by the RF video signal.
The lower the carrier frequency in 4), the better. From the above, the carrier frequency of the QDPSK signal (34) is set to 2.5 MHz.
z.

The QDPSK signal (34) is a PCM audio signal recording amplifier (1
8) The information is recorded on the magnetic tape (5) via a rotary transformer (not shown) built in the rotating drum (3) and the PCM head (19).

The QDPSK signal reproduced by the PCM head (19) is amplified by a PCM audio signal reproduction amplifier (20), and then restored to a PCM signal by a four-phase modulation circuit (21). After processing such as error correction is performed by (22), the signal is restored to an audio signal by the DAC (23) and output.

As shown in FIG. 5, the carrier frequency is the FMA signal (3
Since the order is 2), (33), the QDPSK signal (34), and the RF video signal (30), the order of recording on the magnetic layer (36) of the magnetic tape (5) is also as shown in FIG. FMA signal, QDPSK signal,
In the order of the RF video signal, an FM audio signal recording layer (37), a PCM audio signal recording layer (39) and a video signal recording layer (38) are formed in this order from the deep side of the magnetic layer (36). This is called a three-layer recording method.

In the three-layer recording method as described above, since three types of signals are recorded in substantially the same recording track, each of the video head (4), the FMA head (11) and the PCM head (19) is reproduced. In addition to the power signal, two types of signals are reproduced as noise components. Therefore, since the azimuth angle of the FMA head (11) is set to ± 30 ° with respect to the azimuth angle of the video head (4) ± 6 °, the azimuth angle of the PCM head (19) is different from that of the video head (4). The azimuth angle is set to ± 20 ° to make it 12 ° or more. FIG. 9 shows the combinations of the azimuth angles of these heads (4), (11), and (19) separately for the SP mode and the EP mode.

As described above, the function of recording and reproducing PCM audio signals can be added to the S-VHS system VTR system, but the FMA signal and the QDPSK signal are signaled by the QDPSK signal and the RF video signal recorded in the upper layer, respectively. Of the FMA signal, the QDPSK signal, and the C (L) signal of the RF video signal are relatively low frequency signals, so that the signals are not sufficiently separated due to azimuth loss and interfere with each other as noise. Will be.

FIGS. 10 (a), (b) and (c) show examples of signal spectra reproduced by the video head (4), the PCM head (19) and the FMA head (11). -The FM signal (3) and the C (L) signal (31) are output from the PCM head (19) by the QDPSK partially erased by the RF video signal.
The signal (34) and the FMA head (11) reproduce the FMA-L signal (32) and the FMA-R signal (33), which are partially deleted by the QDPSK signal.

The C (L) signal (31) becomes noise as shown by (40) and (41) with respect to the PCM head (19) and the FMA head (11), and similarly, the FMA-L signal (32) and the FMA head (11) -The R signal (33) is (4) relative to the video head (4) and the PCM head (19).
2), (44) and noise (43) and (45), and the QDPSK signal (34) is shown in (46) and (47) for the video head (4) and the FMA head (11). It becomes such noise.

By the way, in a magnetic tape recording / reproducing apparatus, a particular problem is securing S / N for each reproduced signal.
When the MA signal is recorded at an excessive recording signal level, the reproduction signal levels of the FMA-L signal (32) and FMA-R signal (33) increase as shown in FIG. Although the S / N is improved, the noise components of (42) to (45) also increase, so that the S / N of the RF video signal and the QDPSK signal deteriorates.

When the QDPSK signal is recorded at an excessive recording signal level, the QDPSK signal (34) is output as shown in FIG.
Since the degree of erasure of the FMA-L signal (32) and FMA-R signal (33) recorded in the lower layer increases, the reproduced signal level decreases and the noise components of (46) and (47) also decrease. Because of the increase, the S / N of the RF video signal and the FMA signal deteriorates.

Similarly, when the RF video signal is recorded at an excessive recording signal level, the degree of erasure of the QDPSK signal recorded in the lower layer of the RF video signal increases, so that the reproduction signal level decreases and the QDPSK signal S / N deteriorates.

Further, when the recording signal level is too low, the reproduction signal level decreases, so that the S / N of each reproduction signal deteriorates.

[Problems to be Solved by the Invention] Since the conventional magnetic tape recording / reproducing apparatus is configured as described above, each signal level differs depending on the variation of the characteristics of the magnetic head and the characteristics of the magnetic tape used. This makes it extremely difficult to set the optimum recording signal level, and has the problem that the S / N of one of the reproduced signals deteriorates.

The present invention has been made in order to solve the above-mentioned problems. The recording signal level can be easily set to an appropriate value in accordance with the variation in the characteristics of each magnetic head, and the characteristics of the magnetic tape to be used can be easily set. It is an object of the present invention to provide a magnetic tape recording / reproducing apparatus which can always obtain good S / N reproduction signals without being affected.

[Means for Solving the Problems] A magnetic tape recording / reproducing apparatus according to the present invention is arranged such that a video signal and an audio signal are recorded on a magnetic tape by a video signal magnetic head and an audio signal magnetic head, respectively. A test corresponding to a video signal and an audio signal in a magnetic tape recording / reproducing apparatus configured and having two or more types of recording modes corresponding to magnetic modes in which the traveling speed (recording time) of the magnetic tape or the type of magnetic tape is different. A test signal recording / reproducing means for recording and reproducing a signal on a magnetic tape in advance in accordance with a recording mode, and a frequency component corresponding to each signal for detecting each reproduction test signal level reproduced by the test signal recording / reproducing means And a reproduction signal level of a frequency component corresponding to each signal obtained by the filter. Signal level detecting means for outputting, a recording signal level setting means for setting a recording signal level by controlling a gain of a recording processing circuit of each signal based on a detection result of the signal level detecting means, and a recording signal level setting means Storage means for storing a recording signal level corresponding to the recording mode, and transferring an appropriate recording signal level according to the recording mode to the recording signal level setting means at the time of recording. The test signal is reproduced, the reproduction signal level is detected for each of the video signal and the audio signal by the signal level detection means, and based on the detection result, the gain of the recording processing circuit of each signal is controlled to record the recording signal level. It is noted that the magnetic tape is rewound to the recording start point after being set in the level setting means and stored in the storage means. To.

[Operation] According to the present invention, a video signal, an FM audio signal, and a PCM
Each signal of the audio signal is recorded and reproduced in advance as a test signal, and by detecting the level of the reproduced signal, it is possible to determine the suitability of each recording signal level and then control each recording signal level to an appropriate value. it can. Therefore, it is possible to easily set the recording signal level according to the variation in the characteristics of each magnetic head, and it is less affected by the characteristics of the magnetic tape to be used.
S / N playback can be realized.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a magnetic tape recording / reproducing apparatus according to one embodiment of the present invention. In the figure,
(1) is a video signal recording processing circuit, (2) is a video signal recording amplifier, (3) is a rotating drum, (4) is a video head,
(5) is a magnetic tape, and (6) is a video signal reproducing amplifier.

(8) is an FM audio signal recording processing circuit, (9) is an addition circuit, (10) is an FM audio signal recording amplifier, (11) is an FMA head, and (12) is an FM audio signal reproduction amplifier. (17) is 4
(18) PCM audio signal recording amplifier, (1)
9) is a PCM head, and (20) is a PCM audio signal reproduction amplifier.

(50) is a VTR control unit, and (51) is a gain control unit. The gain control unit (51) is configured as follows.

That is, in FIG. 1, (52) represents the Y-FM signal (3
(53) is a filter for separating the FMA-R signal (33) (hereinafter, referred to as a second BPF), and (54) is a QDPSK signal (hereinafter, referred to as a second BPF). Three
4) A filter for separating (hereinafter referred to as a third BPF), (55) to (57) are filters described above in the first to third BPFs (52) to (5).
A signal level detector (hereinafter referred to as first to third DETs) for detecting each test signal level separated by 4), (58)
Is a coefficient control circuit for selecting an appropriate recording level in accordance with the signal level detected by each of the DETs (55) to (57), and (59) to (61) are a video signal and an FM signal by the coefficient control circuit (58). A gain control circuit (hereinafter, referred to as first to third GC) for controlling the recording signal level of the audio signal and the PCM audio signal, and (62) stores an appropriate recording signal level selected by the coefficient control circuit (58). Memory.

Next, the operation of the above configuration will be described. In addition, (1)-(6), (8)-(12), (17) in FIG.
Operations (20) to (20) are the same as those in FIG.

The VTR control unit (50) receives a command signal (hereinafter, referred to as TEST) for setting each recording signal level, and outputs a video signal recording processing circuit (1), an FM audio signal recording processing circuit (8),
Each recording signal obtained from the phase / phase modulation circuit (17) is converted into an unmodulated signal, for example, an RF video test signal, an FM test signal, and a PCM test signal on a magnetic tape (5) as shown in FIG. Recording (hereinafter, referred to as TEST REC) operation for recording three layers over the same length, rewinding the magnetic tape (5) to the recording start point after the TEST REC (hereinafter, referred to as REW), and a test signal after the REW Playback (hereinafter, T
EST PB) and a REW operation for rewinding the magnetic tape (5) to the recording start point after the TEST PB.

Each of the recording test signals is reproduced by a video head (4), an FMA head (11), and a PCM head (19), respectively, and a video signal reproduction amplifier (6), an FM audio signal reproduction amplifier (12), and a PCM audio signal reproduction amplifier. After being amplified by (20), they are input to the gain control units (51).

The reproduced and amplified RF video test signal, FMA test signal, and PCM test signal are the first BPF (52) and the second BPF, respectively.
(53) and the third BPF (54), the Y-FM signal (30),
FMA-R signal (33) and QDPSK signal (34)
The reproduced signal level of each of the reproduced test signals is detected by the ET (56), the second DET, and the third DET (57).

The coefficient control circuit (58) sets appropriate recording signal levels based on the above detection result, and for example, a first GC (59), a second GC (60), and a third GC (6) each configured by a variable gain amplifier.
By controlling the coefficient of 1), each recording signal level is set to an appropriate value.

After this setting is completed, the magnetic tape (5) is moved to the recording start point by the VTR control unit (50) as shown in FIG.
Since EW has been performed, recording at an appropriate recording signal level from the recording start point can be realized by performing the original REC next.

The S-VHS system VTR has a SP mode and an EP mode as recording modes. Since each recording condition is different, a plurality of recording signal levels are stored in a coefficient control circuit (58) in the gain control section (51). By adding a memory (62) capable of storing the information, it is possible to cope with a case where the recording mode is switched in the middle during timer recording or the like.

FIG. 3 is a diagram for explaining the setting of the recording level at the time of the timer recording or the like.
For the EP mode, test signal TEST REC and TEST PB are respectively performed to set appropriate recording signal levels and stored in the memory (62), so that the coefficient control circuit ( 58) can read out each recording signal level stored in the memory (62) and realize recording at an appropriate recording signal level according to the recording mode.

In the above embodiment, each recording test signal is recorded as a non-modulated signal. However, even if it is a specific modulated signal, each signal input to the VTR may be recorded as it is as a test signal.

Further, the detection of each reproduction test signal was performed only for the Y-FM signal (30), the FMA-R signal (33) and the QDPSK signal (34), but the C (L) signal (31) and the FM
A filter for separating each signal and a DET for detecting each signal level may be additionally provided so as to be able to perform the A-L signal (32).

The control of each recording signal level is performed by controlling the Y-FM signal (30) and the C (L) signal (31) for the video signal, and the FMA-L signal (32) and the FMA-R signal (3) for the FMA signal.
3) is simultaneously controlled, but a coefficient control circuit for controlling the recording signal level so that each can be controlled independently; and
GCs may be added.

In the above embodiment, the first GC to the third GC (59) to (61)
Is constituted by a variable gain amplifier, but may be constituted by a variable attenuator using a resistor array or the like.

Further, in the above embodiment, the recording test signal is recorded in three layers and each reproduction signal level is detected. However, even if each signal is recorded in a single layer and each reproduction signal level is detected, An effect similar to that of the embodiment is obtained.

The recording signal level in the EP mode may be set for each channel of the rotating head in order to avoid the influence of adjacent tracks.

[Effects of the Invention] As described above, according to the present invention, each signal of the video signal, the FM audio signal, and the PCM audio signal is recorded and reproduced as a test signal in advance, and based on the detection result of each reproduction signal level at that time. By controlling each recording signal level to an appropriate value, it is possible to always obtain a good S / N reproduction signal even when the characteristics of each magnetic head and the characteristics of the magnetic tape used are different. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of a magnetic tape recording / reproducing apparatus according to one embodiment of the present invention, FIG. 2 is a diagram for explaining the setting operation of each recording signal level, and FIG. FIG. 4 is a block diagram showing the configuration of a conventional magnetic tape recording / reproducing apparatus, and FIG. 5 is a block diagram showing the configuration of a conventional magnetic tape recording / reproducing apparatus. FIG. 6 is a diagram showing a spectrum of a signal and a PCM audio signal, FIG. 6 is a cross-sectional view of a magnetic tape for explaining two-layer recording, and FIG. 7 is an example of an azimuth angle of a magnetic head for video and FM audio in two-layer recording. FIG. 8 is a sectional view of a magnetic tape for explaining three-layer recording, and FIG. 9 is a picture, FM sound and PC in three-layer recording.
Diagram showing an example of the azimuth angle of the magnetic head for M audio,
FIG. 10 is a diagram showing a reproduction signal spectrum of a video signal, an FM audio signal, and a PCM audio signal by a conventional magnetic tape recording / reproducing apparatus. FIGS. 11 and 12 are diagrams showing improper recording of the conventional magnetic tape recording / reproducing apparatus. Video signal depending on signal level,
FIG. 3 is a diagram illustrating reproduction signal spectra of an FM audio signal and a PCM audio signal. (1) Video signal recording processing circuit, (2) Video signal recording amplifier, (3) Rotating drum, (4) Video head, (5) Magnetic tape, (6) Video signal reproduction amplifier, (8) FM audio signal recording processing circuit, (9)
... Addition circuit, (10) ... FM audio signal recording amplifier, (1
1) FMA head, (12) FM audio signal reproduction amplifier,
(17) ... 4 phase phase modulation circuit, (18) ... PCM audio signal recording amplifier, (19) ... PCM head, (20) ... PCM audio signal reproduction amplifier, (50) ... VTR control unit, (51) Gain control section, (52) to (54) BPF, (55) to (57)
... Signal level detector (58) ... Coefficient control circuit (59)
~ (61) ... gain control circuit, (62) ... memory. The same reference numerals in the drawings indicate the same or corresponding parts.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-102002 (JP, A) JP-A-61-117703 (JP, A) JP-A-63-234402 (JP, A) JP-A-1- 130304 (JP, A) Actually open 1-15359 (JP, U)

Claims (2)

(57) [Claims] A video signal and an audio signal are recorded on a magnetic tape by a video signal magnetic head and an audio signal magnetic head, respectively. The running speed (recording time) of the magnetic tape or the magnetic tape In a magnetic tape recording and reproducing apparatus having two or more types of recording modes corresponding to different types of magnetic modes, a test signal corresponding to the video signal and the audio signal is previously recorded on a magnetic tape corresponding to the recording mode. A test signal recording / reproducing means for recording and reproducing, a filter for separating frequency components corresponding to the respective signals in order to detect each reproduction test signal level reproduced by the test signal recording / reproducing means, Signal level detecting means for detecting a reproduced signal level of a frequency component corresponding to each of the obtained signals; Recording signal level setting means for setting the recording signal level by controlling the gain of the recording processing circuit for each signal based on the detection result of the bell detecting means; and setting the recording signal level of the recording signal level setting means to the recording mode. Storage means for correspondingly storing and transferring an appropriate recording signal level corresponding to a recording mode to the recording signal level setting means at the time of recording, wherein the test signal recording / reproducing means reproduces the test signal of the magnetic tape. The reproduction signal level is detected for each of the video signal and the audio signal by the signal level detection means, and the gain of the recording processing circuit of each signal is controlled based on the detection result to set the recording signal level to the recording signal level setting. Means is set respectively, and stored in the storage means, and then the magnetic tape is rewound to a recording start point. Magnetic tape recording and reproducing apparatus characterized. 2. A signal obtained by converting a frequency-modulated audio signal into digital data and then a phase-modulated signal as a composite signal of a luminance signal obtained by frequency-modulating a video signal and a color signal subjected to low-frequency conversion. 2. The magnetic tape recording / reproducing apparatus according to claim 1, wherein the magnetic tape is recorded and reproduced.