JPH01194103A - Magnetic recording method - Google Patents

Abstract

PURPOSE:To record a sound signal and a video signal with them overlapped on the same track by arranging the frequency spectrum of the pulse FM modulating signal of the sound signal in the neighborhood of the high area of the frequency spectrum of a low-area-converted chrominance signal. CONSTITUTION:First, the sound signal is recorded and next, the video signal is superimposed and recorded on it. The sound signal is sampled, after that, converted into a digital signal word, further, converted into a PCM signal to which an error correcting word and a program searching word, etc., are added, further, PFM (pulse FM)-converted and recorded. The frequency spectrum of the PFM modulating signal is arranged in the neighborhood of the high area of the frequency spectrum of the chrominance signal. Thus, the sound signal and the video signal can be overwrite-recorded on the same track on a tape.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention is applicable to a VCR (or VTR) with PCM audio recording or a VCR (or VTR) compatible with satellite broadcasting mode, in which a video recording head and an audio recording head are independent. The present invention relates to a magnetic recording method for overwriting audio and video signals on the same track on a tape in a helical scan magnetic recording/reproducing device having a head.

"Prior Art" Conventionally, when recording audio signals, there are two methods: an analog signal recording method and a digital signal recording method. Among these methods, analog signal recording methods include an AC bias recording method in general RCR and an FM modulation recording method on an FM track in VH3 Hi-Fi. Further, as methods for recording digital signals, there are two methods: one is to record a PCM audio signal instead of a video signal, and the other is to compress the signal to about 8 bits and record the PCM audio signal on a dedicated track, as in the case of 8m video.

"Problem to be Solved by the Invention" In order to record a PCM signal of about 14 bits that can support satellite broadcast mode audio at the same time as recording a video signal on the VH8 Hi-Fi track, an additional recording track is not provided. , recording and playback is not possible. Also,
Even if you try to record a video signal after recording an audio signal using the overwriting method, since the audio signal has a wide band on VH8 Hi-Fi tracks, it will interfere with the color signal and brightness signal of the video signal, and recording will not be possible. .

The present invention provides a method for recording an audio signal and overlapping a video signal thereon in a state that does not overlap with the color signal of the video signal and is also acceptable for the luminance signal. The purpose is to obtain.

"Means for Solving the Problems" The present invention has been made to solve the above-mentioned problems, and is a helical scan type having an independent video recording head and an audio recording head, and is capable of recording audio signals on a tape. In a magnetic recording/reproducing device which records a video signal and then overwrites the video signal, the azimuth difference between the tracks of the video signal and the audio signal is several tens of degrees or more when recording onto the tape. The azimuth of the video track has an inclination of several degrees with respect to the adjacent track, the azimuth of the audio track has an inclination of several tens of degrees with respect to the adjacent track, and among the video signals, the luminance signal is FM modulated and the color signal is separated. The audio signal is then low-band converted and recorded so as to be placed in a band below the FM modulation signal, and the audio signal is sampled and then converted into digital signal words, which are further converted into error correction words, control words, error detection words, PC with cue word added
M signal is further pulsed FM modulated and recorded, and a modulation index is set such that the frequency spectrum of this pulsed FM modulated signal is placed adjacent to the high frequency spectrum of the low frequency converted color signal. and limit its sideband components to within the first upper sideband spectrum;
This magnetic recording method is characterized in that the first lower sideband spectrum is cut off.

"Function" When recording on a tape, the azimuth of the video track is set by several degrees relative to the adjacent track, specifically ±3 to 10 degrees, and the azimuth of the audio track is set several dozen degrees relative to the adjacent track, specifically has an inclination of ±20 to 35 degrees, and the azimuth difference between the video and audio tracks is several tens of degrees, specifically 20 degrees or more, and when recording, the audio signal is first recorded, and then the video signal is Record over and over again.

Among the video signals, the luminance signal is FM-modulated, and the chrominance signal is separated, then low-frequency converted and placed in a band below the FM modulation signal. Both signals are recorded on the tape by a video head.

After the audio signal is sampled, it is converted into a digital signal word by an A/D converter, and further converted into a PCM signal to which an error correction word, a control word, an error detection word, a cue word, etc. are added, and then a PFM signal. (Pulse FM)
It is modulated and recorded onto tape by an audio head.

Since the frequency spectrum of the PFM modulated signal is located adjacent to the high frequency spectrum of the low-pass converted color signal, the PFM modulation index (ΔfFM/fI”C
M) is 0.5 or less and its sideband components are limited within the first upper sideband spectrum, and the first lower sideband spectrum is blocked. Magnetic recording is performed under the above conditions.

"Example" Hereinafter, one embodiment of the present invention will be described based on the drawings.

In Figure 1, (1a) Ob) is the L and R audio signal input terminals of the PCM, and this audio signal input terminal (1a) (
1b) is 24KI via the switching circuit (2a) (2b) that switches between recording mode (RFC) and playback mode (PB).
LPF (low pass filter) (3a) that limits the band to h
) (3b), amplifier (4a) (4b), 44.1K
) lz sampling and hold circuit (5a) (
5b) is coupled to a PCM processor (7) which converts it into a PCM signal via an A/D conversion circuit (6) which converts it into a 14-bit digital signal. This PCM processor (
7) is the R, L sampling data input terminal (8a)
(8b), switching circuit (9), correction word generation circuit (1
0), an address controller (51), an interleave memory (11), an error detection word generation circuit (12), and a PCM signal output terminal (13). This output terminal (13) is coupled to a PFM encoder (14) for pulsed FM modulation.

As shown in FIG. 2, this PFM encoder (14)
It consists of an NRZ signal input terminal, two frequency input terminals, two NAND circuits, one OR circuit, and one flip-flop circuit, and its output terminal is a BPF for making only the carrier of the FM signal and the first upper sideband. (bandpass filter) (15), amplifier (16).

Switching circuit (17a) (17b) for switching audio FM signal (A-FM) and PCM signal, recording amplifier (18
a) Rotating sound head (19a) via (18b) (
19b) and faces the magnetic tape (20).

Normal FM L and R audio input terminals <21a) (21
b) is the amplifier (22a) (22b), 20KI (z
LPF (23a) (23b), amplifier (
24a) (24b), 1.3MHz and 1.7M)lz
FM modulation circuit (25a) that modulates with the FMlfl transmission wave of
(25b), L P F (26
a) (26b), and are coupled to the A-FM side of the switching circuit (17a) (17b) via the amplifier (27a) (27b).

The rotating audio head (28a) (28b) on the playback side includes a playback amplifier (29a) (29b) and a mode detection circuit (3).
0) to switch between pcM and A-FM (31
a) Combined with (31b). This switching circuit (3
1a) The PCM side of (31b) is an L/R channel switcher (32), an AGC circuit (33) that absorbs output level fluctuations, and an AGC detection circuit (34), 3.6 to 1.0
B P F (35) to pass through M soil, wave-shaped,
Waveform shaping circuit (36) that returns to PFM signal, PFM decoder (37) that decodes to NRZ format PCM signal
via a reproduced PCM signal input terminal (38) of the PCM processor (7).

The reproduced PCM signal input terminal (38) of this PCM processor (7) includes an error data detection circuit (39), an address controller (40), an interleave memory (41),
L and R output terminals (44a) (44b) of reproduced data are passed through an error data correction circuit (42) and a switching circuit (43).
) is combined with This output terminal (44a) (44
b) is a D/A conversion circuit (45) that converts into an analog signal
, are coupled to the PB side of the switching circuits (2a) (2b) via amplifiers (46a) (46b), and furthermore, an amplifier (47a) is connected to the L P F (3a) (3b).
(47b) to the PCM L and R output terminals (48
a) Combined with (48b).

A-F of the switching circuit (31a) (31b) on the reproduction side
On the M side, amplifiers (49a) (49b), B P F
(50a) (50b), limiter (60a) (6
0b), FM demodulation circuit (61a) (61b), LP
F (62a) (62b), amplifier (63a) (6
3b) to the L and R audio FM signal output terminals (64a
) (64b) are combined.

In the circuit configuration as described above, when L and R PCM audio signals are input to the input terminals (la) and (lb), they are sent to the switching circuits (2a) and (2b) via amplifiers. record(
REC) side, the LPF (
3a) Input to (3b) and limited to 24K) lx bandwidth.

Furthermore, the sampling and hold circuit (5a) (5b) passes through the amplifier (4a) (4b) and the output power is 44.1K).
z sampling signal, and further A/D conversion circuit (
At step 6), the signal is converted into a 14-bit digital signal and input to the PCM processor (7). Then, this PCM processor (7) generates a general PCM signal to which correction words, control words, error detection words, cue words, etc. are added. This PCM signal format is N RZ (Non R
(eturn to Zero) signal as shown in Figure 3 (b
) is output, and in order to convert the frequency spectrum of the signal, it is PFM-modulated by the PFM encoder (14) as shown in Figure 3(c), and further, B P
Figure 3(d) and Figure 5(C) by F (15)
Only the carrier and the first upper sideband component of the FM signal of 3°6 to 1.0M1]z as shown in FIG. Here, PFM
The signal modulation index (Δf IH/ f eCM) is 0.5
The following shall apply.

Note that Δ”Fll” is the maximum FM carrier deviation frequency.

f,,M: N Basic bit frequency of RZ signal.

The output of the B P F (15) passes through an amplifier (16), further passes through the PCM side of the switching circuit (17a) (17b), is amplified by the amplifier (18a) (18b), and is sent to the rotating audio head (19a) (19b). ) by tape (20)
recorded above.

A normal audio FM signal is sent to the A-FM input terminal (21a) (
21b), L P F (23a) (
23b) to 20K) (z band, FM modulation circuit (25a) (25b) each L and R signal is 1.3MI
(z and 1.7M) It is modulated by FMW1 transmission wave of tz. F
The M modulated signal is L P F (26a) (26b
), and the A-FM signal is limited to only the fundamental wave by the switching circuit (1
7a) Pass through the A-FM side of (17b) to the amplifier (18a)
) (18b) and a rotating audio head (19a).
(19b) is recorded on the tape (20).

Regardless of whether it is the PCM signal or the A-FM signal, the azimuth of the audio track is ±20 with respect to the adjacent track on the tape (20), as shown by the dotted line in FIG. Record with an inclination of ~35 degrees.

After recording this audio signal, the video signal is overwritten and recorded. That is, as shown by the solid line in Figure 4, the video track has an azimuth of ±3 to 1 with respect to the adjacent track.
Recording is performed with an inclination of 0 degrees, and the azimuth difference between the audio/video tracks is set to be 20 degrees or more.

Incidentally, among the video signals, the luminance signal is FM-modulated, and the color signal is separated and then low-band converted and placed in a band below the FM modulation signal.

Next, the case of reproduction will be explained. Recorded signals on the tape (20) are detected by rotating audio heads (28a) (28b) and amplified by amplifiers (29a) (29b). The mode detection circuit (30) detects the PCM of the reproduced signal.
By detecting the W1 transmission signal, the switching circuit (31a)
(31b) is automatically switched between the A-FM signal side and the PCM signal side.

If it is a P CM signal, the reproduced signal is selected by the L/R channel switcher (32), and the AGC circuit (32) selects the reproduced signal.
3) and the AGC detection circuit (34) absorb the fluctuations in the output level, and the B P F (35) detects the 3
．． 6-1゜0 MI (passes only the z signal and removes unnecessary signals. The output signal shown in FIG. 3(d) from this B P F (35) is sent to the third The waveform is shaped as shown in Figure (e) and returned to the PFM signal, and this reproduced PFM signal is sent to the PFM decoder (37) as shown in Figure 3 (
The signal is decoded into an NRZ format PCM signal as shown in f).

This PCM signal is input to a PCM processor (7), subjected to error checking and error correction, and converted into 14-bit sampling data. Furthermore, the D/A conversion circuit (
45), the signal is returned to an analog signal, and the switching circuit (2a) (
2b) via the PB side, L P F (3a) (3b)
The sampling noise is removed, and the PCM audio signal is output from the output terminals (48a) and (48b). When the reproduction signal is detected as an A-FM signal by the mode detection circuit (30), the switching circuit (31a) (31b)
Switched to M side, B P F (50a) (50b
), limiter (60a) (60b), FM demodulation circuit (
61a) (61b), L P F (62a) (6
2b) and the A-FM audio signal is output to the output terminal (64a).
(64b).

The video signal is also reproduced and displayed by a known reproduction circuit (not shown).

"Effects of the Invention" According to the present invention, in a VH3 Hi-Fi track,
Simultaneously with video signal recording, PCM signals can be recorded and played back without additional recording tracks.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a magnetic recording/reproducing apparatus for embodying the magnetic recording method according to the present invention, Fig. 2 is a block diagram of a PFM encoder, Fig. 3 is an output waveform diagram of each part, and Fig. 4 is a diagram of a tape. An explanatory diagram of the recording state, FIG. 5 is a frequency characteristic diagram. (la) (lb) -P CM audio signal input terminal, (
2a) (2b) ”・Mode switching circuit, (5a) (
5b)...Sampling and hold circuit, (6)
... A/D conversion circuit, (7) ... PCM processor, (14)-PFM encoder, (19a) (19
b)...Rotary audio head for recording, (20)...Magnetic tape, (28a) (28b)...Rotary audio head for playback, (30)...Mode detection circuit, (31a)
(31b)...Switching circuit, (32)...Channel switcher, (36)...Waveform shaping circuit, (37)...
・PFM decoder, (45)...D/A conversion circuit, (
48a) (48b) ,,,Audio PCM4'' output terminal. Applicant: Fujitsu General Ltd. Figure 3 T+=T T2=2T Figure 4 Figure 5

Claims (3)

[Claims] (1) In a helical scan type magnetic recording and reproducing apparatus having an independent video recording head and an audio recording head, which records an audio signal on a tape and then overwrites and records a video signal, When recording, the azimuth of the video track should be ± several degrees with respect to the adjacent track, and the azimuth of the audio track should be set with respect to the adjacent track, so that the azimuth difference between the video signal and audio signal tracks is several tens of degrees or more. The luminance signal of the video signal is FM modulated, the color signal is separated and low frequency converted and recorded so as to be placed in a band below the FM modulation signal. After the signal is sampled, it is converted to a digital signal word, and an error correction word, a control word, an error detection word, and a cue word are added to the PC.
M signal is further pulsed FM modulated and recorded, and a modulation index is set such that the frequency spectrum of this pulsed FM modulated signal is placed adjacent to the high frequency spectrum of the low frequency converted color signal. and limit its sideband components to within the first upper sideband spectrum;
A magnetic recording method characterized in that a first lower sideband spectrum is cut off. (2) Claim that the azimuth of the video track is ±3 to 10 degrees with respect to the adjacent track, the azimuth of the audio track is ±20 to 35 degrees with respect to the adjacent track, and the azimuth difference between the video and audio tracks is 20 degrees or more The magnetic recording method according to item (1). (3) Modulation index of pulse FM modulation signal (Δf_F_M:
Claim (1) in which the maximum FM carrier deviation frequency (/f_P_C_M: fundamental bit frequency of NRZ signal) is 0.5 or less
) or the magnetic recording method described in (2).