JPH0760483B2 - Magnetic recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention relates to an independent video recording head and audio recording such as a VCR (or VTR) with PCM audio recording and a VCR (or VTR) compatible with satellite broadcasting B mode. The present invention relates to a magnetic recording method for overwriting and recording an audio signal and a video signal on the same track on a tape in a helical scan type magnetic recording / reproducing apparatus having a head.

"Prior Art" Conventionally, when recording an audio signal, there are an analog signal recording method and a digital signal recording method. Among them, the analog bias recording method includes a general VCR AC bias recording method and a VHS Hi-Fi FM track FM modulation recording method. In addition, in the digital signal recording method, instead of the video signal, a PCM audio signal is recorded, and as in the case of 8mm video, it is compressed to about 8 bits and recorded on a dedicated track.
There is a method of recording PCM audio signals.

[Problems to be Solved by the Invention] In the VHS Hi-Fi track, about 14 bits which can support satellite broadcasting B mode audio at the same time as recording of video signal
To record the PCM signal, it is impossible to record and reproduce unless an additional recording track is provided. Also, even if you try to record a video signal after recording an audio signal using the overwriting method, the VHS Hi-Fi track has a wide audio signal band, so it interferes with the color signal and luminance signal of the video signal. I can't record.

The present invention provides a method for recording an audio signal and superimposing a video signal on the audio signal so that the audio signal does not overlap with the color signal of the video signal and can be recorded in a state in which the luminance signal is acceptable. The purpose is to obtain.

[Means for Solving the Problems] The present invention is a helical scan type having an independent video recording head and audio recording head, and is designed so that after recording an audio signal on a tape, the video signal is overwritten and recorded. In the magnetic recording / reproducing apparatus, when recording on the tape, the azimuth difference between both tracks of the video signal and the audio signal is
The azimuth of the video track has a slope of ± 3 to 10 degrees with respect to the adjacent track, and the azimuth of the audio track has a slope of ± 20 to 35 degrees with respect to the adjacent track so that the angle becomes 20 degrees or more.
A luminance signal and a color signal are both FM-modulated and recorded in the video signal, and an audio signal is sampled and then converted into a digital signal word, and an error correction word, a control word, an error detection word, and a cue word are added. It is converted to a PCM signal that has been recorded, and is further pulse-FM modulated and recorded.The frequency spectrum of the pulse FM-modulated signal of this audio signal is placed close to the low range of the frequency spectrum of the FM-modulated signal of the video signal. , The modulation index (ΔfFM: maximum FM carrier shift frequency, / fPCM: basic bit frequency of ZRZ signal) is as low as 0.5 or less, and its sideband component is limited to within the first sideband spectrum. Magnetic recording method.

"Operation" When recording on the tape, the azimuth of the video track is ± several degrees relative to the adjacent track, specifically ± 3-10 degrees,
The azimuth of the audio track is ± several tens of degrees to the adjacent track, specifically ± 20 to 35 degrees, and the azimuth difference between the video and audio tracks is several tens of degrees, specifically 20 degrees or more. That is, when recording, the audio signal is first recorded, and then the video signal is superposed and recorded.

The luminance signal and color signal of the video signal are FM-modulated and recorded on the tape by the video head.

The voice signal is sampled and then converted into a digital signal word by the A / D converter, and error correction words, control words, error detection words, and cue words are added.
It is converted to a PCM signal, then PFM (pulse FM) modulated and recorded on the tape by the voice head.

The frequency spectrum of the PFM-modulated signal is placed adjacent to the low range of the frequency spectrum of the FM-modulated signal, and the PF
The modulation index (ΔfFM / fPCM) of M is 0.5 or less, and its sideband component is limited within the first sideband spectrum. Magnetic recording is performed under the above conditions.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, (1a) and (1b) are L and R audio signal input terminals of PCM, and these audio signal input terminals (1a) and (1b) are switching modes for switching between recording mode (REC) and playback mode (PB). LPF (low pass filter) (3a) (3b), amplifier (4a) (4b), which limits to the band of 24KHz through the circuit (2a) (2b)
44.1KHz sampling and hold circuit (5a) (5
b), it is connected to a PCM processor (7) for converting into a PCM signal through an A / D conversion circuit (6) for converting into a 14-bit digital signal. This PCM processor (7) has R and L sampling data input terminals (8a) and (8b), a switching circuit (9), a correction word generation circuit (10), an address controller (51), an interleave memory (11), and an error. It is coupled to the PCM signal output terminal (13) through the detection word generation circuit (12). This output terminal (13) is coupled to a PFM encoder (14) for pulse FM modulation. This PFM
As shown in FIG. 2, the encoder (14) has an NRZ signal input terminal, two frequency input terminals, two NAND circuits, 1
One OR circuit, one flip-flop circuit,
Its output terminal is a BPF (bandpass filter) (15) and an amplifier (1
6), the switching circuit (17a) (17b) for switching the audio FM signal (A-FM) and the PCM signal, the recording amplifier (18a) (18b) and the rotary audio head (19a) (19b), It is exposed to a magnetic tape (20).

The L and R audio input terminals (21a) (21b) of ordinary FM are amplifiers (22a) (22b) and LPF (23a) (23
b), amplifier (24a) (24b), FM modulation circuit (25a) (25b) that modulates with 1.3MHz FM carrier, and limit to fundamental wave only
LPFs (26a) (26b) and amplifiers (27a) (27b) are connected to the switching circuits (17a) (17b) on the A-FM side.

The rotary audio heads (28a) and (28b) on the playback side are connected to PCM and A by the playback amplifiers (29a) and (29b) and the mode detection circuit (30).
It is coupled to switching circuits (31a) and (31b) for switching to -FM. The PCM side of this switching circuit (31a) (31b) is an L / R channel switcher (32), an AGC that absorbs fluctuations in output level.
Circuit (33) and AGC detection circuit (34), BPF (35) that passes 3.6 to 1.0 MHz, waveform shaping circuit (36) that shapes the waveform and returns it to the PFM signal, PFM decoder (decodes into the NRZ format PCM signal ( It is connected to the reproduction PCM signal input terminal (38) of the PCM processor (7) via 37). The reproduction 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), an error data correction circuit (42) and a switching circuit (43). Playback data L and R output terminals (44
a) bound to (44b). This output terminal (44a) (4
4b) is a D / A conversion circuit (45) for converting into an analog signal, and the switching circuits (2a) and (2b) through the amplifiers (46a) and (46b).
Of the PCM, and further to the LPFs (3a) and (3b) are connected to the L and R output terminals (48a) and (48b) of the PCM through the amplifiers (47a) and (47b).

On the A-FM side of the switching circuit (31a) (31b) on the reproducing side,
Amplifier (49a) (49b), BPF (50a) (50b), Limiter (60a) (60b), FM demodulator (61a) (61b), LPF (62
The audio FM signal output terminals (64a) and (64b) of L and R are coupled via a) (62b) and amplifiers (63a) (63b).

In the circuit configuration as described above, when L and R PCM audio signals are input to the input terminals (1a) and (1b), they are sent to the switching circuits (2a) and (2b) via the amplifier. If it is switched to the recording (REC) side, it is input to LPF (3a) (3b) and is limited to the 24 KHz band. Amplifier (4a) (4
b) via sampling and hold circuit (5a) (5
It becomes a 44.1KHz sampling signal in b) and is further converted into a 14-bit digital signal in the A / D conversion circuit (6) and then converted to a PC.
Input to M processor (7). Then, the PCM processor (7) becomes a general PCM signal to which a correction word, a control word, an error detection word, a cue word, etc. are added. This PCM signal format becomes an NRZ (Non Return to Zero) signal, and a signal with a waveform as shown in Fig. 3 (b) is output, and a PFM encoder (14) is used to convert the frequency spectrum of the signal. PFM-modulated as shown in c), and further, by BPF (15), carrier of FM signal of 3.6 to 1.0 MHz and its first upper sideband component as shown in Fig. 3 (d) and Fig. 5 (c). Will only be. Here, the modulation index (ΔfFM / fPCM) of the PFM signal is 0.5 or less.

ΔfFM: Maximum FM carrier deviation frequency.

fPCM: Basic bit frequency of NRZ signal.

The output of the BPF (15) passes through the amplifier (16), and further passes through the PCM side of the switching circuits (17a) (17b) and then the amplifiers (18a) (18).
It is amplified in b) and recorded on the tape (20) by the rotary audio heads (19a) (19b).

When a normal voice FM signal is input from the A-FM input terminals (21a) and (21b), it is limited to the 20KHz band by the LPF (23a) and (23b), and L and R are set by the FM modulation circuit (25a) and (25b). Each signal is 1.3M
Modulated with FM carrier at Hz and 1.7MHz. The FM-modulated signal is limited to the fundamental wave only by the LPF (26a) (26b), and the A-FM signal is amplified by the amplifier (18a) (18b) through the A-FM side of the switching circuit (17a) (17b). , Rotating voice head (19a) (1
It is recorded on the tape (20) by 9b).

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 as shown by the dotted line in FIG. 4 on the tape (20). Record with an inclination of ~ 35 degrees.

After recording this audio signal, the video signal is overwritten and recorded. That is, the video track has an azimuth of ± 3 to 10 with respect to the adjacent track, as shown by the solid line in FIG.
Record with a degree of inclination so that the azimuth difference between audio and video tracks is 20 degrees or more.

The luminance signal of the video signal is FM-modulated, and the chrominance signal is separated, then low-frequency converted and placed in the band below the FM-modulated signal.

Next, the case of reproduction will be described. The recording signal on the tape (20) is detected by the rotary audio heads (28a) (28b) and amplified by the amplifiers (29a) (29b). The mode detection circuit (30) automatically switches between the A-FM signal side and the PCM signal side in the switching circuits (31a) and (31b) by detecting the PCM carrier signal of the reproduced signal.

If it is a PCM signal, L / R channel switcher (3
The reproduction signal is selected in 2), the fluctuation of the output level is absorbed by the AGC circuit (33) and the AGC detection circuit (34), and the BPF (35) signal of 3.6 ~ 1.0MHz as shown in Fig. 5 (c). Only pass through and remove unwanted signals. The output signal shown in FIG. 3 (d) from the BPF (35) is waveform-shaped by the waveform shaping circuit (36) as shown in FIG. 3 (e) and returned to the PFM signal. This reproduced PFM signal is PFM signal. The decoder (37) decodes it into a NRZ format PCM signal as shown in FIG. This PCM signal is input to the PCM processor (7) for error checking,
Error correction is performed and converted into 14-bit sampling data. Further, it is converted back to an analog signal by the D / A conversion circuit (45), passes through the PB side of the switching circuits (2a) and (2b), and the LPF (3
The sampling noise is removed by a) and (3b), and the PCM audio signal is output from the output terminals (48a) and (48b). When the reproduction signal is detected as the A-FM signal by the mode detection circuit (30), the switching circuits (31a) (31b) are switched to the A-FM side, the BPFs (50a) (50b), the limiter (60a) ( 60b), FM
Demodulation circuit (61a) (61b), LPF (62a) (62b)
-FM audio signals are output from the output terminals (64a) and (64b).

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

[Advantages of the Invention] According to the present invention, it is possible to record and reproduce a PCM signal on a VHS Hi-Fi track simultaneously with recording of a video signal without an additional recording track.

In addition, the voice signal is sampled, then converted to a digital signal word, further converted to a PCM signal with error correction word, control word, error detection word, and cue word added, and further pulse FM modulated. The frequency spectrum of the recorded pulse FM signal is arranged adjacent to the high frequency band of the frequency spectrum of the low-pass converted color signal, and the sideband component of the pulse FM signal is the first sideband. Since it is limited to within the spectrum, it is possible to perform accurate recording and reproduction while saving the frequency band. further,
The frequency spectrum of the pulse FM modulation signal of the audio signal is
Since the modulation index (ΔfFM: maximum FM carrier shift frequency, / fPCM: basic bit frequency of NRZ signal) is set to 0.5 or less and its sideband component is limited to within the first sideband spectrum,
It can be placed close to the low band of the frequency spectrum of the FM modulation signal of the video signal.

[Brief description of drawings]

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 section, and FIG. FIG. 5 is a frequency characteristic diagram for explaining the recording state. (1a) (1b) …… PCM 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)
(19b) …… Rotating voice head for recording, (20) …… Magnetic tape, (28a) (28b) …… Rotary voice head for playback, (3
0) ... 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 PCM signal output terminal.

Claims (1)

[Claims] 1. A magnetic recording / reproducing apparatus of a helical scan type having an independent video recording head and audio recording head, wherein an audio signal is recorded on a tape and then an image signal is overwritten and recorded. When recording on tape, the azimuth of the video track is ± 3 to 10 degrees to the adjacent track, and the azimuth of the audio track is adjacent so that the azimuth difference between both tracks of the video signal and the audio signal is 20 degrees or more. The video signal has an inclination of ± 20 to 35 degrees, the luminance signal and the chrominance signal are both FM-modulated and recorded, and the audio signal is sampled and then converted into a digital signal word for further error correction. Converted to a PCM signal to which words, control words, error detection words, and cue words are added, and then pulse FM modulated and recorded. Frequency spectrum, for placement in proximity to the low frequency of the frequency spectrum of the FM modulated signal of the video signal, modulation index (ΔfFM: Up FM
Carrier deviation frequency, / fPCM: ZRZ signal basic bit frequency)
Of 0.5 or less and the sideband component thereof is limited to within the first sideband spectrum.