JP2000030373A - Digital information reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reproducing device which is provided with a time base extending function in a system in which soft information of a video or the like are transmitted via a radio wave and a cable to be recorded. SOLUTION: A received signal is made to be recording codes by a recording system encoder 40 and the signal made to be recording codes are recorded on a magnetic tape 60 by magnetic heads 51a, 51b while setting the rotational speed of a rotating drum 50 and the running speed of the magnetic tape 60 to R1 and V1 respectively. At the time of reproduction, the signal reproduced by the magnetic heads 51a, 51b is decoded by a reproduction system decoder 70 while rotating the drum 50 at the m/n-fold speed of a speed at the time of the recording and running the tape 60 at the 1/n-fold speed of the speed at the time of the recording to extend the time base of the recorded digital information signal to n-times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital information signal reproducing apparatus, and more particularly, to a digital information reproducing apparatus having a time axis extending function.

[0002]

2. Description of the Related Art The Journal of the Institute of Television Engineers of Japan Vol. 47, No. 4 (1.
(April 993) Systems such as those described on pages 494 to 497, transmitting audio and video software via radio waves and cables, and recording the same at homes have been considered.

[0003]

However, in the above-mentioned prior art, the speed of transmission, recording and reproduction of the soft information is constant, and no special consideration is given to the function of extending the time axis.

An object of the present invention is to solve such a problem,
An object of the present invention is to provide a digital information reproducing apparatus having a time axis extending function.

[0005]

According to the present invention, there is provided a magnetic head group mounted on a rotating drum for reproducing digital information signals recorded on a magnetic tape. Servo means for rotating the magnetic tape at a rotational speed and running the magnetic tape at a running speed of 1 / n at the time of recording, and decoding means for decoding a digital information signal extended on the time axis from a signal reproduced by the magnetic head group.

[0006]

When the rotating drum is rotated at the same rotation speed as during recording, and the magnetic tape is run at 1 / n the running speed during recording, the scanning angle of the magnetic head is slightly different from that during recording, but one track. Is scanned n times.

The decoding means partially restores the data having the highest reproduction output level from the n scans of the same track, synthesizes them using a storage circuit, and expands the digital information expanded in time. Decode the signal.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an entire system including an embodiment of a digital information reproducing apparatus according to the present invention. The system is broadly divided into a transmitting system 100, a receiving system 200, and a recording / reproducing system 300. Terminal 10, transmission system encoder, 20 is a time axis compressor, 25 is a modulator, 30 is a transmission line, 35 is a demodulator, 40 is a recording system encoder, 45 is a switching switch, 50 is a rotating drum, 51a, 51b is a magnetic head, 60 is a magnetic tape, 70 is a reproducing decoder, 80 is a receiving decoder, and 9 is an output terminal. The magnetic head 51
In a and 51b, (+) indicates positive azimuth and (-) indicates negative azimuth.

Referring to FIG. 1, a transmission system 100 encodes a digital information signal input from an input terminal 1 by a transmission system encoder 10 in a predetermined format. The transmission rate is increased by n times by compressing the time axis to n and modulated by the modulator 25. Then, the modulated signal is sent out to the transmission path 30.

In the receiving system 200, a signal received via the transmission line 30 is demodulated by a demodulator 35, and the demodulated signal is directly recorded by the recording / reproducing system 300 in a state of being encoded by the transmitting system. It is supplied to the system encoder 40. The recording encoder 40 records and encodes the supplied signal in a format suitable for recording and reproduction.

FIG. 2 is a block diagram showing an example of the configuration of the recording encoder 40, wherein 41 is a storage circuit, 42 is an interface circuit, 43 is a parity generation circuit, and 44 is a recording signal generation circuit. In FIG.
The data demodulated by the demodulator 35 is first stored in the storage circuit 41 via the interface circuit 42. FIG. 3A shows this demodulated data. Parity generation circuit 4
In 2, a parity is generated from the demodulated data stored in the storage circuit 41 and stored in the storage circuit 41. The recording signal generation circuit 43 reads out the demodulated data and parity stored in the storage circuit 41, adds a synchronization signal and an ID signal, and outputs the signal as a block signal as shown in FIG. FIG. 4 shows an example of the configuration of an ID signal. For example, a track number for identifying a recording track, a block number for identifying a position in the track, and control of a recording time and a program number on a tape. It consists of information and parity for error detection and correction of the ID signal.

The signal coded in the recording system in this way is transmitted to the 18
Magnetic heads 51a, 5
1b, and azimuth-recorded on the magnetic tape 60. The rotational speed of the rotary drum 50 is R ₁ , and the running speed of the magnetic tape 60 is V ₁ . FIG. 5 shows a track pattern at the time of this recording. P is a track pitch, and W is a head width of the magnetic heads 51a and 51b. In this embodiment, the head width W is larger than the track pitch P,
For example, it is set to 1.5 times.

At the time of reproduction, the rotating drum 50 is set to m / m at the time of recording.
The magnetic tape 60 is rotated at a speed R ₁ × m / n, which is n times (1 ≦ m ≦ n), and the magnetic tape 60 is run at a speed V ₁ / n, which is 1 / n times that at the time of recording. , 51b. FIG. 6 is a diagram showing a track pattern at the time of this reproduction. A solid line shows a recorded track pattern, and a broken line shows a scanning locus of the magnetic heads 51a and 51b. As described above, since the rotating drum 50 is rotated at the speed R ₁ × m / n of m / n at the time of recording and the magnetic tape 60 is run at the speed V ₁ / n of 1 / n at the time of recording, The scanning pitch of the heads 51a and 51b is 1 / m of the track pitch P, and the scanning angle is slightly shifted, but scanning is performed almost m times per track. In this embodiment,
For simplicity, m is set to 3.

FIG. 7 shows a signal taken from the m scans.
FIG. 7 is a waveform diagram showing a process of outputting. In the figure, (A)
Is the speed R of 1 / n times the speed of recording the rotating drum 50₁/ N
The timing at the time of rotation is shown.₀,
b₀, A₁, B₁, A_Two, B_Two, A _Three, B_ThreeThe signal plays in the order of
Shall be performed. T is this rotation cycle. (B)
R according to the present embodiment₁Xm / n (m = 3)
(C) shows the timing when the magnetic head
The envelope of the signal reproduced by the pads 51a and 51b
is there. In this way, scanning three times per track
Also, as described above, the magnetic heads 51a, 51a,
1b head width W is set to 1.5 times track pitch P
The scanning angle is greater than the recording track angle.
Even if it is off, it will be on track in a considerable part. Follow
The signal with the highest playback output level.
To obtain the original data (waveform D)
it can. And if this is extended three times in time axis,
Can reproduce a low-speed signal (waveform E)
You.

As described above, at the time of reproduction, the rotating drum 50 is rotated at a speed of m / n times that of the recording, and the magnetic tape 60 is caused to run at a speed of 1 / n times that of the recording. Time axis extension can be performed.

By appropriately setting the value of m, the reproduction frequency can be increased irrespective of the time axis compression coefficient n, and a desired reproduction output level can be secured.
Further, since scanning is performed m times per track, data can be reproduced even if tracking is shifted, so that there is an effect that precise tracking control is not required.

FIG. 8 is a block diagram showing an example of the configuration of a reproducing system decoder 70 for performing the entire processing of the reproducing system including the process of extracting a signal from the above m scans. , 72 is a block reproduction circuit, 73 is an error correction circuit, and 74 is a reproduction signal output circuit. In the figure, signals reproduced by the magnetic heads 51a and 51b are first input to a block reproducing circuit 72. The block reproduction circuit 72 detects a synchronization signal and an ID signal,
The data is stored at a predetermined position on the storage circuit 71 based on the track number and the block number in the ID signal. Error correction circuit 73
Then, an error in the reproduced data is corrected using the parity stored in the storage circuit 71, and at the same time, a pointer indicating the error state is generated and stored in the storage circuit 71. At this time, data of the same track number and block number is input to the memory circuit 71 m times, but data with the best error state is finally stored by the pointer. The reproduction signal output circuit 74 reads the error-corrected data stored in the storage circuit 71 in accordance with the order of the track number and the block number, and outputs low-speed data with the time axis expanded.

The low-speed data signal thus decoded in the reproduction system is sent to the reception system 200, and the decoding in the transmission system is canceled by the reception decoder 80. The signal decoded into the original digital information signal is supplied to an output terminal 9.
Output.

By arranging the receiving-side decoder 80 after the recording / reproducing section 300, the receiving-side decoder 80 can perform low-speed processing.

FIG. 9 is a block diagram of the whole system including another embodiment of the digital information reproducing apparatus according to the present invention. The present invention is applied to a system in which video software is transmitted in a confidential manner and only subscribers can record and reproduce. This is an example of application.
In the figure, 15 is a scrambler, 52a and 52b are magnetic heads, 75 is a descrambler, 101, 102,
103 is an input terminal, 111 and 112 are A / D converters, 1
21 and 122 are information amount compressors, 201 and 202 are information amount decompressors, 211 and 212 are D / A converters, 221, 22
Reference numerals 2 and 223 denote output terminals, and portions corresponding to those in FIG. In the magnetic heads 52a and 52b, (+) indicates positive azimuth,
(-) Indicates negative azimuth.

In the transmission system 100, an image signal input from an input terminal 101 is converted into an A / D signal by an A / D converter 111.
/ D conversion, and the information amount is compressed by the information amount compressor 121 to an appropriate rate. The audio signal input from the input terminal 102 is subjected to A / D conversion by the A / D converter 112, and the information amount is compressed to an appropriate rate by the information amount compressor 122. The A / D-converted and information-compressed image signal and audio signal are confidentialized and time-division multiplexed by the scrambler 15 together with the independent data input from the input terminal 103. Encoded. Hereinafter, this polarized signal is time-axis-compressed to 1 / n by the time-axis compressor 20 as in the embodiment of FIG.
The signal is modulated by the modulator 25 and sent out to the transmission path 30.

In the receiving system 200, as in the embodiment of FIG.
A signal received via the transmission path 30 is demodulated by a demodulator 35 and demodulated data is supplied to a recording encoder 40 of the recording / reproducing system 300.

In the recording / reproducing system 300, the supplied demodulated data is recorded and encoded by the recording system encoder 40, and two magnetic heads 51 a, 51 are switched via a switching switch 45.
b, 52a, and 52b, and two-channel azimuth recording is performed on the magnetic tape 60. These two sets of magnetic heads 51
The recording frequency can be reduced to に よ り by two-channel recording using a, 51b, 52a, and 52b.
The rotation speed of the rotating drum 50 and the traveling speed of the magnetic tape 60 are set to, for example, R ₂ and V ₂ .

At the time of reproduction, the rotating drum 50 is rotated at the same speed R ₂ (that is, m = n) as during recording, and the magnetic tape 60 is rotated.
Drives at a speed V ₂ / n of 1 / n at the time of recording, and reproduces the recorded signal by a pair of magnetic heads 51a and 51b. In the present embodiment, the time axis compression coefficient n is set to be sufficiently large (originally, it is desirable that n is large).
Even one-channel reproduction by one set of magnetic heads 51a and 51b can be traced n / 2 times per track,
By performing the same processing as in the embodiment of FIG. 1 in the reproduction system decoder 70, sufficient data reproduction is possible. This allows
There is an effect that only one system of the reproduction system is required, and the circuit scale can be reduced. Further, since the rotating drum 50 is rotated at the same speed as during recording, the rotation control is also simplified.

The reception system 200 receives the signal decoded by the reproduction system decoder 70, decodes the signal coded by the transmission system by the reception system decoder 80, and decrypts the signal by the descrambler 75 in the transmission system. Decompose the signal and separate the image signal, audio signal and independent data. The separated image signal and audio signal are respectively supplied to the information amount expander 201,
The data is expanded to the original information amount by the D / A converter 2.
D / A conversion is performed by the output terminals 221 and 212,
Output from 222. The separated independent data is output from the output terminal 223.

As described above, by disposing the descrambler 75 after the recording / reproducing system 300, the recorded image signal and audio signal can be protected.

[0028]

[Table 1]

Table 1 shows the transmission system 10 in the embodiment of FIG.
This shows a specific example of transmission specifications of 0. For example,
The compressed image information amount is 2.5 Mbps, the compressed audio information amount is 256 kbps, and the independent data information amount is 2 Mbps.
Assuming 56 kbps, the total information amount after transmission system coding is 4
Mbps. If this is compressed on the time axis to 1/6 (n = 6), the transmission rate becomes 24 Mbps. If the transmission path is a cable for CATV, the bandwidth per TV channel is 6 MHz, and the transmission rate is 24 Mbps.
In order to transmit this signal within a bandwidth of 6 MHz, the modulation method is optimally 32QAM (32-level quadrature amplitude modulation).

Although the transmission path is a cable for CATV in Table 1 above, for example, a communication satellite or the like may be used and the modulation method may be QPSK (four-phase modulation). in this case,
Communication satellite bandwidth is 3 per transponder channel
Since it is about 0 MHz, the transmission rate can be about 48 Mbps. Accordingly, with the same amount of information as in Table 1, two pieces of program software can be time-division multiplexed and transmitted simultaneously. Alternatively, the image amount and the sound quality may be improved by doubling the information amount (the information amount of the compressed image and audio is 5 Mbps, 512 kbps, and the information amount of the independent data is 512 kbps). / 12 (n =
12), the transmission time may be shortened.

[0031]

[Table 2]

Table 2 shows specific examples of the data of the recording / reproducing system 300 for the transmission data shown in Table 1 in the embodiment of FIG. 9, and Example 1 is a half-inch wide iron oxide. Example 2 is an example using a tape, and Example 2 is an example using a metal evaporation tape having a width of 8 mm. The input information amount is the transmission rate of 24 Mbps shown in Table 1, and the recording information amount after recording system coding is about 36 Mbps. If this is recorded on two channels, the recording rate per channel becomes 18 Mbps. In Example 1, for example, the drum diameter is 62 mm, the drum rotation speed during recording and the tape feed speed are 1800 rpm,
66.7 mm / s. At this time, the track pitch is 58 μm. The recording wavelength is about 0.64 μm, and a sufficient reproduction output level can be obtained by using a high-performance iron oxide tape. On the other hand, in Example 2, for example, when the drum diameter is 4
0 mm, the number of rotations of the drum at the time of recording, and the tape feed speed are 1800 rpm and 28.69 m / s. The track pitch is 20.5 μm. At this time, the recording wavelength becomes as short as about 0.42 μm, but the reproduction output level can be secured because the metal vapor-deposited tape is used. In both Examples 1 and 2, the drum rotation speed during reproduction was the same as that during recording: 1800 rpm.
m, and the tape feeding speed is 1/6 of the recording time, which is 11.1
Needless to say, they are 2 mm / s and 4.78 mm / s.

[0033]

As described above, according to the present invention, in a system for transmitting and receiving software information such as audio and video via radio waves and cables, and recording and reproducing the same, a digital system having a function of extending a time axis is provided. An information reproducing apparatus can be realized, and the reliability of reproduced data can be improved, and a decoding circuit and a tracking control circuit can be simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram of an entire system including a digital information reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration example of a recording system encoder.

FIG. 3 is a diagram showing input / output signals of the recording system encoder shown in FIG. 2;

FIG. 4 is a diagram illustrating a configuration example of an ID signal.

FIG. 5 is a diagram showing a track pattern at the time of recording in the embodiment of FIG. 1;

FIG. 6 is a diagram showing a track pattern at the time of reproduction in the embodiment of FIG. 1;

FIG. 7 is a waveform chart showing an operation at the time of reproduction in the embodiment shown in FIG. 1;

FIG. 8 is a block diagram illustrating a configuration example of a reproduction system decoder according to the present invention.

FIG. 9 is a block diagram of an entire system including a digital information reproducing apparatus according to another embodiment of the present invention.

[Explanation of symbols]

10: transmission encoder, 15: scrambler, 20: time axis compressor, 25: modulator, 35: demodulator, 40: recording encoder, 50: rotating drum, 51a, 51b, 52a,
52b: magnetic head, 60: magnetic tape, 70: reproducing decoder, 75: descrambler, 80: receiving decoder
111, 112: A / D converter, 121, 122: Information amount compressor, 201, 202: Information amount decompressor, 211, 2
12 ... D / A converter.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Keiji Noguchi, Inventor Keiji Noguchi 292, Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture Inside the Hitachi Media Research Laboratory (72) Inventor Hiroo Okamoto 292, Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa, Japan (72) Shigeru Yamazaki, Hitachi, Ltd. 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa

Claims (3)

[Claims] A digital information reproducing apparatus which reproduces a digital information signal recorded at a predetermined speed at a speed of 1 / n of the predetermined speed, thereby extending the time axis of the digital information signal by n times. A magnetic head group mounted on a rotating drum and reproducing the digital information signal recorded on the magnetic tape; and rotating the rotating drum at the same rotational speed as during recording, and rotating the magnetic tape by 1 / servo means for traveling at a traveling speed of n; and decoding means for decoding the digital information signal extended in time axis from the signal reproduced by the magnetic head group, wherein the decoding means scans the same track n times. A digital information reproducing apparatus for synthesizing data partially restored from the above and decoding the digital information signal expanded in the time axis. 2. The digital information reproducing apparatus according to claim 1, wherein said digital information signal is a video signal and / or an audio signal subjected to band compression encoding. 3. The digital information reproducing apparatus according to claim 2, further comprising second decoding means for decoding the reproduced signal into an original video signal and / or audio signal.