JPH07130089A - Digital signal recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a digital signal recording and reproducing device capable of recording and reproducing plural bit rate digital signals without changing the number of revolutions of a rotary cylinder. CONSTITUTION:A magnetic tape 1 is wound on a rotary cylinder 2 mounted with magnetic head pair 5a and 5b and digital information is successively recorded on and reproduced from a recording track by moving the tape 1 at a constant speed. In accordance with the bit rate of an input signal, the recording length of tilted tracks is changed by giving instructions from a terminal 13. Thus, recording and reproducing of different bit rate digital signals are accomplished without changing the number of revolutions of the cylinder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital signal recording / reproducing apparatus such as a digital VTR or a PCM tape recorder for recording digital information such as a video signal or an audio signal on a magnetic tape, and more particularly to a plurality of digital information having different bit rates. The present invention relates to a digital signal recording / reproducing apparatus capable of recording and reproducing.

[0002]

2. Description of the Related Art In recent years, in a digital signal recording / reproducing apparatus, due to advances in compression / expansion technology and error correction technology, digital information is band-compressed and recorded instead of being recorded directly on a magnetic tape. .

For example, a video signal is digitized and DC
A digital video signal is compressed and recorded on a magnetic tape by using a compression method such as T, DPCM, and ADRC. As an example thereof, a technique has been reported in which a coded video signal having an information amount of 115 Mb / s is converted into a bit rate of 25 Mb / s by compression and compression-recorded (a journal of the Institute of Television Engineers, "Image Information Recording Technology"). Future ”Vol.46, No.10, pp1
222-1229).

As a result, when the bit rates of the recording information are different, in order to keep the recording density on the tape constant,
The rotation speed of the rotating cylinder and the running speed of the magnetic tape must be changed according to the bit rate. For example, if the bit rate becomes 1/2, the rotation speed of the rotating cylinder and the running speed of the magnetic tape are reduced to 1/2. (For example, Japanese Patent Laid-Open No. 63-155877).

[0005]

However, in the above configuration, in order to record digital signals of different bit rates, the number of revolutions of the rotary cylinder and the running speed of the magnetic tape are changed, so that the bit rate is changed. It is difficult to maintain the contact state (head touch) between the magnetic head and the magnetic tape at all times according to
This causes a problem that the contact state between the magnetic head and the magnetic tape is deteriorated. Further, in the above configuration, it is necessary to switch the frequency characteristics (filter constant, equalizer constant) of the head amplifier that amplifies the input / output signal of the magnetic head according to the bit rate, and the circuit configuration of the head amplifier becomes complicated. Also had.

In view of the above problems, the present invention can cope with a plurality of bit rates without changing the number of rotations of the rotary cylinder even when recording digital signals of different bit rates, and by azimuth recording. It is an object of the present invention to provide a digital signal recording / reproducing device capable of high density recording.

[0007]

In order to solve the above problems, a digital signal recording / reproducing apparatus of the present invention winds a magnetic tape around a rotary cylinder on which a magnetic head is mounted and runs the magnetic tape at a constant speed. By doing so, it is configured to record and reproduce digital information on the inclined tracks in sequence.
The configuration is such that the bit rate of the input signal is converted to a predetermined bit rate, and the recording length of the inclined track is changed according to the bit rate of the input signal without changing the rotation speed of the rotary cylinder. .

[0008]

With the above-described structure, the present invention can cope with a plurality of bit rates without changing the number of rotations of the rotary cylinder, so that the contact state (head touch) between the magnetic head and the magnetic tape can be improved. Further, since the input signals of a plurality of bit rates are once converted into digital information of a predetermined bit rate and the bit rate of recording / reproducing is constant or substantially constant, the frequency characteristic of the head amplifier is changed according to the bit rate of the input signal. (Filter constant,
It is not necessary to switch the equalizer constant). That is,
Multiple bit rates can be supported without changing the circuit configuration of the head amplifier. As a result, it is possible to realize a digital signal recording / reproducing apparatus capable of recording digital signals of different bit rates with a simple configuration.

[0009]

Embodiments of the digital signal recording / reproducing apparatus of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the structure at the time of recording of a digital signal recording / reproducing apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 1 is a magnetic tape, which is wound around a rotary cylinder 2. The rotary cylinder 2 is rotated at a constant speed by the cylinder motor 3 and the control circuit 4. 5
a and 5b are magnetic heads having different azimuth angles R and L of 1
A pair of magnetic heads are mounted on the rotary cylinder 2 so as to face each other by 180 degrees. 6 is a capstan, and a pinch roller 7
Holds the magnetic tape 1 together with the capstan motor 8
The control circuit 4 causes the magnetic tape 1 to run at a constant speed. An A / D converter 10 converts the analog signal input to the input terminal 9 into a digital signal. Reference numeral 11 denotes an encoder, which is composed of a memory for sequentially storing the digital signals output from the A / D converter 10 and a compression encoding circuit (not shown) for compression encoding the digital signals and further generating / adding an error correction code. The digital signal input to the encoder 11 is converted into compressed coded data according to the command signal input to the terminal 13. A time axis compression / expansion circuit 12 performs time axis expansion / compression processing according to a command signal input to the terminal 13. For example, when the bit rate output from the encoder 11 is low, the time axis compression / expansion circuit 12 time axis compresses the input compression coded data. That is, the time axis compression / decompression circuit 12
Performs a time axis compression process so that the bit rate recorded on the magnetic tape 1 is constant or substantially constant. 14
Is a modulator for converting the output signal of the time axis compression / expansion circuit 12 into a recording signal of a predetermined format. A head amplifier 15 inputs the amplified signal to the head switching circuit 16. The head switching circuit 16 selects one of the two magnetic heads 5a and 5b in response to a command from the control circuit 4.
It is selected which magnetic head the recording signal is supplied to.

The operation of the digital signal recording / reproducing apparatus configured as described above will be described in detail below.

2 and 3 are respectively a recording timing chart showing the operation when a high bit rate digital signal is recorded in the digital signal recording / reproducing apparatus of this embodiment, and are formed on a magnetic tape. It is a track pattern figure.

In FIG. 2, HSW is a head switching signal corresponding to the pair of magnetic heads 5a and 5b, and corresponds to the rotation phase of the rotary cylinder 2. The head switching circuit 16 causes the magnetic head 5a to operate while the head switching signal HSW is "H".
The R azimuth of the magnetic head 5b is used for recording while the head switching signal HSW is "L". Therefore, as shown in FIG. 3, the recording signal is alternately recorded on the magnetic tape 1 by using the R and L azimuths of the magnetic heads 5a and 5b, so that the recording is performed with the R azimuth while the rotary cylinder 2 makes one revolution. The recorded track and the track recorded in L azimuth are continuously recorded at the track pitch Tp. The track indicated by the solid line is the recorded track. The running speed of the magnetic tape 1 is set by the control circuit 4 so as to move by two tracks while the rotating cylinder 2 makes one rotation. Moreover, since the azimuth angle of the recorded track is different from the azimuth angle of the adjacent track, it is possible to perform recording without providing a guard band between the tracks, and high density recording is possible.

FIGS. 4 and 5 respectively show a recording signal of a low bit rate (in this example, the bit rate is 1/2 times that in FIGS. 2 and 3) in the digital signal recording / reproducing apparatus of this embodiment. FIG. 3 is a recording timing diagram showing an operation when recording is performed and a track pattern diagram formed on the magnetic tape.

In FIG. 4, HSW is a head switching signal corresponding to the pair of magnetic heads 5a and 5b and corresponds to the rotation phase of the rotary cylinder 2. The head switching circuit 16 causes the magnetic head 5a to operate while the head switching signal HSW is "H".
The R azimuth of the magnetic head 5b is used for recording while the head switching signal HSW is "L". However, the bit rate of the compression-encoded data output from the encoder 11 is 1/2 that in the cases of FIGS. 2 and 3.
The time-base compression / expansion circuit 12 time-compresses the input compression-coded data by half in accordance with the command signal input to the switching terminal 13. That is, since the bit rate of the compression-encoded data output from the encoder 11 is 1/2 times that in the cases of FIGS. 2 and 3, the time-axis compression / decompression circuit 12 performs the time-axis compression process to record the bits. Processing is performed so that the rate is the same as in the cases of FIGS.

Therefore, as compared with the cases of FIGS.
A recording signal time-compressed by a factor of ½ is recorded on the magnetic tape 1 by using the R and L azimuths of the pair of magnetic heads 5a and 5b. Therefore, the recording period of each magnetic head is as shown in FIG. As shown in R and L and FIG. 5, only 1/2 track is left, and the remaining 1/2 track remains unrecorded. However, as in the case of FIGS. 2 and 3, the rotary cylinder 2
There is no change in recording two tracks in total, that is, the track recorded in R azimuth and the track recorded in L azimuth at the track pitch Tp during one rotation of.
The running speed of the magnetic tape 1 is set by the control circuit 4 so as to move by two tracks while the rotating cylinder 2 makes one rotation. This is the same tape speed as in FIGS. 2 and 3, and it is not necessary to change the tape speed in accordance with the bit rate of the input signal. Also, as in the case of high bit rate, the azimuth angle of the recorded track is different from the azimuth angle of the adjacent track, so it is possible to record without providing a guard band between tracks, and high density recording is possible. is there.

In the embodiment of FIGS. 4 and 5, the track length used for recording is only 1/2 of the total track length, and the remaining 1/2 track is in a non-recorded state. It is also possible to redundantly record the signal extracted from the recording signal for 1/2 track of the above (not shown). For example, digital information such as still image information extracted from the recording signal at predetermined intervals may be recorded. Then, still images can be sequentially reproduced by reproducing the redundant signals recorded in the remaining 1/2 tracks. Further, it becomes possible to restore the data lost due to the tape scratch by using this redundant signal.

Next, the operation during reproduction for reproducing the signal thus recorded will be described. FIG. 6 is a block diagram showing the structure at the time of reproduction of the digital signal recording / reproducing apparatus in one embodiment of the present invention. It should be noted that components having the same functions as those in FIG. 1 are designated by the same reference numerals, and redundant description will be omitted.

In FIG. 6, reference numeral 16 is a head switching circuit,
From a pair of magnetic heads 5a and 5b having different azimuth angles R and L mounted on the rotary cylinder 2,
The magnetic head to be used is selected and the reproduction signal is input to the head amplifier 15. A demodulator 17 is a head amplifier 15
The signal amplified by is input and demodulated into a digital signal of a predetermined bit rate. The digital signal demodulated by the demodulator 17 is supplied to the time axis compression / expansion circuit 12.
The time axis compression / expansion circuit 12 has a memory for sequentially storing digital signals, performs time axis expansion processing in accordance with a command signal input to the terminal 13, and supplies the digital signal to the decoder 18. The decoder 18 decodes the input compression-coded digital signal and performs an error correction process using an error correction code. The signal output from the decoder 18 is converted into an analog signal by the D / A converter 19 and output from the output terminal 20.

In this embodiment, the magnetic heads are mounted on the rotary cylinder one by one, facing each other by 180 degrees.
The number of heads is not limited to one, and more heads may be provided. Further, in the present embodiment, the magnetic heads are arranged 180 degrees opposite to each other and arranged at two places. However, the magnetic heads may be arranged not only at two places but at equal angular intervals at four places, or collectively at one place of the rotary cylinder. You may.

[0021]

As described above, according to the present invention, the recording length of the inclined track is changed according to the bit rate of the input signal, so that the digital signal of high bit rate and low bit rate can be obtained. It is possible to record and reproduce without changing the rotation speed of the rotary cylinder.
Since it is not necessary to change the number of rotations of the rotary cylinder, the contact state (head touch) between the magnetic head and the magnetic tape can be kept optimum. Further, since the input signals of a plurality of bit rates are once converted into the digital signals of a predetermined bit rate, the bit rate of recording / reproducing becomes constant or substantially constant. Multiple bit rates can be supported without switching frequency characteristics.

As described above, according to the present invention, it is possible to provide a digital signal recording / reproducing apparatus capable of recording / reproducing digital signals of a plurality of bit rates with a simple structure.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration during recording in an embodiment of a digital signal recording / reproducing apparatus of the present invention.

FIG. 2 is a timing diagram at a high bit rate according to an embodiment of the present invention.

FIG. 3 is a track pattern diagram at a high bit rate according to an embodiment of the present invention.

FIG. 4 is a timing chart of an embodiment according to the present invention at a low bit rate.

FIG. 5 is a track pattern diagram at a low bit rate according to an embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration at the time of reproduction in an embodiment of a digital signal recording / reproducing apparatus of the present invention.

[Explanation of symbols]

 1 magnetic head 2 rotating cylinders 5a, 5b magnetic head 16 head switching circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiro Takeuchi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A magnetic tape is wound around a rotary cylinder on which a magnetic head is mounted, and the magnetic tape is run at a constant speed so that digital information is sequentially recorded and reproduced on inclined tracks. Convert the input signal of to the digital information of the predetermined bit rate,
A digital signal recording / reproducing apparatus, which records the digital information by changing a recording length of the inclined track according to a bit rate of the input signal. 2. A magnetic tape is wound around a rotary cylinder on which a magnetic head is mounted, and the magnetic tape is run at a constant speed so that digital information is sequentially recorded and reproduced on inclined tracks. Convert the input signal of to the digital information of the predetermined bit rate,
The digital information is recorded on a part of the inclined track by changing the recording length according to the bit rate of the input signal, and the redundant digital information is recorded on the remaining track part of the inclined track. Digital signal recording / reproducing device. 3. The digital signal recording / reproducing apparatus according to claim 1, wherein the recording length of the inclined track is configured to be proportional to the bit rate of the input signal. 4. The digital signal recording / reproducing apparatus according to claim 1, wherein the recording bit rate of the digital information is selected to be the highest bit rate of the input signals of a plurality of bit rates. 5. The digital signal recording / reproducing apparatus according to claim 1 or 2, wherein recording is performed such that adjacent recording tracks have different azimuth angles from each other.