JP3232731B2 - Digital information recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital information recording / reproducing apparatus for recording digital information such as digital video signals and digital audio signals on a magnetic tape by a helical scan type magnetic recording apparatus and reproducing the digital information. In particular, the present invention relates to a digital recording / reproducing apparatus which is useful when recording information is recorded in a long time mode.

[0002]

2. Description of the Related Art In recent years, a digital VTR for digitizing a color video signal and recording it on a recording medium such as a magnetic tape.
However, it is widespread especially in the field of business use. Such a digital VTR is compared with a conventional analog VTR in editing and C / C.
It is excellent in the S ratio, and has an advantage that the image quality does not deteriorate even when dubbing is performed. However, since high-density magnetic recording is required as compared with an analog VTR, when recording for a long time, the amount of tape used increases remarkably, making it difficult to reduce the size of the VTR.

Therefore, image data and audio data converted into digital data are compressed by a predetermined method to reduce the amount of transfer information, so that a small-sized cassette tape close to a current home VTR can be used. Various signal processing and recording formats have been proposed. For example, the input image signal is converted into data of a block unit composed of a plurality of pixel data, and the block output data is compression-coded in block units, and a parity is added to the compression-coded data. Then, pre-encoding suitable for the recording characteristics of the magnetic tape is performed, and the pre-encode is supplied to a rotary head and recorded on the magnetic tape by a helical scan method.

FIG. 5 is a block diagram showing an outline of a magnetic recording apparatus for recording a color television image as digital information previously proposed by the present applicant. In this figure,
Reference numeral 1 denotes an effective information extracting unit for extracting effective information from an input image signal (digital information), for example, a digital luminance signal Y and a digital color difference signal formed from three primary color signals R, G, and B from a video camera or the like. U and V are input.

The digital luminance signal Y and the digital color difference signals U and V are 13.5 MHz and 6.75 MHz, respectively.
The effective information extraction unit 1 removes the data during the blanking period and compresses the data to about 167 Mbps.

Reference numeral 2 denotes a data block processing unit. The luminance signal component input to the block processing unit 2 has a sampling frequency of 3/4 by a thinning filter or the like.
, And is divided into blocks in a predetermined block unit. The chrominance signal component is converted from 6.75 MHz to half the sampling data by sub-sampling, and is line-sequentially formed into blocks in a predetermined block unit. The luminance signal is blocked by dividing a screen over two frames, for example, as shown in FIG.
A large number of unit blocks of [4 pixels × 2 frames] are formed,
Here, the information amount is reduced to about 84 Mbps. 6B, the information of x is reduced by the sub-sampling as shown in FIG. 6B, and similarly, [4 lines × 4 pixels × 2
Frame].

[0007] The luminance signal component and the color difference signal component that have been blocked are then supplied to a block coding and framing processing unit 3. The encoding circuit is based on the ADRC (Adeptive Dynamei Ra) method adapted to the dynamic range of each block.
nge Coding) or DCT (Discrete Cosine Transt)
orm), the information amount is compressed to about 25 Mbps by compressing and encoding the data.

The ADRC is disclosed, for example, in Japanese Patent Application No. 59-2698.
No. 66, a maximum value MAX and a minimum value MIN of a plurality of pixel data included in each block are detected, and a dynamic range DR of the block is detected from the maximum value MAX and the minimum value MIN. Then, by performing encoding adapted to the dynamic range DR, re-encoding is performed to a bit number smaller than the bit number of the original pixel data. The compression-encoded data is converted into frame-structured data by switching between an image-based clock and a recording-based clock. Then, an error correction code is added by the parity adding circuit 4.

The audio signal data A is similarly compressed in data volume by the DPCM in the audio signal processing unit 5, added with an error correction code in the parity addition circuit 6, and supplied to the mixing circuit 7.

The sub-data which has been subjected to error correction coding is input to the mixing circuit 7, and is arranged at a predetermined position of one segment together with the above-mentioned image data and audio data.

The recording data output from the mixing circuit 7 is then input to a channel encoder 8. The channel encoder 8 is disclosed by the applicant of the present invention in Japanese Patent Application No. 1-143391, and is formed of an adaptive scramble and a precoder for a partial response / 4 detection system.

In the adaptive scrambling, a plurality of M-sequence scrambling circuits are prepared, and an M-sequence signal which can provide an output with the least high frequency component and the least DC component with respect to an input signal is selected. It has been done.

Further, a delay element D having a precoder bit cycle
And an adder M performing a modulo 2 operation,
It is to the arithmetic processing to be D ^2. Such precoders were used in the field of data communications,
The precoded data corresponds to interleaved NRZi (partial response / 4 transmission system).

The data converted to the interleaved NRZi code by the channel encoder 8 is distributed to two output amplifiers 9A and 9B, and supplied to the rotary magnetic heads 10A and 10B. Then, the data is sequentially recorded in a predetermined format on the track formed in the oblique direction of the magnetic tape T.

Although not shown, a pilot signal for tracking, a preamble, a postamble and the like are applied to the data for one track immediately before the recording amplifier. Further, the signal of the erasing signal source 11 is supplied to the erasing rotary head 10C via the erasing amplifier 12.

At the time of reproduction, the rotary magnetic heads 10A, 10A,
The reproduced RF data from 0B is input to a channel decoder via a reproducing amplifier, and detailed data is omitted, but error data is corrected by a correction code added at the time of recording. Then, the framing process, the encoding process, and the blocking process are sequentially decompressed, and the original video data Y, U, V, and audio data A are decoded and output.

In the above-described digital information recording / reproducing apparatus, for example, one frame of video data is recorded on a magnetic tape T.
This is a so-called segment recording formed by ten tracks formed in an oblique direction. Therefore, 1
A pair of rotary magnetic heads 10A that are opposed to each other in the 80 °, 1
0B, the rotating drum is 150 rps (NTS
(C method).

[0018]

When the above-described recording / reproducing system is used, the magnetic tape serving as an information recording medium can be made to have substantially the same shape as that of a current VTR tape cassette. Is recorded in ten tracks, so that the consumption of the magnetic tape increases. Therefore, it is preferable to reduce the track pitch of the magnetic tape so as to achieve a long-time recording mode as employed in a conventional VTR. If the value is increased, the error rate of the data suddenly increases, and it becomes extremely difficult to put it to practical use.

Therefore, in the case of digital video information, the compression ratio of the input data is increased so that the amount of recorded information is reduced, and the number of recording tracks per frame is reduced. For example, if data compression is performed such that recording information per frame is accommodated in five tracks, a long time mode in which the recording (reproduction) time is doubled even if the image quality is slightly reduced can be realized. .

However, in order to reduce the number of recording tracks by half using a normal rotary head facing at 180 degrees by performing data compression, the number of rotations of the rotary drum must be one.
/ 2, which requires a significant improvement in the characteristics of the servo system of the rotating drum and the drive device. In addition, since the clock frequency and the RF frequency for processing digital data are halved, it is necessary to change the circuit constants and formats of the equalizer and various control systems, resulting in a problem of increasing the cost.

[0021]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention converts an input signal into digital data, and performs at least a blocking process and an encoding process on the digital data. In a digital information recording / reproducing apparatus for recording data on a track formed in a diagonal direction of a magnetic tape, a double azimuth magnetic head comprising a pair of first and second magnetic heads having different azimuth angles, A third magnetic head disposed opposite to the magnetic head is provided on a peripheral side of the rotating drum,
In a normal recording / reproducing mode, recording / reproducing of digital data is performed by alternately switching the first magnetic head and the third magnetic head of the double azimuth magnetic head. In the case of long-time mode, both when the recording / reproducing of digital data compressed and coded by switching alternately the first magnetic head and the second magnetic head of the double azimuth magnetic head, the recording mode Re-appear with the corresponding identification code.
The raw mode can be set automatically.

[0022]

A single rotary head is added to the rotary head facing at 180 degrees to support the long-time mode by using the same drive system as the conventional one, and to simultaneously perform the recording mode.
Automatically selects the signal processing of the device by playing
Can add a great added value.

[0023]

FIG. 1 is a block diagram of a digital information recording / reproducing apparatus showing an embodiment of the present invention, and shows a recording system when video information is supplied as an input signal. In this figure,
Reference numeral 1 denotes an effective information extracting unit for extracting effective information obtained by removing information such as a blanking period from the input image information. Output.

The first digital video data processing unit 3A
As described with reference to FIG. 5 described above, the data block processing, the coding processing, and the frame processing are performed to compress the amount of digital data. In particular, the second digital video data processing unit 3B Performs signal processing so that the compression amount of this data is further reduced to １ ／. The video frame data output from the second digital video data processing unit 3B is such that one frame of data is accommodated in five recording tracks by, for example, setting the sampling rate at the time of blocking processing to １ ／. And the image quality is slightly reduced, but the amount of information to be recorded is halved.

The reference numerals 4, 5, 6, 7, and 8 denote the same functional parts as those shown in FIG. 5, and a detailed description thereof will be omitted. It is preferable to provide a data compression function. 3
Numeral 0 designates a recording amplifier 9 which converts the recording data converted by the channel encoder 8 to three rotating magnetic heads arranged on the peripheral side of the rotating drum as will be described later.
A head switching switching circuit for distributing the signals via A, 9B and 9a. Reference numeral 40 denotes a capstan (pinch roller) for running the magnetic tape T at a predetermined speed.
And the servo device.

FIG. 2 shows the three rotating magnetic heads H described above.
_A, H _B, in which the arrangement of the H _a schematically showing a tape angle magnetic tape T is in a predetermined relative rotary drum D (180
(Degree). Rotary magnetic head H _A and the rotary magnetic head H _B are arranged opposite at an angle of 180 degrees, the azimuth angle is set to be different from each other. The rotary magnetic head H _a rotary magnetic head H _B
Azimuth angle is the same as that of the rotary magnetic head H
_It is arranged at the same position as _A and forms a so-called double azimuth head. The signal processing of the reproduction system may be performed by decompressing data encoding and framing at the time of recording, and is not shown in FIG.

Since the digital information recording / reproducing apparatus of the present invention is configured as described above, the standard mode for recording / reproducing a video signal at a constant speed as described below and a long time ( (2 times) recording time can be obtained. When the mode is set to the standard mode, the mode changeover switch 20 is controlled so that the input video signal is supplied to the first digital video data processing unit 3A, and the compression encoding of the data as described in FIG. Done. The head switching circuit 30 converts the compressed encoded data into rotating magnetic heads H _A and H _A.
Set to be distributed to _B and supplied. Therefore, as shown in FIG. 3A, the magnetic tape T wound around the rotating drum has two rotations per rotation of the rotating drum D as shown in FIG.
Recording tracks A and B of the book are recorded. Then, video data for one frame is recorded by five rotations of the rotating drum D.

On the other hand, when the digital information recording / reproducing apparatus of the present invention is set to the long time mode, the input signal is supplied to the second digital video data processing section 3B by the mode changeover switch circuit 20. Then, in the second digital video data processing section 3B, data corresponding to a further half of the data compressed in the standard mode is compressed, encoded, framed, and output. In the compression encoding corresponding to the long time (double) mode, only the sampling frequency may be reduced to に 際 し て at the time of blocking, and in this case, most of the digital video data processing units 3A and 3B are used. Can be shared, and it is not always necessary to separate them. However, when performing data interpolation processing for code compression or when compressing data in frame units, a method of switching data processing by a switch is preferable.

[0029] In the compression-encoded data for a long time mode, likewise the addition of parity, and then was subjected channel encoder processing, the rotary magnetic head H _A at the head switching circuit switching circuit 30, supply was partitioned H _a Is done. Rotary magnetic head H _A, H _a is as described above, arranged in substantially the same position, so there is a double azimuth head wearing a predetermined step, rotation and the feed speed of the tape to half drum D can be the magnetic head H _a in one rotation of the form a single recording track a, and the rotating head H _a in the next one rotation so that the next track a is formed. Therefore, as shown in FIG. 3B, tracks A and a are recorded alternately, and one frame of video data is recorded by five tracks at the same track pitch as in the standard mode.

In the long time mode, the tape feed speed is controlled to be １ ／, so that the consumption of the magnetic tape is に 対 し て of the standard mode, and the recording / reproducing time is reduced. It can be doubled. The tracks have different azimuth angles from one another, and the occurrence rate of error data is reduced. It is preferable that an identification code is inserted into a part of the recording track to automatically switch between the standard mode and the long-time mode during reproduction.

FIG. 4 shows the recording / reproducing state of data in the standard mode and the recording / reproducing state of data in the long-time mode arranged side by side in the time axis direction. It can be seen whether the RF frequency and the clock of the data to be performed are the same. In addition, since the control of the rotation speed of the rotary drum is performed by the same control circuit in the standard mode and the long-time mode except when the tape speed is reduced to half, there is no increase in cost.

[0032]

As described above, the digital information recording / reproducing apparatus of the present invention comprises a double azimuth head having a different azimuth angle, and a single rotary head arranged opposite to the double azimuth head. Since the three rotary heads are switched between the standard mode and the long-time mode to perform data recording and reproduction, the long-time mode recording / reproduction is performed without significant changes in the apparatus.
In particular, since the recording mode can be known, there is an effect that a use mode similar to that of a conventional analog VTR can be added.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a recording system of a digital information recording / reproducing apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing a position of a rotating magnetic head employed in the present invention.

FIG. 3 is an explanatory diagram showing a state of tracks in a standard mode (a) and a long time mode (b).

FIG. 4 is a diagram showing a state of recording / reproducing data.

FIG. 5 is a block diagram showing a prior art of a digital information recording device for recording information on a magnetic tape medium.

FIG. 6 is an explanatory diagram of data blocking and encoding.

[Explanation of symbols]

1 Valid information extraction section 2 mode switch circuits 3A, 3B first and second digital processing unit 4 parity adding circuit 8 channel encoder H _A, H _a first and second rotary magnetic head (double azimuth head) H _B3rd rotating magnetic head

Claims (2)

(57) [Claims] An input signal is converted into digital data, the digital data is subjected to at least a blocking process and an encoding process, and then recorded on a track formed diagonally on a magnetic tape. in the digital information recording and reproducing apparatus, a Jimasu angle are located at the same position is disposed opposite to the double azimuth magnetic head according to the pair of different first and second magnetic heads to each other, and the double azimuth magnetic head A third magnetic head is provided on the peripheral side of the rotating drum, and in a normal recording / reproducing mode, different azimuth angles are set.
Comprising a first magnetic head and the third magnetic head of the double azimuth magnetic head is switched alternately performs recording / reproducing of digital data, in the case of long-time mode, the upper Symbol double the tape speed 1/2 The first magnetic head and the second magnetic head of the azimuth magnetic head are alternately switched to record / reproduce the compression-encoded digital data and the identification code indicating its recording mode. Digital information recording and reproducing device. 2. A standard mode upon reproduction based on the identification code.
The digital information recording / reproducing apparatus according to claim 1, wherein the mode and the long time mode are automatically switched .