JP3144095B2 - Digital information recording and playback 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 information recording / reproducing apparatus having means for reducing an error rate of a reproduced RF signal.

[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. 6 is a block diagram 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 extraction unit for extracting effective information from an input image signal (digital information), for example, a digital luminance signal Y formed from three primary color signals R, G, B from a video camera or the like. , Digital color difference signals 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. For example, as shown in FIG. 7A, the luminance signal is divided into four frames by dividing a screen over two frames.
A large number of unit blocks of [4 pixels × 2 frames] are formed,
Here, the information amount is reduced to about 84 Mbps. In addition, as shown in FIG. 7B, the information of x is reduced by the sub-sampling of the color difference signal, 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 as Japanese Patent Application No. 1-143391, and is formed by an adaptive scrambling circuit 8A and a precoder 8B for a partial response / 4 detection method as shown in FIG. ing.

In the adaptive scrambling circuit 8A, a plurality of M-sequence scramble circuits are prepared, and among these, an M-sequence signal which can provide an output with the least high-frequency component and DC component with respect to the input signal is selected. It has been made like that.

Further, the precoder 8B, the arithmetic processing to be 1/1-D ² by using an adder M for performing the calculation of the delay elements D and modulo 2 bit period as shown in FIG. 9 (a) Things. Such a precoder 8B is used in the field of data communication, and precoded data corresponds to interleaved NRZi (partial response / 4 transmission system).

The transmission characteristic of the transmission line conforming to the partial response 4 is a band pass type as shown in FIG. 9B, and a signal having a frequency component equal to or higher than the Nyquist frequency fb / 2 is theoretically "0". can do. The dotted line indicates the amplitude characteristic under the Nyquist condition when the roll-off rate K = 0.5.

Incidentally, since the electromagnetic conversion system in the magnetic recording apparatus is a differential system (1-D), a decoder (1 + D) for adding the output of the 1-bit delay element D is provided on the reproducing side as described later. If you have a partial response 4
If the signal having the Nyquist frequency signal component or less is transmitted as shown by the curve in FIG. 9B in the transmission system of (1), it becomes possible to extract data without intersymbol interference on the reproducing side.

The data converted into 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 tracking pilot signal, a preamble, a postamble and the like are applied to the data for one track immediately before the recording amplifier.

In this apparatus, as shown in FIG. 10, a flying erase head 10C is provided for a rotating drum 10 having rotating magnetic heads 10A and 10B. Then, an erasing signal is supplied from the erasing oscillator 11 to the flying erase head 10C via the output amplifier 12, and when the data on the recording track is rewritten, the data recorded on the immediately preceding track is erased. The configuration is as follows. The rotating heads 10A, 10A
B may be arranged at the same angular position with a step.

The erasing signal frequency supplied to the flying erase head 10C is set to the Nyquist frequency fb / 2 shown in FIG. 9B or higher. It is preferable that the frequency fb / 2 is made to match the Nyquist frequency fb / 2 using a clock in the recording apparatus.
It may be slightly lower than 2.

When the frequency of the erasure signal is near the Nyquist frequency, the frequency higher than the Nyquist frequency can be sufficiently attenuated on the reproduction side in the data recorded in the transmission system of the partial response 4 as described above. Even if the data remains on the magnetic tape, the data is sufficiently attenuated at the data detection point, and an excellent effect that the error rate hardly deteriorates can be obtained.

FIG. 11 is a block diagram of a reproducing system of the above-described digital information magnetic recording / reproducing apparatus.
The recording data precoded by the partial response 4 in the recording system can be recorded on the ME tape T with the shortest recording wavelength of about 0.5 μm, and the relative speed between the tape heads is about 10 m / s. , About 20M
In the frequency band of Hz, digital data of 40 Mbps is transferred. This recording data is taken into a channel decoder 32 via a pair of rotary heads 10A and 10B and reproduction amplifiers 31A and 31B.

In the channel decoder 32, the reproduced signal waveform is shaped by an adaptive equalizer 33, and at the same time, supplied to an arithmetic circuit 34 whose transfer characteristic is (1 + D) by a 1-bit delay element D. And
The Nyquist frequency f described above in the encoding circuit 35 constituted by a Viterbi decoder, a descrambling circuit, etc.
The signal of b / 2 or less is restored and converted into a binary signal by the data detector 36. The data detector 36 has a PLL circuit 3
The clock signal formed at 7 is supplied.

The demodulated signal converted to binary data further includes T
The jitter component is removed via the BC 38, and the image-based recording data is subjected to error correction by the ECC circuit 39A. Similarly, the audio recording data is subjected to error correction by the ECC circuit 39B, and the audio signal is demodulated by the audio data processing unit 41.

Numeral 40 encodes a digital code (blocking, framing, etc.) band-compressed on the recording side, and switches from a recording sample clock to a signal sample clock for a luminance signal component.
A predetermined interpolation process is performed and output as a digital luminance signal Y 'and digital color difference signals U' and V '.

[0024]

Various algorithms have been proposed for the algorithm for setting the tap coefficient of the equalizer which is considered to be the best in the adaptive equalizer 33 (Automaticc Equalization) of the reproduction system. In the method of the part, the intersymbol interference value of the equalized signal waveform is obtained as an absolute value, and the tap coefficient of the equalizer is automatically set so that the absolute value is reduced.

However, such an equalizer responds to a sudden change in the frequency characteristic of the reproduced data due to instantaneous clogging or dropout of the magnetic head during data recording / reproducing. It operates to equalize the reproduced data whose frequency characteristics have changed.

As a result, the equalizer may set a tap coefficient which is considerably far from the normal operation center point, and the function as the equalizer may be lost from the convergence direction to the divergence direction due to the algorithm. .

[0027]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a first invention is to preliminarily determine the recording / reproducing characteristics of a single magnetic tape or a cassette-formed magnetic tape. The standard tap coefficient information is recorded in the tape case or cassette, and the value is transferred to the tap coefficient setting unit of the adaptive equalizer when the magnetic tape is mounted. The optimum tap coefficient is set while evaluating the signal waveform being reproduced within a predetermined range from the standard tap coefficient thus obtained.

In the second invention, when a magnetic tape is mounted in the apparatus, it is determined whether or not the tape is a virgin tape, and when it is determined that the tape is a virgin tape, a test is performed before reproduction. A process of recording a signal and reading out the test signal is added. Then, the optimum tap coefficient obtained by this process is determined as a standard tap coefficient, the operating center point of the adaptive equalizer is set with the standard tap coefficient, and this value is attached to the magnetic tape. The standard tap coefficient of the magnetic tape is transferred to the storage means and stored.

[0029]

An apparatus for magnetically recording and reproducing digital information greatly depends on characteristics of an RF system including a magnetic tape, a head, and a recording / reproducing system. The characteristics will change greatly. Since the present invention sets a standard coefficient for the equalizer of the magnetic tape at the time of installation in the apparatus, and during the reproduction, an optimal tap coefficient is generated around the standard tap coefficient, Stable reproduction characteristics can be maintained even when clogging or dropout occurs in which the frequency characteristics of the reproduction RF signal suddenly change during reproduction.

[0030]

FIG. 1 is a block diagram of a reproducing-side RF signal equalizing section in a digital information recording / reproducing apparatus according to the present invention. In the figure, reference numeral 20 denotes a cassette case having a built-in magnetic tape, 21 denotes an IC board provided in the cassette case 20, and the IC board 21 has various data related to a magnetic tape and its recording data. Is stored.

Reference numeral 23 denotes a connector having four spring pieces 24 which come into contact with the contacts of the IC substrate when the cassette case 20 is loaded into the apparatus. Information is exchanged via the connector 23. Set CPU
25.

When the loaded cassette case 20 is in a rotating state, a tape is drawn on a rotating drum (not shown), and the recording / reproducing rotary head 10 is mounted on the tape.
(A, B) collide. 26 denotes a reproduction amplifier, and 27 denotes an adaptive equalizer for equalizing the signal waveform of the reproduction RF signal output from the reproduction amplifier.

As is well known, the adaptive equalizer 27 includes delay elements 27A and 27 for providing a one-bit delay.
B, 27C and coefficient units 27D, 27E, 27F, 27G
And the configuration is such that the output of each coefficient unit is added by the combining circuit 27H. Then, by setting the tap coefficients (multiplication coefficients) of the respective coefficient units 27 (D to G) from the outside, waveform shaping that minimizes intersymbol interference is performed.

Reference numerals 28 and 29 denote magnetic fields proposed by the present applicant earlier.
Applied to recording / reproducing devices (Japanese Patent Application No. 2-412921)
Equivalent error judgment cycle corresponding to the equalizer arithmetic processing
2 shows a path and a tap coefficient generator, and error data output from the equalization error determination circuit 28 is sequentially supplied to a microprocessor 30 via a control bus in the apparatus.

The microprocessor 30 has an algorithm for calculating a tap coefficient in a direction in which the intersymbol interference is reduced based on the error data, and the output is output to the tap coefficient generator 29. The output of the tap coefficient generator 29 is supplied to each of the coefficient units 27 (D to G), and the control is performed so that the intersymbol interference is minimized automatically.

According to the first aspect of the present invention, by providing the above-described configuration on the magnetic tape side and the reproducing side of the apparatus,
The following operational effects can be obtained. First, a magnetic tape produced at a factory or the like has specific recording / reproducing characteristics according to a manufacturing method and a magnetic material, and information indicating the specific recording / reproducing characteristics is provided in a cassette tape. 22. Since this information is slightly different for each manufacturing date and each manufacturing lot even for the same type of tape, the recording / reproducing characteristics are evaluated for each original magnetic tape drum, and the evaluation data is written to the memory 22. .

As shown in the flowchart of FIG. 2, when the cassette tape 20 made into a cassette is mounted on the digital information recording / reproducing apparatus of the present invention, the tape evaluation data is transmitted to the CPU 25 via the connector 23. Is read. Among the read evaluation data, information on the recording / reproducing characteristics is decoded by the microprocessor 30 and supplied to the standard tap coefficient setting unit of the tap coefficient generator 29.
The center coefficient value of each coefficient unit 27 (D to G) forming the adaptive equalizer 27 is used. Further, the moving range of the tap coefficient indicating the center coefficient value is limited to be within a predetermined range.

When this setting is made, the magnetic tape is set to the standby state for reproduction or recording. The digital RF signal output by the reproduction is subjected to waveform shaping by the adaptive equalizer 27 as described above, for example, as shown in FIG.
When the reproduced RF signal having the intersymbol interference as shown in FIG. 3 also passes through the adaptive equalizer 27, the value becomes close to "0" at each sample interval point as shown in FIG. Waveform shaping is performed.

This output waveform is output to the equalization error setting circuit 2.
8, the error data is supplied to the microprocessor 30 when the intersymbol interference increases due to tape unevenness or the like, and a tap in a direction to reduce the intersymbol interference by an algorithm stored therein. The coefficients are output to the coefficient generator of the tap coefficient generator 29. When the tap coefficient generator 29 determines that this value is within the limited range of the standard tap coefficient set first, the tap coefficient of the adaptive equalizer 27 is made variable based on this data, and the Is controlled in a direction to reduce However, when the error data output from the equalization error determination circuit 28 indicates a tap coefficient larger than the moving range of the standard tap coefficient initially set, the tap coefficient is calculated by limiting the upper or lower limit of the moving range. Algorithm to diverge due to clogging, dropout, etc., to prevent erroneous equalization.

FIG. 4 shows a second embodiment of the present invention in which the operation of the above-mentioned basic adaptive equalizer is further developed. In this figure, reference numeral 40 denotes a tape cassette provided with a memory section 41 in the cassette as described above. Data of the memory section 41 is read out from the connector 42 which comes into contact with the tape cassette, and is taken into the CPU 43. As described later, when the optimum standard tap coefficient set by the algorithm is obtained from the evaluation data on the intersymbol interference of the reproduced digital RF signal,
It is configured to be stored in the memory 41 in the cassette tape via U43.

Reference numeral 44 denotes a reproduction amplifier. The reproduction output signal is supplied to an adaptive equalizer 45. Then, as in the configuration example of FIG. 1, equalization processing of the reproduced digital RF signal is performed by the tap coefficient set in the adaptive equalizer 45, and the output is supplied to the equalization error determination circuit 46. .
When the error data of the intersymbol interference is detected by the equalization error judgment circuit 46, a tap coefficient in the direction in which the intersymbol interference is reduced is calculated by the algorithm of the microprocessor 48, and the calculation result is used as the tap coefficient generator 4.
7 is supplied to each coefficient unit (5 steps) of the adaptive equalizer 45.

In the case of this embodiment, when a cassette tape is mounted on a digital information recording / reproducing apparatus as shown in the flowchart of FIG. 5, it is determined whether or not this cassette tape is a virgin tape (unrecorded tape). (100)
Done in In the case of an unrecorded tape, the flag 0 is stored in the memory section in the cassette tape. In this case, the above-described test oscillator 49 is driven, and this signal is transmitted to the REC processing section 50, the recording amplifier 51, and the REC. The rotary head 10 via the switch SW ₂ set on the side
(A, B) is supplied, predetermined recording data is recorded for several seconds, and the tape is slightly rewound to read out the recorded test signal (101). The digital reproduced RF signal read in this step is shaped by an adaptive equalizer 44, and its output is evaluated by an equalization error determination circuit 46 to detect the degree of intersymbol interference as error data.

This data is recorded in the microprocessor 48. When such writing and reading tests are performed Q times, the microprocessor 4 calculates the average value or the square mean value of the error data indicating the intersymbol interference obtained each time.
8 determines the optimum standard tap coefficient for the recording / reproducing characteristics of the tape (S101), and sets the standard tap coefficient in the tap coefficient generator 47 based on the calculation result.

The standard tap coefficient is written into the memory section of the cassette tape 40 via the CPU 43, and a flag 1 is set as information indicating that the standard tap coefficient has been set . (S103) Therefore, when a tape with the flack 1 is mounted on the memory section 41 of the cassette tape, it is determined that the tape is not a virgin tape. Such a tape is used in the same manner as in the flowchart shown in FIG. The standard tap coefficient is immediately set in the adaptive equalizer 45 without performing the writing / reading test after the mounting, and the waveform shaping without the intersymbol interference is performed (S104). In addition, the memory unit attached to the cassette tape may be a unit for magnetically writing and reading.

[0045]

As described above, in the digital information recording / reproducing apparatus of the present invention, at least information indicating the recording / reproducing characteristics of the magnetic tape is recorded on the cassette tape side. Even if a tape or a new tape to be developed in the future is used in a recording / reproducing apparatus for digital information, the tap coefficient of the adaptive equalizer can be automatically set to always be optimal, and the error rate is extremely small. It can be a magnetic recording / reproducing device.

Also, the tap coefficients set in the adaptive equalizer are standard tap coefficients that provide optimal intersymbol interference.
In addition, since the adaptive equalizer is set to operate only within a predetermined range around the tap coefficient, the best tap coefficient is detected even when a clog or dropout is encountered during tape playback. The algorithm does not diverge or malfunctions, and an adaptive equalizer that is more stable can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an adaptive equalizer for digitally reproduced RF signals in a digital information recording and reproducing apparatus according to the present invention.

FIG. 2 is a flowchart of setting tap coefficients set in an adaptive equalizer.

FIG. 3 is an explanatory diagram of a signal waveform for removing intersymbol interference.

FIG. 4 is a schematic diagram of an adaptive equalizer for digitally reproduced RF signals according to another embodiment of the present invention.

FIG. 5 is a flowchart in the case of setting with a tap coefficient corresponding to a recording tape.

FIG. 6 is a block diagram showing an example of a magnetic recording system for digital information according to the present invention.

FIG. 7 is an explanatory diagram of encoding for compressing recording data.

FIG. 8 is a block diagram illustrating an example of a channel encoder.

9A is a transmission circuit diagram applied to the transmission system of the partial response 4 and FIG. 9B is a frequency characteristic diagram showing the output of the transmission circuit.

FIG. 10 is an explanatory diagram showing an example of the arrangement of a magnetic head of a rotating drum.

FIG. 11 is a block diagram illustrating a configuration example of a reproduction circuit that reproduces digital information recorded on a magnetic tape.

[Explanation of symbols]

 Reference Signs List 20 tape cassette 21 IC board 22 memory 23 connector 25 CPU 27 adaptive equalizer 28 equalization error determination circuit 29 tap coefficient generator 30 microcomputer

Claims (4)

(57) [Claims] A magnetic head for reproducing digital information recorded on a magnetic tape, an adaptive equalizer for equalizing an RF signal reproduced by the magnetic head, and an output waveform of the adaptive equalizer are evaluated. An equalization error determination circuit for detecting the equalization error, a microprocessor for calculating an optimum tap coefficient of the adaptive equalizer from a determination output output from the equalization error determination circuit, and a microprocessor controlled by the microprocessor. in the recording and reproducing apparatus of the digital information and a tap coefficient setting device for setting a predetermined coefficient to the coefficient unit of the adaptive equalizer is, the cassette tape to be played to the tap coefficient setter is <br A digital information recording / reproducing apparatus characterized in that information indicating recording / reproducing characteristics of a magnetic tape is inputted as a standard tap coefficient when it is mounted. 2. The digital information recording / reproducing apparatus according to claim 1, wherein the information indicating the recording / reproducing characteristics of the magnetic tape is supplied by an IC memory provided in a cassette of the magnetic tape. . 3. A magnetic head for reproducing digital information recorded on a magnetic tape, an adaptive equalizer for equalizing an RF signal reproduced by the magnetic head, and an output waveform of the adaptive equalizer are evaluated. An equalization error determination circuit for detecting the equalization error, a microprocessor for calculating an optimum tap coefficient of the adaptive equalizer from a determination output output from the equalization error determination circuit, and a microprocessor controlled by the microprocessor. A tap coefficient setting device that sets a predetermined coefficient for the coefficient device of the adaptive equalizer, and for the attached magnetic tape,
A test signal recording means for recording a test signal in advance is provided, and a standard tap coefficient is set based on an equalization error obtained when reproducing the magnetic tape on which the test signal is recorded. A recording / reproducing apparatus for digital information, wherein the apparatus is configured to have a standard value of a coefficient. 4. An operation of discriminating whether a magnetic tape on which data is to be recorded is an unrecorded tape or a recorded tape, recording a test signal only when it is determined to be an unrecorded tape, and evaluating a reproduced equalized output thereof. 4. The digital information recording / reproducing apparatus according to claim 3, wherein the digital information is recorded.