JPS62287469A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To remove DC component of digital data sufficiently by providing plural converting means of different data converting system and corresponding plural reverse converting means and recording and reproducing after selecting the most suitable converting means and reverse converting means according to the property of inputted digital data. CONSTITUTION:In a data converting circuit 9, first and second memories 11, 12 become the first and second converting means for digital data, and every time digital data are inputted and address is changed successively, change the value of data accordingly, and convert to data constitution of small DC component. Third and fourth memories 14, 15 of a data converting circuit 10 are reverse converting means that correspond to a data converting system recorded in the first and second memories 11, 12 of the data converting circuit 9, and change the value of data and convert reversely to the original data constitution every time the digital data read out from a recording and reproducing section 5 are inputted and address is changed successively.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Industrial Application Field The present invention relates to a digital video tape recorder (hereinafter referred to as "digital
The present invention relates to a magnetic recording and reproducing device such as a data recorder that records and reproduces digital data other than images (abbreviated as TRJ) or images, and particularly relates to a magnetic recording and reproducing device that can efficiently remove DC components contained in digital data depending on the nature of the data.

BACKGROUND OF THE INVENTION In recent years, there has been a demand for higher image quality in video tape recorders, and progress has been made in the development of digital VTRs that digitize television video signals and enable high image quality recording and playback.

As shown in FIG. 8, such a digital VTR includes an A/D converter 1 that digitizes a video signal input from another image device, etc., and digital data from this A/D converter 1. a correction code generation circuit 2 that adds an error correction code to correct code errors during recording during playback; and a data conversion circuit that converts digital data to which this error correction code is added into a data configuration with less DC components. 3, a recording and reproducing unit 5 which inputs the digital data whose data structure has been converted through the rotary transformer 4 and records or reproduces it on a magnetic recording medium such as a magnetic tape;
A data inversion circuit 6 inputs the digital data read out from the recording and reproducing section 5 via the rotary transformer 4 and converts it back to the original data configuration, and inputs this inversely converted digital data and corrects code errors thereof. A correction circuit 7 and a D/A converter 8 convert the code error-corrected digital data into a video signal. Here, the rotary transformer 4 has a recording/reproducing section 5.
The high-speed rotating magnetic head, the data conversion circuit 3, and the data inverse conversion circuit 6 are connected to each other by a transformer while rotating.Since it is a transformer, AC components pass therethrough, but DC components do not pass therethrough.

Next, the reason for providing the data conversion circuit 3 will be explained. The digital data is It Q as shown in Figure 9.
It consists of a combination of II and “1”, and is converted into N RZ (Non Return T-
When magnetic recording is performed using the NRZ method, as shown in the lower part of FIG. In the signal, the number of l(OIt and "1" is random, and "OIt" may follow as in area A in FIG. 9, or Pa1 may follow as in area B. Then, Where the same value continues like the above region A or B, it becomes a DC component, and as a result, the above NRZ signal contains a large amount of DC component.However, the NRZ signal containing a large amount of DC component like this Since the signal does not pass through the rotary transformer 4, it is necessary to convert the signal to be recorded in the recording/reproducing section 5 from one containing a DC component, such as the NRZ signal, to a signal with the DC component removed. As shown in Fig. 10, the recording and reproducing characteristics of magnetic recording media such as magnetic tapes have the characteristic that low frequency parts and high frequency parts cannot be recorded.In other words, something close to a direct current component cannot be recorded.
It is necessary to convert it into a signal that removes it. For this reason,
The data conversion circuit 3 converts the digital data into a data structure with less DC components.

The data conversion in the data conversion circuit 3 is generally called mapping, in which input digital data is converted into another value according to a certain rule. The first data conversion method takes advantage of the fact that adjacent image data have strong correlation and similar data is continuous.
As shown in Figure 11, when 1, for example II OII, is input, it is converted to "128" and output, and the input "1" is "2".
55", input "2" is converted to "1" and output, and similar data is input continuously, but adjacent data is arranged in a discrete arrangement. However, with this conversion method, if there is no correlation in the image data, for example if the data is compressed, the data after conversion will not necessarily become discrete, and it may not be effective. The second data conversion method is called scrambled interleaved NRZI signal, which randomizes input digital data by adding random numbers. (Exclusive OR).By considering random numbers according to this logic, an NRZ signal containing a DC component is converted into a random NRZ signal.

Of the two data conversion methods above, the first data conversion method is extremely effective when there is a strong correlation between adjacent images, such as image data, and conversely, when data has little correlation between adjacent images, the first data conversion method is extremely effective. The first data conversion method described above is ineffective, and the second data conversion method is effective.

Problems to be Solved by the Invention However, in the conventional digital VTR shown in FIG. 8, the data conversion circuit 3 only had conversion means for one type of data conversion method. Correspondingly, the data inverse conversion circuit 6 also had only one type of inverse conversion means. Therefore, if the data conversion circuit 3 has only a conversion means of the first data conversion method that utilizes the correlation of image data, the DC component of image data with strong correlation between adjacent images is removed and the rotary Although it is possible to record and reproduce data in the recording/reproducing section 5 via the transformer 4, it is not possible to sufficiently remove DC components of uncorrelated compressed data or digital data other than images. The playback error rate was high. On the other hand, if the data conversion circuit 3 has only a conversion means of the second data conversion method using random numbers, it is possible to remove DC components from uncorrelated compressed data or digital data other than image data; This method was not necessarily effective for image data with strong contrast. In other words, when both highly correlated image data and non-image digital data are input, using only one conversion means will cause the DC component removal ability of the data conversion circuit 3 to change depending on the nature of the input digital data, and all digital It was not possible to efficiently remove the direct current component from the data.As a result, the quality of recorded and reproduced images deteriorated.The present invention aims to solve these problems. .

Means for Solving the Problems The means of the present invention for solving the above problems is a data conversion method that inputs image data obtained by digitizing a video signal or digital data other than images and converts it into a data structure with less DC components. a circuit, a recording and reproducing unit that inputs digital data whose data structure has been converted through a rotary transformer and records or reproduces it on a magnetic recording medium, and inputs the digital data read from this recording and reproducing unit through the rotary transformer. In a magnetic recording and reproducing device having a data inversion circuit that inverts the original data structure,
The data conversion circuit is provided with a plurality of conversion means having different data conversion methods for digital data, and the data inversion circuit is provided with a plurality of inverse conversion means corresponding to the data conversion methods of the data conversion circuit, and input This is done by a magnetic recording and reproducing apparatus which selects the most suitable converting means and inverse converting means according to the nature of the digital data for recording and reproducing.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of a magnetic recording/reproducing apparatus according to the present invention. This magnetic recording and reproducing device digitizes and records and reproduces video signals, such as a digital VTR, and includes an A/D converter 1, a correction code generation circuit 2, a data conversion circuit 9, and a rotary transformer 4. , a recording/reproducing section 5, a data inverse conversion circuit 10, and a correction circuit 7.

and a D/A converter 8.

The A/D converter 1 digitizes a video signal input from a television system, etc. not shown, and outputs image data. The correction code generation circuit 2 is connected to the A/D
An error correction code is added to the digital data output from the converter 1 to correct code errors during recording during reproduction. The data conversion circuit 9 receives the digital data to which the error correction code has been added by the correction code generation circuit 2 and converts it into a data structure with less DC components. The rotary transformer 4 connects the data conversion circuit 9 and the magnetic head of the recording/reproducing section 5, and since the magnetic head rotates at high speed, the transformer connection is performed while rotating. The recording/reproducing section 5 inputs the digital data whose data structure has been converted by the data converting circuit 9 via the rotary transformer 4, and records or reproduces it on a magnetic recording medium such as a magnetic tape.

The data inversion circuit 10 inputs the digital data read out from the recording/reproducing section 5 via the rotary transformer 4 and inversely converts it into the original data configuration. The correction circuit 7 inputs the digital data inversely converted by the data inverse conversion circuit 10, and corrects the code errors therein using the error correction code added by the correction code generation circuit 2. Further, the D/A converter 8 converts the digital data whose code errors have been corrected by the correction circuit 7 into a video signal, and sends the video signal to a television system or the like (not shown).

Here, in the present invention, the data conversion circuit 9 includes:
A plurality of conversion means with different data conversion methods for digital data are provided.

The data inverse conversion circuit 10 is provided with a plurality of inverse conversion means corresponding to the data conversion method of the data conversion circuit 9.

First, the data conversion circuit 9 has a first memory 11 and a second memory 12, as shown in FIG.

It consists of a changeover switch 13. The first memory 11 serves as a first conversion means for digital data, and stores a conversion table for converting input digital data into another value according to a certain rule.
It's OM. and.

Assume that the conversion method is, for example, the first data conversion method using the correlation of image data described above.

At each address of the first memory 11, for example, data to be converted according to the input and output relationship shown in FIG. The data value is converted accordingly, converting it into a data structure with less DC component. The second memory 12 serves as a second conversion means for digital data, and is, for example, a ROM in which a conversion table for converting input digital data into another value according to other rules is recorded. and.

If the conversion method is, for example, the second data conversion method using random numbers mentioned above, data to which an appropriate random number is added is recorded in each address of the second memory 12, and the digital data is Each time the data is input to the second memory 12 and the address changes sequentially, the data value is converted accordingly, and the data is converted into a data structure with less DC components. These first and second memories 11.12 are provided in parallel, and digital data from the correction code generation circuit 2 is commonly input to the address lines of both memories 11.12. The changeover switch 13 switches the output of the first memory 11 or the second memory 12, and is composed of, for example, a multiplexer. When recording digital data, for example, an operator operates an operation button or the like depending on the image quality and switches between the first and second memories 11 and 12 using the changeover switch 13, thereby selecting the optimum memory for the image. It is possible to select and record a suitable conversion method.

Next, the data inverse conversion circuit 10, as shown in FIG.
It consists of a third memory 14, a fourth memory 15, and a changeover switch 16. The third memory 14 serves as an inverse conversion means corresponding to the data conversion method 1 recorded in the first memory 11 of the data conversion circuit 9, for example, the first data conversion method described above. It is, for example, a ROM in which a conversion table that performs conversion in an inverse relationship to the conversion table recorded in the memory 11 is recorded. Then, the recording/reproducing section 5
The digital data read from the third memory 14 is input to the third memory 14, and each time the address sequentially changes, the data value is converted accordingly, and the data is converted back to the original data configuration. The fourth memory 15 serves as an inverse conversion means corresponding to the data conversion method recorded in the second memory 12 of the data conversion circuit 9, for example, the above-mentioned second data conversion method. For example, a ROM in which a conversion table that performs conversion in the opposite relationship to the conversion table recorded in the memory 12 is recorded.
It is. Then, the digital data read from the recording/reproducing section 5 is input to the fourth memory 15, and each time the address changes sequentially, the data value is converted accordingly, and the data value is converted back to the original data configuration. These third and fourth memories 14.15 are provided in parallel, and digital data from the rotary transformer 4 is commonly input to the address lines of the two memories 14.15. The changeover switch 16 switches the output of the third memory 14 or the fourth memory 15, and is composed of, for example, a multiplexer. When reproducing digital data, the operator operates operation buttons or the like in accordance with the data conversion method at the time of recording and switches between the third and fourth memories 14 and 15 using the changeover switch 16. It is possible to select the most suitable inverse transformation means for the image and reproduce it.

FIG. 4 is a block diagram showing a second embodiment of the present invention. This embodiment consists of the data conversion circuit 9 and the recording/reproducing section 5.
A mode recording circuit 17 is provided between the recording and reproducing section 5 and the data inversion circuit 10, and a mode determining circuit 18 is provided between the recording and reproducing section 5 and the data inversion circuit 10. The mode recording circuit 17
is a part of the magnetic recording medium of the recording/reproducing unit 5 that stores selection information as to whether the first memory 11 or the second memory 12 is selected as a conversion means for converting the digital data input to the data conversion circuit 9. As shown in FIG. 5, the selection information I is taken out from the changeover switch 13, and this selection information (■) is recorded on part of the audio track or the blanking of the video track on a magnetic tape or the like in the recording/reproducing section 5. The timing is now recorded.

The mode determination circuit 18 reads out the selection information I' recorded on the magnetic tape or the like of the recording/reproducing section 5 and converts it into a third memory 14 or a fourth memory 1 as a corresponding inverse conversion means.
5 is selected, selection information 1' is read out from the recording/reproducing section 5, and this selection information 1' is sent to the changeover switch 16 of the data inversion circuit 10 as shown in FIG. Then, by switching the changeover switch 16 according to this selection information 1', either the third memory 14 or the fourth memory 15 is selected.

In the case of this embodiment, simply by selecting the most suitable conversion means when recording digital data, this selection information I is automatically recorded in the recording and reproducing section 5, and during reproduction, the selection information I' is sent from the recording and reproducing section 5. can be read out and automatically select the optimal inverse conversion means.

FIG. 7 is a block diagram showing a third embodiment of the present invention. This embodiment includes an A/D converter 1 and a correction code generation circuit 2.
A data recognition circuit 19 is provided between the two. The data recognition circuit 19 determines whether adjacent digital data output from the A/D converter 1 have a strong correlation or no correlation, and performs data conversion according to the nature of the digital data. The optimum conversion means of the circuit 9 is automatically selected, and consists of, for example, one field or one frame image memory. The result determined by the data recognition circuit 19 is sent as a selection signal S to the changeover switch 13 (see FIG. 5) of the data conversion circuit 9, and the changeover switch 13 is switched according to the nature of the digital data. It has become. In the case of this embodiment, it is possible to automatically select the optimum conversion means and inverse conversion means according to the nature of the digital data for recording and reproduction.

In addition, in FIGS. 2 and 5, the data conversion circuit 9
Although only two memories are used as conversion means, the present invention is not limited to this, and three or more memories may be used depending on the type of data conversion method. Accordingly, the number of memories serving as the inverse conversion means of the data inverse conversion circuit 10 shown in FIGS. 3 and 6 may also be three or more.

In addition, in the above explanation, digital video signals that mainly digitize video signals and record and reproduce image data are used.
Although the TR has been described, the present invention is not limited thereto, and can be similarly applied to magnetic recording and reproducing apparatuses such as data recorders that directly input and record and reproduce digital data other than images.

In this case, the digital data may be input to the correction code generation circuit 2.

Effects of the Invention As described above, the present invention provides the data conversion circuit 9 with a plurality of conversion means (11, 12) having different data conversion methods for digital data, and the data inverse conversion circuit 10 includes a data conversion circuit. Since a plurality of inverse conversion means (14, 15) corresponding to the data conversion method of 9 are provided,
Recording and reproduction can be performed by selecting the optimum conversion means and inverse conversion means according to the nature of the input digital data.

Therefore, the data conversion circuit 9 can efficiently remove DC components by applying an optimal data conversion method to the input of highly correlated image data or digital data other than image data, for example. As a result, the error rate in recording and reproducing in the recording/reproducing section 5 is reduced, making it possible to record and reproduce with high image quality. In addition, when the mode recording circuit 17 and the mode determination circuit 18 are provided, selection information (■) of the conversion means of the data conversion circuit 9 can be recorded in the recording/reproducing section 5, and during reproduction, this selection information (■) can be recorded.
The optimal inverse transformation means can be automatically selected by

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the magnetic recording/reproducing apparatus according to the present invention, FIG. 2 is a block diagram showing details of a data conversion circuit, FIG. 3 is a block diagram showing details of a data inversion circuit, and FIG. The figure is a block diagram showing a second embodiment of the present invention, FIG. 5 is a block diagram showing details of a data conversion circuit in the second embodiment, and FIG. 6 is a block diagram showing details of a data inversion circuit in the second embodiment. A block diagram showing the details, FIG. 7 is a block diagram showing the third embodiment, FIG. 8 is a block diagram showing a conventional magnetic recording/reproducing device, and FIG. 9 is an explanation showing an example of digital data and its NRZ signal. 10 is a graph showing the recording and reproducing characteristics of a magnetic recording medium, and FIG. 11 is a graph showing an example of a data conversion method that utilizes data correlation to convert into a data structure with less DC components. 1... A/D converter 2... Correction code generation circuit 4... Rotary transformer 5... Recording and reproducing section 7... Correction circuit 8... D/A converter 9... Data Conversion circuit 1o...Data inverse conversion circuit 11...First memory (conversion means) 12...Second memory (conversion means) 13...Selector switch 14...Third memory (inverse Conversion means) 15... Fourth memory (inverse conversion means) 16... Changeover switch 17... Mode recording circuit 18... Mode determination circuit 1, I'... Selection information

Claims (2)

[Claims] (1) A data conversion circuit that inputs image data obtained by digitizing a video signal or digital data other than images and converts it into a data structure with less DC components, and converts the converted digital data through a rotary transformer. A magnetic recording device comprising: a recording and reproducing unit that inputs data and records or reproduces it on a magnetic recording medium; and a data inversion circuit that inputs digital data read from the recording and reproducing unit via the rotary transformer and converts it back to the original data configuration. In the playback device, the data conversion circuit is provided with a plurality of conversion means having different data conversion methods for digital data, and the data inversion circuit is provided with a plurality of inverse conversion means corresponding to the data conversion methods of the data conversion circuit. What is claimed is: 1. A magnetic recording and reproducing apparatus characterized in that the optimum converting means and inverse converting means are selected according to the properties of input digital data for recording and reproducing. (2) A mode recording circuit is provided between the data conversion circuit and the recording/reproducing section to record selection information of a converting means for converting input digital data onto a part of the magnetic recording medium of the recording/reproducing section; A mode determining circuit is provided between the recording/reproducing section and the data inversion circuit for reading selection information recorded on the magnetic recording medium and selecting the corresponding inversion means. The magnetic recording and reproducing device according to scope 1.