JPH11191268A - Digital magnetic recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable diagnosing simultaneously functions of both signal processing circuits of a signal system and a reproduction system without being handicapped by a space and a cost, though a data compression system of a nonreversible system is adopted. SOLUTION: In a diagnosis mode, a picture input data limiting circuit 12 limits picture input data inputted to a DCT operation variable length coding 3 so that a data value is varied making 1 DCT block or a block having magnitude of an integer multiple of 1 DCT block as the maximum unit. In DCT operation variable length coding, code quantity of a DC component is not reduced in a signal processing of after that as an AC component, also all AC components are made zero. and do not appear. Therefore. picture input data inputted to a recording system 1 coincides with output data from a reproducing system 2 perfectly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital magnetic recording / reproducing apparatus, such as a video tape recorder, for recording / reproducing a digital image signal.

[0002]

2. Description of the Related Art Digital magnetic recording / reproducing apparatuses have various signal processing circuits. One of the techniques for diagnosing whether or not these signal processing circuits are functioning properly is as follows.
Some use test data. That is, predetermined test data is input to a signal processing circuit to be diagnosed,
The output data of the signal processing circuit is compared with expected value data obtained in advance based on the input test data,
If they match, it is diagnosed as normal, and if they do not match, it is diagnosed as abnormal.

On the other hand, a digital magnetic recording / reproducing apparatus is composed of a recording system and a reproducing system. The recording system and the reproducing system have their own signal processing circuits independently of each other. Therefore, if a configuration is provided in which a diagnostic circuit for performing the above-described diagnosis is separately provided for each of the recording system and the reproducing system, it is possible to easily perform diagnosis for all the signal processing circuits in the apparatus. The circuit scale in the device increases, which is disadvantageous in terms of space and cost.

[0004] In order to perform such a diagnosis, it is conceivable to adopt a configuration in which the test data described above is input to a recording system, and output data of the recording system is input to the reproduction system as input data of the reproduction system. Can be Then, by comparing the output data from the reproduction system with the test data input to the recording system, it is possible to simultaneously diagnose the signal processing circuits of both the recording system and the reproduction system.

By the way, the data amount of a digital image is
It is very large compared to text information, etc.
In order to record and reproduce moving images, higher communication speeds and larger storage capacities are required. Recently, there has been an increasing demand for digital magnetic recording / reproducing devices capable of performing data compression. Is coming. Data compression methods include a so-called reversible method in which data decompressed after compression completely matches the original data before compression, and a so-called irreversible method in which data does not match because original data is partially lost. . In applications where image quality degradation is not allowed, a reversible method is adopted. In applications where image quality degradation is allowed to some extent, an irreversible method is adopted. Variable-length coding).

FIG. 5 shows a conventional digital magnetic recording system in which a signal processing circuit of both a recording system and a reproducing system can be diagnosed at the same time. FIG. 3 is a block diagram illustrating a configuration of a playback device. In this figure, a recording system 1 has a DCT operation / variable length encoding circuit 3 and a formatting / error correction encoding circuit 4, and a reproducing system 2 has a deformatting / error correction decoding circuit 5 and an IDCT operation / variable circuit. It has a long decoding circuit 6.

The output of the recording system 1 is recorded on a magnetic tape 8 as image information via a magnetic head 7, and the image information recorded on the magnetic tape 8 is taken into a reproducing system 2 via a magnetic head 9. In order to perform self-diagnosis, the output side of the recording system 1 and the input side of the reproduction system 2 are connected by a line 10 (this connection is called EE return). The output data is input to the reproduction system 2 as input data of the reproduction system 2. The reproduction data from the reproduction system 2 is output to an external device such as a TV receiver and also to the self-diagnosis circuit 11. The self-diagnosis circuit 11 compares the reproduction data from the reproduction system 2 with the image input data input to the recording system 1, and based on the comparison, the signal processing circuits of the recording system 1 and the reproduction system 2 operate normally. And outputs a determination signal as to whether or not it functions.

Next, the operation of the conventional digital magnetic recording / reproducing apparatus configured as described above will be described. First,
Image input data including one analog-digital converted luminance signal and two color difference signals is input to a DCT operation / variable length encoding circuit 3 from an external device (not shown) such as a TV receiver. After the DCT operation is performed,
Variable length coding is performed. The data subjected to the variable length coding is input from the DCT operation / variable length coding circuit 3 to the formatting / error correction coding circuit 4, where the data is added with a parity bit and subjected to correction coding. Formatting is performed.

The signal processing is performed as described above, and the recording system 1
Is output from the reproduction system 2 through the line 10.
And the signal processing is performed in the reverse order of the signal processing in the recording system 1. That is, the data from the recording system 1 is first input to the deformattering / error correction decoding circuit 5, where the error correction decoding is performed after the reformatting. The data on which the error correction decoding has been performed is input from the deformattering / error correction decoding circuit 5 to the IDCT operation / variable length decoding circuit 6, where the deforming is performed after the variable length decoding is performed.

[0010] The output data from the reproduction system 2 after the reformatting is performed is output to the self-diagnosis circuit 11.
The self-diagnosis circuit 11 compares the output data from the reproduction system 2 with the image input data input to the recording system 1,
If they match, it is determined to be normal, and if they do not match, it is determined to be abnormal. This discrimination signal is displayed on a display unit not shown.

[0011]

The function of the signal processing system is diagnosed based on the coincidence / mismatch between the image input data input to the recording system 1 and the output data output from the reproduction system 2. For this purpose, it is required as a precondition that the two data should be originally identical. However, as described above, in the case of irreversible data compression, part of the original data is lost in the process of compression / decompression, so that the image input data of the recording system 1 and the output data of the reproduction system 2 are lost. Do not essentially match.

Therefore, as shown in FIG. 5, by performing the EE return of the output side of the recording system 1 to the input side of the reproduction system 2, it is possible to simultaneously diagnose the signal processing circuits of both the recording system and the reproduction system. Is not particularly problematic when applied to a digital magnetic recording / reproducing apparatus employing a reversible data compression method or a non-compression method. When applied to a recording / reproducing device, sufficient diagnostic accuracy cannot be obtained. Therefore, in order to ensure sufficient diagnostic accuracy, a self-diagnosis circuit 11 is provided for each of the recording system 1 and the reproduction system 2 with the above-mentioned space and cost disadvantages taken into consideration. The diagnostic operation had to be performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and while adopting an irreversible data compression method, does not introduce disadvantages in terms of space and cost. It is an object of the present invention to provide a digital magnetic recording / reproducing apparatus capable of simultaneously diagnosing the functions of both signal processing circuits.

[0014]

As means for solving the above-mentioned problems, the present invention according to the first aspect of the present invention is to input image input data including one luminance signal and two color difference signals which are analog-digital converted. And a DCT operation / variable length coding circuit for performing variable length coding after performing a DCT operation, and performing formatting after performing error correction coding on output data from the DCT operation / variable length coding circuit. A formatting / error correction encoding circuit, a deformatting / error correction decoding circuit for performing error correction decoding after deforming output data from the formatting / error correction encoding circuit, and the deformatting / error correction decoding After performing variable length decoding on the output data from the
An IDCT operation / variable length decoding circuit for performing a DCT operation;
A self-diagnosis circuit for diagnosing the presence or absence of an abnormality in a signal processing system based on a comparison between output data from the IDCT calculation / variable length decoding circuit and the image input data At
When the self-diagnosis circuit performs a diagnosis, each data value in one DCT block is made the same with respect to the image input data input to the DCT calculation / variable-length coding circuit so that one DCT block is minimized. A diagnostic image input data limiting circuit for limiting the data value to change as a unit is provided.

According to a second aspect of the present invention, in the first aspect of the present invention, the diagnostic image input data limiting circuit includes one
The image input data is restricted so that the data value changes with an integral multiple of the DCT block as a minimum unit.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. However, in FIG. 1, the same components as those in FIG. 5 are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 is a block diagram showing the configuration of the embodiment of the present invention. FIG. 1 differs from FIG. 5 in that an image input data limiting circuit 12 is newly provided. The image input data limiting circuit 12 outputs the D signal of the recording system 1 based on the input data limiting command signal from the self-diagnosis circuit 11.
It has a function of limiting the value of image input data input to the CT operation / variable length coding circuit 3.

The restriction on the value of the image input data is, specifically, that the data values in one DCT block are the same as the image input data input to the DCT operation / variable length coding circuit 3. In other words, the data value is changed with a minimum unit of one DCT block or a block having an integral multiple of one DCT block. In the present embodiment, the size of one DCT block is set to 8 × 8 pixels according to the consumer DV standard or the like.

Next, the operation of the present embodiment configured as described above will be described. When switching from the normal recording mode or the reproduction mode to the diagnosis mode, the self-diagnosis circuit 11 sends the input data restriction command signal to the image input data restriction circuit 12.
Output to The image input data restriction circuit 12 receives the input data restriction command signal, and imposes the above restriction on the image input data input to the DCT calculation / variable length coding circuit 3 from an external device.

FIG. 2 is an explanatory diagram showing data values for frequency components in one DCT block when the image data is restricted by the image input data restriction circuit 12. As shown in this figure, all data values in one DCT block are a1.

As described above, the image input data sent from the external device to the recording system 1 in the diagnostic mode is limited by the image input data limiting circuit 12 so that the data value changes with one DCT block as a minimum unit. After that, it is input to the DCT operation / variable length coding circuit 3. D
The CT operation / variable length coding circuit 3 performs a variable length coding after performing a DCT operation on the image input data subjected to the restriction.

FIG. 3 shows a DCT operation / variable length coding circuit 3
FIG. 3 is an explanatory diagram showing data values in one DCT block after such DCT operation and variable-length coding have been performed. As shown in this figure, the DC component is b1, but the AC components are all zero. this is,
As shown in FIG. 2, this is based on the fact that all data values in one DCT block have the same value.

As is well known, the DC component is transmitted as it is without reducing the code amount unlike the AC component in the subsequent signal processing process. On the other hand, since the AC component does not appear as all zeros as described above,
As a result, the data output from the IDCT conversion / variable length decoding circuit 6 of the reproduction system 2 completely matches the image input data input to the DCT operation / variable length coding circuit 3 of the recording system 1. . Therefore, by examining the coincidence / mismatch of both data, it is possible to determine the presence or absence of an abnormality in the signal processing process in the middle. That is, the self-diagnosis circuit 11 performs the IDCT conversion / variable-length decoding circuit 6 of the reproduction system 2 based on the image input data restricted by the image input data restriction circuit 12 and the image input data restricted by the restriction. Is detected, it is determined that the data is normal if they match, and it is determined that they are normal if they do not match.

FIG. 4 is an explanatory diagram showing an example of an image obtained based on the image input data subjected to the above-described restriction by the image input data restriction circuit 12. In this figure,
n1, n2, and n3 indicate preset integer values, and DB indicates the width of one DCT block. That is, this image is composed of seven blocks having a size of n1 DB × n3 DB, two blocks having a size of n2 DB × n2 DB, and one block having a size of n2 DB × n3 DB. Block. Each pixel in these blocks has the same pixel value. FIG. 4 shows a simple image pattern used in the diagnostic mode.
Diagnosis can be performed using a more complicated pattern with different pixel values for each CT block.

[0025]

As described above, according to the present invention, even in a digital magnetic recording / reproducing apparatus which performs irreversible data compression, in the diagnostic mode, image input data is restricted by a certain limit. It is characterized in that the data compression system can be apparently made a reversible system. Therefore, it is possible to apply the diagnostic processing using test data to a configuration in which the output side of the recording system is EE-returned to the input side of the reproduction system,
In fact, although the lossy data compression method is adopted, it is possible to simultaneously diagnose the functions of the signal processing circuits of both the recording system and the reproduction system without incurring a space and cost disadvantage. become able to.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a digital magnetic recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing data values of frequency components in one DCT block when a restriction is applied by an image input data restriction circuit 12 in FIG. 1;

FIG. 3 is an explanatory diagram showing data values in one DCT block after being subjected to processing by a DCT calculation / variable length coding circuit 3 after being restricted by an image input data restriction circuit 12 in FIG. 1;

FIG. 4 is an explanatory diagram showing an example of an image obtained based on image input data restricted by the image input data restriction circuit 12 in FIG. 1;

FIG. 5 is a block diagram showing a configuration of a conventional digital magnetic recording / reproducing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Recording system 2 Reproduction system 3 DCT calculation / variable length coding circuit 4 Formatting / error correction coding circuit 5 Deformatting / error correction decoding circuit 6 IDCT conversion / variable length decoding circuit 7 Magnetic head 8 Magnetic tape 9 Magnetic head 10 lines 11 self-diagnosis circuit 12 image input data restriction circuit

Claims (2)

[Claims] 1. An image input data including one luminance signal and two color difference signals which have been subjected to analog-digital conversion, and are subjected to DCT operation and then subjected to variable length coding.
A CT calculation / variable length coding circuit; a formatting / error correction coding circuit for performing formatting after performing error correction coding on output data from the DCT calculation / variable length coding circuit; A deformatting / error correction decoding circuit for performing error correction decoding after deforming the output data from the correction encoding circuit; anda variable length decoding for the output data from the deforming / error correction decoding circuit. IDCT after going
An IDCT operation / variable length decoding circuit for performing an operation; and a diagnosis as to whether or not there is an abnormality in the signal processing system based on a comparison between output data from the IDCT operation / variable length decoding circuit and the image input data. A digital magnetic recording / reproducing apparatus comprising: a self-diagnosis circuit, wherein when the self-diagnosis circuit performs a diagnosis, one DCT is applied to the image input data input to the DCT calculation / variable-length coding circuit. A digital magnetic recording / reproducing apparatus comprising: a diagnostic image input data limiting circuit for limiting each data value in a block to be the same and changing the data value in one DCT block as a minimum unit. 2. The diagnostic image input data limiting circuit according to claim 1, wherein
2. The digital magnetic recording / reproducing apparatus according to claim 1, wherein a limit is applied to the image input data so that a data value changes with an integral multiple of a DCT block as a minimum unit.