JP3543595B2 - Digital magnetic recording and reproducing device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a digital magnetic recording and reproducing apparatus, such as a video tape recorder, for recording and reproducing digital image signals.
[0002]
[Prior art]
A digital magnetic recording / reproducing apparatus has various signal processing circuits. One method of diagnosing whether or not these signal processing circuits are functioning properly is to use test data. That is, predetermined test data is input to a signal processing circuit to be diagnosed, and 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.
[0003]
On the other hand, a digital magnetic recording / reproducing apparatus is composed of a recording system and a reproducing system, and 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 diagnosis is separately provided for each of the recording system and the reproduction 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]
Therefore, when performing such a diagnosis, it is conceivable to adopt a configuration in which the test data described above is input to the recording system and the output data of the recording system is input to the reproduction system as input data of the reproduction system. Then, by comparing the output data from the reproducing 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 reproducing system.
[0005]
By the way, the data amount of a digital image is very large as compared with character information and the like. In particular, a higher communication speed and a larger storage capacity are required for recording and reproducing moving images. Recently, there has been an increasing demand for digital magnetic recording / reproducing devices of the type capable of performing data compression. Data compression methods include a so-called reversible method in which data decompressed after compression completely matches 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. ) Based on variable-length coding.
[0006]
FIG. 5 shows a conventional digital magnetic recording / reproducing apparatus which can simultaneously diagnose both the signal processing circuits of the recording system and the reproducing system and which employs the irreversible data compression method. FIG. 3 is a block diagram showing a configuration. In this figure, a recording system 1 has a DCT calculation / variable length coding circuit 3 and a formatting / error correction coding circuit 4, and a reproduction system 2 has a deformatting / error correction decoding circuit 5 and an IDCT calculation / variable circuit. It has a long decoding circuit 6.
[0007]
The output of the recording system 1 is recorded on the magnetic tape 8 as image information via the magnetic head 7, and the image information recorded on the magnetic tape 8 is taken into the reproducing system 2 via the magnetic head 9. However, 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 an EE return), and the output data from the recording system 1 The 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.
[0008]
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 coding 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.
[0009]
The signal processing is performed as described above, and the data output from the recording system 1 is input to 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. Is That is, the data from the recording system 1 is first input to the deformattering / error correction decoding circuit 5, where the data is deformed and then error correction decoded. 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, which outputs the output data from the reproduction system 2 and the image input data input to the recording system 1. Are determined to be normal if they match, and determined to be abnormal if they do not match. This discrimination signal is displayed on a display unit (not shown).
[0011]
[Problems to be solved by the invention]
By the way, in order to diagnose the function of the signal processing system 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, it is necessary to use both data. Is required as a precondition. 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.
[0012]
Therefore, as shown in FIG. 5, a configuration in which the output side of the recording system 1 is EE-returned to the input side of the reproduction system 2 to simultaneously diagnose both the signal processing circuits of the recording system and the reproduction system. Does not cause any particular problem when applied to a digital magnetic recording / reproducing apparatus employing a reversible data compression method or an uncompressed method, but a digital magnetic recording / reproducing apparatus employing an irreversible data compression method. When applied to, sufficient diagnostic accuracy cannot be obtained. Therefore, in order to secure sufficient diagnostic accuracy, a self-diagnostic circuit 11 is provided for each of the recording system 1 and the reproducing system 2 with the space and cost disadvantages as described above. The diagnostic operation had to be performed.
[0013]
The present invention has been made in view of the above circumstances, and while adopting the irreversible data compression method, does not cause disadvantages in terms of space and cost, and provides both a recording system and a reproduction system. It is an object of the present invention to provide a digital magnetic recording / reproducing apparatus which can simultaneously diagnose functions of a signal processing circuit.
[0014]
[Means for Solving the Problems]
As means for solving the above problems, the invention according to claim 1 is to input image input data including one luminance signal and two color difference signals which have been converted from analog to digital, and perform a DCT operation on the input data to change the image input data. A DCT calculation / variable length coding circuit for performing long coding, 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, and A deformatting / error correction decoding circuit that performs error correction decoding after deforming the output data from the formatting / error correction encoding circuit, and an output data from the deforming / error correction decoding circuit. IDCT operation / variable length decoding circuit for performing IDCT operation after performing variable length decoding 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 operation / variable length decoding circuit and the image input data. In the apparatus, 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 operation / variable-length coding circuit, and 1DCT A diagnostic image input data limiting circuit for limiting the data value to be changed with a block as a minimum unit is provided.
[0015]
According to a second aspect of the present invention, in the first aspect of the present invention, the diagnostic image input data limiting circuit is configured to apply a function to the image input data such that a data value changes with an integral multiple of one DCT block as a minimum unit. It is characterized by adding restrictions.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
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.
[0017]
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 restriction circuit 12 is newly provided. The image input data restriction circuit 12 restricts the value of image input data input to the DCT calculation / variable length coding circuit 3 of the recording system 1 based on an input data restriction command signal from the self-diagnosis circuit 11. have.
[0018]
Specifically, the limitation of the value of the image input data means that the data values in one DCT block are made identical to the image input data input to the DCT operation / variable-length coding circuit 3 by 1DCT. This is to change a data value with a block or a block having an integral multiple of one DCT block as a minimum unit. 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.
[0019]
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 outputs an input data restriction command signal to the image input data restriction circuit 12. 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 operation / variable length coding circuit 3 from the external device.
[0020]
FIG. 2 is an explanatory diagram showing data values for frequency components in one DCT block when the image input data restriction circuit 12 restricts the frequency components. As shown in this figure, all data values in one DCT block are a1.
[0021]
As described above, the image input data sent from the external device to the recording system 1 in the diagnosis mode is subjected to the DCT after the image input data limiting circuit 12 restricts the data value to be changed with one DCT block as a minimum unit. It is input to the arithmetic / variable-length coding circuit 3. The DCT calculation / variable-length coding circuit 3 performs a DCT calculation on the image input data to which the restriction is applied, and then performs a variable-length coding.
[0022]
FIG. 3 is an explanatory diagram showing data values in one DCT block after such DCT operation and variable-length encoding have been performed by the DCT operation / variable-length encoding circuit 3. As shown in this figure, the DC component is b1, but the AC components are all zero. This is based on the fact that all data values in one DCT block have the same value, as shown in FIG.
[0023]
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 components are all zero as described above and do not appear, the data output from the IDCT conversion / variable-length decoding circuit 6 of the reproducing system 2 is eventually converted by the DCT operation / variable-length encoding of the recording system 1. This completely matches the image input data input to the circuit 3. Therefore, by examining the coincidence / mismatch of both data, it is possible to determine the presence or absence of an abnormality in the middle of the signal processing process. 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. And a match with the output data output from is detected, and if they match, it is determined to be normal, and if they do not match, it is determined to be normal.
[0024]
FIG. 4 is an explanatory diagram illustrating 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. In other words, 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 diagnosis mode. Needless to say, diagnosis can be performed using a more complicated pattern with different pixel values for each DCT block.
[0025]
【The invention's effect】
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, the data compression method is restricted by applying a certain limit to image input data. It is characterized by the fact that it is possible to make it seem reversible. Therefore, it is possible to apply the diagnostic processing using the test data to the configuration in which the output side of the recording system is EE-returned to the input side of the reproduction system. In spite of the adoption, it is possible to simultaneously diagnose the functions of the signal processing circuits of both the recording system and the reproduction system without incurring disadvantages in space and cost.
[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 operation / variable length coding circuit 3 after being restricted by an image input data restriction circuit 12 in FIG. 1;
4 is an explanatory diagram showing an example of an image obtained based on image input data restricted by an 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 Line 11 Self-diagnosis circuit 12 Image input data restriction circuit

Claims (2)

DCT calculation / variable length coding circuit for inputting image input data including one luminance signal and two color difference signals subjected to analog-digital conversion, performing DCT calculation on the input data and performing variable length coding,
A formatting / error correction encoding circuit that performs formatting after performing error correction encoding on output data from the DCT operation / variable length encoding circuit;
Deformatting / error correction decoding circuit for performing error correction decoding after deforming the output data from the formatting / error correction encoding circuit,
An IDCT operation / variable length decoding circuit for performing an IDCT operation after performing a variable length decoding on output data from the deformattering / error correction decoding circuit;
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 operation / variable length decoding circuit and the image input data;
In a digital magnetic recording and reproducing apparatus having
When the self-diagnosis circuit performs a diagnosis, the data values in one DCT block are made the same with respect to the image input data input to the DCT operation / variable-length coding circuit so that one DCT block is minimized. A diagnostic image input data limiting circuit that limits the data value to change as a unit,
A digital magnetic recording / reproducing apparatus characterized by being provided. The diagnostic image input data limiting circuit limits the image input data so that a data value changes with an integral multiple of one DCT block as a minimum unit.
2. The digital magnetic recording / reproducing apparatus according to claim 1, wherein:

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