JP2671749B2 - Recording apparatus, reproducing apparatus, recording method and reproducing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording device and a reproducing device , a recording method and a reproducing method which are used for highly efficient encoding and recording or transmission of a video signal.

[0002]

2. Description of the Related Art As a method for reducing the data amount of a video signal, a method using high efficiency coding is known. High-efficiency coding is a coding method that removes the redundancy of a video signal to reduce the amount of data.

As a high-efficiency coding method, a method of collecting adjacent pixels to form a block and compressing each block using orthogonal transform is often used. A conventional example using orthogonal transformation will be described below.

Here, a luminance signal and two color difference signals (R-
An example will be described in which a video signal composed of a Y signal and a BY signal is independently high-efficiency coded for each frame and recorded. First, the luminance signal data of one frame is divided into blocks each consisting of adjacent 8 pixels in horizontal 8 pixels and vertical 8 lines.

Next, the two color-difference signals form one orthogonal transformation block with pixels included in the same area on the screen as four adjacent luminance signal blocks. Further, a total of 6 blocks of four luminance signal blocks located at the same position on the screen, one RY signal block and one BY signal block are collectively referred to as one macroblock.

FIG. 5 is a block diagram of a conventional example. In FIG. 5, 1 is an input unit, 2 is a blocking unit, 3 is an orthogonal transformation unit, 4 is an encoding unit, 5 is a first recording unit, 6 is a second recording unit, and 7 is an output unit.

The video signal input from the input unit 1 is divided into blocks of 64 pixels by the blocking unit 2. The video signal blocked by the blocking unit 2 is orthogonally transformed for each block by the orthogonal transformation unit 3. Although discrete cosine transform (DCT) is usually used as the orthogonal transform, other methods such as wavelet can also be applied.

The data orthogonally transformed by the orthogonal transformation unit 3 is
In the encoding unit 3, the DC component is fixed-length encoded and the AC component is variable-length encoded for each block. The AC component is
Variable-length coding is performed in order from a component that represents a visually important low band. Further, when all the AC components behind a certain non-zero AC component are 0, the AC components of all 0s behind are represented by a block end codeword. Further, control data and the like necessary for decoding the block are also encoded at the same time.

The blocks encoded as described above are input to the first recording unit 5 in macro block units. FIG.
An example of the amount of data in one macroblock after encoding is shown in (a) of FIG. As shown in FIG. 6A, the amount of data differs for each block due to the variable length coding.

Next, FIG. 6B shows a recording format for macroblocks. In the recording format of FIG. 6B, the recording area for the luminance signal (Y0, Y1, Y2, Y3) block is 14 bytes, and the color difference signal (RY, B).
-Y) The recording area for the block is set to 10 bytes.

In the first recording unit 5 of FIG. 5, data is recorded in the recording area corresponding to each block of FIG. 6B until the recording area is filled.
In the example of FIG. 6, the data of the blocks of Y0, Y2, and R-Y has a large amount of data, and therefore there is excess data that cannot be recorded even after recording in the corresponding recording area. On the other hand, since the data of the Y1, Y3, and BY blocks has a small amount of data, all the data can be recorded in the corresponding recording area, and even after recording, there is still a free area in the recording area. To do.

In the second recording section 6 of FIG. 5, there is a free area even if all the data is recorded in the remaining data of the block where all the data could not be recorded in the corresponding recording area in the first recording section 5. Record in the recording area of the block. In this way, all recording areas are effectively used.

[0013]

Now, let us consider a case where the data recorded with the above-mentioned structure is reproduced and recorded on another medium. In this case, if no error has occurred during recording / reproduction, variable-length decoding may not be executed and recording may be performed again.

However, if an error occurs during recording / reproduction, it is necessary to execute variable length decoding once to correct the error and then perform variable length coding again and record. In this case, there is a problem that the circuit scale increases because the variable length decoding and the variable length encoding must be executed at the same time.

An object of the present invention is to solve the problems of the recording apparatus using such conventional variable length coding.

[0016]

According to a first aspect of the present invention, a block forming means for collecting adjacent pixels of an input video signal to form a block, and an orthogonal transform for transforming each block into an orthogonal component. Transforming means, DC component of the orthogonally transformed block, control necessary for decoding the block
Data, AC components, and subsequent
A block end signal indicating that the AC components are all 0
A recording device having block encoding means for encoding.
When the recorded data is reproduced, the reproduced data
Is a recording device for recording the
If there is a possibility that there is an error
Control component required for decoding the DC component of
A code that does not normally generate at least one of the code words
To the first AC component in the block.
Replace the codeword to be replaced with the block end codeword
A recording apparatus having means .

A second invention is a recording apparatus which is the first invention.
Which is a reproducing device for decoding the data recorded in
Is it possible that there is an uncorrectable error in the lock?
Error flag detecting means for detecting whether or not the error flag is detected.
The error that the uncorrectable error is detected by the
If the recording area is included in the
In the first block end codeword, or in the recording area
If there is no block end codeword,
Variable length recovery using only the code word for the included AC component
And the DC component of the block or its block.
A small number of codewords that represent the control data required for lock decoding
At least one has been replaced with a codeword that does not normally occur
And a special code detecting means for detecting that
Modify the data of the block in which an error was detected by the output means
The reproducing apparatus is characterized by having a modifying means.

A third invention is a recording corresponding to the first invention.
And a reproducing method corresponding to the second invention. One
Block, collect adjacent pixels of the input video signal and
Block forming means for configuring the
Orthogonal transformation means for performing alternating transformation and transformation into orthogonal components;
DC component of alternating block, decoding of the block
Sometimes required control data, AC components, and their blocks
A block showing that the AC components after that are all 0
Block coding means for coding the clock end signal.
When the data recorded by the recording device
When recording the raw data, corrections can be made in the blocks.
If there is a possibility that there is an error
Control component required for decoding the DC component of
A code that does not normally generate at least one of the code words
To the first AC component in the block.
To replace the code word to be
This is the recording method to be used. Also, record using the recording method.
A reproducing method for decoding the
Whether there may be uncorrectable errors in
An error that is detected and cannot be corrected by the error flag detecting means.
In the recording area included in the error correction area in which the presence of
Is the block end code that appears first in the recording area.
Word or the block end codeword does not exist in the recording area
If not, the code for the AC component contained in the recording area
Variable length decoding using only words and
Control data required when decoding a stream component or its block
A codeword that normally does not occur in at least one of the codewords
It is detected that the special code has been replaced by
Recorrect the data of the block in which the error was detected by
It is a raw method.

[0019]

With the above-mentioned structure, the recording apparatus of the present invention ,
In the recording method and the recording method, by replacing the DC component of the recording block in which the error has occurred with a special code word, it becomes possible to record that the block has an error when recording again. At the same time, by replacing the code word for the first AC component with the block end code word,
By variable length decoding during reproduction, it becomes possible to automatically decode all the AC components of the block having an error to zero.

Next, when an error occurring in the recording area occurs in the code word of the insignificant AC component of the block, the erroneous code word is first replaced with the block end code word, so that at the time of reproduction. The significant components of that block become decodable.

Further, when reproducing the data processed as described above, the block is decoded by using only the data contained in the recording area corresponding to each block. Further, when the direct current component is replaced with the above special code word, the influence of past errors can be minimized by modifying the data of that block in block units. Further, it is possible to avoid a malfunction at the time of decoding due to an error.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. Here, the description will be made based on the format of the conventional example described with reference to FIGS. It is assumed that the data formatted by the apparatus of FIG. 5 is error-correction-coded and recorded for each recording area (recording area for 6 blocks) for the macroblock shown in FIG. 6B. Further, in the present invention, this unit for error correction coding is called an error correction area, and an error flag indicating the presence of an error is recorded in the error correction area unit. In addition, the error correction code described here can detect an error position in units of 1 byte.

FIG. 1 is a block diagram showing an embodiment of the first invention. In FIG. 1, 8 is an input unit, 9 is an error correction unit, 10 is a DC component replacement unit, 11 is an error flag change unit, and 12 is an output unit.

The reproduced output of the data recorded by the apparatus shown in FIG. 5 is input from the input unit 8, and the error correction unit 9 performs error correction processing in macro block units.
If all the errors cannot be corrected by the error correction unit 9, the position of each byte in which an error may occur is output. The DC component replacement unit 10 detects a recording area in which an error may occur in block units. In a block in which an error exists in the recording area, the code word representing the DC component of the block is replaced with a special code word that is not normally used. For example, the code word that represents the DC component is -25
When expressed from 5 to +255, -256 can be used as a code word indicating that there is an error in the recording area.

At the same time, in a block having an error in the recording area, the code word for the AC component appearing at the beginning of the block is replaced with the block end code word. As a result, at the time of variable-length decoding, the code word that is first decoded in the block is the block end code word, so that all AC components are decoded to a value of 0.

The data in which the code words of the direct current component and the first alternating current component are replaced in block units in this way is input to the error flag changing unit 11. Here, the error flag is changed to a code word indicating that an error exists in the error correction area, and the code word is output to the output unit 12. The data that has been subjected to the error code processing in this way is recorded again.

A concrete example of the above error code processing will be described with reference to FIG. FIG. 2A shows an example of a recording area for each block. In FIG. 2A, the first 9 bits of the recording area represent the code word for the DC component, the subsequent 3 bits represent the control information necessary for decoding, and the subsequent bits represent the code word for the AC component. In this way, the direct current component and the control information are recorded in fixed 12 bits, and the alternating current component is recorded after variable length coding.

On the other hand, the result of the DC component replacement process of the present invention is shown in FIG. In FIG. 2B, an error codeword indicating that there is an error in the recording area of the first 9 bits in which the codeword of the DC component is recorded in FIG. 2A (for example, -256) Replace with. Also 12
The first 4 bits of the code word of the AC component starting from the bit-th bit are replaced with 4 bits indicating the block end code word.

As described above, the present invention can be realized by replacing the leading 16-bit (2-byte) data of the recording area for each block. In the example of FIG. 2, since the 2-byte data at the beginning of the recording area in which an error exists is simply replaced with a fixed bit pattern in byte units,
It can be realized with a very simple circuit.

Next, FIG. 3 shows another embodiment. In FIG. 3, 13 is an input unit, 14 is an error correction unit, 15 is an importance degree selection unit, 16 is a DC component replacement unit, 17 is a block end codeword insertion unit, 18 is an error flag change unit, and 19 is an output unit. is there.

In this embodiment as well, as in the first embodiment, the data recorded by the conventional apparatus is reproduced and input from the input section 13. The input reproduction data is subjected to error correction processing by the error correction unit 14, and if the error correction is impossible, the position where the error exists is detected in byte units.

For the uncorrectable error whose position has been detected by the error correction unit 14, the importance level selection unit 15 checks the importance level of the position where the error exists. Therefore, if an uncorrectable error exists in relatively important data (DC component, control information, AC component representing a low frequency band, etc.) in the recording area, the DC component replacing unit 16 does the same as in the first embodiment. The DC component is replaced by the error code word, and the code word representing the first AC component is replaced by the block end code word.

If an uncorrectable error exists in relatively unimportant data (such as an AC component representing a high frequency band) in the recording area, the block end codeword inserting unit 17 first exists in the recording area. The code word that first represents the AC component at the error position is replaced with the block end code word.

The data thus processed for error is
It is input to the error flag changing unit 18. Here, the error flag is changed to a code word indicating that an error exists in the error correction area, and the code word is output to the output unit 19. The data that has been subjected to the error code processing in this way is recorded again.

In this embodiment, when an uncorrectable error occurs in a codeword that has a small effect on the image quality such as an AC component representing a high frequency band, the codeword affected by the error is first set as the block end codeword. By replacing it, the decoded value of the AC component after that can be made zero. This can minimize the effects of errors.

Next, in FIG. 4, Ru used when reproducing the recorded data in the recording apparatus using an error process of the first aspect of the invention
The block diagram of the reproducing | regenerating apparatus which is 2nd invention is shown. In FIG. 4, 20 is an input unit, 21 is an error flag detection unit, 22 is an all data decoding unit, 23 is a recording area decoding unit, 24 is an error correction unit, and 25 is an output unit.

The reproduced data input from the input unit 20 is input to the error flag detection unit 21. Error flag detector 2
When it can be detected in step 1 that there is no error in the error correction area, the all-data decoding unit 22 decodes using all the data in the error-correction area as in normal decoding, and outputs it to the output unit 25. To do.

If the error flag detecting section 21 detects that an error exists in the error correction area and that the error processing is being executed by using the first or second invention, the error flag detection section 21 detects that the error correction area is in the recording area. The decoding unit 23 performs decoding using only the data in the recording area for each block. Here, variable length decoding is performed using only the data up to the block end codeword that first appears in the recording area for each block or the last codeword that appears first in the recording area, whichever comes first. The data of the codeword recorded in the recording area of another block is not used for decoding.

In the data decoded by the in-recording area decoding unit 23, when the DC component of the block is the above error code word, the error correction unit 24 corrects and outputs the decoded data in the block. Output to the unit 25.

By carrying out such decoding, it is possible to avoid using data in which an error has occurred for decoding. Therefore, it is possible to prevent the image quality from being deteriorated due to an erroneous decoding operation due to an error.

Although the present invention has been described above , the present invention can be implemented by a configuration other than the block diagram of the embodiment, and can also be implemented by software. The present invention can also be applied to formats other than those described in the conventional example. Also,
As a third invention, a recording method and a reproducing method are listed.
However, the main part thereof is the same as that of the first and second inventions.

As described above, the present invention can solve the drawbacks of the high-efficiency coding apparatus using variable-length coding with a relatively simple structure, and its practical effect is very large.

[0043]

As is apparent from the above description, in the recording apparatus and the recording method of the present invention, by replacing the DC component of the recording block in which an error has occurred with a special code word, the block is recorded in the block again when recording again. It becomes possible to record the existence of errors. At the same time, by replacing the code word for the first AC component with the block end code word, all the AC components of the block in which the error exists are set to 0.
It becomes possible to decrypt. Further, these processes can be realized by a very simple circuit because only a part of the data in the recording area is replaced with fixed data.

When an error occurring in the recording area occurs in the code word of the insignificant AC component of the block, the erroneous code word is first replaced with the block end code word so that the error occurs during reproduction. The significant AC component of the block becomes decodable.

Further, when reproducing the data processed as described above, the block is decoded using only the data contained in the recording area corresponding to each block. Further, when the direct current component is replaced with the above special code word, the influence of past errors can be minimized by modifying the data of that block in block units.

As described above, by using the present invention, it is possible to record a block in which an error has occurred with a relatively simple circuit, and it is possible to minimize the influence of the error. The practical effect is very large.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment according to a recording apparatus of the first invention.

FIG. 2 is an explanatory diagram of a DC component replacement unit according to the recording apparatus of the first invention.

FIG. 3 is a block diagram of an embodiment of the recording apparatus of the first invention

FIG. 4 is a block diagram of an embodiment of a reproducing apparatus of the second invention.

FIG. 5 is a block diagram of a conventional recording device.

FIG. 6 is an explanatory diagram of a conventional recording format.

[Explanation of symbols]

 9, 14 Error correction unit 10, 16 DC component replacement 11, 18 Error flag change unit 17 Block end code insertion unit 20 Error flag detection unit 21 Error flag detection unit 22 All data decoding unit 23 In-recording area decoding unit

Claims (8)

(57) [Claims] 1. A block forming means for collecting adjacent pixels of an input video signal to form a block, an orthogonal transforming means for orthogonally transforming each block to transform into an orthogonal component, and the orthogonally transformed block. DC component of the
Control data, AC component, and
AC components after that are all 0 in the block
Block coder for coding a block end signal indicating
When the data recorded by the recording device having a step is reproduced.
Recording device that records the reproduced data
Te, may uncorrectable error in the block is present
DC component of the block or its block, if any
At least a codeword that represents the control data required when decoding
Replace one with a codeword that does not normally occur, or block
The code word for the first AC component in the block end code
Characterized by having a replacement means for replacing with a word
Recording device. 2. The position of the error in the block is a DC component or
Is a code that represents the control data required for decoding the block
Present in a word or codeword for a relatively important AC component
Block, the DC component of the block or its
The number of code words that represent the control data required for decoding
Replace one with a codeword that does not normally occur,
Block code for the first AC component of the clock
The replacement means for replacing the word with the word and the AC component where the error position in the block is relatively unimportant.
For blocks that exist in the codeword for
Block the codeword for the first AC component present
A block end codeword inserting means for replacing with the end codeword
The recording apparatus according to claim 1, further comprising: 3. An error correction area is provided and the error correction area is provided.
Corrected when setting the error flag indicating whether there is an error in
If there is a possibility that there is an error that cannot be
Change the flag to a value indicating that an error exists and record
The recording device according to claim 1 or 2, characterized in that
Place. 4. A data recorded by the recording device according to claim 3.
It is a playback device that decodes data, and there is a possibility that an uncorrectable error exists in the block.
An error flag detection means for detecting whether there, the presence of uncorrectable errors by the error flag detection means
In the recording area included in the detected error correction area,
The block end codeword that appears first in the recording area, or
If there is no block end codeword in the recording area
Use only codewords for AC components included in the recording area
Decoding means for variable-length decoding, and DC component of block or required when decoding that block
At least one of the codewords that represent various control data is normally generated
Special to detect that it has been replaced with a codeword
The code detecting means and the data of the block in which the error is detected by the special code detecting means.
And a modification means for modifying the data.
Raw equipment. 5. A method for collecting adjacent pixels of an input video signal.
And a block forming means for forming a block.
Orthogonal transformation means for orthogonally transforming each
And the DC component of the orthogonally transformed block, its
Control data, AC component, and
AC components after that are all 0 in the block
Block coder for coding a block end signal indicating
When the data recorded by the recording device having a step is reproduced.
When recording the reproduced data, there is a possibility that an uncorrectable error exists in the block.
DC component of the block or its block, if any
At least a codeword that represents the control data required when decoding
Replace one with a codeword that does not normally occur, or block
The code word for the first AC component in the block end code
A recording method characterized by replacement with words. 6. An error position in a block is a DC component or
Is a code that represents the control data required for decoding the block
Present in a word or codeword for a relatively important AC component
Block, the DC component of the block or its
The number of code words that represent the control data required for decoding
Replace one with a codeword that does not normally occur,
Block code for the first AC component of the clock
Replaced issue words, alternating formation position errors in the block is relatively unimportant
For blocks that exist in the codeword for
Block the codeword for the first AC component present
6. The end code word is replaced with the end code word.
Recording method. 7. An error correction area is provided, and the error correction area is provided.
Corrected when setting the error flag indicating whether there is an error in
If there is a possibility that there is an error that cannot be
Change the flag to a value indicating that an error exists and record
Recording method according to claim 5 or 6, characterized in that
Law. 8. A data recorded by the recording method according to claim 7.
This is a playback method for decoding data, and there is a possibility that uncorrectable errors may exist in the block.
Whether or not there is an uncorrectable error is detected by the error flag detecting means.
In the recording area included in the detected error correction area,
The block end codeword that appears first in the recording area , or when there is no block end codeword in the recording area
In the case of the code word of the AC component included in the recording area
Variable length decoding using only the block, and is required when decoding the DC component of the block or that block.
At least one of the codewords that represent various control data is normally generated
It is detected that the block has been replaced with a code word that is
Playback method to modify data.