JP2682375B2 - Image data recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image data recording apparatus, and more particularly, it divides an image into video blocks of a predetermined size and performs discrete cosine transform (hereinafter referred to as DCT transform), and a direct current component (DC) of its transform coefficient. Value) and AC component (AC
Value) to set the DC setting value and the AC setting value respectively corresponding to each video block to generate video data, and further divide the video data into a certain number of bits to form a video sync block and record it. The present invention relates to an image data recording device.

[0002]

2. Description of the Related Art When recording image data, an image is divided into video blocks of a predetermined size (8 pixels × 8 lines), and each video block is compressed and encoded by DCT conversion for efficient recording. ing. Image compression by DCT conversion is described in detail, for example, in “Outline of MPEG and Standardization Trend”, Katayama, Monthly Interface, August 1992.

Referring to FIG. 4 showing an example of a conventional image data recording apparatus, a DCT conversion section 11 performs a two-dimensional DCT conversion for each video block on image data D11 divided into video blocks and input. Quantizer 1
2 quantizes the transform coefficient obtained by the DCT transform.
The zigzag scanning unit 13 performs zigzag scanning in the high frequency direction from the DC value of the conversion coefficient to the AC value, and outputs the conversion coefficient as a data string. The variable-length coding unit 14 encodes variable-length code data by the Huffman code, and sends the variable-length code data D12 indicating the DC value of the transform coefficient and the variable-length code data D13 indicating the AC value of the transform coefficient.

The video sync block generator 35 is also provided.
Receives the variable-length code data D12 and D13, generates video data for each video block based on the DC value and the AC value of the transform coefficient, as shown in FIG. It is divided and output as a video sync block D22. After that, although not shown, a sync code, an ID code (a code for identifying the position of the signal, etc.) and an error correction code are added to each video sync block and recorded on a recording medium.

By the way, the video sync block generator 3
In No. 5, the video data of the video sync block is generated so as to have a numerical value smaller than the DC value of the conversion coefficient in order to suppress the bit rate low and improve the efficiency of data compression. That is, as a value (DC setting value) set corresponding to the DC value of the conversion coefficient, the DC value of the conversion coefficient of each video block except the first video block and the value of the previous value in units of one frame or one field. The difference value from the DC value of the conversion coefficient of the video block is set. In addition,
Value to be set corresponding to the AC value of the conversion coefficient (AC setting value)
As for, the AC value of the conversion coefficient is set as it is.

As shown in FIG. 5, the video sync block sets the AC value continuing from the immediately preceding video sync block to the 0th video block, and thereafter, the first video block, the second video block ,. The data of the DC setting value and the AC setting value are arranged in this order in the order of ..., nth video block ,.
It ends in the middle of the setting value or at the break.

Now, the DC value of the conversion coefficient of the last video block of the immediately preceding video sync block is "97", and the DC value of the conversion coefficient of the first video block of this video sync block is "103". Yes, and if the DC value of the conversion coefficient of the second video block is “110”, the DC setting value (D
C1) is the DC of the transform coefficient of the first video block.
The difference value “6” (103−97 = 6) between the value “103” and the DC value “97” of the conversion coefficient of the last video block of the immediately preceding video sync block is set, and the DC of the second video block is set. As the set value (DC2), the difference value “7” (1) between the DC value “110” of the conversion coefficient of the second video block and the DC value “103” of the conversion coefficient of the first video block.
10-103 = 7) is set. Similarly, a difference value from the DC value of the conversion coefficient of the immediately preceding video sync block is set as the DC setting value of the third video block and thereafter.

As described above, in order to set the DC set value of each video block, the video sync block generator 35
Is a DC difference value calculation circuit 351 that calculates a difference value from the DC value of the immediately preceding conversion coefficient, as shown in FIG.
Data D13 indicating an AC value according to the / AC switching signal S2
And a selector 352 for selecting either DC difference value
And

[0009]

In the above-mentioned conventional image data recording apparatus, the DC value of the conversion coefficient of each video block and the preceding video block are excluded in units of one frame or one field except the first video block. The difference value between the conversion coefficient and the DC value is recorded. However, when an uncorrectable error occurs in the recording / reproducing system, D
When an error occurs even at one C setting value, the error propagates to the entire screen of one field or one frame after the DC setting value where the error occurs, and the image deteriorates and becomes very unsightly. Have

An object of the present invention is to use a DC in a recording / reproducing system.
An object of the present invention is to provide an image data recording apparatus capable of preventing the error from propagating to the entire screen and reducing image deterioration even if an error occurs in the DC setting value of the T conversion coefficient.

[0011]

The image data recording apparatus of the present invention divides an image into video blocks of a predetermined size and performs discrete cosine transform, and the DC value and A of the transform coefficient.
A DC setting value and an AC setting value corresponding to the C value are set for each video block to generate video data, and the video data is divided for each fixed number of bits to form a video sync block and recorded. In the image data recording device, means for setting a reference DC value as a reference at the head of the video sync block, and a DC value of the conversion coefficient of the first video block of the first video sync block and the reference DC value. Means for setting the difference as the DC setting value of the first video block, and the D after the second video block of the video sync block
As the C setting value, D of the conversion coefficient of each video block
Means for respectively setting the difference between the C value and the DC value of the conversion coefficient of the immediately preceding video block, and the AC setting value of each video block of the video sync block is the AC of the conversion coefficient of each video block. And a means for setting the value as it is. The reference DC value may be the DC value of the transform coefficient of the last video block of the immediately preceding video sync block, or the DC value of the transform coefficient of the first video block. Good.

Further, the image data recording apparatus of the present invention divides an image into video blocks of a predetermined size and performs discrete cosine transform, and sets DC and AC corresponding to the DC value and the AC value of the conversion coefficient, respectively. In an image data recording apparatus that sets a setting value for each video block to generate video data, divides the video data into a certain number of bits to form a video sync block, and records the video sync block, Means for directly setting the DC value of the conversion coefficient of the first video block as the DC setting value of the first video block;
A unit for setting a difference between the DC value of the conversion coefficient of each video block and the DC value of the conversion coefficient of the immediately preceding video block as the DC setting value of the video sync block after the second video block; And a means for setting the AC value of the conversion coefficient of each video block as it is as the AC setting value of each video block of the video sync block.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, which has the same configuration as that of the conventional example shown in FIG. 4 except for a video sync block generator 15, and the same components are designated by the same reference numerals. It is attached.

The DCT transform unit 11 performs a two-dimensional DCT transform for each video block on the input image data D11 divided into video blocks. The quantizer 12 quantizes the transform coefficient obtained by the DCT transform. The zigzag scanning unit 13 performs zigzag scanning in the high frequency direction from the DC value of the conversion coefficient to the AC value, and outputs the conversion coefficient as a data string. The variable-length coding unit 14 encodes variable-length code data by the Huffman code, and sends the variable-length code data D12 indicating the DC value of the transform coefficient and the variable-length code data D13 indicating the AC value of the transform coefficient. In addition, the video sync block generation unit 15 uses the variable length code data D12 and D13.
In response, the video data is generated for each video block based on the DC value and the AC value of the conversion coefficient, and this video data is divided into a certain number of bits and output as a video sync block D21. After that, although not shown, a synchronization code, an ID code, and an error correction code are added to each video sync block and recorded on a recording medium.

By the way, the video sync block generator 1
In 5, the DC setting value and the AC setting value are set based on the conversion coefficient of each video block to generate video data. In this case, the AC value of the conversion coefficient is set as it is as the AC setting value, but the DC setting value is set as follows.

That is, as shown in FIG. 2, a reference DC value (DC0) is set at the beginning of the video sync block, and the AC value continuing from the immediately preceding video sync block is set to the 0th video block. After setting, the data of the DC setting value and the AC setting value is arranged in the order of the first video block, the second video block, ..., The nth video block ,.
It ends in the middle of the setting value or at the break. As the DC setting value (DC1) of the first video block, a difference value between the reference DC value (DC0) and the DC value of the conversion coefficient of the first video block is set, and the DC setting value (DC2) of the second video block and thereafter is set. , ...), the DC value of the transform coefficient of the preceding video block and the D of the transform coefficient of each video block.
The difference value from the C value is set.

For example, the DC value of the conversion coefficient of the last video block of the immediately preceding video sync block is "97", and the DC value of the conversion coefficient of the first video block of this video sync block is "103". If the DC value of the conversion coefficient of the second video block is “110”, the reference DC value (DC0) set at the beginning of the video sync block is “97”, and the DC setting value (DC of the first video block is DC
As 1), the difference value “6” (1 between the DC value “103” of the conversion coefficient of the first video block and the reference DC value “97”
03-97 = 6) and sets the DC of the second video block.
As the setting value (DC2), the difference value “7” (110-10) between the DC value “110” of the conversion coefficient of the second video block and the DC value “103” of the conversion coefficient of the first video block.
3 = 7) is set. Similarly, as the DC setting value after the third video block, the DC value of the conversion coefficient of the previous video block and the D of the conversion coefficient of each video block are similarly set.
The difference value from the C value is set.

In order to generate such a video block, as shown in FIG. 1, the video sync block generator 15 presets the reference DC value in accordance with the signal S1 indicating the head of the video sync block and converts the conversion coefficient into a preset value. A DC difference value calculation circuit 151 that calculates a difference value from the DC value and a reference DC value when receiving the signal S1 indicating the beginning of the video sync block, and then selects the output of the DC difference value calculation circuit 151. Selector 152 and DC / AC switching signal S
2 and a selector 153 for selecting either the output of the selector 152 or the data D13 indicating the AC value.

With the above configuration, even if an uncorrectable error occurs in the DC setting value in the recording / reproducing system, the error propagation can be suppressed within one video sync block. In addition, except the reference DC value, the other DC difference values are used, so that the bit rate can be suppressed lower than in the case where all the DC values of the conversion coefficient are transmitted as they are.

As the reference DC value, it is obvious that the same effect can be obtained by setting the DC value of the conversion coefficient of the first video block as it is or setting another appropriate value. .

Another example of the structure of the video sync block is shown in FIG.
Is shown in Here, the setting of the reference DC value at the beginning of the video sync block is omitted, and instead of the first DC value, the first DC value is set.
The DC value of the conversion coefficient of the video block is directly used as the DC setting value (DC1) of the first video block. For the DC setting values (DC2, ...) After the second video block, the difference value between the DC value of the conversion coefficient of the preceding video block and the DC value of the conversion coefficient of each video block is set. .

For example, if the DC value of the conversion coefficient of the first video block is "103" and the DC value of the conversion coefficient of the second video block is "110", the DC setting value of the first video block ( "103" is set as DC1), and the DC value "11" of the conversion coefficient of the second video block is set as the DC setting value (DC2) of the second video block.
0 ”and the DC value“ 10 ”of the conversion coefficient of the first video block.
3 ”is set to the difference value“ 7 ”(110−103 = 7), and the DC set value after the third video block is similarly set to the difference value with the DC value of the conversion coefficient of the immediately preceding video block. Set sequentially.

Even if the video sync block is constructed in this way, as in the video sync block having the construction shown in FIG. 2, even if an uncorrectable error occurs in the DC set value in the recording / reproducing system, the error propagation is prevented. It can be suppressed within one video sync block, and the bit rate can be suppressed low.

[0025]

As described above, according to the present invention, the DCT conversion is performed for each video block having a predetermined size, and the DC setting value and the AC setting value are calculated based on the DC value and the AC value of the conversion coefficient. When setting and configuring a video sync block with a certain number of bits, a reference DC value that is a reference is set at the beginning of each video sync block, and the DC setting value of the first video block in the video sync block is the reference DC value. Value and the DC value of the conversion coefficient of the first video block are set, and the DC value of the conversion coefficient of each video block and the conversion of the previous video block are set as the DC setting value after the second video block. By setting the difference value between the coefficient and the DC value, even if an uncorrectable error occurs in the DC setting value in the recording / reproducing system, error propagation is reduced to 1
Since it can be suppressed within the video sync block, it is possible to prevent the image from being deteriorated due to the error propagation to the entire screen as in the conventional case. In addition, since all the DC setting values other than the reference DC value are difference values, the bit rate can be suppressed lower than in the case where all the DC values of the conversion coefficient are transmitted as they are.

Further, when forming a video sync block, the reference DC value set at the beginning is omitted, and instead, the DC value of the conversion coefficient of the first video block is directly used as the DC setting value of the first video block. The same applies to the DC setting value after the second video block and the difference value between the DC value of the conversion coefficient of each video block and the DC value of the conversion coefficient of the immediately preceding video block. It is possible to obtain various effects.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a video sync block generation unit 15 shown in FIG.
It is a figure which shows the structure of the video sync block which this produces | generates.

FIG. 3 is a diagram illustrating another configuration example of a video sync block.

FIG. 4 is a block diagram showing an example of a conventional image data recording device.

5 is a video sync block generation unit 35 shown in FIG.
It is a figure which shows the structure of the video sync block which this produces | generates.

[Explanation of symbols]

 11 DCT conversion unit 15 Video sync block generation unit 151 DC difference value calculation circuit 152, 153 Selector S1 Signal indicating the beginning of video sync block S2 DC / AC switching signal

Claims (4)

(57) [Claims] 1. An image is divided into video blocks of a predetermined size, discrete cosine transform is performed, and DC setting values and AC setting values respectively corresponding to the DC value and AC value of the conversion coefficient are set for each video block. In the image data recording apparatus for generating video data, dividing the video data into a predetermined number of bits to form a video sync block, and recording the video sync block, a reference DC serving as a reference is provided at the head of the video sync block.
Means for setting a value, and a difference between the DC value of the transform coefficient of the first video block of the first video block of the video sync block and the reference DC value of the DC value of the first video block.
Means for setting as a set value, and the DC set value of the video sync block after the second video block is the DC value of the transform coefficient of each video block and the DC value of the transform coefficient of the immediately preceding video block. Image data recording, and means for setting the respective differences of the video sync blocks and means for directly setting the AC value of the conversion coefficient of each video block as the AC setting value of each video block of the video sync block. apparatus. 2. The image data recording apparatus according to claim 1, wherein the reference DC value is a DC value of the conversion coefficient of the last video block of the video sync block immediately before. 3. The image data recording apparatus according to claim 1, wherein the reference DC value is a DC value of the conversion coefficient of the first video block. 4. An image is divided into video blocks of a predetermined size, discrete cosine transform is performed, and DC setting values and AC setting values respectively corresponding to the DC value and AC value of the conversion coefficient are set for each video block. In the image data recording device for generating video data by dividing the video data into a predetermined number of bits to form a video sync block and recording the video sync block, the DC of the first video block of the first video sync block is recorded. As a set value, means for setting the DC value of the conversion coefficient of the first video block as it is, and the D after the second video block of the video sync block
As the C setting value, D of the conversion coefficient of each video block
Means for respectively setting the difference between the C value and the DC value of the conversion coefficient of the immediately preceding video block, and the AC setting value of each video block of the video sync block is the AC of the conversion coefficient of each video block. An image data recording apparatus, comprising: means for setting a value as it is.