JPH05130585A - Encoding device - Google Patents

Abstract

PURPOSE:To make deterioration at a border inconspicuous by encoding plural image data, which succeed in the direction of the time base, while shifting their block division positions, data by data. CONSTITUTION:A block generation part 102 determines the position of a block for each image data. For 1st image data among the image data which succeed in the time-base direction, for example, a block consisting of 8X8 picture elements in an (x) and a (y) direction is generated without any gap according to positions (0,0)-(7,7). For 2nd picture data, a block of 8X8 picture elements in the (x) and (y) directions is generated without any gap according to positions (5,4)-(12,11) shifted by five and four picture elements in the (x) and (y) directions respectively. For 3rd and succeeding image data, the positions are shifted in the (x) and (y) directions similarly, data by data, to change the positions of blocks, and an encoding part 105 encodes the data. Then the border lines of the blocks are different, data by data, and the discontinuity of colors and brightness becomes inconspicuous.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a coding device for compressing a plurality of image data continuous in the time axis direction and reproducing it as a moving image, and in particular, it has better image quality and high compression efficiency. The present invention relates to an encoding device in which is required.

[0002]

2. Description of the Related Art When encoding image data and compressing the data, a method of dividing the image data into a plurality of blocks and compressing each block is used, paying attention to the high correlation between adjacent pixel data. May be For example, JP, which is an international standardized method for still image compression
EG system and CCiTT video conference / telephone coding system H.264. 261 is this system.

[0003]

However, in the above-mentioned conventional coding apparatus, when the compression ratio is increased, the continuity before and after the boundary line of the block is lost, and the change of the image data at the boundary line of the block is lost. It becomes large, and discontinuity in color and brightness that does not exist in the original image data occurs, which causes deterioration of image quality. This is because even if a plurality of image data that are continuous in the time axis direction are played back as a moving image, the block division method is the same for all image data, so there is a block boundary line at the same position on the screen. However, color and brightness discontinuities occur at that location,
The image quality deteriorates.

According to the present invention, when reproducing a plurality of image data which are continuous in the time axis direction as a moving image, deterioration at the boundary line of this block is obscured and the apparent image quality is improved. To aim.

[0005]

According to the present invention, in an encoding apparatus for dividing image data into a plurality of blocks and compressing the image data, a plurality of image data that are continuous in the time axis direction are provided for each image data. , At least one of the block division position, the block size, and the block shape is changed and encoded.

Then, the coded data is decoded in the same block as when it was coded, and a plurality of image data different in block division method and continuous in the time axis direction are reproduced as a moving image.

[0007]

According to the present invention, with the above configuration, when reproducing a plurality of image data continuous in the time axis direction as a moving image,
Since the division position of the block, the size of the block, and the shape of the block are different for each image data, the boundary line of the block is also different for each image data. Therefore, the discontinuity of the color and the brightness generated on the boundary line of the block also has a different position on each image.

In the case of a moving image, since a large number of images are displayed per second, the discontinuity in color and brightness that can be recognized when they occur at a fixed position on the screen is uncertain at the position on the screen. , It becomes impossible to distinguish. Therefore, the visual quality of a moving image is improved.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following is an example of application to a JPEG type coding device as a coding device according to an embodiment of the present invention.
A description will be given with reference to the drawings. FIG. 1 shows an image data encoding process of the encoding apparatus according to the present embodiment. Further, FIG. 2 shows a reproducing process of encoded data. In FIG. 1, 101 is a memory that temporarily stores image data, 102 is a block generation unit that determines at what position the image data is divided into blocks, and 10
3 is an orthogonal transform unit that performs orthogonal transform on the image data divided into blocks, 104 is a quantizer that quantizes the coefficient obtained by the orthogonal transform unit 103, and 105 is the coefficient that is quantized by the quantizer 104. An encoding unit that encodes.

In FIG. 2, reference numeral 201 is a decoding unit for returning coded data to quantized coefficients, 202 is an inverse quantization unit for returning quantized coefficients to coefficients before being quantized, and 203 is an inverse orthogonal transform. , An inverse orthogonal transform unit for returning the data of each pixel, 204 is a block generation unit for reproducing the division position of the block performed in the image data encoding process based on the block data, and 205 is for expanding the image data. Is a memory for storing.

The orthogonal transform section 103, the quantizing section 104, the coding section 105 in FIG. 1 and the decoding section 20 in FIG.
1, the inverse quantization unit 202, and the inverse orthogonal transformation unit 203 have the same configuration as the conventional JPEG system, and detailed description thereof will be omitted. Furthermore, regarding the JPEG system, the Draft of the JPEG algorithm (1990) (Draft
vision 6) of the JPEG algorithm (1990)).

In the case of the conventional JPEG system, as shown in FIG. 3, a block of 8 × 8 pixels is divided from the upper left corner of the screen. When the x-axis (the right direction is positive) and the y-axis (the downward direction is positive) are taken in the horizontal direction and the vertical direction of the image data and the pixel at the upper left corner is the origin, the block at the upper left starts from (0, 0). (7,
It can be expressed as being in position 7).

The block generator 102 of FIG. 1 determines the position of the block for each image data. For example, with respect to the first image data of a plurality of image data that are continuous in the time axis direction, x, y are set with reference to the positions (0, 0) to (7, 7) as in the normal JPEG system. 8x8 in the direction
Blocks of pixels are generated without gaps, and for the second image data, for example, 5 pixels in the x direction and 4 pixels in the y direction are shifted, and the positions from (5, 4) to (12, 11) are used as references, A block of 8 × 8 pixels is generated without gaps in the x and y directions. Then, information indicating how much the position of the block is shifted is stored as block data separately from the code data of the image data. Similarly, with respect to the image data of the third and subsequent images, the position of each block of the image data is shifted in the x and y directions, the position of the block is changed, and the encoding process is performed.

Next, regarding the reproduction operation of the encoded data of FIG. 2, the block generation unit 204 regenerates a block at the same position as that generated at the time of the encoding processing based on the block data. , The decoded, dequantized, and inverse orthogonal transformed code data is expanded in each block, and the image data is reproduced in the memory.

By the above operation, when the encoded and reproduced continuous image data in the time axis direction is viewed as a moving image, the block boundaries are equalized over the entire screen as shown in FIG. Therefore, discontinuity of color and brightness does not occur at a certain place, and the apparent image quality is significantly improved.

By shifting in the x and y directions, a block smaller than other blocks is generated in the peripheral portion of the image data. However, this processing differs depending on the encoding algorithm. , This invention does not particularly define. For example, an algorithm that can encode a block of an arbitrary size can be processed as it is.
If it can only be processed by a block of × 8, prepare the original image data slightly larger by 7 pixels vertically and horizontally, or the encoded data is valid only in a range that is smaller by 7 pixels vertically and horizontally. Alternatively, if there are insufficient pixels, other pixels may be copied and diverted. In the block generation unit, x,
As a method of determining the shift amount in the y direction, a random number, a constant sequence predetermined so that the block positions are appropriately dispersed, or the like can be used.

In this embodiment, JPEG encoding is taken as an example, but the same can be realized in the case of other encoding algorithms in which image data is divided into fixed blocks and then encoded. Further, although the position of the block is changed in this embodiment, in the case of an algorithm of dividing into blocks of arbitrary size or arbitrary shape and encoding, it can be realized by changing the size or shape of the block. it can. In addition, in this embodiment, the block is changed for each image data, but when the block is reproduced as a moving image,
If the number of frames per second is sufficiently large, the same effect can be achieved by using the same block for several frames.

[0018]

According to the present invention, since the block division position, the block size, and the block shape are changed and encoded for each image data continuous in the time axis direction, the image data is divided into a plurality of blocks. When the coded data that has been encoded is reproduced as a moving image, the boundary line of the block that causes the deterioration of the image quality differs for each image data, and the discontinuity of the color and brightness at the boundary line of the block is noticeable. It is possible to improve the image quality. This is extremely effective in an encoding device that requires better image quality and a high compression rate.

[Brief description of drawings]

FIG. 1 is a block diagram showing an image data encoding process of an encoding device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a process of reproducing image data of the encoding device according to the present embodiment.

FIG. 3 is a diagram showing a block division method similar to the JPEG method.

FIG. 4 is a diagram showing a state in which a block position is changed and divided.

FIG. 5 is a diagram showing an example in which a block division position is changed for each image data and reproduced as a moving image.

[Explanation of symbols]

 101 Memory 102 Block Generation Unit 103 Orthogonal Transformation Unit 104 Quantization Unit 105 Encoding Unit 201 Decoding Unit 202 Inverse Quantization Unit 203 Inverse Orthogonal Transformation Unit 204 Block Generation Unit 205 Memory

Claims (2)

[Claims] 1. A coding device for dividing image data into a plurality of blocks and compressing the blocks, and for a plurality of image data continuous in a time axis direction, a block division position and a block size for each image data. An encoding device, characterized in that at least one of the shapes of blocks is changed for encoding. 2. A block similar to that at the time of encoding is generated based on data regarding division of a block at the time of encoding by the encoding device according to claim 1, and encoded image data is continuously generated. A decoding device that decodes and plays back as a moving image.