JP2017192080A - Image compression device, image decoding device, image compression method, and image compression program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image compression device, an image compression method, an image compression program which are capable of quickly compressing an image into a normal file format, and an image decoding device capable of quick decoding.SOLUTION: An image compression device 1 comprises: a division part 11 for dividing an image into plural images; a coding part 12 for parallelly coding each divided images by using a common coding parameter; and a combination processing part 13 which integrates header parts including image size information of respective pieces of the divided and coded data and combines data portions to generate a single compression file 20.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an apparatus, a method, and a program for compressing a high-definition image.

  In recent years, captured images have become higher definition, and the capacity of image data has increased as the resolution and frame rate have improved. When compressing and decoding a high-definition image, the processing speed decreases in proportion to an increase in the number of pixels representing the definition of the image. Therefore, in order to process a high-definition image in real time, the image is divided, and compression processing is performed on each of the divided images in parallel, thereby speeding up the processing in proportion to the parallel number.

For example, Patent Document 1 proposes a technique of dividing an image into a plurality of parts in the vertical direction, searching for a specific restart interval marker and the number thereof, searching for the number of divisions and division positions, and performing parallel decoding.
For example, in Patent Document 2, the image is divided into a plurality of parts in the vertical direction, the number of lines of the divided image and the compressed data size are recorded in the comment segment, and the data is started by referring to the comment segment at the time of decoding. A method for detecting the position has been proposed.

JP 2007-267349 A JP 2008-113268 A

  However, when dividing an image, image compression parameters are set independently for each divided image, and each of the divided images is independently processed in parallel. Therefore, a boundary line is seen at the boundary position of the divided image, and depending on the design, It looks like noise. For this reason, processing for making the division boundary inconspicuous is usually performed. Furthermore, since division processing results in a plurality of files depending on the encoding method, editing processing or the like cannot be performed in the same file format.

In the method of Patent Document 1, it is necessary to examine the marker by performing a full scan of the compressed data, which is not suitable for real-time processing because the marker scan becomes a large overhead.
In the method of Patent Document 2, since a plurality of compressed images processed in parallel are simply merged into one image file, the merged data does not satisfy the compression standard, and preview or editing with existing software I can't.

  An object of the present invention is to provide an image compression apparatus, an image compression method, an image compression program, and an image decoding apparatus capable of decoding at high speed, which can compress an image into a prescribed file format at high speed.

  An image compression apparatus according to the present invention includes a dividing unit that divides an image into a plurality of pieces, an encoding unit that encodes each of the divided images divided by the dividing unit in parallel using a common encoding parameter, and A concatenation processing unit that integrates a header portion including image size information of each of a plurality of pieces of divided encoded data encoded by the encoding unit and concatenates the data units to generate a single compressed file.

  The encoding unit encodes the divided image by a JPEG method, and the dividing unit divides the image so that each of the divided images includes an encoding unit that is a multiple of a cycle of a restart interval marker. May be.

  The dividing unit may divide the image in the vertical direction so that a difference in size between the divided images is minimized.

  The connection processing unit may add division information data indicating a position where the data units are connected to the compressed file.

  The image decoding device according to the present invention divides a compressed file generated by the image compression device into a plurality of the data portions based on the division information data, rewrites the image size information in the integrated header portion, and By adding to each data part, a plurality of the divided encoded data are restored.

  An image compression method according to the present invention includes a dividing step of dividing an image into a plurality of pieces, an encoding step of encoding each of the divided images divided in the dividing step in parallel using a common encoding parameter, A computer that combines a header portion including image size information of each of a plurality of pieces of divided encoded data encoded in the encoding step and connects the data portions to generate a single compressed file; Run.

  An image compression program according to the present invention includes a dividing step for dividing an image into a plurality of pieces, a coding step for coding in parallel using a common coding parameter for each of the divided images divided in the dividing step, A concatenation processing step of integrating a header portion including image size information of each of a plurality of divided encoded data encoded in the encoding step and concatenating the data portions to generate a single compressed file; Let it run.

  According to the present invention, an image can be compressed at a high speed into a prescribed file format and decoded at a high speed.

It is a block diagram which shows the function structure of the recording device which concerns on embodiment. It is a figure which shows the division method of the image which concerns on embodiment. It is a figure which shows the encoding process which concerns on embodiment. It is a figure which illustrates the method of insertion and replacement of a marker in division coding data concerning an embodiment. It is a figure which shows the structure of the JPEG file which concerns on embodiment, and the structural example of division | segmentation information data. It is a figure which shows the decoding process which concerns on embodiment.

Hereinafter, an example of an embodiment of the present invention will be described.
FIG. 1 is a block diagram showing a functional configuration of a recording apparatus 1 (image compression apparatus, image decoding apparatus) according to the present embodiment.

  The recording device 1 is an information processing device (computer) such as a server device or a PC (Personal Computer) provided with a storage unit and a control unit. The recording apparatus 1 realizes various functions of the present embodiment by causing the control unit to execute software (image compression program) stored in the storage unit.

The control unit of the recording apparatus 1 includes a dividing unit 11, an encoding unit 12, a concatenation processing unit 13, and a decoding unit 14, and these functions perform image compression processing and decoding processing.
In addition, although the encoding system used for compression and decoding is not limited, this embodiment demonstrates to a JPEG system as an example.

The dividing unit 11 divides the input image into a plurality of parts.
At this time, the dividing unit 11 divides the image so that each of the divided images includes an encoding unit that is a multiple of the cycle of the restart interval marker, that is, an encoding unit that is a multiple of 8. Here, in the case of JPEG, 8 × 8 pixels, 16 × 8 pixels, or 16 × 16 pixels are adopted as a coding unit (MCU; Minimum Coded Unit) depending on the sampling ratio. Note that dummy data may be inserted into an image region that is less than the encoding unit and an encoding unit that is less than a multiple of 8.

  The dividing unit 11 divides the image in the vertical direction so that the difference in size of the divided images is minimized. Since the divided images are processed in parallel by the encoding unit 12, the processing time is made efficient by dividing the image size almost equally in this way.

FIG. 2 is a diagram illustrating an image dividing method according to the present embodiment.
JPEG compression is processed for each coding unit. Image sampling formats include 4: 4: 4 (no thinning), 4: 2: 2 (horizontal thinning), 4: 2: 0 (longitudinal thinning), for example, 4: 2: 0. The encoding unit is 16 × 16 pixels.
It is desirable that the number of vertical and horizontal pixels of the divided image is an integral multiple of the encoding unit. Assuming reading in a DRAM (Dynamic Random Access Memory) or the like, it is desirable to keep the number of pixels in the horizontal direction and to divide the vertical direction in order to facilitate processing. In this case, for example, an 8K (7680 × 4320 pixel) image can be divided into 2, 3, 5, 6, 9, 10,.

The encoding unit 12 encodes each of the divided images divided by the dividing unit 11 in parallel using a common encoding parameter (quantization table and Huffman table).
Normally, processing is performed in units of one image in JPEG, but in a high-definition image such as 8K, the number of pixels increases, so that real-time compression becomes difficult. For this reason, the recording apparatus 1 achieves higher speed by dividing an image and performing compression processing in parallel.
At this time, if the divided images are independently processed in parallel and decoded to reconstruct an 8K image, the divided lines may be seen. Therefore, the encoding unit 12 uses the JPEG method quantization table and Huffman table in common for all the divided images to prevent the division lines from being displayed.

  The concatenation processing unit 13 integrates the header portions including the image size information of each of the plurality of pieces of divided encoded data encoded by the encoding unit 12 and concatenates the data units to generate a single compressed file 20. .

FIG. 3 is a diagram showing an encoding process according to the present embodiment.
In the normal encoding process (a), for example, an 8K (7680 × 4320 pixel) image is encoded into one JPEG file. A JPEG file is composed of a header portion and a data portion, and the header portion includes image size information.
In the parallel encoding process (b) performed by the encoding unit 12, for example, three divided images (each 7680 × 1440 pixels) are encoded into three JPEG files.

The concatenation processing unit 13 replaces only the header portion of a plurality of JPEG files and merges them into one file.
At this time, the number of restart interval markers in the data portion needs to be continuously circulated so that the connected file satisfies the JPEG standard and can be processed by another device or software.

Therefore, the dividing unit 11 divides the divided image so that the number of encoding units in the divided image is a multiple of 8, and sequentially inserts a restart interval marker of a multiple of 8. However, the end of the data part is an end marker.
Furthermore, when the data processing unit 13 connects the data units, the connection processing unit 13 replaces an EOF marker that is an end marker of the divided image with a restart interval marker, thereby maintaining data continuity.

FIG. 4 is a diagram illustrating a marker insertion and replacement method in the divided encoded data according to the present embodiment.
In this example, restart interval markers RST0 to RST6 are sequentially inserted in the data portions 1 to 3 in the three divided encoded data (JPEG file) with data corresponding to a predetermined number of encoding units, respectively. . Since the location where the next restart interval marker RST7 is to be inserted is the end of the data portion, the end marker EOF is set.

  When these three data parts are connected, the end marker EOF is replaced with the eighth restart interval marker RST7. As a result, eight types of restart interval markers circulate normally.

Further, the concatenation processing unit 13 adds division information data indicating a portion where the data portions are concatenated to the compressed file 20.
If encoding is performed using a common encoding parameter, the data size is different for each piece of divided encoded data, so that the connected portion cannot be determined during decoding and parallel processing cannot be performed. Therefore, the concatenation processing unit 13 adds division information data to the end of the compressed file 20 in order to enable parallel processing for each divided image even during decoding.

FIG. 5 is a diagram showing an example of the structure of the JPEG file and the division information data according to the present embodiment.
A normal JPEG file is configured by adding an encoded data portion (JPEG data) after a header portion (JPEG header).
In the compression method according to the present embodiment, the number of divided JPEG files (three in this example) processed in parallel is generated. In order to make these into one JPEG file, the concatenation processing unit 13 rewrites the image size included in the header portion of the first file, and after the first JPEG data 1, the second and subsequent JPEG data 2 and 3 are rewritten. Append, and finally add division information data.

  The division information data includes, for example, the number of image divisions (1 byte), the number of vertical and horizontal pixels of the division image (2 bytes each), the start address (4 bytes) and the data size ( 4 bytes) is recorded. In the case of supporting up to 30 divisions, the division information data is 245 bytes.

  The decoding unit 14 divides the compressed file 20 generated by the concatenation processing unit 13 into a plurality of data units based on the division information data. Further, the decoding unit 14 rewrites the image size information in the integrated header part and adds it to each of the divided data parts, thereby restoring a plurality of divided encoded data.

FIG. 6 is a diagram showing a decoding process according to the present embodiment.
The decoding unit 14 reads the division information data from the JPEG fill, and separates the compressed data portion into data portions (JPEG data 1, 2, 3) for the number of divisions based on the start address information of the division information data.
Next, the decoding unit 14 rewrites the header part (JPEG header 1, 2, 3) with the number of pixels of each divided image and creates JPEG files for the number of divisions. At this time, since the encoding parameters are common, the rewritten portion is easily limited to the size information. For example, if the divided images have the same size, the header part is also the same.

Thereafter, the decoding unit 14 performs parallel decoding processing for the number of divisions. Parallel processing enables real-time processing even for high-definition images. For example, when the processing speed of 6 to 7 frames / second is obtained when decoding 8K video by hardware using FPGA (Field-Programmable Gate Array), the frame rate of 60 frames / second is obtained by parallel processing of 10 divisions. Real-time processing is possible.
Further, since the quantization table and the Huffman table used for encoding are common, a decoded image without a division line can be obtained.

According to the present embodiment, the recording apparatus 1 encodes each of the divided images in parallel using a common encoding parameter, and then integrates the header portions and connects them to a single compressed file 20. Therefore, the recording apparatus 1 can compress an image at high speed by parallel processing, and can generate a compressed file 20 in a prescribed file format having a header part and a data part. The generated compressed file 20 has a format that can be handled by other devices or software, and the recording device 1 can compress images at high speed without losing versatility.
Furthermore, since the encoding parameter used for each divided image is common, no divided line appears when displaying the decoded image.

  In addition, since the recording apparatus 1 divides the image so that each of the divided images includes eight types of restart interval markers in the JPEG format that are multiples of 8, the restart interval markers are continuous across the plurality of divided images. To do. Therefore, the recording apparatus 1 can generate one compressed file 20 without losing a prescribed format when the divided encoded data is connected.

  In addition, the recording apparatus 1 can optimize the processing time when the divided images are encoded in parallel by dividing the image substantially equally, and can efficiently compress the image.

Moreover, since the recording apparatus 1 includes the division information data indicating the connection position of the data part in the compressed file 20, the division position can be easily grasped at the time of decoding.
The recording apparatus 1 can rewrite the image size information of the integrated header portion to add to each divided data portion, and can easily divide one compressed file 20 into a plurality of files. As a result, the recording apparatus 1 can execute decoding processing at high speed by parallel processing.

  As mentioned above, although embodiment of this invention was described, this invention is not restricted to embodiment mentioned above. Further, the effects described in the present embodiment are merely a list of the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the present embodiment.

  In the present embodiment, the recording apparatus 1 includes the decoding unit 14, but the present invention is not limited to this. For example, an image decoding device including the decoding unit 14 may be provided separately.

  The program for realizing the function of the recording apparatus 1 may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read by a computer system and executed.

  The “computer system” here includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, or a hard disk built in a computer system.

  In addition, “computer-readable recording medium” means that a program is dynamically stored for a short time, like a communication line when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. It is also possible to include one that holds a program for a certain time, such as a volatile memory inside a computer system that becomes a server or client in that case. Further, the program may be for realizing a part of the above-described functions, and may be capable of realizing the above-described functions in combination with a program already recorded in the computer system. .

1. Recording device (image compression device, image decoding device)
11 Dividing Unit 12 Encoding Unit 13 Concatenation Processing Unit 14 Decoding Unit 20 Compressed File

Claims (7)

A dividing unit for dividing the image into a plurality of parts;
For each of the divided images divided by the dividing unit, an encoding unit that encodes in parallel using a common encoding parameter;
A concatenation processing unit that integrates a header portion including image size information of each of a plurality of pieces of divided encoded data encoded by the encoding unit and generates a single compressed file by concatenating the data units. Image compression device. The encoding unit encodes the divided image by a JPEG method,
The image compression apparatus according to claim 1, wherein the division unit divides the image so that each of the divided images includes an encoding unit that is a multiple of a cycle of a restart interval marker.   The image compression apparatus according to claim 1, wherein the division unit divides the image in the vertical direction so that a difference in size between the divided images is minimized.   4. The image compression apparatus according to claim 1, wherein the connection processing unit adds division information data indicating a location where the data units are connected to the compressed file. 5.   The compressed file generated by the image compression apparatus according to claim 4 is divided into a plurality of data parts based on the division information data, and the image size information in the integrated header part is rewritten to each of the data parts. An image decoding apparatus that restores a plurality of the divided encoded data by adding. A division step for dividing the image into a plurality of parts;
An encoding step of encoding in parallel using a common encoding parameter for each of the divided images divided in the dividing step;
A concatenation processing step of integrating a header portion including image size information of each of a plurality of divided encoded data encoded in the encoding step and concatenating the data portions to generate a single compressed file; Image compression method executed by. A division step for dividing the image into a plurality of parts;
An encoding step of encoding in parallel using a common encoding parameter for each of the divided images divided in the dividing step;
A concatenation processing step of integrating a header portion including image size information of each of a plurality of divided encoded data encoded in the encoding step and concatenating the data portions to generate a single compressed file; An image compression program to be executed.

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