JP3357468B2 - Image compression system and image reproduction system - 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 compression system, and more particularly to an image compression system including partial reproduction of compressed image data, and an image reproduction system thereof.

[0002]

2. Description of the Related Art JPEG (Joint Photographic Expert Grou
p) According to the color still image coding method of the standard (ISO DIS-10918), compressed data in which data representing an image is compression-coded is composed of a plurality of blocks, and each block has a restart marker code (RSTm, m). = 0 to 7) can be inserted. The restart marker code is a marker code for resetting the decoding condition of the DC component taken over between blocks in the process of compression coding performed in units of 8 × 8 pixels and resetting the initial condition. That is, the DC component is transmitted as a difference from the immediately preceding DC component, and is set to the first value by the restart marker code.

[0003] The restart marker is also used when a compressed code is partially reproduced, and if a restart marker code of a corresponding block is detected, the block can be selectively reproduced. The restart marker code can stop the transmission of the error to the subsequent data when a transmission error occurs during the transmission of the compressed image data and the next restart marker code occurs. In addition, the use of the restart marker code has the effect of enabling random access to a partial area of the compressed data. In the case of the compressed data without the restart marker code, in order to perform the partial reproduction, the DC component has to be decoded from the head of the compressed data of the entire image.

[0004]

However, even in the case of compressed image data having a restart marker code, when a desired block is partially reproduced, one unit (image) is required to detect the restart marker code of that block. ) Had to be searched from the beginning. The restart marker code RSTm is a 16-bit code. The upper one byte is “all 1”, that is, “FF”, and the lower one byte is a code “Dm”. Here, m is an integer from 0 to 7, and is the number of rounds that increments from 0 to 7 every time a restart marker code occurs from the beginning of one unit of compressed data and returns to 0 again. So, in the reproduction system,
One unit of compressed data must be searched from the beginning, and every time a restart marker code occurs, its value must be read and counted. When the count value indicates a value corresponding to a desired reproduction portion, decompression of the compressed data is started from that portion. Such a restart marker code search and counting requires time, and thus has a disadvantage that partial reproduction is slow.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image compression system and an image reproduction system capable of solving the above-mentioned drawbacks of the prior art and performing high-speed partial reproduction of compressed image data.

[0006]

In order to solve the above-mentioned problems, an image compression system according to the present invention divides a first image data representing one unit of image into a plurality of blocks to form a first image data. Encoding means for compression-encoding compressed data including a DC signal component and an AC signal component, and a display insertion means for inserting a restart indication for resetting a DC signal component for each predetermined number of blocks in the compressed data Address information forming means for calculating a position where the restart indication is inserted in the compressed data, and forming address information indicating a correspondence between the calculated position and the restart indication; and Processing means for assembling the second image data by incorporating the address information into the compressed data.

[0007] The image compression system according to the present invention further comprises:
Decoding and reproducing means for decoding and decompressing the second image data to reproduce the first image data, and detecting the restart display position in the compressed data with reference to the address information included in the second image data Means, and the detecting means comprises:
When partially reproducing one unit of image, a restart display position corresponding to a block to be reproduced among a plurality of blocks is detected from address information included in the second image data, and the second image data is detected. The compressed data corresponding to the detected restart display position may be selectively provided to the decoding / reproducing means.

According to the present invention, in the image compression system, when assembling the second image data, the address information is not incorporated in the second image data, but the address information is stored in association with the first image data. Storage means for
Instruction information for instructing the address information in the storage means is incorporated in the compressed data into which the restart indication is inserted, and
And processing means for assembling the image data.

According to the present invention, there is further provided decoding / reproducing means for receiving the second image data incorporating such address information, decoding and expanding the second image data to reproduce the first image data, Detecting means for detecting the position of the restart display in the compressed data with reference to the address information included in the second image data. A restart display position corresponding to a block to be reproduced among the blocks is detected from address information included in the second image data, and compression corresponding to the detected restart display position of the second image data is performed. An image reproduction system for selectively providing data to a decoding / reproduction means is also provided.

According to the present invention, the address information is not incorporated in the second image data, and the image reproducing system includes a storage means for storing the address information in association with the first image data. In the image data, the instruction information for instructing the address information in the storage means is incorporated in the compressed data in which the restart display is inserted, and the image reproduction system receives the second image data and decodes the second image data. Decoding and reproducing means for decompressing and reproducing the first image data; and address information stored in the storage means based on instruction information included in the second image data. Detecting means for detecting the position of the restart display, wherein the detecting means includes: Is detected from the address information by referring to the address information of the storage means based on the instruction information included in the second image data, and the detected restart of the second image data is detected. A configuration in which the compressed data corresponding to the display position is selectively provided to the decoding / reproducing means may be employed.

[0011]

According to the present invention, a restart display placed for each of a predetermined number of blocks of a plurality of blocks constituting a series of compressed image data and address information corresponding to the addresses are converted into compressed image data as parameters. Insert or
Alternatively, when the image of one screen is partially reproduced by separately registering it in a file, the address information is used to access a restart display of a block corresponding to partial reproduction and selectively reproduce the block. Can be.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an image compression system according to the present invention; FIG. 1 is a block diagram of an image compression system 10 according to the embodiment. The image compression system 10 includes an encoder 11, which is a circuit for converting an input image signal 100 into JPEG compressed data 101. Forward discrete cosine transform circuit (FDCT) of encoder 11 12
The luminance signal Y and the chrominance signals P _B of the high-definition still image signal of 8 bit precision, including the input image signal 100, horizontal and P _R respectively, is divided into blocks of 8 × 8 pixels in the vertical direction, for each block 2 This is a circuit that performs dimensional DCT (discrete cosine) transformation and outputs DCT coefficients of its direct current (DC) component and alternating current (AC) component to the quantization circuit 13. Cosine conversion circuit
Numeral 12 also has a function of assembling DCT coefficients into JPEG format compressed data 101 (FIG. 2) in this embodiment. This will be described later in detail with reference to FIG.

The quantizing circuit 13 is a circuit for quantizing the DCT coefficient from the cosine transform circuit 12, and an output of the quantizing circuit 13 is connected to an entropy coding circuit 14. Encoding circuit 14
Is a circuit that performs Huffman coding on the quantized data from the quantizing circuit 13 in this embodiment, and outputs compressed data 101 including parameters and code data. The output of the encoding circuit 14 is connected to a buffer 15, and the buffer 15
This is a memory for temporarily storing and outputting 1. The output 102 of the buffer 15 is connected to the main processing system (MP
U) Connected to 18. In the following description,
The reference number of the signal is designated by the reference number of the connecting line in which it appears.

FIG. 2 shows the structure of the compressed data 101 according to the JPEG standard. SOI and EOI are codes indicating the start and end of image data representing an image of one unit (frame). The table / misc 110 is an area including a compression code algorithm such as a quantization table and a Huffman coding table to be used, and a restart interval DRI described later. The frame header 111 contains one frame of image data.
This area includes a code indicating whether the format is the RGB format or the YCC format, and the type of the sub-sampling method. The scan header 112 has a scan method, R / G / B pixel signal or R / G / B
This area contains a code indicating whether it is a G / B field signal. This is followed by the compressed data code 113.

The data code 113 is composed of a plurality of blocks. At the beginning of each block or at the beginning of every predetermined number (for example, 4) of blocks, a restart marker code 114 (RSTm, m = 0 to 7) is provided. Is inserted. It is advantageous that the interval at which the restart marker code 114 is inserted is set to a size suitable for reproducing only a desired portion of one frame of image in data block units. In this embodiment, for example, every four blocks, that is, two blocks each in the horizontal and vertical directions of the screen are appropriate. This number is constant throughout one screen in this embodiment, but does not necessarily have to be a fixed number. In this embodiment, the insertion interval of the restart marker code 114 is recorded as the restart interval DRI in the table / misc 110. The restart interval DRI is
A display word “FFDD” indicating that the code is included, followed by a word indicating the interval between the restart marker codes 114.

[0016] JPEG format compressed data shown in FIG.
101 is basically assembled by the cosine conversion circuit 12. The cosine transform circuit 12 divides the input image signal 100 into a plurality of blocks, performs two-dimensional DCT transform for each block, and generates DCT coefficients of the DC component and the AC component. At this time, in the present embodiment, a restart marker code 114 is inserted after the code 113 for every four blocks, and a table / misc 110, a frame header 111 and a scan header 112 are created. Thus, the compressed data 101 of the JPEG format shown in FIG. 2 is assembled. As you know, JP
In the EG method, a difference between a DC component of a still image signal and a previous value other than the initial value is transmitted. In the decoding system, the difference is added to or subtracted from the initial value to reproduce the current value. The restart marker code 114 is a restart display for resetting the decoding based on the difference to the initial value. The restart marker code is
If a transmission error occurs during the transmission of compressed image data,
This reset function can prevent the propagation of the error to the subsequent data.

The main processing system (MPU) 18 includes a data bus 17
Is connected to a large-capacity storage device (M) 19, a decoder 30, and a communication device (T) 40 through the storage device. This is a control circuit for recording compressed data in a file 120 described later stored in the file. File 120
Is created for each image of one unit (frame). The main processing system 18 also creates an address table 130 in the storage device 19 as illustrated in FIG. 4 for each unit of image, and stores the number 0 to N (natural number) of the restart marker code 114 in the unit of image. ) And the corresponding byte address 131 are also recorded. Further, in reproducing the recorded data, the file 120 is read and the data is read from the decoder 30 or the communication device.
Control to give this to 40 is also performed.

The storage device 19 is a large-capacity file storage device including, for example, an optical disk, a magneto-optical disk, a magnetic disk, and a memory card, and stores various data such as a file 120, compressed data 101, and an address table 130. Storage area. Address table 130
Is the byte address 131 of the restart marker code RSTm
Is a correspondence table stored in correspondence with the numbers 0 to N of the restart marker code 114. The byte address 131 is the restart marker code 11 in one unit of compressed image data.
Address 4 is indicated by the number of bytes from the beginning of the compressed data. The file 120 is created for each unit of compressed image data, and includes a file name 121 and corresponding address pointers (AP) 122 and 123 as shown in FIG. The address pointers 122 and 123 indicate the file addresses of the compressed data 101 (FIG. 2) and the address table 130 (FIG. 4) in the storage area of the storage device 19, respectively. As another recording format of the compressed data, the compressed data 101 and the address table 130 may be stored in different files.

At the time of decoding, the main processing system 18 assigns a file name 121 in the file 120 for the image to be decoded.
Is read from the storage device 19 and inserted into the application marker 141. The application marker 140 is added after the SOI in the compressed data 101, and is converted into the structure of the compressed code 140 shown in FIG. When the compressed code 140 is transferred from the communication device 40 to a remote location, the address table 13 is added to the application marker 141.
Insert 0. However, when decoding is performed in the present system 10, the address table is added to the application marker 141.
Do not include 130. In the latter case, one of file 120
In the full decoding mode in which the unit (frame) of compressed image data is decoded, the main processing system 18 sends the entire unit of the compressed code 140 to the decoder 30. In the partial playback mode in which only the desired block is played, the main processing system 18 obtains the address of the restart marker RSTm of the desired block to be partially played back from the address pointer 123 of the file 120 corresponding to the desired image. Then, the block of the compressed data 101 following the address of the restart marker RSTm is read from the storage device 19, and the compressed code 140 is sent to the decoder 30.

A remote system is connected to the communication device 40 via a communication line. The remote system may have basically the same configuration as the present system 10, and includes at least the decoder 30 and its related functional units.

The decoder 30 is a circuit for expanding the compressed code 140 input from the data bus 17 to generate a reproduced image signal 150. The decoder 30 has a buffer 31, which is a memory for temporarily storing the compressed code 140 and outputting it to the decoding circuit 32. The decoding circuit 32 is a decoder that decodes the compressed code 140 from the buffer 31 according to the Huffman coding rule. The decoded signal is input to the inverse quantization circuit 33, which has a function of dequantizing the decoded signal. The quantized signal is the inverse discrete cosine transform circuit
(IDCT) 34, the latter being a functional unit that solves the discrete cosine transform of the quantized signal and outputs a reproduced image signal 150.

In the image compression operation of one frame of image data, the encoder 11 converts the input image signal 100 into JPEG compressed data 101 and stores it in the buffer 15. The main processing system 18 reads the compressed data 101 from the buffer 15 in byte units, and stores the file name in the file 120 of the storage device 19.
121, and pointer data for connecting the compressed data 101 and the address table 130 are recorded in the address pointers 122 and 123, respectively. At the same time, the storage device 19 pointing the compressed data 101 to the address pointer 122
In the storage area. Thus, the recording of the compressed data is completed.

In the decoding operation of the compressed image data, the main processing system 18 reads out the compressed code 101 from the file 120 of the image to be decoded,
A compression code 140 is formed by adding 1 to the compression code. At this time, when transferring to a remote place from the communication device 40, the address table 130 is included in the application marker 141. In the decryption in the present system 10, the address table 130 is not included in the application marker 141. In the full decoding mode of the file 120, the main processing system 18 reads out all the compressed codes 140 of one frame of an image to be reproduced from the storage device 19 and sends it to the decoder 30. In the partial playback mode, the main processing system 18 determines the number of the restart marker code 114 corresponding to the desired playback block from the restart marker code / address table 130 of the image file 120 containing the block to be played back. The byte address 131 to be obtained is obtained. Therefore, the storage device 19 is accessed, the compressed image data in the block, that is, the code 113 is read from the storage position indicated by the byte address 131, and this is included in the compression code 140 and supplied to the decoder 30.

The decoder 30 expands the compressed code 140 input from the storage device 19 to generate a reproduced image signal 150.
More specifically, the compressed code 140 is temporarily stored in the buffer 31, and the decoding circuit 32 reads out the compressed code 140 from the buffer 31 and decodes it according to the Huffman coding rule. The Huffman coding rules and quantization tables used can be known from the table / misc 110 of the compressed code 140. The decoded signal is input to the inverse quantization circuit 33, and the inverse quantization circuit 33 dequantizes the decoded signal. The quantized signal is subjected to a discrete cosine transform by an inverse discrete cosine transform circuit 34, and is output as a reproduced image signal 150.

The compression code 140 transmitted from the communication device 40
In the partial playback mode, the remote system refers to the address table 130 of the application marker 141 included in the received compression code 140 from the received compression code 140 in the partial playback mode. By reading the byte address 131 corresponding to the number of the restart marker code RSTm of the block to be reproduced from the address table 130, it is possible to randomly access the partial reproduction portion of the compression code 140.

[0026]

As described above, according to the present invention, address information in which each restart marker code of a plurality of blocks constituting an image compression code is associated with an address in the compressed image data is recorded. In the case of partial reproduction of a desired block of one unit image, the address of the restart marker code of the corresponding block is detected from the address information, and the compressed code of the partial reproduction is directly accessed according to this address, so that 1 is represented in the image The reproduction speed of a desired portion can be increased.

In a method of transmitting a compressed code including a restart marker code, conventionally, a search is performed from the restart marker code of each block to the end code of the block to determine whether the length (interval) matches the specified length. A determination time was required because a transfer error was detected based on whether or not the error occurred. However, according to the present invention, if a restart marker code exists at the address indicated by the address information, it can be understood that no transmission error has occurred. Therefore, the time required to determine a transmission error is reduced.

Although the embodiment in which the image compression system of the present invention is applied to the JPEG system has been described, the present invention is not limited to this. The present invention can be effectively applied to any encoding system that can transmit or record an initial value and a difference with respect to the DC component of an image signal and set a reset display that resets the initial value to the initial value.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an image compression system according to the present invention.

FIG. 2 is a configuration diagram of a compressed code output from the encoder of the embodiment shown in FIG.

FIG. 3 is an explanatory diagram illustrating a configuration example of a file that stores a compressed code and an address table in the embodiment of FIG. 1;

FIG. 4 is a configuration diagram illustrating the address table shown in FIG. 3;

FIG. 5 is a configuration diagram showing an example of a compression code related to the address table shown in FIG. 4;

[Explanation of symbols]

 10 Image compression system 11 Encoder 18 Main processing system 19 Storage device 30 Decoder 40 Communication device

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-95471 (JP, A) JP-A-7-336676 (JP, A) JP-A-7-193810 (JP, A) JP-A-7-193 177509 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04N 1/41-1/419 H04N 7/30

Claims (6)

(57) [Claims] 1. First image data representing one unit of image is
DC signal of the first image data divided into a plurality of blocks
Compression coding into compressed data containing components and AC signal components
Encoding means for performing a predetermined block on the plurality of blocks of the compressed data.
A restarter for resetting the DC signal component for each lock number
Display inserting means for inserting a restart indication, and the compressed data at a position where the restart indication is inserted.
The byte address assigned the number from the beginning of the data
Address information that corresponds to the restart display number
Address information forming means for forming, the compressed data inserted with the restart indication and the address
Address information and pointers corresponding to
2 processing means for assembling the image data asSee The system further comprises: The second image data is decoded and expanded, and the first image data is reproduced.
Decoding / playback means to be generated, Referring to the address information included in the second image data,
The restart display position in the compressed data.
Outgoing detection means, The detecting means performs partial reproduction of the one unit image.
In response to a block of the plurality of blocks to be reproduced.
The position of the restart display corresponding to the
Detected from the address information contained in the
Corresponding to the position of the detected restart display of the image data.
Selectively providing the compressed data to the decoding / reproducing means, Further, the start of the image is indicated in response to the transfer of the compressed data.
Including the address information in the area next to the area Features
Image compression system. 2. The image compression system according to claim 1, wherein said predetermined number of blocks is a minimum number of blocks for partially reproducing said one unit of image. . 3. The first image data representing one unit of image is
DC signal of the first image data divided into a plurality of blocks
Compression coding into compressed data containing components and AC signal components
Encoding means for performing a predetermined block on the plurality of blocks of the compressed data.
Restarting to reset the DC signal component for each number of blocks
Display insertion means for inserting the restart indication, and the compressed data at a position where the restart indication is inserted.
The byte address assigned the number from the beginning of the data
Address information that corresponds to the restart display number
Address information forming means for forming, and storing the address information in association with the first image data
Storage means for storing compressed data having the restart indication inserted therein and the storage means
Means for indicating the address information in the means.
And assemble them as second image data
Processing means to assembleSee The system further comprises: The second image data is decoded and expanded, and the first image data is reproduced.
Decoding / playback means to be generated, Based on the instruction information included in the second image data,
Refer to the address information stored in the storage means
And based on the address information,
Detecting means for detecting the position of the restart display, The detecting means performs partial reproduction of the one unit image.
In response to a block of the plurality of blocks to be reproduced.
The position of the restart display corresponding to the
Before the storage means based on the instruction information contained in the data
The address information by referring to the address information.
Detected from the second image data,
Selectively decodes the compressed data corresponding to the position of the
Given to the reproduction means, Further, the start of the image is indicated in response to the transfer of the compressed data.
Compressed data corresponding to the area next to the area from the storage means
And include the address information Characterized by
Image compression system. 4. The image compression system according to claim 3 , wherein said predetermined number of blocks is a minimum number of blocks for partially reproducing said one unit of image. . 5. The first image data representing an image of one unit is divided into a plurality of blocks, compression-encoded into compressed data including a DC signal component and an AC signal component of the first image data, and A restart indicator for resetting the DC signal component for each predetermined number of blocks of the plurality of blocks is inserted, and a number from the beginning of the compressed data is assigned to an insertion position of the restart indicator in the compressed data. Decoding / reproducing means for receiving second image data in which address information corresponding to the address and the restart display number are incorporated, decoding and expanding the second image data and reproducing the first image data; Detecting means for detecting a restart display position in the compressed data with reference to the address information included in the second image data. In response to the partial reproduction of the one unit image, the detecting means sets a restart display position corresponding to a block to be reproduced among the plurality of blocks in the address information included in the second image data. , And selectively supplies the compressed data corresponding to the detected restart display position of the second image data to the decoding / reproducing means, and further starts the image in response to the transfer of the compressed data. An image reproducing system comprising: a region next to a region to be displayed, including the address information. 6. The first image data representing one unit of image is divided into a plurality of blocks, compression-encoded into compressed data including a DC signal component and an AC signal component of the first image data, and A restart indicator for resetting the DC signal component for each predetermined number of blocks of the plurality of blocks is inserted, and a number from the beginning of the compressed data is assigned to an insertion position of the restart indicator in the compressed data. Storage means for storing address information indicating the correspondence between the address and the number of the restart indication in association with the first image data; and storing the compressed data inserted with the restart indication and the address information in the storage means. Receiving the second image data incorporated in association with the instruction information to instruct,
Decoding and reproducing means for decoding and decompressing the image data to reproduce the first image data, and referring to the address information stored in the storage means based on the instruction information included in the second image data, Detecting means for detecting a restart display position in the compressed data based on the address information, wherein the detecting means reproduces one of the plurality of blocks when partially reproducing the one unit image. The position of the restart display corresponding to the power block is detected from the address information by referring to the address information of the storage unit based on the instruction information included in the second image data. The compressed data corresponding to the detected restart display position is selectively supplied to the decoding / reproducing means, and further, the image is opened in response to the transfer of the compressed data. Image reproduction system, characterized in that inclusion of the address information in the next area of the region representing the.