Abstract:
The present invention intends to provide an encoded data conversion method for speeding up conversion processing by eliminating re-encoding processing when predetermined data is inserted into encoded data. The encoded data conversion method is a conversion method for converting encoded image data comprising: a step of decoding encoded image data; and a step of inserting a code for eliminating re-encoding of subsequent data after the predetermined data.

Description:
FIELD OF THE INVENTION 
   The present invention relates to an encoded data conversion method. 
   BACKGROUND OF THE INVENTION 
   Japanese Patent Laid-Open No. 2003-209639 describes a header inserting method (JPEG (Joint Photographic Experts Group) encoded data conversion method) with re-encoding processing. That method inserts a header into JPEG encoded data by deleting 0x00, which follows 0xFF, from the JPEG encoded data, bit-shifting attached JPEG encoded data by header insertion, and inserting 0x00 after 0xFF into the bit-shifted JPEG encoded data. 
   A data structure of a JPEG encoded image will be briefly described with reference to  FIG. 10 . 
   A JPEG image is generated by encoding an inputted original image is divided into blocks of 8 pixels×8 pixels. First, DCT (Discrete Cosine Transform) processing and quantization processing are performed for each block of 8 pixels×8 pixels. A block denoted by the reference numeral  1001  in  FIG. 10  represents a block after the DCT processing. Each pixel after the DCT processing is called a DCT coefficient. Huffman encoding is performed after the DCT processing. The Huffman encoding is performed in the order of the numbers given to each pixel in the block  1001  of  FIG. 10 . 
   In the block  1001 , 0 th  coefficient is called a DC coefficient and the other coefficients are called AC coefficients. 
   The reference numeral  1002  of  FIG. 10  denotes an MCU (Minimum Coded Unit). The MCU is a set of blocks  1001 . In the example of  FIG. 10 , four blocks make one MCU. 
   A set of MCUs makes a JPEG encoded image. Between an MCU and an MCU, a marker code called an RST marker (Restart Marker) can be inserted at a certain interval. The RST markers may or may not be inserted. The RST markers may be inserted at any interval.  FIG. 10  shows a case where an RST marker  1003  is inserted for every two MCUs. The marker code of JPEG must be inserted as it is byte-aligned. Therefore, when an RST marker  1003  is inserted, “1” bit needs to be inserted by the number necessary to byte-align and the RST marker needs to be inserted after the byte-align. 
   When the DC coefficient in a block is encoded, a DC coefficient of a previously encoded block is used. That is called DC coefficient prediction. The DC coefficient prediction is effective in an interval for an RST marker to be inserted. The DC coefficient prediction is not performed on a block immediately after an RST marker is inserted. 
   A JPEG image is subjected to processing called byte stuff processing. The byte stuff processing is the processing for inserting 0x00 immediately after 0xFF code when 0xFF code in a byte-aligned state is in a JPEG image. In order to decode the processed image, the inserted 0x00 is deleted first, and then decoding processing is performed. 
   A usual procedure for inserting an RST marker into a JPEG encoding image without an RST marker being inserted will be described with reference to  FIG. 11 . 
     FIG. 11  is a flowchart showing a conversion procedure for inserting an RST marker into a JPEG encoded image without an RST marker being inserted and converting it into a JPEG encoded image with an RST marker being inserted. 
   First at step S 1101 , changing processing is performed on a header. At this step, a marker code indicating that the JPEC encoded image includes an RST marker is added. The other headers are not changed. 
   Conversion processing is performed by each MCU. At step S 1102 , decoding processing is performed on an MCU. The decoding processing is the Huffman decoding processing and the DC coefficient prediction decoding processing. In this conversion processing, neither invert quantization processing nor invert DCT processing is needed. Decoding processing up to the DC coefficient prediction is performed here from the viewpoint of conversion efficiency. The DCT coefficient prediction is needed because a DC coefficient prediction is reset after an RST marker is inserted and a DC coefficient value of an MCU immediately after the RST marker is inserted changes. 
   After decoding processing of an MCU, encoding processing is performed on an MCU as shown in step S 1103 . The encoding processing performed in this step is a re-encoding of a DC coefficient value and a byte stuff processing. The re-encoding of a DC coefficient value is performed when DC coefficient prediction processing changes due to RST marker insertion as mentioned above. Similarly, the byte stuff processing has to be performed again because an encoded image is bit-shifted when an RST marker is inserted. Japanese Patent Laid-Open No. 2003-209639 describes a method for performing byte stuff processing again and re-converting a JPEG encoded image. At step S 1104 , whether or not to insert an RST marker is determined. Insertion of an RST marker is performed for each previously designated MCU interval. After the designated MCU decoding processing and encoding processing, insertion of an RST marker is performed at step S 1105 . As mentioned above, when an RST marker is inserted, byte-align processing is performed and the head position of an RST marker is set to the head position of a byte. 
   Processing mentioned above is performed on all the MCUs in a JPEG image. Then, the conversion processing of the JPEG image ends. 
   As mentioned above, in usual conversion processing performed when an RST marker is inserted into a JPEG image encoded image, decoding processing and encoding processing (re-encoding processing of a DC coefficient and byte stuff processing) have to be performed on all the MCUs. That causes a problem of slowing the conversion processing. 
   The encoded data conversion method of the present invention adds codes for avoiding bit-shift after predetermined data is inserted to eliminate byte stuff processing which is applied to an encoded image. As the invention described in Japanese Patent Laid-Open No. 2003-209639 does not have this technique, it needs a series of re-encoding processing including deletion of 0x00 which follows 0xFF in unconverted JPEG encoded data, bit-shift processing due to insertion of predetermined data, and insertion of 0x00 after 0xFF into bit-shifted JPEG encoded data, as described in the claim 4 in Japanese Patent Laid-Open No. 2003-209639. 
   The invention described in Japanese Patent Laid-Open No. 2003-209639 has a problem in that it slows down conversion processing as when it performs conversion by inserting a header into JPEG encoded data it needs re-encoding processing of JPEG encoded data. 
   SUMMARY OF THE INVENTION 
   The present invention intends to provide an encoded data conversion method for speeding up conversion processing by eliminating re-encoding processing when predetermined data is inserted into encoded data. 
   The present invention is a conversion method for converting encoded image data comprising: a first inserting step of inserting predetermined data into encoded image data; and a second inserting step of inserting a code for eliminating re-encoding of subsequent data after the predetermined data. 
   Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
       FIG. 1  is a block diagram showing an embodiment of the present invention; 
       FIGS. 2A and 2B  are diagrams illustrating a method of inserting a code for adjusting a bit position at an MCU inserting unit and the code; 
       FIG. 3  is a flowchart showing a method for adjusting a bit position by converting an existing MCU at an MCU inserting unit; 
       FIG. 4  is a flowchart showing a method for adjusting a bit position by adding a new MCU at an MCU inserting section; 
       FIG. 5  is a flowchart showing the first embodiment of the present invention; 
       FIG. 6  is a diagram showing MCU arrangements before and after the conversion of a JPEG encoded image of the first embodiment of the present invention; 
       FIG. 7  is a diagram showing a size of a JPEG image and an effective image size of the first embodiment of the present invention; 
       FIG. 8  is a flowchart showing the second embodiment of the present invention; 
       FIG. 9  is a diagram showing MCU arrangements before and after the conversion of JPEG encoded image of the second embodiment of the present invention; 
       FIG. 10  is a diagram illustrating an arrangement of a JPEG encoded image; and 
       FIG. 11  is a flowchart showing a conventional approach of implementing RST marker insertion processing to a JPEG image into which no RST marker is inserted. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawings. 
   The encoded data conversion method of the present invention relates to a conversion method of inserting predetermined data into JPEG encoded data. Specifically, the present invention is preferably applied to the case where an RST maker is inserted into a JPEG encoded data. This is because the present invention can implement flexible decoding processing such as decoding processing performed by extracting a part in the JPEG image by inserting an RST marker into the JPEG encoded data. 
   An embodiment of the present invention will be detailed by exemplifying a case where the present invention is applied to a JPEG image with reference to  FIG. 1 . 
     FIG. 1  is a block diagram showing an embodiment of the present invention. 
   A decoding processing unit  101  in  FIG. 1  performs decoding processing on an encoded data before conversion  105  to be inputted. The decoding processing implemented at the decoding processing unit  101  is desirably the minimum decoding processing which is necessary to convert JPEG encoded data from a viewpoint of throughput. First, at the decoding processing unit  101 , decoding processing of Huffman encoding is performed on the encoded data before conversion  105 . Then, predictive decoding processing of a DC coefficient is performed. The decoded DC coefficient and AC coefficient information are sent to an MCU insertion unit  103  to be described later, as required. Prior to decoding processing, deletion of “0x00” (removing processing of byte stuff) immediately after “0xFF” in encoded data is performed at the decoding processing unit  101 . 
   The decoding processing unit  101  selects and sends out data to be outputted from output selection signals which are sent from an RST marker insertion unit to be described later. In such a case, the data to be outputted is sent out as a decoded DC coefficient and a decoded AC coefficient are sent out to the MCU insertion unit  103  or as encoded data before conversion  105  is sent out to an encoded data copying controller  104 . Here, the output selection signal sent out from the RST marker insertion unit  102  is a signal for switching the outputting ways above. 
   The number of MCUs decoded at the decoding processing unit  101  is sent to the RST marker insertion unit  102  to be described later, as required. For example, the decoding processing unit  101  counts the number of MCUs each time it decodes an MCU and informs the RST marker insertion unit  102  on the number of MCUs. The decoding processing unit  101  may inform the RST marker insertion unit  102  that an MCU is decoded each time it decodes an MCU and the RST marker insertion unit  102  may count the number of MCUs each time the RST marker insertion unit  102  gets the information. 
   The RST marker insertion unit  102  sends out an RST marker to be inserted for each designated insertion interval of RST markers (MCU unit) according to the result of the decoding processing. The sent out RST marker is sent to the encoded data copying controller  104  and incorporated in an encoded data after conversion  106 . 
   Sending out of an RST marker is determined by a previously designated insertion interval (MCU interval) and the number of decoded MCUs which is sent from the decoding processing unit  101 . If the number of decoded MCUs reaches the MCU interval for an RST marker to be inserted, the RST marker insertion unit  102  sends out an RST marker to be inserted. The RST marker insertion unit  102  sends an output selection signal to the decoding processing unit  101  according to the result of the decoding processing (the number of MCUs). If the RST marker insertion unit  102  sends out an RST marker, the output selection signal is a signal indicating that a decoded DC coefficient and a decoded AC coefficient are sent out to the MCU insertion unit  103 . If the RST marker insertion unit  102  does not send out an RST marker, the output selection signal is a signal indicating that the encoded data before conversion  105  is sent out to the encoded data copying controller  104 . 
   Although the RST marker may be inserted at any interval, it is preferably inserted for each line in a JPEG encoded image from the viewpoint of efficiency of conversion processing. 
   The MCU insertion unit  103  creates an MCU to be inserted immediately after an RST marker. Processing performed at the MCU insertion unit  103  includes: (1) conversion processing of an existing MCU and (2) adding processing of a new MCU. (1) and (2) will be described below, respectively. 
   (1) Description of Conversion Processing of an Existing MCU 
   Conversion processing of an existing MCU performed by the MCU insertion unit  103  is re-encoding performed to eliminate re-encoding processing on MCUs after the converted MCUs. Specifically, the processing eliminates change in a bit position due to insertion of an RST marker and re-encoding of a DC coefficient in converting an MCU immediately after an RST marker is inserted and makes MCUs after the converted MCUs have no change in a bit position. If a bit position is not changed, the encoded data before conversion can be copied as it is, which can omit unnecessary re-encoding processing. 
   In order to keep the state that a bit position is not changed for as many MCUs as possible, a code for absorbing a change in a bit position is added at the end of an MCU at the MCU insertion unit  103 . The method will be described with reference to  FIGS. 2A and 2B . 
   First, as shown in  FIG. 2A , a correction area  201  for absorbing a change in a bit position is set in a high frequency component area of a block. In  FIG. 2A , an area of 12 pixels is set as the correction area  201 . Then, AC coefficients which should exist in the correction area  201  are deleted and an encoded code which can absorb a change in a bit position is added (inserted) to eliminate a change in a bit position. The encoded code needs to meet two points: it can absorb a change in a bit position and a decoded pixel of an encoded code can be included in the correction area  201 . 
   Affects of degradation in image quality due to added encoded codes can be reduced as the correction area  201  is set in a high frequency component area. The encoded code to be added is preferably determined to lessen the decoded pixel value similarly because of the affects of degradation in image quality. 
   Examples of an encoded code to be added are shown in  FIG. 2B .  FIG. 2B  is an example of a typical color difference Huffman table described in JPEG standards (JISX4301: digital compression and encoded processing of continuous gradation static image). The encoded code to be added is not limited to one and a plurality of codes can be added even in the same Huffman table. As a change in a bit position is a shift by the number of bits from the byte head, the changes are eight types from 0 to 7 (If the change exceeds eight, eight subtracted from the number is the change in a bit position). In  FIG. 2B , examples of encoded codes to be added for eight types are shown respectively. 
   For example, if a bit position changes by “1 bit” compared to the encoded data before conversion, “7 bits” needs to be added to absorb a change in a bit position. By adding “7 bits”, a change in a bit position becomes 8 bits, which causes the shift from a byte position to result in the same position as in the original state. If “7 bits” are added, the code No.  8  in  FIG. 2B  is added. That can realize re-conversion of an MCU which absorbed a change in a bit position and MCUs thereafter can be kept in a state of no change in a bit position. 
   Re-conversion processing at the MCU insertion unit  103  will be described with reference to a flowchart of  FIG. 3 .  FIG. 3  is a diagram showing a flow of processing steps at the MCU insertion unit  103 . 
   At step S 301 , re-encoding of the decoded DC coefficient and coupling of the decoded AC coefficient are performed. As the MCU converted at the MCU conversion unit  103  is an MCU immediately after an RST marker is inserted, a predicted value of the DC coefficient is reset to 0. Accordingly, re-encoding processing of the DC coefficient is required. Re-encoding processing of the DC coefficient is performed as a Huffman code corresponding to the DC coefficient value decoded at the decoding processing unit  101  of  FIG. 1  is selected from a Huffman table. As prediction such as in encoding of a DC coefficient does not exist for an AC coefficient, Huffman code of a decoded and divided AC coefficient is coupled with an AC coefficient value again to make an encoded code. As a bit position may be shifted due to insertion of an RST marker and re-encoding of a DC coefficient, byte stuff processing needs to be performed again. The byte stuff processing may be performed as required at outputting an encoded code, performed when encoded data in a certain unit quantity is created, or the like. In the flow of  FIG. 3 , the case where the byte stuff processing is performed when encoded data in a certain unit quantity (MCU) is created is described (step S 308 ). 
   At step S 302 , whether it is conversion of the final block in an MCU or not is determined. If it is the final block in an MCU, the operation proceeds to S 303  and after. 
   Step S 303  is re-encoding processing of a DC coefficient on the final block in an MCU. Re-encoding processing of a DC coefficient is the same as the re-encoding processing on the other blocks. Coupling of AC coefficient is performed thereafter. Every time coupling of an AC coefficient is performed, whether the AC coefficient to be coupled goes into a correction area or not is determined at step S 304 . If a correction area is set from pixel No.  52  to No.  63  as shown in  FIG. 2A  and a decoded pixel of the AC coefficient to be coupled is in No.  52  to No.  63 , the operation proceeds to step S 305  without coupling the pixels. If the pixels do not reach the correction area, coupling of the next AC coefficient is performed. A value decoded at the decoding processing unit  101  of  FIG. 1  is used in determination on whether the pixel to be coupled goes into a correction area or not. 
   After coupling of an AC coefficient finished on the final block, a change in a bit position changed in re-conversion processing till then is calculated at step S 306 . Then, an encoded code for correction is added at step S 307  according to the number of changed bit positions and a change in a bit position is absorbed. 
   (2) Description of Adding Processing of a New MCU 
   Processing of adding a new MCU, which is performed at the MCU insertion unit  103 , is processing for absorbing a change in a bit position by adding an invalid new MCU which has nothing to do with an image, immediately after an RST marker is inserted. Processing for adding a new MCU, which is performed at the MCU insertion unit  103 , will be described with reference to the flowchart of  FIG. 4 . 
   At step S 401 , encoding of a DC coefficient is performed. The DC coefficient is a DC coefficient predicted value used in an MCU after the MCU added. As a predicted value of a DC coefficient is reset by an RST marker in process of decoding processing, this processing is for making an original DC coefficient predicted value available by the added new MCU. 
   At step S 402 , the EOB (End Of Block) code is added and blocks in an MCU finishes. At step S 403 , whether it is the final block in an MCU or not is determined. If it is the final block, the operation proceeds to step S 404 . 
   Step S 404  is the same encoding of a DC coefficient as that in S 401 . Then at step S 405 , a change in a bit position which is changed in a series of processing till then is calculated. Then, an encoded code for correction is added according to the number of changed bit positions at step S 406  and the change in the bit position is absorbed. 
   As the converted MCU is a part of an image in re-conversion processing of an existing MCU, which is performed at the MCU insertion unit  103 , a small value is selected to be an encoded code for correction so as not to affect image quality as shown in  FIG. 2B . As an added MCU does not form a part of an image in adding processing of a new MCU shown in  FIG. 4 , the MCU does not affect the image. Therefore, the encoded code for correction added at step S 406  may be any code if only it can absorb a change in a bit position and meet the JPEG standard. 
   The encoded data copying controller  104  of  FIG. 1  creates encoded data after conversion  106  by copying or inserting the encoded data to be sent out from the decoding processing unit  101 , the addition MCU to be sent out from the MCU insertion unit  103 , and the RST marker to be sent out from the RST marker insertion unit  102  in an appropriate position. 
   When an RST marker is inserted, a bit position may change due to the insertion of the RST marker. In such a case, the variation of bit position is sent to the MCU insertion unit  103  as the number of bit-shifts. At the MCU insertion unit  130 , a change in a bit position is calculated in consideration of the number of bit-shifts as mentioned above ( FIG. 3  step S 306  and  FIG. 4  step S 405 ). 
   The present invention will be described in detail with a specific example. 
   First Embodiment 
   This embodiment is an example in which the present invention is applied to the case where an RST marker is inserted into a JPEG encoded data and converted as shown in  FIG. 1 . 
   As an applicable condition, an interval to insert an RST marker is for each MCU interval in the image width of JPEG encoded data. Processing performed at the MCU inserting unit  103  of  FIG. 1  is insertion of a new MCU (invalid MCU). If an RST marker is inserted at the image width and an invalid MCU is added immediately after that, the encoded data after conversion is in the state shown in  FIG. 7 . 
   This embodiment will be described with reference to the flowchart shown in  FIG. 5  and  FIG. 1 . 
   First, at step S 501 , changing processing of a header of a JPEG encoded image is performed. The changing processing performed at step S 501  is addition of a marker code accompanying a change in a JPEG image size (width), a change in an effective size (width) of an image, and insertion of an RST marker. As an invalid MCU (data which has nothing to do with an image) is added in this embodiment, the effective image size and the JPEG image size are different. Accordingly, both sizes need to be rewritten at step S 501 . For example, image data is rewritten so that a bit which inserts information indicating the number of all the pixels for one line of image data or information indicating the number of effective pixels in a pixel of one line can be ignored. After step S 501 , the operation proceeds to a conversion processing steps of an actual image. The conversion processing of an image is basically performed for each MCU. 
   First, at step S 502 , decoding processing of an MCU is performed. That is processing performed at the decoding processing unit  101  of  FIG. 1 , and decoding of a Huffman code and decoding of a DC coefficient are performed. Then, at step S 503 , encoded data corresponding to the decoded MCU is copied as encoded data after conversion. That processing is performed at the encoding data copying controller  104  of  FIG. 1 . 
   Each time decoding and copying of an MCU complete, whether an RST marker is inserted or not is determined at step S 504 . As an RST marker is inserted for each width of an image in this embodiment, the RST marker is inserted each time processing of an MCU for an image width ends. Insertion of an RST marker is performed at S 505 . If no RST marker is inserted but it is determined that not all the MCUs in an image ends at step S 507 , processing of an MCU is performed again from step S 502 . 
   After an RST marker is inserted at step S 505 , a dummy invalid MCU (dummy data) is created and inserted at step S 506 . Creation of dummy MCU to be inserted is as described with reference to  FIG. 4 . The dummy MCU is created in a form of absorbing a change in a bit position due to insertion of an RST marker. 
   A series of processing is repeated for all the MCUs in an image to perform conversion processing of encoded data. 
   Advantages of this embodiment will be described with reference to  FIG. 6 . The reference character (a) in  FIG. 6  denotes encoded data before conversion and (b) denotes encoded data after conversion. If an RST marker is inserted in  FIG. 6  (a), MCUs after MCU 3  can be copied from encoded data before conversion by inserting a dummy MCU after an RST marker is inserted. As no conversion processing of MCU need to be performed, efficiency of conversion processing of encoded data due to insertion of an RST may be improved. 
   Second Embodiment 
   This embodiment is the present invention applied to the case where an RST marker is inserted into a JPEG encoded data and converted as shown in  FIG. 1 . 
   As an applicable condition, an interval to insert an RST marker is smaller than an MCU in the image width of the JPEG encoded data. Processing performed at the MCU insertion unit  103  of  FIG. 1  is conversion of an existing MCU. 
   This embodiment will be described with reference to the flowchart shown in  FIG. 8  and  FIG. 1 . 
   First, at step S 801 , changing processing of a header of a JPEG encoded image is performed. The changing processing performed at step S 801  is addition of a marker code accompanying insertion of an RST marker. 
   A series of processing from step S 802  to step S 805  is the same as a series of processing from step S 502  to step S 505  described in the first embodiment. 
   After an RST marker is inserted, conversion processing of an MCU is performed at step S 806 . Then it is inserted as encoded data after conversion. The conversion processing is the same as that described based on a flowchart of  FIG. 3  in the preferable embodiment above. 
   A series of processing above is repeated until all the MCUs in an image finishes performing conversion processing of encoded data. 
   Advantages of this embodiment will be described with reference to  FIG. 9 . The reference character (a) in  FIG. 9  denotes encoded data before conversion and (b) denotes encoded data after conversion. If an RST marker is inserted in  FIG. 9  (a), only MCU 3  after an RST marker is inserted is converted so as to absorb a bit position. That enables encoded data before conversion to be copied for MCUs after MCU 3  (in  FIG. 9 , MCU 4  and MCU 5 ). As conversion processing is limited to some MCUs leaving the other MCUs need not to be converted. That can realize improvement of efficiency in conversion processing of encoded data due to insertion of an RST. 
   Other Embodiments 
   Note that the present invention can be applied to an apparatus comprising a single device or to system constituted by a plurality of devices. 
   Furthermore, the invention can be implemented by supplying a software program, which implements the functions of the foregoing embodiments, directly or indirectly to a system or apparatus, reading the supplied program code with a computer of the system or apparatus, and then executing the program code. In this case, so long as the system or apparatus has the functions of the program, the mode of implementation need not rely upon a program. 
   Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. In other words, the claims of the present invention also cover a computer program for the purpose of implementing the functions of the present invention. 
   In this case, so long as the system or apparatus has the functions of the program, the program may be executed in any form, such as an object code, a program executed by an interpreter, or scrip data supplied to an operating system. 
   Example of storage media that can be used for supplying the program are a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a CD-RW, a magnetic tape, a non-volatile type memory card, a ROM, and a DVD (a DVD-ROM, a DVD-R and a DVD-RW). 
   As for the method of supplying the program, a client computer can be connected to a website on the Internet using a browser of the client computer, and the computer program of the present invention or an automatically-installable compressed file of the program can be downloaded to a recording medium such as a hard disk. Further, the program of the present invention can be supplied by dividing the program code constituting the program into a plurality of files and downloading the files from different websites. In other words, a WWW (World Wide Web) server that downloads, to multiple users, the program files that implement the functions of the present invention by computer is also covered by the claims of the present invention. 
   It is also possible to encrypt and store the program of the present invention on a storage medium such as a CD-ROM, distribute the storage medium to users, allow users who meet certain requirements to download decryption key information from a website via the Internet, and allow these users to decrypt the encrypted program by using the key information, whereby the program is installed in the user computer. 
   Besides the cases where the aforementioned functions according to the embodiments are implemented by executing the read program by computer, an operating system or the like running on the computer may perform all or a part of the actual processing so that the functions of the foregoing embodiments can be implemented by this processing. 
   Furthermore, after the program read from the storage medium is written to a function expansion board inserted into the computer or to a memory provided in a function expansion unit connected to the computer, a computer processor, for example, a Central Processing Unit (CPU) or the like mounted on the function expansion board or function expansion unit performs all or a part of the actual processing so that the functions of the foregoing embodiments can be implemented by this processing. 
   As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims. 
   This application claims the benefit of Japanese Application No. 2005-123502, filed Apr. 21, 2005, which is hereby incorporated by reference herein in its entirety.