JP4971807B2 - Image storage device, control method thereof, program, and digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image storage device writing compressed image data into one storage means which serves as both a first buffer and a second buffer without overwriting the compressed image data onto image data while maintaining the use efficiency of the storage means. <P>SOLUTION: When JPEG data is written in at least part of a RAW buffer 302 and a JPEG buffer 301 of a RAM 206 and when the size of the JPEG data is equal to or smaller than a preset size and the JPEG data is overwritten onto the RAW data, a compression processing part 209 compresses again the RAW data (YUV data) read from the RAW buffer 302 at a set compression rate and the JPEG data is generated. The generated JPEG data is written in the RAW buffer 302 and the JPEG buffer 301. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to an image storage device, a control method thereof, a program, and a digital camera equipped with the image storage device.

  In devices that capture and record images, such as digital cameras, the performance of image sensors, for example, the number of pixels has been increased. As a result, the size of the captured image data increases, that is, the size of the file that records the image data increases. As the file size increases, a large-capacity memory is required as a memory for recording the file.

  In order to avoid an increase in memory capacity, a method has been proposed in which one memory is used so as to serve both as a buffer for recording RAW data that is imaging data and a buffer for recording JPEG data that is compressed data. (For example, refer to Patent Document 1).

Also, there is a method of having a buffer for recording JPEG data, obtaining the compression rate when compressing the image data and recording it in the JPEG buffer, and compressing the image data at the compression rate (see, for example, Patent Document 2). .
Japanese Patent Registration No. 0342388 Japanese Patent Laid-Open No. 2003-199052

  However, when one memory is used as both a buffer for storing RAW data and a buffer for storing JPEG data, the RAW data before compression may be overwritten by JPEG data, and compression may not be performed again.

  The problem that the original RAW data is overwritten with JPEG data occurs when the JPEG data obtained by compression becomes large, that is, when the JPEG data exceeds the size of the buffer for storing the JPEG data. For example, a case where a high-frequency image is taken will be described.

  RAW data is 10 bits per pixel, and YUV data obtained by signal processing is 16 bits. When a standard chart is photographed, JPEG data obtained by compressing YUV data is about 4 bits per pixel. However, when a high-frequency image is taken, the JPEG data obtained by compressing YUV data is 12 bits per pixel, and the JPEG data size when a high-frequency image is taken is larger than when a standard image is taken. . In the memory also serving as a buffer, a JPEG buffer and a RAW buffer are continuous on the address, and the JPEG buffer is secured in accordance with the compression size of a normal image. Therefore, if the JPEG data size is large, the JPEG data write address catches up with the RAW data read address, and the original RAW data is overwritten by the JPEG data. In order to avoid this, a large JPEG buffer area can be secured in the memory corresponding to an exceptional high-frequency image. However, in that case, the memory use efficiency is reduced in a normal image, and the effect of the dual buffer is also reduced.

  The object of the present invention is to maintain the use efficiency of one storage means that serves as both the first buffer and the second buffer, without overwriting the compressed image data on the image data to the storage means, It is to make it possible to write compressed image data.

  Another object of the present invention is to provide an image storage device that enables the writing, a control method and program thereof, and a digital camera equipped with the image storage device.

  In order to achieve the above object, the present invention achieves the above-described object, storage means serving as both a first buffer and a second buffer, image writing means for writing input image data into the first buffer, and the first buffer Image reading means for reading the image data from the buffer, image compression means for compressing the image data read from the first buffer at a set compression rate, and generating compressed image data; and the image compression Compressed image writing means capable of writing the compressed image data generated by the means from the second buffer to the first buffer, and the compressed image data from the second buffer to the first buffer. The compressed image data is written into the storage means by the compressed image writing means. A stop unit for stopping the writing, a determination unit for determining whether a write address of the compressed image data catches up with a read address of the image data after the writing is stopped by the stop unit, and the compression unit by the determination unit When it is determined that the image data write address cannot catch up with the image data read address, the compressed image writing means controls to write again the compressed image data compressed at the compression rate before the stop to the storage means. And an image storage device.

  In order to achieve the above object, the present invention achieves the above-described object, storage means serving as both a first buffer and a second buffer, image writing means for writing input image data into the first buffer, and the first buffer Image reading means for reading the image data from the buffer, image compression means for compressing the image data read from the first buffer at a set compression rate, and generating compressed image data; and the image compression And a compressed image writing unit capable of writing the compressed image data generated by the first buffer from the second buffer to the first buffer, wherein the compressed image data is In the case where writing is performed from the second buffer over at least a partial area of the first buffer, the compressed image writing means performs the A stop step of stopping writing of the compressed image data to the storage means, and a determination step of determining whether or not a write address of the compressed image data catches up with a read address of the image data after the writing is stopped. When it is determined that the write address of the compressed image data cannot catch up with the read address of the image data, the compressed image writing means again stores the compressed image data compressed at the compression rate before the stop to the storage means. And a control step for controlling writing. An image storage device control method is provided.

  In order to achieve the above object, the present invention achieves the above-described object, storage means serving as both a first buffer and a second buffer, image writing means for writing input image data into the first buffer, and the first buffer Image reading means for reading the image data from the buffer, image compression means for compressing the image data read from the first buffer at a set compression rate, and generating compressed image data; and the image compression And a compressed image writing unit capable of writing compressed image data generated by the first buffer from the second buffer to the first buffer, the program for controlling the image storage device, In the case where image data is written from the second buffer to at least a partial area of the first buffer, the compressed image writing Stopping the writing of the compressed image data to the storage means by the means, and determining whether the write address of the compressed image data catches up with the read address of the image data after the writing is stopped And when it is determined that the write address of the compressed image data cannot catch up with the read address of the image data, the compressed image writing means again reads the compressed image data compressed at the compression rate before the stop. And a control step for controlling to write to the storage means.

  In order to achieve the above object, the present invention provides a digital camera equipped with the above image storage device.

  According to the present invention, while maintaining the use efficiency of one storage means serving as both the first buffer and the second buffer, without overwriting the compressed image data on the image data to the storage means, Compressed image data can be written.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing the configuration of a digital camera equipped with an image storage device according to an embodiment of the present invention. FIG. 2 is a diagram showing a memory map of the RAM 206 in FIG.

  As shown in FIG. 1, the digital camera includes a lens 201 and an image sensor 202 that converts an object image captured via the lens 201 into an analog signal by photoelectric conversion. The analog signal output from the image sensor 202 is converted into a digital signal (RAW data) by the A / D converter 203. This digital signal is input to the memory controller 204 or to the signal processing unit 207 via the memory controller 204.

  The memory controller 204 writes or reads RAW data or compressed image data (JPEG data) to the RAM 206 or the memory card 216 based on the input write address or read address. Here, writing of data to the memory card 216 is performed via an I / F (interface) 215.

  Here, a write address and a read address for the RAW data are generated by a RAW data write address generation unit 205 and a RAW data read address generation unit 212, respectively. A write address for the JPEG data is generated by the JPEG data write address generation unit 211.

  As shown in FIG. 2, the RAM 206 is provided with a RAW buffer 302 and a JPEG buffer 301. The RAW buffer 302 is a buffer to which RAW data output from the A / D conversion unit 203 is written, and the JPEG buffer 301 is a buffer to which JPEG data obtained by compressing the RAW data is written. For example, the size of the JPEG buffer 301 is set to the JPEG file size when a standard chart is captured. Here, in the RAM 206, it is assumed that the address increases in the direction indicated by the arrow in FIG. JPEG data obtained by the compression process is normally written in the JPEG buffer 301. Here, when the size of the JPEG data to be written is larger than the capacity of the JPEG buffer 301, a part of the JPEG data is written to the RAW buffer 302.

  The signal processing unit 207 performs predetermined signal processing on the input RAW data, and converts the RAW data into YUV data that is a luminance color difference signal. This YUV data is input to the compression processing unit 209 via the switch 208. The YUV data is written to the RAM 206 via the memory controller 204 based on the YUV data write address generated by the YUV data write address generation unit 217.

  Here, the switch 208 is a switch for selecting either YUV data output from the signal processing unit 207 or YUV data read from the RAM 206 as data input to the compression processing unit 209. The selection operation of the switch 208 is controlled by a system controller 210 described later.

  For example, when the system controller 210 sets “0” for the switch 208, the switch 208 operates to select the YUV data output from the signal processing unit 207 and input it to the compression processing unit 209. On the other hand, when “1” is set for the switch 208, the switch 208 operates to select the YUV data read from the RAM 206 and input it to the compression processing unit 209. The YUV data read from the RAM 206 is data read based on the YUV data read address generated by the YUV data read address generation unit 218.

  The compression processing unit 209 generates JPEG data by compressing YUV data input according to the JPEG method. The generated JPEG data is recorded on the memory card 216 via the memory controller 204 and the I / F 215.

  The JPEG data write address generated by the JPEG data write address generator 211 is input to the memory controller 204 and also input to the RAW buffer intrusion detector 213 and the catch-up detector 214. The RAW data read address generated by the RAW data read address generator 212 is input to the memory controller 204 and also to the catch-up detector 214.

  The RAW buffer intrusion detection unit 213 compares the JPEG data write address with the RAW buffer start address input from the system controller 210. The RAW buffer start address is an address set in advance as an address at which writing of RAW data to the RAM 206 is started. Then, the RAW buffer intrusion detection unit 213 detects whether the JPEG data write address has reached the address in the RAW buffer 302 based on the comparison result. This detection result indicates whether JPEG data is written over at least a partial area of the RAW buffer 302 from the JPEG buffer 301. A signal indicating the detection result is output to the system controller 210, and the system controller 210 changes the value of the RAW buffer intrusion flag held therein in accordance with this signal.

  The catch-up detection unit 214 compares the value of the RAW data read address with the value of the JPEG data write address, and detects whether the JPEG data write address has caught up with the RAW data read address based on the comparison result. Specifically, when the JPEG data write address is larger than the RAW data read address, it is detected that the JPEG data write address has caught up with the RAW data read address. The detection result of the catch-up detection unit 214 indicates whether or not JPEG data is overwritten on the RAW data in the RAW buffer 302. A signal indicating the detection result is output to the system controller 210, and the system controller 210 changes the value of the catch-up detection flag held therein according to the signal.

  The system controller 210 includes a CPU (not shown), a ROM (not shown) in which programs for various controls and processes are stored, and a RAM (not shown) for providing a work area for the CPU. Composed. When the CPU executes a program stored in the ROM, overall control of the digital camera is performed and various processes are performed.

  Next, the JPEG data writing operation will be described with reference to FIGS. 3 to 5 are flowcharts showing the procedure of JPEG data writing operation in the digital camera of FIG. Here, the procedure shown in the flowcharts of FIGS. 3 to 5 is a procedure executed under the control of the system controller 210.

  As shown in FIG. 3, the system controller 210 controls to write RAW data (step S101). As a result, the RAW data write address generated by the RAW data write address generator 205 is input to the memory controller 204. Then, the memory controller 204 writes the RAW data obtained by A / D converting the electrical signal output from the image sensor 202 to the generated RAW data write address of the RAW buffer 302 of the RAM 206. At this time, the RAW data is written in order starting from the RAW buffer start address.

  Next, the system controller 210 sets “0” in the RAW buffer intrusion flag held therein (step S102). This RAW buffer entry flag is a flag for indicating that the value of the JPEG data write address is larger than the value of the RAW buffer start address. That is, the RAW buffer entry flag is a flag for indicating that the JPEG data write address has reached the address in the RAW buffer 302. When “0” is set in the RAW buffer intrusion flag, the RAW buffer intrusion flag indicates that the JPEG data write address has not reached the address in the RAW buffer 302. On the other hand, when “1” is set in the RAW buffer intrusion flag, the RAW buffer intrusion flag indicates that the JPEG data write address has reached the address in the RAW buffer 302.

  Next, the system controller 210 sets “0” in the catch-up detection flag held inside (step S103). This catch-up detection flag is a flag for indicating that the JPEG data write address 106 is larger than the RAW data read address. That is, the catch-up detection flag is a flag for indicating that the JPEG data write address has caught up with the RAW data read address.

  Next, the system controller 210 sets a RAW buffer start address as an initial value of the RAW data read address to the RAW data read address generation unit 212 (step S104). Then, the system controller 210 sets the JPEG buffer start address as the initial value of the JPEG data write address in the JPEG data write address generation unit 211 (step S105).

  Next, the system controller 210 reads RAW data from the RAW buffer 302 of the RAM 206, and controls to start compression processing for converting the read RAW data into JPEG data (step S106). Then, the system controller 210 determines whether or not the entire image has been compressed (step S107). The determination of the end of compression is performed according to whether or not the number of pixels to be compressed is counted in the compression processing unit 209 and the counted number of pixels has reached a predetermined value.

  Here, conversion from RAW data to JPEG data will be described. The RAW data is stored in the RAW buffer 302 of the RAM 206 in step S101. The memory controller 204 reads RAW data corresponding to the RAW data read address generated by the RAW data read address generation unit 212 from the RAW buffer 302. The read RAW data is converted into YUV data by the signal processing unit 207 and then input to the compression processing unit 209 via the switch 208. The compression processing unit 209 compresses the input YUV data at a preset compression rate, and generates JPEG data. This JPEG data is written to the JPEG data write address generated by the JPEG data write address generation unit 211 by the memory controller 204.

  If it is determined in step S107 that the compression of the entire image has not ended, the system controller 210 determines whether or not the relationship of RAW buffer start address <JPEG data write address is satisfied, as shown in FIG. (Step S108). This determination is made based on the detection result of the RAW buffer intrusion detection unit 213. If the relationship of RAW buffer start address <JPEG data write address is not established, the system controller 210 updates the JPEG data write address (step S112) and updates the RAW data read address (step S113). Then, the system controller 210 determines again whether or not the entire image has been compressed (step S107).

  If the relationship of RAW buffer start address <JPEG data write address is established in step S108, the system controller 210 sets “1” in the RAW buffer entry flag (step S109). In this case, since the JPEG data write address has reached the address in the RAW buffer 302, the memory controller 204 is controlled to stop writing the JPEG data to the RAM 206.

  Next, the system controller 210 determines whether or not the relationship of RAW data read address <JPEG data write address is established based on the detection result of the catch-up detection unit 214 (step S110). Here, if the relationship of RAW data read address <JPEG data write address is not established, the system controller 210 updates the JPEG data write address and the RAW data read address (steps S112 and S113). Then, the system controller 210 determines again whether or not the entire image has been compressed (step S107).

  If it is determined in step S110 that the relationship RAW data read address <JPEG data write address is established, the system controller 210 sets “1” in the catch-up detection flag (step S111). This indicates that the JPEG data write address has reached the RAW data read address.

  Next, the system controller 210 updates the JPEG data write address and the RAW data read address (steps S112 and S113). Then, the system controller 210 determines again whether or not the entire image has been compressed (step S107).

  If it is determined in step S107 that the compression of the entire image has been completed, the system controller 210 determines whether or not the RAW buffer entry flag is “1” as shown in FIG. 5 (step S114). ). Here, when the RAW buffer entry flag is 1, the system controller 210 determines whether or not the size of the JPEG data is larger than a preset size A (step S115). When the size of the JPEG data is larger than the size A, the system controller 210 changes the compression rate of the compression processing unit 209 to a compression rate that allows the size of the JPEG data to be within the size A (step S116).

  Next, the system controller 210 initializes the RAW buffer intrusion flag and the catch-up detection flag, and the RAW data read address and JPEG data write address (steps S102 to S105). Then, the system controller 210 sets the changed compression rate in the compression processing unit 209 and controls to start the compression processing using this compression rate (step S106).

  If it is determined in step S115 that the size of the JPEG data is equal to or smaller than size A, the system controller 210 determines whether or not the catch-up detection flag is “1” (step S117). If the catch-up detection flag is “1”, the system controller 210 changes the compression rate of the compression processing unit 209 to a compression rate at which the JPEG data write address does not catch up with the RAW data read address (step S118). Then, the system controller 210 returns to step S102, sets the changed compression rate in the compression processing unit 209, and controls to start compression processing using this compression rate (step S106).

  Here, an operation when the JPEG data write address enters the RAW buffer again after increasing the compression rate will be described. Steps S107 to S113 are repeated until the compression of the entire image is completed according to the compression rate increased in step S118. At this time, if “1” is set to the RAW buffer intrusion flag in step S109, the memory controller 204 is controlled to stop writing the JPEG data to the RAM 206. Since “1” is set in the RAW buffer intrusion flag in step S114, the process proceeds to step S115 and step S117.

  Since it is determined in step S117 that the catch-up detection flag is not “1”, the system controller 210 controls the compression processing unit 209 to perform main compression from the top of the image (step S119).

  The compression processing according to the present embodiment includes main compression and temporary compression. Specific processing will be described in the description of FIG.

  The JPEG data obtained by the main compression is written to the JPEG buffer 301 of the RAM 206 or from the JPEG buffer 301 to the RAW buffer 302. Next, the system controller 210 controls the memory controller 204 to record the JPEG data written in the RAM 206 on the memory card 216 (step S120). Then, the system controller 210 ends this process.

  As another case, the operation when the JPEG data write address does not enter the RAW buffer after increasing the compression rate will be described. Also in this case, after increasing the compression rate, steps S107 to S113 are repeated until the compression of the entire image is completed, but no entry into the RAW buffer is detected. Therefore, in step S114, it is determined that the RAW buffer entry flag is not “1”, and the process proceeds to step S120. In step S <b> 120, the system controller 210 controls the memory controller 204 to record the JPEG data on the memory card 216. Then, the system controller 210 ends this process.

  If it is determined in step S114 that the RAW buffer entry flag is not “1”, the system controller 210 controls the memory controller 204 to record the JPEG data in the memory card 216 (step S120). Then, the system controller 210 ends this process.

  Next, the JPEG data write operation when the JPEG data write address reaches the address in the RAW buffer 302 will be described with reference to FIG. FIG. 6 is a diagram showing the memory map and the relationship between the RAW data read address and the JPEG data write address when the JPEG data write address reaches the address in the RAW buffer 302. Here, “0” is set to the switch 208, and the YUV data output from the signal processing unit 207 is input to the compression processing unit 209.

  As shown in FIG. 6, the RAW data read address 105 is sequentially generated with the RAW buffer start address 103 as an initial value, and RAW data corresponding to the generated RAW data read address 105 is read from the RAW buffer 302. The compression processing unit 209 performs compression processing on the RAW data (YUV data) until the RAW data read address 105 reaches the RAW data read end address 111 corresponding to the end of compression. Here, the vertical axis in FIG. 6 represents an address, and the value of the address is assumed to increase downward. The horizontal axis represents the degree of compression, the left end indicates the start of compression, and the right end indicates the end of compression.

  As the RAW data read address is generated, the JPEG data write address 106 is sequentially generated with the JPEG buffer start address 104 as an initial value. Here, it is assumed that the JPEG data write address 106 reaches the JPEG data write end address 108 when the JPEG data has been written to the RAM 206. In the case of the example shown in FIG. 6, it is assumed that this JPEG data write end address 108 is an address in the RAW buffer 302. Here, since the compression by the JPEG method is variable length compression, the JPEG data write address 106 is not actually represented by a straight line but is represented by a straight line for convenience.

  In such a case, the JPEG data write address 106 reaches the address in the RAW buffer 302 via the RAW buffer start address 103 (intersection 107 in the figure). That is, a part of the JPEG data is written into the RAW buffer 302.

  In the present embodiment, when the JPEG data write address 106 reaches the address in the RAW buffer 302, compression for calculating the size of JPEG data is performed, and this compression is defined as temporary compression in the present embodiment. ing. The JPEG data size is calculated from the JPEG buffer start address 104 based on the JPEG data write end address. During this temporary compression, generation of the JPEG data write address 106 is continued, but part of the JPEG data is not written to the RAM 206. That is, data between the JPEG data write end address 108 from the time (intersection 107) when the JPEG data write address 106 reaches the RAW buffer start address of the RAW buffer 302 is not written to the RAM 206. Then, the temporary compression is performed until the entire image is compressed.

  When the compression of the entire image is completed, in order to write JPEG data into the RAM 206 again, compression for compressing the image (RAW data) from the head is performed again. This compression is defined as main compression in this embodiment.

  The write operation in this case will be specifically described. The RAW data obtained by A / D converting the electric signal output from the image sensor 202 is the generated RAW data write address of the RAW buffer 302 of the RAM 206. Is written to. At this time, the RAW data is sequentially written starting from the RAW buffer start address 103 (step S101).

  Next, “0” is set to the RAW buffer intrusion flag held in the system controller 210 (step S102), and “0” is set to the catch-up detection flag (step S103).

  Next, the RAW buffer start address 103 is set as an initial value of the RAW data read address 105 to the RAW data read address generation unit 212 (step S104). Then, the JPEG buffer start address 104 is set as the initial value of the JPEG data write address 106 to the JPEG data write address generator 211 (step S105).

  Next, RAW data is read from the RAW buffer 302 of the RAM 206, and a compression process for converting the read RAW data into JPEG data is started (step S106).

  In the case of this example, the JPEG data write address 106 reaches the RAW buffer start address 103 (intersection 107 in the figure) during the compression of the entire image. That is, the relationship RAW buffer start address 103 <JPEG data write address 106 is established (step S108 in FIG. 4).

  When the relationship of RAW buffer start address 103 <JPEG data write address 106 is established, the RAW buffer entry flag is set to “1” (step S109). When “1” is set to the RAW buffer intrusion flag, temporary compression for calculating the size of JPEG data between the addresses is performed based on the JPEG data write end address 108 and the JPEG buffer start address 104. During this temporary compression, writing of JPEG data to the RAM 206 is stopped. In the case of this example, the relationship of the RAW data read address 105 <JPEG data write address 106 does not hold, so that the catch-up detection flag is not set to “1”. Then, the update of the JPEG data write address 106 and the RAW data read address 105 is continued (steps S112 and S113).

  In this way, steps S107 to S113 are repeated until the compression of the entire image is completed. When the entire image has been compressed (step S107), the RAW buffer entry flag is set to “1” (step S114).

  Next, it is determined whether or not the calculated JPEG data size exceeds a preset size A (step S115). When the calculated JPEG data size exceeds the size A, the compression rate of the compression processing unit 209 is changed to a compression rate that allows the calculated JPEG data size to be within the size A. (Step S116).

  When the compression rate is changed, initialization of the RAW buffer entry flag and catch-up detection flag, and initialization of the RAW data read address and JPEG data write address are performed (steps S102 to S105). Then, a compression process for compressing RAW data using the changed compression rate is started (step S106).

  Even when the compression rate is changed, “1” may be set in the RAW buffer intrusion flag, but the JPEG data fits in the size A or smaller. Therefore, it is determined whether or not the catch-up detection flag is “1” (step S117). In this example, since “1” is not set in the catch-up flag, the compression processing unit 209 compresses the RAW data from the head again, and performs the main compression to write the JPEG data obtained by the compression to the RAM 206. (Step S119). In this main compression, even if the JPEG data write address reaches the address in the RAW buffer 302, the JPEG data is written to the RAW buffer 302 without stopping the JPEG data write. The JPEG data written from the JPEG buffer 301 to the RAW buffer 302 by the main compression is recorded on the memory card 216 (step S120).

  Next, a case where the JPEG data write address reaches the RAW buffer 302 and catches up with the RAW data read address will be described with reference to FIG. FIG. 7 is a diagram showing the memory map and the relationship between the RAW data read address and the JPEG data write address when the JPEG data write address reaches the address in the RAW buffer 302 and catches up with the RAW data read address.

  As shown in FIG. 7, the JPEG data write address 506 may coincide with the RAW data read address 106 via the RAW buffer start address 103 of the RAW buffer 302 (intersection 509) and catch up.

  When the JPEG data write address 506 exceeds the RAW buffer start address 103 of the RAW buffer 302, the relationship of RAW buffer start address 103 <JPEG data write address 506 is established (step S108 in FIG. 4). As a result, “1” is set to the RAW buffer entry flag (step S109). When “1” is set to the RAW buffer intrusion flag, writing of JPEG data to be written to the subsequent JPEG data writing address 506 is stopped. Then, temporary compression is performed, and the JPEG data size is calculated based on the JPEG data write end address and the JPEG buffer start address 104. During this temporary compression, writing of JPEG data to the RAM 206 is stopped, but generation of the JPEG data write address 506 and the RAW data read address 105 is continued. That is, temporary compression is performed until the entire image is compressed.

  In the case of this example, the relationship of RAW data read address 105 <JPEG data write address 506 is established during the period until the entire image is compressed (step S110), and the catch-up detection flag is set to “1”. (Step S111). Then, the processing from step S107 to step S113 is repeated until the compression of the entire image is completed. In a state where the compression of the entire image has been completed (step S107), “1” is set to the RAW buffer entry flag and “1” is set to the catch-up detection flag.

  Next, since “1” is set in the RAW buffer intrusion flag, it is determined whether or not the calculated size of the JPEG data exceeds a preset size A (step S115). When the calculated JPEG data size exceeds the size A, the compression rate of the compression processing unit 209 is changed to a compression rate that allows the calculated JPEG data size to be within the size A. (Step S116).

  When the compression rate is changed, initialization of the RAW buffer entry flag and catch-up detection flag, and initialization of the RAW data read address and JPEG data write address are performed (steps S102 to S105). Then, a compression process for compressing RAW data using the changed compression rate is started (step S106).

  The relationship between the JPEG data write address and the address in the RAW buffer 302 at the time of recompression according to the compression rate changed here is one of the following three.

(1) The JPEG data write address at the time of recompression reaches the address in the RAW buffer 302 depending on the compression rate to be changed, but cannot catch up with the RAW data read address.
(2) A case where the address in the RAW buffer 302 is reached and the RAW data read address is caught up.
(3) When the address in the RAW buffer 302 is not reached.

  Hereinafter, each of the three cases will be described.

  First, the case of (1), that is, the case where the JPEG data write address reaches the address in the RAW buffer 302 in the recompression after changing the compression rate, but does not catch up with the RAW data read address will be described.

  In this case, it is assumed that the JPEG data write address becomes the JPEG data write address 510. The JPEG data write address 510 reaches the address in the RAW buffer 302 via the intersection 507 with the RAW buffer start address, but does not catch up with the RAW data read address.

  Therefore, since the JPEG data size does not exceed the size A and the catch-up detection flag is not “1”, the compression processing unit 209 again compresses the entire image at the changed compression rate. Full compression is performed. In this main compression, even if the JPEG data write address reaches the address in the RAW buffer 302, the JPEG data is written to the RAW buffer 302 without stopping the JPEG data write. The JPEG data written from the JPEG buffer 301 to the RAW buffer 302 by the main compression is recorded on the memory card 216 (step S120).

  Next, the case of (2), that is, the case where the JPEG data write address reaches the address in the RAW buffer 302 and catches up with the RAW data read address in the recompression after changing the compression rate will be described.

  In this case, since the catch-up flag is set to “1”, the compression rate of the compression processing unit 209 is changed to a compression rate at which the JPEG data write address cannot catch up with the RAW data read address (step S118). Then, the compression process using the changed compression rate is performed again.

  Finally, the case of (3), that is, the case where the JPEG data write address does not reach the address in the RAW buffer 302 in the recompression after changing the compression rate will be described.

  In this case, it is determined that the RAW buffer has not been reached after completion of the recompression process (step 114). The JPEG data written by compression is recorded on the memory card 216 (step 120).

  Next, a case where the JPEG write data address does not reach the address in the RAW buffer 302 will be described with reference to FIG. FIG. 8 is a diagram showing the relationship between the memory map, the RAW data read address, and the JPEG data write address when the JPEG write data address does not reach the address in the RAW buffer 302.

  The case where the JPEG write data address does not reach the address in the RAW buffer 302 is a case where the image is compressed by the compression processing unit 209 at a compression rate that allows the JPEG data to be stored in the JPEG buffer 301.

  In such a case, the relationship of RAW buffer start address 103 <JPEG data write address 106 does not hold until the entire image is compressed (step S108). Further, the relationship RAW data read address 105 <JPEG data write address 506 is not established (step S110). That is, “1” is not set in the RAW buffer intrusion flag and the catch-up detection flag (steps S109 and S111).

  When the entire image is compressed (step S107), the JPEG data written in the JPEG buffer 301 is recorded in the memory card 216 (step S120).

  As described above, according to the present embodiment, JPEG data can be written to the RAM 206 serving as the JPEG buffer 301 and the RAW buffer 302 without overwriting the RAW data with the JPEG data.

  In the present embodiment, the size of the JPEG buffer 301 is set to the JPEG file size when a standard chart is captured. As a result, only when a special image typified by a high-frequency image is taken, a part of the JPEG data is written in the RAW buffer 302. In other words, the JPEG data write address is less likely to reach the address in the RAW buffer, and the frequency of compression such as performing the main compression after the temporary compression can be reduced, thereby preventing a reduction in processing speed. can do.

  In the present embodiment, the case where the JPEG data is overwritten on the RAW data has been described. However, the JPEG data may be overwritten on the YUV data held in the RAM 206.

  In the present embodiment, the case where the raw data is read from the RAM 206 and compressed is described. However, for example, when the YUV data is read from the RAM 206 and compressed, the YUV buffer is also used as the JPEG buffer. Is also possible. In this case, the RAM 206 is provided with a YUV buffer into which YUV data is written.

  In the present embodiment, the JPEG method is used as the compression method of the compression processing unit 209, but other compression methods can be used instead.

  The object of the present invention is achieved by executing the following processing. That is, a storage medium that records a program code of software that realizes the functions of the above-described embodiments is supplied to a system or apparatus, and a computer (or CPU, MPU, etc.) of the system or apparatus is stored in the storage medium. This is the process of reading the code.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code and the storage medium storing the program code constitute the present invention.

  Moreover, the following can be used as a storage medium for supplying the program code. For example, floppy (registered trademark) disk, hard disk, magneto-optical disk, CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD + RW, magnetic tape, nonvolatile memory card, ROM or the like. Alternatively, the program code may be downloaded via a network.

  Further, the present invention includes a case where the function of the above-described embodiment is realized by executing the program code read by the computer. In addition, an OS (operating system) running on the computer performs part or all of the actual processing based on an instruction of the program code, and the functions of the above-described embodiments are realized by the processing. Is also included.

  Furthermore, a case where the functions of the above-described embodiment are realized by the following processing is also included in the present invention. That is, the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, based on the instruction of the program code, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing.

It is a block diagram which shows the structure of the digital camera carrying the image storage device which concerns on one embodiment of this invention. It is a figure which shows the memory map of RAM206 of FIG. 3 is a flowchart showing a procedure of JPEG data writing operation in the digital camera of FIG. 1. 3 is a flowchart showing a procedure of JPEG data writing operation in the digital camera of FIG. 1. 3 is a flowchart showing a procedure of JPEG data writing operation in the digital camera of FIG. 1. It is a figure which shows the memory map in case a JPEG data write address reaches the address in the RAW buffer 302, and the relationship between a RAW data read address and a JPEG data write address. It is a figure which shows the memory map when the JPEG data write address reaches the address in the RAW buffer 302 and catches up with the RAW data read address, and the relationship between the RAW data read address and the JPEG data write address. It is a figure which shows the relationship between a memory map in case a JPEG write data address does not reach the address in the RAW buffer 302, a RAW data read address, and a JPEG data write address.

Explanation of symbols

204 Memory controller 205 RAW data write address generator 206 RAM
209 Compression processing unit 210 System controller 211 JPEG data write address generation unit 212 RAW data read address generation unit 213 RAW buffer intrusion detection unit 214 Catch-up detection unit

Claims (12)

Storage means serving both as a first buffer and a second buffer;
Image writing means for writing input image data into the first buffer;
Image reading means for reading the image data from the first buffer;
Image compression means for compressing the image data read from the first buffer at a set compression rate to generate compressed image data;
Compressed image writing means capable of writing the compressed image data generated by the image compression means from the second buffer to the first buffer;
When the compressed image data is written from the second buffer over at least a partial area of the first buffer, the stop for stopping the writing of the compressed image data to the storage unit by the compressed image writing unit Means,
Determination means for determining whether or not the write address of the compressed image data catches up with the read address of the image data after the writing is stopped by the stop means;
When the determination unit determines that the write address of the compressed image data cannot catch up with the read address of the image data, the compressed image writing unit again stores the compressed image data compressed at the compression rate before the stop. An image storage device comprising: control means for controlling writing to the storage means.   When the determination unit determines that the write address of the compressed image data catches up with the read address of the image data, the control unit sets the compression rate of the image compression unit higher than the compression rate before the stop. The image storage device according to claim 1, wherein the image storage device is changed to:   When the compressed image data compressed at the high compression rate is not written from the second buffer to the area of the first buffer, the control unit compresses the compressed image writing unit at the high compression rate. 3. The image storage device according to claim 2, wherein the compressed image data is controlled to be written in the storage means.   In the case where the compressed image data is written from the second buffer to at least a partial area of the first buffer, the control means is configured such that the size of the compressed image data is larger than a preset size. The compression rate of the image compression unit is changed to a compression rate at which the size of the compressed image data is equal to or smaller than a preset size, and the image compression unit reads the compression rate from the first buffer again. The image data is compressed at the changed compression rate to generate compressed image data, and the compressed image writing means controls to write the generated compressed image data from the second buffer. The image storage device according to claim 1. First detection means for detecting that the compressed image data is written from the second buffer over at least a partial region of the first buffer;
Second detection means for detecting the size of the compressed image data;
Third detection means for detecting that the compressed image data is overwritten on the image data,
The stop means determines whether or not the compressed image data is written from the second buffer to at least a partial area of the first buffer based on a detection result of the first detection means. The writing is stopped, and the control means determines whether or not the size of the compressed image data is equal to or smaller than a preset size based on the result of the second detection means, and the determination means 5. The image storage device according to claim 1, wherein a determination is made as to whether a write address of compressed image data catches up with a read address of the image data. 6. Storage means serving both as a first buffer and a second buffer; image writing means for writing input image data into the first buffer; and image reading means for reading out the image data from the first buffer; The image data read from the first buffer is compressed at a set compression ratio to generate compressed image data, and the compressed image data generated by the image compression means is A compressed image writing unit capable of writing from two buffers to the first buffer,
In the case where the compressed image data is written from the second buffer over at least a partial area of the first buffer,
A stop step of stopping writing of the compressed image data into the storage unit by the compressed image writing unit;
A determination step of determining whether or not a write address of the compressed image data catches up with a read address of the image data after stopping the writing;
When it is determined that the write address of the compressed image data cannot catch up with the read address of the image data, the compressed image writing means again writes the compressed image data compressed at the compression rate before the stop to the storage means. And a control step for controlling the image storage device.   When the determination step determines that the write address of the compressed image data catches up with the read address of the image data, the control step sets the compression rate of the image compression unit to a compression rate higher than the compression rate before the stop. The method of controlling an image storage device according to claim 6, wherein:   When the compressed image data compressed at the high compression rate is not written from the second buffer to the area of the first buffer, the control step compresses the compressed image writing means at the high compression rate. 8. The method of controlling an image storage device according to claim 7, wherein the compressed image data is controlled to be written into the storage means. In the control step, when the compressed image data is written from the second buffer to at least a partial area of the first buffer, the size of the compressed image data is larger than a preset size. The compression rate of the image compression means is changed to a compression rate at which the size of the compressed image data is equal to or smaller than a preset size,
Again, the image compression means controls the image data read from the first buffer to be compressed at the changed compression rate to generate compressed image data,
9. The method of controlling an image storage device according to claim 5, wherein the compressed image writing unit controls the generated compressed image data to be written from the second buffer. . The image storage device includes: a first detection unit configured to detect that the compressed image data is written from the second buffer over at least a partial region of the first buffer; and a size of the compressed image data. Second detection means for detecting, and third detection means for detecting that the compressed image data is overwritten on the image data,
The stopping step determines whether or not the compressed image data is written from the second buffer to at least a partial region of the first buffer based on a detection result of the first detection unit. And the control step determines whether or not the size of the compressed image data is equal to or smaller than a preset size based on the result of the second detection unit, 9. The image storage device according to claim 6, wherein a determination is made as to whether or not a write address of the compressed image data catches up with a read address of the image data. Storage means serving both as a first buffer and a second buffer; image writing means for writing input image data into the first buffer; and image reading means for reading out the image data from the first buffer; The image data read from the first buffer is compressed at a set compression ratio to generate compressed image data, and the compressed image data generated by the image compression means is A program for controlling an image storage device comprising compressed image writing means capable of writing from two buffers to the first buffer,
When the compressed image data is written from the second buffer over at least a partial area of the first buffer, the stop for stopping the writing of the compressed image data to the storage unit by the compressed image writing unit Steps,
A determination step of determining whether or not a write address of the compressed image data catches up with a read address of the image data after stopping the writing;
When it is determined that the write address of the compressed image data cannot catch up with the read address of the image data, the compressed image writing means again writes the compressed image data compressed at the compression rate before the stop to the storage means. A control step for controlling
The program characterized by having.   A digital camera comprising the image storage device according to claim 1.

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