JP2013219682A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform high definition still image photographing without stopping video recording in an imaging device performing still image photographing during video recording.SOLUTION: An imaging device includes: a reversible compression unit 110 that divides image data into a plurality of blocks in a predetermined size and performs reversible compression on the divided blocks of the image data; a storage unit 114 that temporarily stores the compressed data compressed by the reversible compression unit; reversible expansion unit 111 that reads the compressed data out of the storage unit, and expands the compressed data; and a signal processing unit 112 that converts the expanded image data expanded by the reversible expansion unit into a brightness signal and a color signal, and performs irreversible compression on the converted image data. The reversible compression unit performs reversible compression by taking a difference of data in an area of the blocks.

Description

  The present invention relates to a technique for performing still image shooting without stopping moving image recording in an apparatus that performs still image shooting during moving image recording.

  In recent years, digital still cameras and digital video cameras have been proposed for the purpose of taking still images during moving image shooting. For example, in Patent Document 1, when there is a request for still image shooting during moving image recording, still image data can be temporarily stored in a memory and written to a recording medium after moving image recording is completed. A digital video camera is described.

  However, in the technique described in Patent Document 1, the recording size of the still image is independent of the image size output from the solid-state imaging device, and a high-definition still image is recorded in order to record one frame of moving image recording. There is a problem that it can not be done.

  On the other hand, as a method for recording still image shooting during moving image recording with high definition, Patent Document 2 proposes a digital camera that temporarily stops moving image recording and then performs still image shooting and resumes moving image recording. . It is described that a moving image can be recorded without skipping the missing frame by inserting a black image into the missing frame at this time.

  However, the technique described in Patent Document 2 has a problem in that since a missing frame exists, the user cannot see an event that occurred between the missing frames during playback of a moving image.

  The following are reasons why a high-definition still image cannot be shot without stopping moving image recording during moving image recording. That is, the moving image recording occupies a large transfer bandwidth of the memory, and the memory transfer bandwidth equivalent to that for normal still image recording cannot be used for still image processing.

  Therefore, in Patent Document 3, the following proposal is made. That is, the image data read from the solid-state image sensor is compressed and temporarily stored in a memory, and when image signal processing is performed, the compressed image data is read and developed while being decompressed. This is a method of reducing the occupancy rate of the memory transfer band. This proposal relates to a signal processing technique for processing a whole screen partially (for example, in the form of a strip in the vertical direction) having only a delay line that is about a fraction of a horizontal size. In order to solve the problem, there is a description that a designated pixel can be read out only by address calculation by performing lossy compression with a fixed quantization word length.

JP-A-9-233410 JP 2006-310907 A JP 2007-228515 A

  In the technique described in Patent Document 3, compression loss occurs because irreversible compression is used to read a designated pixel. In addition, since the read image is subjected to irreversible compression such as JPEG compression after the development circuit division processing, it is difficult to obtain a high-definition image. For this reason, there is a problem that it is not suitable for still image shooting, in which a high-definition image is particularly required.

  Also, in order to make the quantized word length a fixed value by lossless compression, if compression to the target size is not possible, processing such as re-compression with a new encoding table occurs, and the encoding processing time It takes a lot. For this reason, it is considered that high-speed processing is difficult when encoding with a fixed quantized word length, and there is a problem that moving image recording and still image recording cannot be performed simultaneously.

  Furthermore, in general, there is a problem that the compression efficiency is lower in the encoding method in which the quantized word length is a fixed value than in the variable value. For this reason, there is a problem that the occupancy rate of the transfer band of the memory cannot be reduced by encoding with the quantization word length as a fixed value.

  The present invention has been made in view of the above-described problems, and an object thereof is to enable high-definition still image shooting without stopping moving image recording in an imaging device that performs still image shooting during moving image recording. It is.

  An imaging apparatus according to the present invention includes a reversible compression unit that divides image data into a plurality of blocks of a predetermined size and performs lossless compression, a storage unit that temporarily stores compressed data compressed by the lossless compression unit, Reversible decompression means for reading the compressed data from the storage means and decompressing; and signal processing means for converting the decompressed image data decompressed by the reversible decompression means into a luminance signal and a color signal and irreversibly compressing the data, and the lossless compression The means is characterized in that lossless compression is performed by taking a data difference within the block area.

  According to the present invention, it is possible to perform high-definition still image shooting without stopping moving image recording in an imaging apparatus that performs still image shooting during moving image recording.

1 is a block diagram showing a schematic configuration of an imaging apparatus according to a first embodiment of the present invention. The block diagram which shows schematic structure of a still image reversible compression part. Schematic which shows the boundary pixel position for every division | segmentation block, and a division | segmentation left end pixel position. The block diagram which shows schematic structure of a boundary pixel holding | maintenance part. 6 is a timing chart showing the operation of the boundary pixel holding unit. The block diagram which showed the process of the pixel difference calculation part. The figure which showed how to hold the area | region of the division | segmentation compression data in a storage area. The conceptual diagram which shows storing to DRAM of the lossless compression data at the time of performing still image continuous shooting.

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

(First embodiment)
FIG. 1 is a block diagram showing a configuration of an imaging apparatus according to the first embodiment of the present invention.

  The imaging apparatus 100 is an imaging apparatus capable of recording a still image with high definition while recording the two-dimensional image data output from the imaging element 102 as a moving image. In the following description, illustration and description of portions not directly related to the present invention are omitted.

  The imaging apparatus 100 includes an analog signal processing unit 103, an A / D converter 104, a digital signal processing unit 105, a DRAM 114, and a recording medium 115. The digital signal processing unit 105 includes a sensor correction unit 106, a resizing unit 107, a moving image signal processing unit 108, a moving image compression unit 109, a still image signal processing unit 112, and a still image JPEG compression unit 113. Further, in addition to such a configuration, a still image lossless compression unit 110 and a still image lossless decompression unit 111 which are features of the present embodiment are provided.

  The imaging element 102 is a solid-state imaging element such as a CCD or CMOS type image sensor, for example, converts light incident from an optical lens (not shown) into an electrical signal and outputs the electrical signal to the analog signal processing unit 103. The image sensor 102 has a plurality of primary color filters, and includes, for example, a pixel that detects red (R), a pixel that detects green (G), and a pixel that detects blue (B). In the present embodiment, description will be made on the assumption of a Bayer array.

  The analog signal processing unit 103 includes a CDS circuit and a nonlinear amplifier circuit that remove noise on the transmission line included in the image sensor 102, and processes the input analog electric signal by the CDS circuit and the nonlinear amplifier circuit. The result is output to the A / D converter 104. The A / D converter 104 converts the analog electrical signal output from the image sensor 102 and processed by the analog processing circuit 103 into a digital electrical signal (pixel signal), and outputs the digital electrical signal to the sensor correction unit 106.

  The sensor correction unit 106 performs a correction process of defective pixels generated in the manufacture of the sensor, a shading process to correct a decrease in peripheral light amount of the lens, and the like on the pixel signal output from the A / D converter 104, and a resizing unit 107. And output to the still image lossless compression unit 110. The resizing unit 107 reduces the image size of the image input in the Bayer array so as to obtain a predetermined moving image size, and outputs the image to the moving image signal processing unit 108.

  The moving image signal processing unit 108 performs detection processing for AF, AE, white balance control, signal correction processing typified by white balance adjustment, and noise reduction for reducing noise existing in two-dimensional image data output from the sensor. Perform processing. Further, the Bayer array image data is converted into Y (luminance signal) and UV (color difference signal) of a predetermined format such as YUV422, and is output to the moving image compression unit 109.

  The moving image compressing unit 109 JPEG compresses the two-dimensional image data processed by the moving image signal processing unit 108, adds audio input from a microphone (not shown) and a header file, and generates a moving image file in the AVI data format. To do. This moving image file is output to the DRAM 114 by a DRAM controller (not shown).

  The video data and audio data recording processing in the moving image compression unit 109 at this time will be described in detail. For example, if the moving image file is an AVI file, the header of the file head of the AVI file manages the arrangement of video data and audio data. For example, audio data is placed at about 172 kbytes per second following the header. In addition, if JPEG data for each piece of video data is 30 fps, 30 frames are placed per second. Furthermore, audio data and 30 frames of video data are alternately arranged every other second.

  At this time, an image buffer area for buffering JPEG data and an audio buffer area for buffering audio data are secured on the DRAM 114. The image buffer area and the audio buffer area temporarily store the generated image data and audio data, respectively. The video data and audio data in the AVI data format are collected and output to the moving image buffer area on the DRAM 114 every second. At this time, the data stored in the moving image buffer area is written as a moving image file on a recording medium 115 described later.

  The still image reversible compression unit 110 divides and compresses the image data of the Bayer array output from the sensor correction unit 106 by compression means to be described later, and compresses the compressed data as reversible compressed image data by a DRAM controller (not shown). Output to. The division size of the image data performed here is performed in units of division processed by a still image signal processing unit 112 described later. Further, the upper division size is a size equal to or smaller than the size of data to be processed by JPEG compression described later. At this time, the lossless compressed data of the two-dimensional image data output from the still image lossless compression unit 110 is output from the DRAM 114 to the recording medium 115. The lossless compressed data of the two-dimensional image data is generally called RAW data, and a high-definition image without compression distortion can be obtained by the user using external dedicated development processing software.

  The still image lossless decompression unit 111 reads the lossless compressed image data from the DRAM 114 via a DRAM controller (not shown), decompresses the image according to Huffman coding, generates decompressed image data, and outputs the decompressed image data to the still image signal processing unit 112.

  The still image signal processing unit 112 performs signal processing typified by white balance adjustment, noise reduction processing for reducing noise present in the two-dimensional image data output from the sensor, and the like. Further, the image data of the Bayer array is converted into Y (luminance signal) and UV (color difference signal, color signal) of a predetermined format such as YUV422 and output to the DRAM 114. Here, the two-dimensional image data placed in the DRAM 114 is image data obtained by dividing the image data output from the sensor.

  In general, the still image signal processing unit 112 realized by an inexpensive system has a delay line that is only a fraction of a horizontal size, and divides the processing of the entire screen (for example, in a vertical strip shape). In many cases, it has the function of the premise. This is due to the following reason. In other words, in the case of a moving image, the horizontal size is determined by standards such as Full HD (1920 × 1080) and HD (1280 × 720), so that it is easy to determine the capacity of the delay line. However, the horizontal size of the still image is arbitrarily determined depending on the image size that can be captured from the image sensor. Therefore, in order to have a delay line for a plurality of lines with a horizontal pixel size output from an arbitrary image pickup device, it is necessary to have a capacity for the delay line of the maximum possible horizontal pixel. This is because it becomes expensive.

  The DRAM 114 reads the divided two-dimensional image data as undivided batch image data by the reading control of a DRAM controller (not shown), and outputs it to the still image JPEG compression unit 113.

The still image JPEG compression unit 113 performs JPEG compression (irreversible compression) on the two-dimensional image data processed by the still image signal processing unit 112 and writes it to the DRAM 114. At this time, the data written to the DRAM 114 is written as still image data to a recording medium 115 described later. In addition,
The DRAM 114 is a recording area for temporarily recording outputs from the moving image compression unit 109, the still image lossless compression unit 110, and the still image JPEG compression unit 113. Then, the stored data is output to the still image reversible decompression unit 111 and the recording medium 115 under the control of a DRAM controller (not shown). In order to clarify the relationship with each processing, the input / output of the DRAM 114 is shown in a plurality of parts in FIG. 1, but each processing is performed by accessing the DRAM 114 via one bus.

  The recording medium 115 is a semiconductor memory element called SD card or CF card, a magnetic medium, an optical recording medium, or the like. The recording medium 115 is detachable from the main body and can record data stored in the DRAM 114.

  Next, a specific configuration of the still image reversible compression unit 110 will be described in detail with reference to FIG. The still image reversible compression unit 110 includes a pixel difference calculation unit 200, a boundary pixel holding unit 201, an H counter 202, a V counter 203, a divided block determination unit 204, a restart marker generation unit 205, and a Huffman encoding unit 206.

  Next, the operation of the still image reversible compression unit 110 will be described. Here, the number of blocks to be divided and compressed for convenience will be described as four blocks.

  The image data output from the sensor correction unit 106 is input to the pixel difference calculation unit 200, the boundary pixel holding unit 201, and the H counter 202 and V counter 203 that determine the position of each pixel.

  The H counter 202 outputs the horizontal pixel position of the image data output from the sensor correction unit 106 as H counter data, and the V counter 203 calculates the vertical pixel position of the image data output from the sensor correction unit 106 from the value of the H counter. Calculate and output as V counter data.

  The boundary pixel holding unit 201 determines, based on the output of the H counter 202, whether or not the input image data is the right end in the block area to be divided in advance, and is the right end of each block. When the determination is made, the pixel is held. The boundary pixel holding unit 201 determines whether or not the input image data is the leftmost pixel of each block from the output of the H counter 202. Output.

  A specific operation will be described with reference to FIG. FIG. 3 is a diagram for explaining the operation of the pixel holding unit when the image data 300 input from the sensor correction unit 106 is divided into four blocks.

  When the image data 300 input from the image sensor is sequentially input from the upper left, the boundary pixel 304 corresponding to the right end of each block is input until at least the divided left end pixel 305 that is the left end of the next line of each block is input. Hold. The held boundary pixel 304 is output to the pixel difference calculation unit 200 when the divided left end pixel 305 is input. Here, the boundary pixel 304 to be held may be two pixels instead of one pixel. Although the left end portion of the next line is described here, control may be performed so that the pixel difference calculation unit 200 outputs the left end portion after the second line. This is because a boundary pixel is generated in each primary color system of RG or GB when the input is based on the Bayer array.

  Specifically, the configuration of the boundary pixel holding unit 201 will be described with reference to FIG. The boundary pixel holding unit 201 includes a pixel holding block 401 that holds pixels, a boundary pixel determination unit 402 that determines that the pixel is a boundary pixel of each divided block, and holding data held by a plurality of pixel holding blocks 401. An output selection unit 403 for selecting and outputting is provided. Here, the pixel holding block 401 has at least the number of divisions.

  The pixel holding block 401 has a pixel holding unit 400 of the number of pixels to be held, and the pixel holding unit 400 selects whether to hold a pixel according to the output of the boundary pixel determination unit 402. The boundary pixel determination unit 402 notifies the pixel holding unit 400 that holds the boundary pixel that the boundary pixel 304 that is the right end pixel of each divided block has been input as a boundary pulse. When the divided left end pixel 305 of each block is input, it is output to the output selection unit 403 as a left end pulse 405 and simultaneously to the pixel difference calculation unit 200 as a pulse indicating the left end.

  The operation of the boundary pixel determination unit 402 will be described using the timing chart of FIG. The H counter data represents the position of the horizontal pixel of the image data output from the sensor correction unit, and is output from the H counter 202. The sensor correction data is output from the sensor correction unit 106, and the first line data is A, the second line data is B, and the third line data is C.

  The divided data of each block is 1a, 1b, and 1c for the divided area 1. For the divided region 2, 2a and 2b are used. 3a and 3b are assigned to the divided area 3. 4a and 4b are assigned to the divided area 4.

  The boundary pixel determination unit 402 outputs a left end pulse and a boundary pulse when the pixel of the sensor correction data corresponds to a pixel at a predetermined position of each divided block. The left end pulse is output from the value of the H counter that the left end pixel of each divided block has been input. This is a pulse signal output when the pixel of the sensor correction data input to the boundary pixel determination unit is at the left end of each divided region. In this figure, the left end pulse corresponding to the divided region 1 of the left end pulse 1, the one corresponding to the divided region 2 corresponding to the left end pulse 2, the one corresponding to the divided region 3 corresponding to the left end pulse 3 and the divided region 4 are illustrated. The left end pulse 4 is set.

  The boundary pulse is output from the value of the H counter that the boundary pixel of each divided block has been input. This is a pulse signal output when the pixel of the sensor correction data input to the boundary pixel determination unit 402 is the right end of each divided region. In this figure, the boundary pulse corresponding to the divided region 1 is the boundary pulse 1, the one corresponding to the divided region 2 is the boundary pulse 2, the one corresponding to the divided region 3 is the boundary pulse 3, and the one corresponding to the divided region 4 is shown. The boundary pulse 4 is used. The output selection unit 403 selects the output of each pixel holding block 401 by the left end pulse of the boundary pixel determination unit, and outputs it to the pixel difference calculation unit 200 as holding pixel data. The process of the pixel difference calculation unit 200 will be described with reference to FIG. The pixel difference calculation unit 200 delays the pixel signal input from the sensor correction unit 106 and the pixel signal input from the sensor correction unit 106 by two pixels, and the pixel holding data 404 output from the boundary pixel holding unit 201. And a selection unit for selecting whether or not to take the difference, and outputs the difference result to the Huffman encoding unit 206. The reason for performing the two-pixel delay here is to perform comparison with adjacent pixels of each primary color because of the Bayer arrangement. The selection unit is selected to take a difference from the pixel holding data by the left end pulse 405 output from the boundary pixel determination unit 402.

  The Huffman coding unit 206 performs Huffman coding compression on the difference data output from the pixel difference calculation unit 200 according to a predetermined coding table and outputs the data to the DRAM 114.

  In general, the encoding efficiency of lossless compression of natural images is said to be 2: 1. Once an image output from a solid-state image sensor with horizontal 4000 pixels, vertical 3000 pixels, and 1 pixel 16 bits is placed on the memory without being compressed, it uses a capacity of about 23 MB and a memory bandwidth when transferring. It will be. However, if lossless compression is performed as in the present embodiment, the capacity can be reduced to about 12 MB, and the memory bandwidth occupancy can be reduced to about half.

  Access to the DRAM 114 when performing still image shooting during moving image shooting according to the present embodiment includes the output of the moving image compression unit 109, the output of the still image lossless compression unit 110, the reading of the still image lossless expansion unit 111, and the still image signal. The output of the processing unit and the input / output of the still image JPEG compression unit. The transfer amount of each DRAM 114 will be described below.

  The memory bandwidth at the output of the moving picture compression unit 109 is about 18 MB / when a 30 Jps compression JPEG image with 30 1920 pixels in the horizontal direction, 1080 pixels in the vertical direction and 1 pixel in 24 bits of information is created. sec.

  As described above, the output of the still image lossless compression unit 110 and the reading of the still image lossless decompression unit 111 are about 23 MB when the method of the present embodiment is not used, and about 12 MB when the method is used.

  The output of the still image signal processing unit 112 is about 23 MB when handled as data of 4000 horizontal pixels, 3000 vertical pixels, and 16 bits per pixel.

  As for still image JPEG data, when about 23 MB of data output from the still image signal processing unit 112 is read and JPEG output of 1/10 compression rate is performed as an image having an information amount of 1 pixel 24 bits, a bandwidth of about 3 MB is obtained. Is used.

  As described above, when a 1 fps still image is taken during a moving image, the transfer amount of the DRAM 114 per second is 116 MB when the method of this embodiment is not used. When the method of this embodiment is used, the transfer amount of the DRAM 114 per second is 91 MB, and the bandwidth of the DRAM 114 when taking a still image during a moving image can be reduced.

  Based on the output of the H counter 202, the divided block determination unit 204 determines to which block of the four divided blocks the encoded data output from the Huffman encoding unit 206 belongs to the DRAM controller (not shown). Notice. A DRAM controller (not shown) stores data of each block compressed to a specified address.

  The specified address will be described with reference to FIG. FIG. 7 is a diagram showing a storage area of the DRAM 114, which includes a still image lossless compression data area 600. The still image reversible compression data area 600 has a divided compressed area corresponding to divided blocks. Specifically, when divided into four blocks, 601 is divided compressed data area 1, 602 is divided compressed data area 2, 603 is divided compressed data area 3, and 604 is divided compressed data area 4. With one area.

  Each divided compressed data area stores divided compressed data compressed for each divided block. Here, the data 605 stored in the divided compressed data area 1 is divided into the divided compressed data 1, the data 606 stored in the divided compressed data area 2 is divided, and the data 607 stored in the divided compressed data area 3 is divided. Data 608 stored in the compressed data 3 and the divided compressed data area 4 is referred to as divided compressed data 4.

  In general, it is difficult to know the size after compression of a variable length encoding result unless the encoding is completed. Therefore, the address of the DRAM 114 is predicted so that the last data of the divided compressed data 1 is stored during encoding, and the first data of the divided compressed data 2 is stored after the final data of the divided compressed data 1. It is difficult to control. However, as described above, the storage area can be divided into divided blocks so that the system can be established.

  The restart marker generation unit 205 determines from the outputs of the H counter 202 and the V counter 203 whether the encoded data of each block output from the encoding unit has been output. When it is determined that the last data has been output to the DRAM 114, a restart marker is assigned to each block of the encoded data written to the DRAM 114. However, a restart marker is not assigned to the block processed at the end of each block.

  Specifically, a restart marker is added (inserted) to the end of each compressed data in the divided compressed data area 1, divided compressed data area 2, and divided compressed data area 3 in FIG. Does not give a restart marker.

  In this way, the divided lossless compressed image data can be handled as one lossless compressed image data. The still image lossless decompression unit 111 reads the divided blocks of the lossless compressed image data as one data from the DRAM, thereby reducing the overhead when decompressing the divided lossless compressed image data.

  As described above, according to the present embodiment, by performing reversible still image compression and temporarily having a buffer on the memory for still image shooting, the bandwidth of the memory can be reduced, and when still image recording is performed during moving image recording. In addition, still image recording can be performed with the same performance as when only still image recording is performed.

  In this embodiment, the AVI data format (Motion JPEG format) is described as an example. However, the present invention is not limited to the AVI data format. H.264 video compression may be performed.

  In the present embodiment, the case where still image shooting is performed in a moving image is described. However, the same processing may be performed when only still image shooting is performed.

  Also, in this embodiment, the output of the still image reversible compression and the output of the still image JPEG compression are the same size, but after the processing by the still image signal processing unit, resizing is performed to output the still image JPEG compression. It may be changed.

  In this embodiment, the moving image size and the image data output from the still image lossless compression unit are different from each other. However, the image data handled by the still image lossless compression unit is for the moving image output from the resizing unit 107. Image data may be used.

  In the present embodiment, the solid-state imaging device has been described as an example. However, the device is not limited to the solid-state imaging device as long as the device has the same configuration.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described. Since the configuration of the imaging apparatus according to the present embodiment is the same as that of the first embodiment, description thereof is omitted. In this embodiment, how to hold an address for a storage area of data output from the still image lossless compression unit 110 when still image continuous shooting is performed will be described in addition to the first embodiment.

  FIG. 8 is a conceptual diagram illustrating storage of data output from the still image lossless compression unit 110 in the DRAM when still image continuous shooting is performed. When the imaging apparatus 100 has taken the first image, the first data 800 output from the still image lossless compression unit 110 is stored as still image shooting data 1 in the still image lossless compression data area. At this time, each divided block of the still image shooting data 1 is stored in a divided compressed data area 1, a divided compressed data area 2, a divided compressed data area 3, and a divided compressed data area 4, respectively.

  After confirming that the encoding has been completed, the DRAM controller (not shown) continues from the address of the final data of each divided block to the DRAM 114 to be next input to the DRAM 114 from the size of each encoded encoded data. Set the address to store data.

  When the image capturing apparatus 100 captures the second image, the second data 801 output from the still image lossless compression unit 110 is stored as still image shooting data 2 in the still image lossless compression data area. At this time, as shown in FIG. 8, each divided compressed data area is stored in the DRAM 114 following the first divided compressed data.

  By doing so, the image data divided and compressed at the time of still image continuous shooting can be efficiently recorded in the area of the DRAM 114.

  Further, when performing continuous shooting of a plurality of images, the still image signal processing unit 112 performs processing through the still image reversible decompression unit 111 at the same time as it is reversibly compressed and stored in the DRAM 114. At that time, the lack of the area of the DRAM 114 can be alleviated by controlling with a DRAM controller (not shown) so that the reversible compressed data is placed in the empty area of the DRAM 114 by reading to the still image reversible decompression unit 111.

Claims (6)

Lossless compression means for dividing image data into a plurality of blocks of a predetermined size and performing lossless compression;
Storage means for temporarily storing the compressed data compressed by the lossless compression means;
Reversible decompression means for reading and decompressing the compressed data from the storage means;
Signal processing means for converting the decompressed image data decompressed by the reversible decompressing means into a luminance signal and a color signal and irreversibly compressing the data;
The reversible compression unit performs reversible compression by taking a data difference within the block area.   The imaging apparatus according to claim 1, wherein the compressed data stored in the storage unit is temporarily stored with a storage area divided for each block.   The imaging apparatus according to claim 1, wherein the image data is processed by the lossless compression unit and the signal processing unit for each block.   4. When compressing data by the lossless compression unit for each block, the difference between the left end of the block and the right end of the block of the next line is encoded and losslessly compressed. The imaging device according to item.   5. The image pickup apparatus according to claim 1, wherein the predetermined size is a size equal to or smaller than a size of data to be irreversibly compressed by the signal processing unit.   The imaging device according to claim 1, wherein the lossless compression unit inserts a restart marker at the end of the compressed data for each block.

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