linux/Documentation/video4linux/sn9c102.txt
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   1
   2                         SN9C1xx PC Camera Controllers
   3                                Driver for Linux
   4                         =============================
   5
   6                               - Documentation -
   7
   8
   9Index
  10=====
  111.  Copyright
  122.  Disclaimer
  133.  License
  144.  Overview and features
  155.  Module dependencies
  166.  Module loading
  177.  Module parameters
  188.  Optional device control through "sysfs"
  199.  Supported devices
  2010. Notes for V4L2 application developers
  2111. Video frame formats
  2212. Contact information
  2313. Credits
  24
  25
  261. Copyright
  27============
  28Copyright (C) 2004-2007 by Luca Risolia <luca.risolia@studio.unibo.it>
  29
  30
  312. Disclaimer
  32=============
  33SONiX is a trademark of SONiX Technology Company Limited, inc.
  34This software is not sponsored or developed by SONiX.
  35
  36
  373. License
  38==========
  39This program is free software; you can redistribute it and/or modify
  40it under the terms of the GNU General Public License as published by
  41the Free Software Foundation; either version 2 of the License, or
  42(at your option) any later version.
  43
  44This program is distributed in the hope that it will be useful,
  45but WITHOUT ANY WARRANTY; without even the implied warranty of
  46MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  47GNU General Public License for more details.
  48
  49You should have received a copy of the GNU General Public License
  50along with this program; if not, write to the Free Software
  51Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  52
  53
  544. Overview and features
  55========================
  56This driver attempts to support the video interface of the devices assembling
  57the SONiX SN9C101, SN9C102, SN9C103, SN9C105 and SN9C120 PC Camera Controllers
  58("SN9C1xx" from now on).
  59
  60The driver relies on the Video4Linux2 and USB core modules. It has been
  61designed to run properly on SMP systems as well.
  62
  63The latest version of the SN9C1xx driver can be found at the following URL:
  64http://www.linux-projects.org/
  65
  66Some of the features of the driver are:
  67
  68- full compliance with the Video4Linux2 API (see also "Notes for V4L2
  69  application developers" paragraph);
  70- available mmap or read/poll methods for video streaming through isochronous
  71  data transfers;
  72- automatic detection of image sensor;
  73- support for built-in microphone interface;
  74- support for any window resolutions and optional panning within the maximum
  75  pixel area of image sensor;
  76- image downscaling with arbitrary scaling factors from 1, 2 and 4 in both
  77  directions (see "Notes for V4L2 application developers" paragraph);
  78- two different video formats for uncompressed or compressed data in low or
  79  high compression quality (see also "Notes for V4L2 application developers"
  80  and "Video frame formats" paragraphs);
  81- full support for the capabilities of many of the possible image sensors that
  82  can be connected to the SN9C1xx bridges, including, for instance, red, green,
  83  blue and global gain adjustments and exposure (see "Supported devices"
  84  paragraph for details);
  85- use of default color settings for sunlight conditions;
  86- dynamic I/O interface for both SN9C1xx and image sensor control and
  87  monitoring (see "Optional device control through 'sysfs'" paragraph);
  88- dynamic driver control thanks to various module parameters (see "Module
  89  parameters" paragraph);
  90- up to 64 cameras can be handled at the same time; they can be connected and
  91  disconnected from the host many times without turning off the computer, if
  92  the system supports hotplugging;
  93- no known bugs.
  94
  95
  965. Module dependencies
  97======================
  98For it to work properly, the driver needs kernel support for Video4Linux and
  99USB.
 100
 101The following options of the kernel configuration file must be enabled and
 102corresponding modules must be compiled:
 103
 104        # Multimedia devices
 105        #
 106        CONFIG_VIDEO_DEV=m
 107
 108To enable advanced debugging functionality on the device through /sysfs:
 109
 110        # Multimedia devices
 111        #
 112        CONFIG_VIDEO_ADV_DEBUG=y
 113
 114        # USB support
 115        #
 116        CONFIG_USB=m
 117
 118In addition, depending on the hardware being used, the modules below are
 119necessary:
 120
 121        # USB Host Controller Drivers
 122        #
 123        CONFIG_USB_EHCI_HCD=m
 124        CONFIG_USB_UHCI_HCD=m
 125        CONFIG_USB_OHCI_HCD=m
 126
 127The SN9C103, SN9c105 and SN9C120 controllers also provide a built-in microphone
 128interface. It is supported by the USB Audio driver thanks to the ALSA API:
 129
 130        # Sound
 131        #
 132        CONFIG_SOUND=y
 133
 134        # Advanced Linux Sound Architecture
 135        #
 136        CONFIG_SND=m
 137
 138        # USB devices
 139        #
 140        CONFIG_SND_USB_AUDIO=m
 141
 142And finally:
 143
 144        # USB Multimedia devices
 145        #
 146        CONFIG_USB_SN9C102=m
 147
 148
 1496. Module loading
 150=================
 151To use the driver, it is necessary to load the "sn9c102" module into memory
 152after every other module required: "videodev", "v4l2_common", "compat_ioctl32",
 153"usbcore" and, depending on the USB host controller you have, "ehci-hcd",
 154"uhci-hcd" or "ohci-hcd".
 155
 156Loading can be done as shown below:
 157
 158        [root@localhost home]# modprobe sn9c102
 159
 160Note that the module is called "sn9c102" for historic reasons, although it
 161does not just support the SN9C102.
 162
 163At this point all the devices supported by the driver and connected to the USB
 164ports should be recognized. You can invoke "dmesg" to analyze kernel messages
 165and verify that the loading process has gone well:
 166
 167        [user@localhost home]$ dmesg
 168
 169or, to isolate all the kernel messages generated by the driver:
 170
 171        [user@localhost home]$ dmesg | grep sn9c102
 172
 173
 1747. Module parameters
 175====================
 176Module parameters are listed below:
 177-------------------------------------------------------------------------------
 178Name:           video_nr
 179Type:           short array (min = 0, max = 64)
 180Syntax:         <-1|n[,...]>
 181Description:    Specify V4L2 minor mode number:
 182                -1 = use next available
 183                 n = use minor number n
 184                You can specify up to 64 cameras this way.
 185                For example:
 186                video_nr=-1,2,-1 would assign minor number 2 to the second
 187                recognized camera and use auto for the first one and for every
 188                other camera.
 189Default:        -1
 190-------------------------------------------------------------------------------
 191Name:           force_munmap
 192Type:           bool array (min = 0, max = 64)
 193Syntax:         <0|1[,...]>
 194Description:    Force the application to unmap previously mapped buffer memory
 195                before calling any VIDIOC_S_CROP or VIDIOC_S_FMT ioctl's. Not
 196                all the applications support this feature. This parameter is
 197                specific for each detected camera.
 198                0 = do not force memory unmapping
 199                1 = force memory unmapping (save memory)
 200Default:        0
 201-------------------------------------------------------------------------------
 202Name:           frame_timeout
 203Type:           uint array (min = 0, max = 64)
 204Syntax:         <0|n[,...]>
 205Description:    Timeout for a video frame in seconds before returning an I/O
 206                error; 0 for infinity. This parameter is specific for each
 207                detected camera and can be changed at runtime thanks to the
 208                /sys filesystem interface.
 209Default:        2
 210-------------------------------------------------------------------------------
 211Name:           debug
 212Type:           ushort
 213Syntax:         <n>
 214Description:    Debugging information level, from 0 to 3:
 215                0 = none (use carefully)
 216                1 = critical errors
 217                2 = significant information
 218                3 = more verbose messages
 219                Level 3 is useful for testing only. It also shows some more
 220                information about the hardware being detected.
 221                This parameter can be changed at runtime thanks to the /sys
 222                filesystem interface.
 223Default:        2
 224-------------------------------------------------------------------------------
 225
 226
 2278. Optional device control through "sysfs" [1]
 228==========================================
 229If the kernel has been compiled with the CONFIG_VIDEO_ADV_DEBUG option enabled,
 230it is possible to read and write both the SN9C1xx and the image sensor
 231registers by using the "sysfs" filesystem interface.
 232
 233Every time a supported device is recognized, a write-only file named "green" is
 234created in the /sys/class/video4linux/videoX directory. You can set the green
 235channel's gain by writing the desired value to it. The value may range from 0
 236to 15 for the SN9C101 or SN9C102 bridges, from 0 to 127 for the SN9C103,
 237SN9C105 and SN9C120 bridges.
 238Similarly, only for the SN9C103, SN9C105 and SN9C120 controllers, blue and red
 239gain control files are available in the same directory, for which accepted
 240values may range from 0 to 127.
 241
 242There are other four entries in the directory above for each registered camera:
 243"reg", "val", "i2c_reg" and "i2c_val". The first two files control the
 244SN9C1xx bridge, while the other two control the sensor chip. "reg" and
 245"i2c_reg" hold the values of the current register index where the following
 246reading/writing operations are addressed at through "val" and "i2c_val". Their
 247use is not intended for end-users. Note that "i2c_reg" and "i2c_val" will not
 248be created if the sensor does not actually support the standard I2C protocol or
 249its registers are not 8-bit long. Also, remember that you must be logged in as
 250root before writing to them.
 251
 252As an example, suppose we were to want to read the value contained in the
 253register number 1 of the sensor register table - which is usually the product
 254identifier - of the camera registered as "/dev/video0":
 255
 256        [root@localhost #] cd /sys/class/video4linux/video0
 257        [root@localhost #] echo 1 > i2c_reg
 258        [root@localhost #] cat i2c_val
 259
 260Note that "cat" will fail if sensor registers cannot be read.
 261
 262Now let's set the green gain's register of the SN9C101 or SN9C102 chips to 2:
 263
 264        [root@localhost #] echo 0x11 > reg
 265        [root@localhost #] echo 2 > val
 266
 267Note that the SN9C1xx always returns 0 when some of its registers are read.
 268To avoid race conditions, all the I/O accesses to the above files are
 269serialized.
 270The sysfs interface also provides the "frame_header" entry, which exports the
 271frame header of the most recent requested and captured video frame. The header
 272is always 18-bytes long and is appended to every video frame by the SN9C1xx
 273controllers. As an example, this additional information can be used by the user
 274application for implementing auto-exposure features via software.
 275
 276The following table describes the frame header exported by the SN9C101 and
 277SN9C102:
 278
 279Byte #  Value or bits Description
 280------  ------------- -----------
 2810x00    0xFF          Frame synchronisation pattern
 2820x01    0xFF          Frame synchronisation pattern
 2830x02    0x00          Frame synchronisation pattern
 2840x03    0xC4          Frame synchronisation pattern
 2850x04    0xC4          Frame synchronisation pattern
 2860x05    0x96          Frame synchronisation pattern
 2870x06    [3:0]         Read channel gain control = (1+R_GAIN/8)
 288        [7:4]         Blue channel gain control = (1+B_GAIN/8)
 2890x07    [ 0 ]         Compression mode. 0=No compression, 1=Compression enabled
 290        [2:1]         Maximum scale factor for compression
 291        [ 3 ]         1 = USB fifo(2K bytes) is full
 292        [ 4 ]         1 = Digital gain is finish
 293        [ 5 ]         1 = Exposure is finish
 294        [7:6]         Frame index
 2950x08    [7:0]         Y sum inside Auto-Exposure area (low-byte)
 2960x09    [7:0]         Y sum inside Auto-Exposure area (high-byte)
 297                      where Y sum = (R/4 + 5G/16 + B/8) / 32
 2980x0A    [7:0]         Y sum outside Auto-Exposure area (low-byte)
 2990x0B    [7:0]         Y sum outside Auto-Exposure area (high-byte)
 300                      where Y sum = (R/4 + 5G/16 + B/8) / 128
 3010x0C    0xXX          Not used
 3020x0D    0xXX          Not used
 3030x0E    0xXX          Not used
 3040x0F    0xXX          Not used
 3050x10    0xXX          Not used
 3060x11    0xXX          Not used
 307
 308The following table describes the frame header exported by the SN9C103:
 309
 310Byte #  Value or bits Description
 311------  ------------- -----------
 3120x00    0xFF          Frame synchronisation pattern
 3130x01    0xFF          Frame synchronisation pattern
 3140x02    0x00          Frame synchronisation pattern
 3150x03    0xC4          Frame synchronisation pattern
 3160x04    0xC4          Frame synchronisation pattern
 3170x05    0x96          Frame synchronisation pattern
 3180x06    [6:0]         Read channel gain control = (1/2+R_GAIN/64)
 3190x07    [6:0]         Blue channel gain control = (1/2+B_GAIN/64)
 320        [7:4]
 3210x08    [ 0 ]         Compression mode. 0=No compression, 1=Compression enabled
 322        [2:1]         Maximum scale factor for compression
 323        [ 3 ]         1 = USB fifo(2K bytes) is full
 324        [ 4 ]         1 = Digital gain is finish
 325        [ 5 ]         1 = Exposure is finish
 326        [7:6]         Frame index
 3270x09    [7:0]         Y sum inside Auto-Exposure area (low-byte)
 3280x0A    [7:0]         Y sum inside Auto-Exposure area (high-byte)
 329                      where Y sum = (R/4 + 5G/16 + B/8) / 32
 3300x0B    [7:0]         Y sum outside Auto-Exposure area (low-byte)
 3310x0C    [7:0]         Y sum outside Auto-Exposure area (high-byte)
 332                      where Y sum = (R/4 + 5G/16 + B/8) / 128
 3330x0D    [1:0]         Audio frame number
 334        [ 2 ]         1 = Audio is recording
 3350x0E    [7:0]         Audio summation (low-byte)
 3360x0F    [7:0]         Audio summation (high-byte)
 3370x10    [7:0]         Audio sample count
 3380x11    [7:0]         Audio peak data in audio frame
 339
 340The AE area (sx, sy, ex, ey) in the active window can be set by programming the
 341registers 0x1c, 0x1d, 0x1e and 0x1f of the SN9C1xx controllers, where one unit
 342corresponds to 32 pixels.
 343
 344[1] The frame headers exported by the SN9C105 and SN9C120 are not described.
 345
 346
 3479. Supported devices
 348====================
 349None of the names of the companies as well as their products will be mentioned
 350here. They have never collaborated with the author, so no advertising.
 351
 352From the point of view of a driver, what unambiguously identify a device are
 353its vendor and product USB identifiers. Below is a list of known identifiers of
 354devices assembling the SN9C1xx PC camera controllers:
 355
 356Vendor ID  Product ID
 357---------  ----------
 3580x0458     0x7025
 3590x045e     0x00f5
 3600x045e     0x00f7
 3610x0471     0x0327
 3620x0471     0x0328
 3630x0c45     0x6001
 3640x0c45     0x6005
 3650x0c45     0x6007
 3660x0c45     0x6009
 3670x0c45     0x600d
 3680x0c45     0x6011
 3690x0c45     0x6019
 3700x0c45     0x6024
 3710x0c45     0x6025
 3720x0c45     0x6028
 3730x0c45     0x6029
 3740x0c45     0x602a
 3750x0c45     0x602b
 3760x0c45     0x602c
 3770x0c45     0x602d
 3780x0c45     0x602e
 3790x0c45     0x6030
 3800x0c45     0x603f
 3810x0c45     0x6080
 3820x0c45     0x6082
 3830x0c45     0x6083
 3840x0c45     0x6088
 3850x0c45     0x608a
 3860x0c45     0x608b
 3870x0c45     0x608c
 3880x0c45     0x608e
 3890x0c45     0x608f
 3900x0c45     0x60a0
 3910x0c45     0x60a2
 3920x0c45     0x60a3
 3930x0c45     0x60a8
 3940x0c45     0x60aa
 3950x0c45     0x60ab
 3960x0c45     0x60ac
 3970x0c45     0x60ae
 3980x0c45     0x60af
 3990x0c45     0x60b0
 4000x0c45     0x60b2
 4010x0c45     0x60b3
 4020x0c45     0x60b8
 4030x0c45     0x60ba
 4040x0c45     0x60bb
 4050x0c45     0x60bc
 4060x0c45     0x60be
 4070x0c45     0x60c0
 4080x0c45     0x60c2
 4090x0c45     0x60c8
 4100x0c45     0x60cc
 4110x0c45     0x60ea
 4120x0c45     0x60ec
 4130x0c45     0x60ef
 4140x0c45     0x60fa
 4150x0c45     0x60fb
 4160x0c45     0x60fc
 4170x0c45     0x60fe
 4180x0c45     0x6102
 4190x0c45     0x6108
 4200x0c45     0x610f
 4210x0c45     0x6130
 4220x0c45     0x6138
 4230x0c45     0x613a
 4240x0c45     0x613b
 4250x0c45     0x613c
 4260x0c45     0x613e
 427
 428The list above does not imply that all those devices work with this driver: up
 429until now only the ones that assemble the following pairs of SN9C1xx bridges
 430and image sensors are supported; kernel messages will always tell you whether
 431this is the case (see "Module loading" paragraph):
 432
 433Image sensor / SN9C1xx bridge      | SN9C10[12]  SN9C103  SN9C105  SN9C120
 434-------------------------------------------------------------------------------
 435HV7131D    Hynix Semiconductor     | Yes         No       No       No
 436HV7131R    Hynix Semiconductor     | No          Yes      Yes      Yes
 437MI-0343    Micron Technology       | Yes         No       No       No
 438MI-0360    Micron Technology       | No          Yes      Yes      Yes
 439OV7630     OmniVision Technologies | Yes         Yes      Yes      Yes
 440OV7660     OmniVision Technologies | No          No       Yes      Yes
 441PAS106B    PixArt Imaging          | Yes         No       No       No
 442PAS202B    PixArt Imaging          | Yes         Yes      No       No
 443TAS5110C1B Taiwan Advanced Sensor  | Yes         No       No       No
 444TAS5110D   Taiwan Advanced Sensor  | Yes         No       No       No
 445TAS5130D1B Taiwan Advanced Sensor  | Yes         No       No       No
 446
 447"Yes" means that the pair is supported by the driver, while "No" means that the
 448pair does not exist or is not supported by the driver.
 449
 450Only some of the available control settings of each image sensor are supported
 451through the V4L2 interface.
 452
 453Donations of new models for further testing and support would be much
 454appreciated. Non-available hardware will not be supported by the author of this
 455driver.
 456
 457
 45810. Notes for V4L2 application developers
 459=========================================
 460This driver follows the V4L2 API specifications. In particular, it enforces two
 461rules:
 462
 463- exactly one I/O method, either "mmap" or "read", is associated with each
 464file descriptor. Once it is selected, the application must close and reopen the
 465device to switch to the other I/O method;
 466
 467- although it is not mandatory, previously mapped buffer memory should always
 468be unmapped before calling any "VIDIOC_S_CROP" or "VIDIOC_S_FMT" ioctl's.
 469The same number of buffers as before will be allocated again to match the size
 470of the new video frames, so you have to map the buffers again before any I/O
 471attempts on them.
 472
 473Consistently with the hardware limits, this driver also supports image
 474downscaling with arbitrary scaling factors from 1, 2 and 4 in both directions.
 475However, the V4L2 API specifications don't correctly define how the scaling
 476factor can be chosen arbitrarily by the "negotiation" of the "source" and
 477"target" rectangles. To work around this flaw, we have added the convention
 478that, during the negotiation, whenever the "VIDIOC_S_CROP" ioctl is issued, the
 479scaling factor is restored to 1.
 480
 481This driver supports two different video formats: the first one is the "8-bit
 482Sequential Bayer" format and can be used to obtain uncompressed video data
 483from the device through the current I/O method, while the second one provides
 484either "raw" compressed video data (without frame headers not related to the
 485compressed data) or standard JPEG (with frame headers). The compression quality
 486may vary from 0 to 1 and can be selected or queried thanks to the
 487VIDIOC_S_JPEGCOMP and VIDIOC_G_JPEGCOMP V4L2 ioctl's. For maximum flexibility,
 488both the default active video format and the default compression quality
 489depend on how the image sensor being used is initialized.
 490
 491
 49211. Video frame formats [1]
 493=======================
 494The SN9C1xx PC Camera Controllers can send images in two possible video
 495formats over the USB: either native "Sequential RGB Bayer" or compressed.
 496The compression is used to achieve high frame rates. With regard to the
 497SN9C101, SN9C102 and SN9C103, the compression is based on the Huffman encoding
 498algorithm described below, while with regard to the SN9C105 and SN9C120 the
 499compression is based on the JPEG standard.
 500The current video format may be selected or queried from the user application
 501by calling the VIDIOC_S_FMT or VIDIOC_G_FMT ioctl's, as described in the V4L2
 502API specifications.
 503
 504The name "Sequential Bayer" indicates the organization of the red, green and
 505blue pixels in one video frame. Each pixel is associated with a 8-bit long
 506value and is disposed in memory according to the pattern shown below:
 507
 508B[0]   G[1]    B[2]    G[3]    ...   B[m-2]         G[m-1]
 509G[m]   R[m+1]  G[m+2]  R[m+2]  ...   G[2m-2]        R[2m-1]
 510...
 511...                                  B[(n-1)(m-2)]  G[(n-1)(m-1)]
 512...                                  G[n(m-2)]      R[n(m-1)]
 513
 514The above matrix also represents the sequential or progressive read-out mode of
 515the (n, m) Bayer color filter array used in many CCD or CMOS image sensors.
 516
 517The Huffman compressed video frame consists of a bitstream that encodes for
 518every R, G, or B pixel the difference between the value of the pixel itself and
 519some reference pixel value. Pixels are organised in the Bayer pattern and the
 520Bayer sub-pixels are tracked individually and alternatingly. For example, in
 521the first line values for the B and G1 pixels are alternatingly encoded, while
 522in the second line values for the G2 and R pixels are alternatingly encoded.
 523
 524The pixel reference value is calculated as follows:
 525- the 4 top left pixels are encoded in raw uncompressed 8-bit format;
 526- the value in the top two rows is the value of the pixel left of the current
 527  pixel;
 528- the value in the left column is the value of the pixel above the current
 529  pixel;
 530- for all other pixels, the reference value is the average of the value of the
 531  pixel on the left and the value of the pixel above the current pixel;
 532- there is one code in the bitstream that specifies the value of a pixel
 533  directly (in 4-bit resolution);
 534- pixel values need to be clamped inside the range [0..255] for proper
 535  decoding.
 536
 537The algorithm purely describes the conversion from compressed Bayer code used
 538in the SN9C101, SN9C102 and SN9C103 chips to uncompressed Bayer. Additional
 539steps are required to convert this to a color image (i.e. a color interpolation
 540algorithm).
 541
 542The following Huffman codes have been found:
 5430: +0 (relative to reference pixel value)
 544100: +4
 545101: -4?
 5461110xxxx: set absolute value to xxxx.0000
 5471101: +11
 5481111: -11
 54911001: +20
 550110000: -20
 551110001: ??? - these codes are apparently not used
 552
 553[1] The Huffman compression algorithm has been reverse-engineered and
 554    documented by Bertrik Sikken.
 555
 556
 55712. Contact information
 558=======================
 559The author may be contacted by e-mail at <luca.risolia@studio.unibo.it>.
 560
 561GPG/PGP encrypted e-mail's are accepted. The GPG key ID of the author is
 562'FCE635A4'; the public 1024-bit key should be available at any keyserver;
 563the fingerprint is: '88E8 F32F 7244 68BA 3958  5D40 99DA 5D2A FCE6 35A4'.
 564
 565
 56613. Credits
 567===========
 568Many thanks to following persons for their contribute (listed in alphabetical
 569order):
 570
 571- David Anderson for the donation of a webcam;
 572- Luca Capello for the donation of a webcam;
 573- Philippe Coval for having helped testing the PAS202BCA image sensor;
 574- Joao Rodrigo Fuzaro, Joao Limirio, Claudio Filho and Caio Begotti for the
 575  donation of a webcam;
 576- Dennis Heitmann for the donation of a webcam;
 577- Jon Hollstrom for the donation of a webcam;
 578- Nick McGill for the donation of a webcam;
 579- Carlos Eduardo Medaglia Dyonisio, who added the support for the PAS202BCB
 580  image sensor;
 581- Stefano Mozzi, who donated 45 EU;
 582- Andrew Pearce for the donation of a webcam;
 583- John Pullan for the donation of a webcam;
 584- Bertrik Sikken, who reverse-engineered and documented the Huffman compression
 585  algorithm used in the SN9C101, SN9C102 and SN9C103 controllers and
 586  implemented the first decoder;
 587- Ronny Standke for the donation of a webcam;
 588- Mizuno Takafumi for the donation of a webcam;
 589- an "anonymous" donator (who didn't want his name to be revealed) for the
 590  donation of a webcam.
 591- an anonymous donator for the donation of four webcams and two boards with ten
 592  image sensors.
 593
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