linux/Documentation/video4linux/sn9c102.txt
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   1
   2                         SN9C10x 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) 2004-2006 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 mounting the
  57SONiX SN9C101, SN9C102 and SN9C103 PC Camera Controllers.
  58
  59It's worth to note that SONiX has never collaborated with the author during the
  60development of this project, despite several requests for enough detailed
  61specifications of the register tables, compression engine and video data format
  62of the above chips. Nevertheless, these informations are no longer necessary,
  63becouse all the aspects related to these chips are known and have been
  64described in detail in this documentation.
  65
  66The driver relies on the Video4Linux2 and USB core modules. It has been
  67designed to run properly on SMP systems as well.
  68
  69The latest version of the SN9C10x driver can be found at the following URL:
  70http://www.linux-projects.org/
  71
  72Some of the features of the driver are:
  73
  74- full compliance with the Video4Linux2 API (see also "Notes for V4L2
  75  application developers" paragraph);
  76- available mmap or read/poll methods for video streaming through isochronous
  77  data transfers;
  78- automatic detection of image sensor;
  79- support for built-in microphone interface;
  80- support for any window resolutions and optional panning within the maximum
  81  pixel area of image sensor;
  82- image downscaling with arbitrary scaling factors from 1, 2 and 4 in both
  83  directions (see "Notes for V4L2 application developers" paragraph);
  84- two different video formats for uncompressed or compressed data in low or
  85  high compression quality (see also "Notes for V4L2 application developers"
  86  and "Video frame formats" paragraphs);
  87- full support for the capabilities of many of the possible image sensors that
  88  can be connected to the SN9C10x bridges, including, for istance, red, green,
  89  blue and global gain adjustments and exposure (see "Supported devices"
  90  paragraph for details);
  91- use of default color settings for sunlight conditions;
  92- dynamic I/O interface for both SN9C10x and image sensor control and
  93  monitoring (see "Optional device control through 'sysfs'" paragraph);
  94- dynamic driver control thanks to various module parameters (see "Module
  95  parameters" paragraph);
  96- up to 64 cameras can be handled at the same time; they can be connected and
  97  disconnected from the host many times without turning off the computer, if
  98  the system supports hotplugging;
  99- no known bugs.
 100
 101
 1025. Module dependencies
 103======================
 104For it to work properly, the driver needs kernel support for Video4Linux and
 105USB.
 106
 107The following options of the kernel configuration file must be enabled and
 108corresponding modules must be compiled:
 109
 110        # Multimedia devices
 111        #
 112        CONFIG_VIDEO_DEV=m
 113
 114To enable advanced debugging functionality on the device through /sysfs:
 115
 116        # Multimedia devices
 117        #
 118        CONFIG_VIDEO_ADV_DEBUG=y
 119
 120        # USB support
 121        #
 122        CONFIG_USB=m
 123
 124In addition, depending on the hardware being used, the modules below are
 125necessary:
 126
 127        # USB Host Controller Drivers
 128        #
 129        CONFIG_USB_EHCI_HCD=m
 130        CONFIG_USB_UHCI_HCD=m
 131        CONFIG_USB_OHCI_HCD=m
 132
 133The SN9C103 controller also provides a built-in microphone interface. It is
 134supported by the USB Audio driver thanks to the ALSA API:
 135
 136        # Sound
 137        #
 138        CONFIG_SOUND=y
 139
 140        # Advanced Linux Sound Architecture
 141        #
 142        CONFIG_SND=m
 143
 144        # USB devices
 145        #
 146        CONFIG_SND_USB_AUDIO=m
 147
 148And finally:
 149
 150        # USB Multimedia devices
 151        #
 152        CONFIG_USB_SN9C102=m
 153
 154
 1556. Module loading
 156=================
 157To use the driver, it is necessary to load the "sn9c102" module into memory
 158after every other module required: "videodev", "usbcore" and, depending on
 159the USB host controller you have, "ehci-hcd", "uhci-hcd" or "ohci-hcd".
 160
 161Loading can be done as shown below:
 162
 163        [root@localhost home]# modprobe sn9c102
 164
 165At this point the devices should be recognized. You can invoke "dmesg" to
 166analyze kernel messages and verify that the loading process has gone well:
 167
 168        [user@localhost home]$ dmesg
 169
 170
 1717. Module parameters
 172====================
 173Module parameters are listed below:
 174-------------------------------------------------------------------------------
 175Name:           video_nr
 176Type:           short array (min = 0, max = 64)
 177Syntax:         <-1|n[,...]>
 178Description:    Specify V4L2 minor mode number:
 179                -1 = use next available
 180                 n = use minor number n
 181                You can specify up to 64 cameras this way.
 182                For example:
 183                video_nr=-1,2,-1 would assign minor number 2 to the second
 184                recognized camera and use auto for the first one and for every
 185                other camera.
 186Default:        -1
 187-------------------------------------------------------------------------------
 188Name:           force_munmap
 189Type:           bool array (min = 0, max = 64)
 190Syntax:         <0|1[,...]>
 191Description:    Force the application to unmap previously mapped buffer memory
 192                before calling any VIDIOC_S_CROP or VIDIOC_S_FMT ioctl's. Not
 193                all the applications support this feature. This parameter is
 194                specific for each detected camera.
 195                0 = do not force memory unmapping
 196                1 = force memory unmapping (save memory)
 197Default:        0
 198-------------------------------------------------------------------------------
 199Name:           frame_timeout
 200Type:           uint array (min = 0, max = 64)
 201Syntax:         <n[,...]>
 202Description:    Timeout for a video frame in seconds. This parameter is
 203                specific for each detected camera. This parameter can be
 204                changed at runtime thanks to the /sys filesystem interface.
 205Default:        2
 206-------------------------------------------------------------------------------
 207Name:           debug
 208Type:           ushort
 209Syntax:         <n>
 210Description:    Debugging information level, from 0 to 3:
 211                0 = none (use carefully)
 212                1 = critical errors
 213                2 = significant informations
 214                3 = more verbose messages
 215                Level 3 is useful for testing only, when only one device
 216                is used. It also shows some more informations about the
 217                hardware being detected. This parameter can be changed at
 218                runtime thanks to the /sys filesystem interface.
 219Default:        2
 220-------------------------------------------------------------------------------
 221
 222
 2238. Optional device control through "sysfs" [1]
 224==========================================
 225If the kernel has been compiled with the CONFIG_VIDEO_ADV_DEBUG option enabled,
 226it is possible to read and write both the SN9C10x and the image sensor
 227registers by using the "sysfs" filesystem interface.
 228
 229Every time a supported device is recognized, a write-only file named "green" is
 230created in the /sys/class/video4linux/videoX directory. You can set the green
 231channel's gain by writing the desired value to it. The value may range from 0
 232to 15 for SN9C101 or SN9C102 bridges, from 0 to 127 for SN9C103 bridges.
 233Similarly, only for SN9C103 controllers, blue and red gain control files are
 234available in the same directory, for which accepted values may range from 0 to
 235127.
 236
 237There are other four entries in the directory above for each registered camera:
 238"reg", "val", "i2c_reg" and "i2c_val". The first two files control the
 239SN9C10x bridge, while the other two control the sensor chip. "reg" and
 240"i2c_reg" hold the values of the current register index where the following
 241reading/writing operations are addressed at through "val" and "i2c_val". Their
 242use is not intended for end-users. Note that "i2c_reg" and "i2c_val" will not
 243be created if the sensor does not actually support the standard I2C protocol or
 244its registers are not 8-bit long. Also, remember that you must be logged in as
 245root before writing to them.
 246
 247As an example, suppose we were to want to read the value contained in the
 248register number 1 of the sensor register table - which is usually the product
 249identifier - of the camera registered as "/dev/video0":
 250
 251        [root@localhost #] cd /sys/class/video4linux/video0
 252        [root@localhost #] echo 1 > i2c_reg
 253        [root@localhost #] cat i2c_val
 254
 255Note that "cat" will fail if sensor registers cannot be read.
 256
 257Now let's set the green gain's register of the SN9C101 or SN9C102 chips to 2:
 258
 259        [root@localhost #] echo 0x11 > reg
 260        [root@localhost #] echo 2 > val
 261
 262Note that the SN9C10x always returns 0 when some of its registers are read.
 263To avoid race conditions, all the I/O accesses to the above files are
 264serialized.
 265
 266The sysfs interface also provides the "frame_header" entry, which exports the
 267frame header of the most recent requested and captured video frame. The header
 268is always 18-bytes long and is appended to every video frame by the SN9C10x
 269controllers. As an example, this additional information can be used by the user
 270application for implementing auto-exposure features via software.
 271
 272The following table describes the frame header:
 273
 274Byte #  Value         Description
 275------  -----         -----------
 2760x00    0xFF          Frame synchronisation pattern.
 2770x01    0xFF          Frame synchronisation pattern.
 2780x02    0x00          Frame synchronisation pattern.
 2790x03    0xC4          Frame synchronisation pattern.
 2800x04    0xC4          Frame synchronisation pattern.
 2810x05    0x96          Frame synchronisation pattern.
 2820x06    0xXX          Unknown meaning. The exact value depends on the chip;
 283                      possible values are 0x00, 0x01 and 0x20.
 2840x07    0xXX          Variable value, whose bits are ff00uzzc, where ff is a
 285                      frame counter, u is unknown, zz is a size indicator
 286                      (00 = VGA, 01 = SIF, 10 = QSIF) and c stands for
 287                      "compression enabled" (1 = yes, 0 = no).
 2880x08    0xXX          Brightness sum inside Auto-Exposure area (low-byte).
 2890x09    0xXX          Brightness sum inside Auto-Exposure area (high-byte).
 290                      For a pure white image, this number will be equal to 500
 291                      times the area of the specified AE area. For images
 292                      that are not pure white, the value scales down according
 293                      to relative whiteness.
 2940x0A    0xXX          Brightness sum outside Auto-Exposure area (low-byte).
 2950x0B    0xXX          Brightness sum outside Auto-Exposure area (high-byte).
 296                      For a pure white image, this number will be equal to 125
 297                      times the area outside of the specified AE area. For
 298                      images that are not pure white, the value scales down
 299                      according to relative whiteness.
 300                      according to relative whiteness.
 301
 302The following bytes are used by the SN9C103 bridge only:
 303
 3040x0C    0xXX          Unknown meaning
 3050x0D    0xXX          Unknown meaning
 3060x0E    0xXX          Unknown meaning
 3070x0F    0xXX          Unknown meaning
 3080x10    0xXX          Unknown meaning
 3090x11    0xXX          Unknown meaning
 310
 311The AE area (sx, sy, ex, ey) in the active window can be set by programming the
 312registers 0x1c, 0x1d, 0x1e and 0x1f of the SN9C10x controllers, where one unit
 313corresponds to 32 pixels.
 314
 315[1] Part of the meaning of the frame header has been documented by Bertrik
 316    Sikken.
 317
 318
 3199. Supported devices
 320====================
 321None of the names of the companies as well as their products will be mentioned
 322here. They have never collaborated with the author, so no advertising.
 323
 324From the point of view of a driver, what unambiguously identify a device are
 325its vendor and product USB identifiers. Below is a list of known identifiers of
 326devices mounting the SN9C10x PC camera controllers:
 327
 328Vendor ID  Product ID
 329---------  ----------
 3300x0c45     0x6001
 3310x0c45     0x6005
 3320x0c45     0x6007
 3330x0c45     0x6009
 3340x0c45     0x600d
 3350x0c45     0x6024
 3360x0c45     0x6025
 3370x0c45     0x6028
 3380x0c45     0x6029
 3390x0c45     0x602a
 3400x0c45     0x602b
 3410x0c45     0x602c
 3420x0c45     0x602d
 3430x0c45     0x602e
 3440x0c45     0x6030
 3450x0c45     0x6080
 3460x0c45     0x6082
 3470x0c45     0x6083
 3480x0c45     0x6088
 3490x0c45     0x608a
 3500x0c45     0x608b
 3510x0c45     0x608c
 3520x0c45     0x608e
 3530x0c45     0x608f
 3540x0c45     0x60a0
 3550x0c45     0x60a2
 3560x0c45     0x60a3
 3570x0c45     0x60a8
 3580x0c45     0x60aa
 3590x0c45     0x60ab
 3600x0c45     0x60ac
 3610x0c45     0x60ae
 3620x0c45     0x60af
 3630x0c45     0x60b0
 3640x0c45     0x60b2
 3650x0c45     0x60b3
 3660x0c45     0x60b8
 3670x0c45     0x60ba
 3680x0c45     0x60bb
 3690x0c45     0x60bc
 3700x0c45     0x60be
 371
 372The list above does not imply that all those devices work with this driver: up
 373until now only the ones that mount the following image sensors are supported;
 374kernel messages will always tell you whether this is the case:
 375
 376Model       Manufacturer
 377-----       ------------
 378HV7131D     Hynix Semiconductor, Inc.
 379MI-0343     Micron Technology, Inc.
 380OV7630      OmniVision Technologies, Inc.
 381PAS106B     PixArt Imaging, Inc.
 382PAS202BCA   PixArt Imaging, Inc.
 383PAS202BCB   PixArt Imaging, Inc.
 384TAS5110C1B  Taiwan Advanced Sensor Corporation
 385TAS5130D1B  Taiwan Advanced Sensor Corporation
 386
 387All the available control settings of each image sensor are supported through
 388the V4L2 interface.
 389
 390Donations of new models for further testing and support would be much
 391appreciated. Non-available hardware will not be supported by the author of this
 392driver.
 393
 394
 39510. Notes for V4L2 application developers
 396=========================================
 397This driver follows the V4L2 API specifications. In particular, it enforces two
 398rules:
 399
 400- exactly one I/O method, either "mmap" or "read", is associated with each
 401file descriptor. Once it is selected, the application must close and reopen the
 402device to switch to the other I/O method;
 403
 404- although it is not mandatory, previously mapped buffer memory should always
 405be unmapped before calling any "VIDIOC_S_CROP" or "VIDIOC_S_FMT" ioctl's.
 406The same number of buffers as before will be allocated again to match the size
 407of the new video frames, so you have to map the buffers again before any I/O
 408attempts on them.
 409
 410Consistently with the hardware limits, this driver also supports image
 411downscaling with arbitrary scaling factors from 1, 2 and 4 in both directions.
 412However, the V4L2 API specifications don't correctly define how the scaling
 413factor can be chosen arbitrarily by the "negotiation" of the "source" and
 414"target" rectangles. To work around this flaw, we have added the convention
 415that, during the negotiation, whenever the "VIDIOC_S_CROP" ioctl is issued, the
 416scaling factor is restored to 1.
 417
 418This driver supports two different video formats: the first one is the "8-bit
 419Sequential Bayer" format and can be used to obtain uncompressed video data
 420from the device through the current I/O method, while the second one provides
 421"raw" compressed video data (without frame headers not related to the
 422compressed data). The compression quality may vary from 0 to 1 and can be
 423selected or queried thanks to the VIDIOC_S_JPEGCOMP and VIDIOC_G_JPEGCOMP V4L2
 424ioctl's. For maximum flexibility, both the default active video format and the
 425default compression quality depend on how the image sensor being used is
 426initialized (as described in the documentation of the API for the image sensors
 427supplied by this driver).
 428
 429
 43011. Video frame formats [1]
 431=======================
 432The SN9C10x PC Camera Controllers can send images in two possible video
 433formats over the USB: either native "Sequential RGB Bayer" or Huffman
 434compressed. The latter is used to achieve high frame rates. The current video
 435format may be selected or queried from the user application by calling the
 436VIDIOC_S_FMT or VIDIOC_G_FMT ioctl's, as described in the V4L2 API
 437specifications.
 438
 439The name "Sequential Bayer" indicates the organization of the red, green and
 440blue pixels in one video frame. Each pixel is associated with a 8-bit long
 441value and is disposed in memory according to the pattern shown below:
 442
 443B[0]   G[1]    B[2]    G[3]    ...   B[m-2]         G[m-1]
 444G[m]   R[m+1]  G[m+2]  R[m+2]  ...   G[2m-2]        R[2m-1]
 445...
 446...                                  B[(n-1)(m-2)]  G[(n-1)(m-1)]
 447...                                  G[n(m-2)]      R[n(m-1)]
 448
 449The above matrix also represents the sequential or progressive read-out mode of
 450the (n, m) Bayer color filter array used in many CCD/CMOS image sensors.
 451
 452One compressed video frame consists of a bitstream that encodes for every R, G,
 453or B pixel the difference between the value of the pixel itself and some
 454reference pixel value. Pixels are organised in the Bayer pattern and the Bayer
 455sub-pixels are tracked individually and alternatingly. For example, in the
 456first line values for the B and G1 pixels are alternatingly encoded, while in
 457the second line values for the G2 and R pixels are alternatingly encoded.
 458
 459The pixel reference value is calculated as follows:
 460- the 4 top left pixels are encoded in raw uncompressed 8-bit format;
 461- the value in the top two rows is the value of the pixel left of the current
 462  pixel;
 463- the value in the left column is the value of the pixel above the current
 464  pixel;
 465- for all other pixels, the reference value is the average of the value of the
 466  pixel on the left and the value of the pixel above the current pixel;
 467- there is one code in the bitstream that specifies the value of a pixel
 468  directly (in 4-bit resolution);
 469- pixel values need to be clamped inside the range [0..255] for proper
 470  decoding.
 471
 472The algorithm purely describes the conversion from compressed Bayer code used
 473in the SN9C10x chips to uncompressed Bayer. Additional steps are required to
 474convert this to a color image (i.e. a color interpolation algorithm).
 475
 476The following Huffman codes have been found:
 4770: +0 (relative to reference pixel value)
 478100: +4
 479101: -4?
 4801110xxxx: set absolute value to xxxx.0000
 4811101: +11
 4821111: -11
 48311001: +20
 484110000: -20
 485110001: ??? - these codes are apparently not used
 486
 487[1] The Huffman compression algorithm has been reverse-engineered and
 488    documented by Bertrik Sikken.
 489
 490
 49112. Contact information
 492=======================
 493The author may be contacted by e-mail at <luca.risolia@studio.unibo.it>.
 494
 495GPG/PGP encrypted e-mail's are accepted. The GPG key ID of the author is
 496'FCE635A4'; the public 1024-bit key should be available at any keyserver;
 497the fingerprint is: '88E8 F32F 7244 68BA 3958  5D40 99DA 5D2A FCE6 35A4'.
 498
 499
 50013. Credits
 501===========
 502Many thanks to following persons for their contribute (listed in alphabetical
 503order):
 504
 505- Luca Capello for the donation of a webcam;
 506- Philippe Coval for having helped testing the PAS202BCA image sensor;
 507- Joao Rodrigo Fuzaro, Joao Limirio, Claudio Filho and Caio Begotti for the
 508  donation of a webcam;
 509- Jon Hollstrom for the donation of a webcam;
 510- Carlos Eduardo Medaglia Dyonisio, who added the support for the PAS202BCB
 511  image sensor;
 512- Stefano Mozzi, who donated 45 EU;
 513- Andrew Pearce for the donation of a webcam;
 514- Bertrik Sikken, who reverse-engineered and documented the Huffman compression
 515  algorithm used in the SN9C10x controllers and implemented the first decoder;
 516- Mizuno Takafumi for the donation of a webcam;
 517- an "anonymous" donator (who didn't want his name to be revealed) for the
 518  donation of a webcam.
 519
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