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2 SN9C10x PC Camera Controllers
3 Driver for Linux
4 =============================
6 - Documentation -
9 Index
10 =====
11 1. Copyright
12 2. Disclaimer
13 3. License
14 4. Overview and features
15 5. Module dependencies
16 6. Module loading
17 7. Module parameters
18 8. Optional device control through "sysfs"
19 9. Supported devices
20 10. Notes for V4L2 application developers
21 11. Video frame formats
22 12. Contact information
23 13. Credits
26 1. Copyright
27 ============
28 Copyright (C) 2004-2006 by Luca Risolia <luca.risolia@studio.unibo.it>
31 2. Disclaimer
32 =============
33 SONiX is a trademark of SONiX Technology Company Limited, inc.
34 This software is not sponsored or developed by SONiX.
37 3. License
38 ==========
39 This program is free software; you can redistribute it and/or modify
40 it under the terms of the GNU General Public License as published by
41 the Free Software Foundation; either version 2 of the License, or
42 (at your option) any later version.
44 This program is distributed in the hope that it will be useful,
45 but WITHOUT ANY WARRANTY; without even the implied warranty of
46 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
47 GNU General Public License for more details.
49 You should have received a copy of the GNU General Public License
50 along with this program; if not, write to the Free Software
51 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
54 4. Overview and features
55 ========================
56 This driver attempts to support the video interface of the devices mounting the
57 SONiX SN9C101, SN9C102 and SN9C103 PC Camera Controllers.
59 It's worth to note that SONiX has never collaborated with the author during the
60 development of this project, despite several requests for enough detailed
61 specifications of the register tables, compression engine and video data format
62 of the above chips. Nevertheless, these informations are no longer necessary,
63 because all the aspects related to these chips are known and have been
64 described in detail in this documentation.
66 The driver relies on the Video4Linux2 and USB core modules. It has been
67 designed to run properly on SMP systems as well.
69 The latest version of the SN9C10x driver can be found at the following URL:
70 http://www.linux-projects.org/
72 Some of the features of the driver are:
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 instance, 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.
102 5. Module dependencies
103 ======================
104 For it to work properly, the driver needs kernel support for Video4Linux and
105 USB.
107 The following options of the kernel configuration file must be enabled and
108 corresponding modules must be compiled:
110 # Multimedia devices
111 #
112 CONFIG_VIDEO_DEV=m
114 To enable advanced debugging functionality on the device through /sysfs:
116 # Multimedia devices
117 #
118 CONFIG_VIDEO_ADV_DEBUG=y
120 # USB support
121 #
122 CONFIG_USB=m
124 In addition, depending on the hardware being used, the modules below are
125 necessary:
127 # USB Host Controller Drivers
128 #
129 CONFIG_USB_EHCI_HCD=m
130 CONFIG_USB_UHCI_HCD=m
131 CONFIG_USB_OHCI_HCD=m
133 The SN9C103 controller also provides a built-in microphone interface. It is
134 supported by the USB Audio driver thanks to the ALSA API:
136 # Sound
137 #
138 CONFIG_SOUND=y
140 # Advanced Linux Sound Architecture
141 #
142 CONFIG_SND=m
144 # USB devices
145 #
146 CONFIG_SND_USB_AUDIO=m
148 And finally:
150 # USB Multimedia devices
151 #
152 CONFIG_USB_SN9C102=m
155 6. Module loading
156 =================
157 To use the driver, it is necessary to load the "sn9c102" module into memory
158 after every other module required: "videodev", "usbcore" and, depending on
159 the USB host controller you have, "ehci-hcd", "uhci-hcd" or "ohci-hcd".
161 Loading can be done as shown below:
163 [root@localhost home]# modprobe sn9c102
165 At this point the devices should be recognized. You can invoke "dmesg" to
166 analyze kernel messages and verify that the loading process has gone well:
168 [user@localhost home]$ dmesg
171 7. Module parameters
172 ====================
173 Module parameters are listed below:
174 -------------------------------------------------------------------------------
175 Name: video_nr
176 Type: short array (min = 0, max = 64)
177 Syntax: <-1|n[,...]>
178 Description: 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.
186 Default: -1
187 -------------------------------------------------------------------------------
188 Name: force_munmap
189 Type: bool array (min = 0, max = 64)
190 Syntax: <0|1[,...]>
191 Description: 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)
197 Default: 0
198 -------------------------------------------------------------------------------
199 Name: frame_timeout
200 Type: uint array (min = 0, max = 64)
201 Syntax: <n[,...]>
202 Description: 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.
205 Default: 2
206 -------------------------------------------------------------------------------
207 Name: debug
208 Type: ushort
209 Syntax: <n>
210 Description: 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.
219 Default: 2
220 -------------------------------------------------------------------------------
223 8. Optional device control through "sysfs" [1]
224 ==========================================
225 If the kernel has been compiled with the CONFIG_VIDEO_ADV_DEBUG option enabled,
226 it is possible to read and write both the SN9C10x and the image sensor
227 registers by using the "sysfs" filesystem interface.
229 Every time a supported device is recognized, a write-only file named "green" is
230 created in the /sys/class/video4linux/videoX directory. You can set the green
231 channel's gain by writing the desired value to it. The value may range from 0
232 to 15 for SN9C101 or SN9C102 bridges, from 0 to 127 for SN9C103 bridges.
233 Similarly, only for SN9C103 controllers, blue and red gain control files are
234 available in the same directory, for which accepted values may range from 0 to
235 127.
237 There 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
239 SN9C10x 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
241 reading/writing operations are addressed at through "val" and "i2c_val". Their
242 use is not intended for end-users. Note that "i2c_reg" and "i2c_val" will not
243 be created if the sensor does not actually support the standard I2C protocol or
244 its registers are not 8-bit long. Also, remember that you must be logged in as
245 root before writing to them.
247 As an example, suppose we were to want to read the value contained in the
248 register number 1 of the sensor register table - which is usually the product
249 identifier - of the camera registered as "/dev/video0":
251 [root@localhost #] cd /sys/class/video4linux/video0
252 [root@localhost #] echo 1 > i2c_reg
253 [root@localhost #] cat i2c_val
255 Note that "cat" will fail if sensor registers cannot be read.
257 Now let's set the green gain's register of the SN9C101 or SN9C102 chips to 2:
259 [root@localhost #] echo 0x11 > reg
260 [root@localhost #] echo 2 > val
262 Note that the SN9C10x always returns 0 when some of its registers are read.
263 To avoid race conditions, all the I/O accesses to the above files are
264 serialized.
266 The sysfs interface also provides the "frame_header" entry, which exports the
267 frame header of the most recent requested and captured video frame. The header
268 is always 18-bytes long and is appended to every video frame by the SN9C10x
269 controllers. As an example, this additional information can be used by the user
270 application for implementing auto-exposure features via software.
272 The following table describes the frame header:
274 Byte # Value Description
275 ------ ----- -----------
276 0x00 0xFF Frame synchronisation pattern.
277 0x01 0xFF Frame synchronisation pattern.
278 0x02 0x00 Frame synchronisation pattern.
279 0x03 0xC4 Frame synchronisation pattern.
280 0x04 0xC4 Frame synchronisation pattern.
281 0x05 0x96 Frame synchronisation pattern.
282 0x06 0xXX Unknown meaning. The exact value depends on the chip;
283 possible values are 0x00, 0x01 and 0x20.
284 0x07 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).
288 0x08 0xXX Brightness sum inside Auto-Exposure area (low-byte).
289 0x09 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.
294 0x0A 0xXX Brightness sum outside Auto-Exposure area (low-byte).
295 0x0B 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.
302 The following bytes are used by the SN9C103 bridge only:
304 0x0C 0xXX Unknown meaning
305 0x0D 0xXX Unknown meaning
306 0x0E 0xXX Unknown meaning
307 0x0F 0xXX Unknown meaning
308 0x10 0xXX Unknown meaning
309 0x11 0xXX Unknown meaning
311 The AE area (sx, sy, ex, ey) in the active window can be set by programming the
312 registers 0x1c, 0x1d, 0x1e and 0x1f of the SN9C10x controllers, where one unit
313 corresponds to 32 pixels.
315 [1] Part of the meaning of the frame header has been documented by Bertrik
316 Sikken.
319 9. Supported devices
320 ====================
321 None of the names of the companies as well as their products will be mentioned
322 here. They have never collaborated with the author, so no advertising.
324 From the point of view of a driver, what unambiguously identify a device are
325 its vendor and product USB identifiers. Below is a list of known identifiers of
326 devices mounting the SN9C10x PC camera controllers:
328 Vendor ID Product ID
329 --------- ----------
330 0x0c45 0x6001
331 0x0c45 0x6005
332 0x0c45 0x6007
333 0x0c45 0x6009
334 0x0c45 0x600d
335 0x0c45 0x6024
336 0x0c45 0x6025
337 0x0c45 0x6028
338 0x0c45 0x6029
339 0x0c45 0x602a
340 0x0c45 0x602b
341 0x0c45 0x602c
342 0x0c45 0x602d
343 0x0c45 0x602e
344 0x0c45 0x6030
345 0x0c45 0x6080
346 0x0c45 0x6082
347 0x0c45 0x6083
348 0x0c45 0x6088
349 0x0c45 0x608a
350 0x0c45 0x608b
351 0x0c45 0x608c
352 0x0c45 0x608e
353 0x0c45 0x608f
354 0x0c45 0x60a0
355 0x0c45 0x60a2
356 0x0c45 0x60a3
357 0x0c45 0x60a8
358 0x0c45 0x60aa
359 0x0c45 0x60ab
360 0x0c45 0x60ac
361 0x0c45 0x60ae
362 0x0c45 0x60af
363 0x0c45 0x60b0
364 0x0c45 0x60b2
365 0x0c45 0x60b3
366 0x0c45 0x60b8
367 0x0c45 0x60ba
368 0x0c45 0x60bb
369 0x0c45 0x60bc
370 0x0c45 0x60be
372 The list above does not imply that all those devices work with this driver: up
373 until now only the ones that mount the following image sensors are supported;
374 kernel messages will always tell you whether this is the case:
376 Model Manufacturer
377 ----- ------------
378 HV7131D Hynix Semiconductor, Inc.
379 MI-0343 Micron Technology, Inc.
380 OV7630 OmniVision Technologies, Inc.
381 PAS106B PixArt Imaging, Inc.
382 PAS202BCA PixArt Imaging, Inc.
383 PAS202BCB PixArt Imaging, Inc.
384 TAS5110C1B Taiwan Advanced Sensor Corporation
385 TAS5130D1B Taiwan Advanced Sensor Corporation
387 All the available control settings of each image sensor are supported through
388 the V4L2 interface.
390 Donations of new models for further testing and support would be much
391 appreciated. Non-available hardware will not be supported by the author of this
392 driver.
395 10. Notes for V4L2 application developers
396 =========================================
397 This driver follows the V4L2 API specifications. In particular, it enforces two
398 rules:
400 - exactly one I/O method, either "mmap" or "read", is associated with each
401 file descriptor. Once it is selected, the application must close and reopen the
402 device to switch to the other I/O method;
404 - although it is not mandatory, previously mapped buffer memory should always
405 be unmapped before calling any "VIDIOC_S_CROP" or "VIDIOC_S_FMT" ioctl's.
406 The same number of buffers as before will be allocated again to match the size
407 of the new video frames, so you have to map the buffers again before any I/O
408 attempts on them.
410 Consistently with the hardware limits, this driver also supports image
411 downscaling with arbitrary scaling factors from 1, 2 and 4 in both directions.
412 However, the V4L2 API specifications don't correctly define how the scaling
413 factor can be chosen arbitrarily by the "negotiation" of the "source" and
414 "target" rectangles. To work around this flaw, we have added the convention
415 that, during the negotiation, whenever the "VIDIOC_S_CROP" ioctl is issued, the
416 scaling factor is restored to 1.
418 This driver supports two different video formats: the first one is the "8-bit
419 Sequential Bayer" format and can be used to obtain uncompressed video data
420 from 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
422 compressed data). The compression quality may vary from 0 to 1 and can be
423 selected or queried thanks to the VIDIOC_S_JPEGCOMP and VIDIOC_G_JPEGCOMP V4L2
424 ioctl's. For maximum flexibility, both the default active video format and the
425 default compression quality depend on how the image sensor being used is
426 initialized (as described in the documentation of the API for the image sensors
427 supplied by this driver).
430 11. Video frame formats [1]
431 =======================
432 The SN9C10x PC Camera Controllers can send images in two possible video
433 formats over the USB: either native "Sequential RGB Bayer" or Huffman
434 compressed. The latter is used to achieve high frame rates. The current video
435 format may be selected or queried from the user application by calling the
436 VIDIOC_S_FMT or VIDIOC_G_FMT ioctl's, as described in the V4L2 API
437 specifications.
439 The name "Sequential Bayer" indicates the organization of the red, green and
440 blue pixels in one video frame. Each pixel is associated with a 8-bit long
441 value and is disposed in memory according to the pattern shown below:
443 B[0] G[1] B[2] G[3] ... B[m-2] G[m-1]
444 G[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)]
449 The above matrix also represents the sequential or progressive read-out mode of
450 the (n, m) Bayer color filter array used in many CCD/CMOS image sensors.
452 One compressed video frame consists of a bitstream that encodes for every R, G,
453 or B pixel the difference between the value of the pixel itself and some
454 reference pixel value. Pixels are organised in the Bayer pattern and the Bayer
455 sub-pixels are tracked individually and alternatingly. For example, in the
456 first line values for the B and G1 pixels are alternatingly encoded, while in
457 the second line values for the G2 and R pixels are alternatingly encoded.
459 The 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.
472 The algorithm purely describes the conversion from compressed Bayer code used
473 in the SN9C10x chips to uncompressed Bayer. Additional steps are required to
474 convert this to a color image (i.e. a color interpolation algorithm).
476 The following Huffman codes have been found:
477 0: +0 (relative to reference pixel value)
478 100: +4
479 101: -4?
480 1110xxxx: set absolute value to xxxx.0000
481 1101: +11
482 1111: -11
483 11001: +20
484 110000: -20
485 110001: ??? - these codes are apparently not used
487 [1] The Huffman compression algorithm has been reverse-engineered and
488 documented by Bertrik Sikken.
491 12. Contact information
492 =======================
493 The author may be contacted by e-mail at <luca.risolia@studio.unibo.it>.
495 GPG/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;
497 the fingerprint is: '88E8 F32F 7244 68BA 3958 5D40 99DA 5D2A FCE6 35A4'.
500 13. Credits
501 ===========
502 Many thanks to following persons for their contribute (listed in alphabetical
503 order):
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.