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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. How to add plug-in's for new image sensors
21 11. Notes for V4L2 application developers
22 12. Video frame formats
23 13. Contact information
24 14. Credits
27 1. Copyright
28 ============
29 Copyright (C) 2004-2005 by Luca Risolia <luca.risolia@studio.unibo.it>
32 2. Disclaimer
33 =============
34 SONiX is a trademark of SONiX Technology Company Limited, inc.
35 This software is not sponsored or developed by SONiX.
38 3. License
39 ==========
40 This program is free software; you can redistribute it and/or modify
41 it under the terms of the GNU General Public License as published by
42 the Free Software Foundation; either version 2 of the License, or
43 (at your option) any later version.
45 This program is distributed in the hope that it will be useful,
46 but WITHOUT ANY WARRANTY; without even the implied warranty of
47 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
48 GNU General Public License for more details.
50 You should have received a copy of the GNU General Public License
51 along with this program; if not, write to the Free Software
52 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
55 4. Overview and features
56 ========================
57 This driver attempts to support the video and audio streaming capabilities of
58 the devices mounting the SONiX SN9C101, SN9C102 and SN9C103 PC Camera
59 Controllers.
61 It's worth to note that SONiX has never collaborated with the author during the
62 development of this project, despite several requests for enough detailed
63 specifications of the register tables, compression engine and video data format
64 of the above chips. Nevertheless, these informations are no longer necessary,
65 becouse all the aspects related to these chips are known and have been
66 described in detail in this documentation.
68 The driver relies on the Video4Linux2 and USB core modules. It has been
69 designed to run properly on SMP systems as well.
71 The latest version of the SN9C10x driver can be found at the following URL:
72 http://www.linux-projects.org/
74 Some of the features of the driver are:
76 - full compliance with the Video4Linux2 API (see also "Notes for V4L2
77 application developers" paragraph);
78 - available mmap or read/poll methods for video streaming through isochronous
79 data transfers;
80 - automatic detection of image sensor;
81 - support for any window resolutions and optional panning within the maximum
82 pixel area of image sensor;
83 - image downscaling with arbitrary scaling factors from 1, 2 and 4 in both
84 directions (see "Notes for V4L2 application developers" paragraph);
85 - two different video formats for uncompressed or compressed data in low or
86 high compression quality (see also "Notes for V4L2 application developers"
87 and "Video frame formats" paragraphs);
88 - full support for the capabilities of many of the possible image sensors that
89 can be connected to the SN9C10x bridges, including, for istance, red, green,
90 blue and global gain adjustments and exposure (see "Supported devices"
91 paragraph for details);
92 - use of default color settings for sunlight conditions;
93 - dynamic I/O interface for both SN9C10x and image sensor control and
94 monitoring (see "Optional device control through 'sysfs'" paragraph);
95 - dynamic driver control thanks to various module parameters (see "Module
96 parameters" paragraph);
97 - up to 64 cameras can be handled at the same time; they can be connected and
98 disconnected from the host many times without turning off the computer, if
99 your system supports hotplugging;
100 - no known bugs.
103 5. Module dependencies
104 ======================
105 For it to work properly, the driver needs kernel support for Video4Linux and
106 USB.
108 The following options of the kernel configuration file must be enabled and
109 corresponding modules must be compiled:
111 # Multimedia devices
112 #
113 CONFIG_VIDEO_DEV=m
115 # USB support
116 #
117 CONFIG_USB=m
119 In addition, depending on the hardware being used, the modules below are
120 necessary:
122 # USB Host Controller Drivers
123 #
124 CONFIG_USB_EHCI_HCD=m
125 CONFIG_USB_UHCI_HCD=m
126 CONFIG_USB_OHCI_HCD=m
128 And finally:
130 # USB Multimedia devices
131 #
132 CONFIG_USB_SN9C102=m
135 6. Module loading
136 =================
137 To use the driver, it is necessary to load the "sn9c102" module into memory
138 after every other module required: "videodev", "usbcore" and, depending on
139 the USB host controller you have, "ehci-hcd", "uhci-hcd" or "ohci-hcd".
141 Loading can be done as shown below:
143 [root@localhost home]# modprobe sn9c102
145 At this point the devices should be recognized. You can invoke "dmesg" to
146 analyze kernel messages and verify that the loading process has gone well:
148 [user@localhost home]$ dmesg
151 7. Module parameters
152 ====================
153 Module parameters are listed below:
154 -------------------------------------------------------------------------------
155 Name: video_nr
156 Type: int array (min = 0, max = 64)
157 Syntax: <-1|n[,...]>
158 Description: Specify V4L2 minor mode number:
159 -1 = use next available
160 n = use minor number n
161 You can specify up to 64 cameras this way.
162 For example:
163 video_nr=-1,2,-1 would assign minor number 2 to the second
164 recognized camera and use auto for the first one and for every
165 other camera.
166 Default: -1
167 -------------------------------------------------------------------------------
168 Name: force_munmap;
169 Type: bool array (min = 0, max = 64)
170 Syntax: <0|1[,...]>
171 Description: Force the application to unmap previously mapped buffer memory
172 before calling any VIDIOC_S_CROP or VIDIOC_S_FMT ioctl's. Not
173 all the applications support this feature. This parameter is
174 specific for each detected camera.
175 0 = do not force memory unmapping"
176 1 = force memory unmapping (save memory)"
177 Default: 0
178 -------------------------------------------------------------------------------
179 Name: debug
180 Type: int
181 Syntax: <n>
182 Description: Debugging information level, from 0 to 3:
183 0 = none (use carefully)
184 1 = critical errors
185 2 = significant informations
186 3 = more verbose messages
187 Level 3 is useful for testing only, when only one device
188 is used. It also shows some more informations about the
189 hardware being detected. This parameter can be changed at
190 runtime thanks to the /sys filesystem.
191 Default: 2
192 -------------------------------------------------------------------------------
195 8. Optional device control through "sysfs" [1]
196 ==========================================
197 It is possible to read and write both the SN9C10x and the image sensor
198 registers by using the "sysfs" filesystem interface.
200 Every time a supported device is recognized, a write-only file named "green" is
201 created in the /sys/class/video4linux/videoX directory. You can set the green
202 channel's gain by writing the desired value to it. The value may range from 0
203 to 15 for SN9C101 or SN9C102 bridges, from 0 to 127 for SN9C103 bridges.
204 Similarly, only for SN9C103 controllers, blue and red gain control files are
205 available in the same directory, for which accepted values may range from 0 to
206 127.
208 There are other four entries in the directory above for each registered camera:
209 "reg", "val", "i2c_reg" and "i2c_val". The first two files control the
210 SN9C10x bridge, while the other two control the sensor chip. "reg" and
211 "i2c_reg" hold the values of the current register index where the following
212 reading/writing operations are addressed at through "val" and "i2c_val". Their
213 use is not intended for end-users. Note that "i2c_reg" and "i2c_val" will not
214 be created if the sensor does not actually support the standard I2C protocol or
215 its registers are not 8-bit long. Also, remember that you must be logged in as
216 root before writing to them.
218 As an example, suppose we were to want to read the value contained in the
219 register number 1 of the sensor register table - which is usually the product
220 identifier - of the camera registered as "/dev/video0":
222 [root@localhost #] cd /sys/class/video4linux/video0
223 [root@localhost #] echo 1 > i2c_reg
224 [root@localhost #] cat i2c_val
226 Note that "cat" will fail if sensor registers cannot be read.
228 Now let's set the green gain's register of the SN9C101 or SN9C102 chips to 2:
230 [root@localhost #] echo 0x11 > reg
231 [root@localhost #] echo 2 > val
233 Note that the SN9C10x always returns 0 when some of its registers are read.
234 To avoid race conditions, all the I/O accesses to the above files are
235 serialized.
237 The sysfs interface also provides the "frame_header" entry, which exports the
238 frame header of the most recent requested and captured video frame. The header
239 is 12-bytes long and is appended to every video frame by the SN9C10x
240 controllers. As an example, this additional information can be used by the user
241 application for implementing auto-exposure features via software.
243 The following table describes the frame header:
245 Byte # Value Description
246 ------ ----- -----------
247 0x00 0xFF Frame synchronisation pattern.
248 0x01 0xFF Frame synchronisation pattern.
249 0x02 0x00 Frame synchronisation pattern.
250 0x03 0xC4 Frame synchronisation pattern.
251 0x04 0xC4 Frame synchronisation pattern.
252 0x05 0x96 Frame synchronisation pattern.
253 0x06 0x00 or 0x01 Unknown meaning. The exact value depends on the chip.
254 0x07 0xXX Variable value, whose bits are ff00uzzc, where ff is a
255 frame counter, u is unknown, zz is a size indicator
256 (00 = VGA, 01 = SIF, 10 = QSIF) and c stands for
257 "compression enabled" (1 = yes, 0 = no).
258 0x08 0xXX Brightness sum inside Auto-Exposure area (low-byte).
259 0x09 0xXX Brightness sum inside Auto-Exposure area (high-byte).
260 For a pure white image, this number will be equal to 500
261 times the area of the specified AE area. For images
262 that are not pure white, the value scales down according
263 to relative whiteness.
264 0x0A 0xXX Brightness sum outside Auto-Exposure area (low-byte).
265 0x0B 0xXX Brightness sum outside Auto-Exposure area (high-byte).
266 For a pure white image, this number will be equal to 125
267 times the area outside of the specified AE area. For
268 images that are not pure white, the value scales down
269 according to relative whiteness.
271 The AE area (sx, sy, ex, ey) in the active window can be set by programming the
272 registers 0x1c, 0x1d, 0x1e and 0x1f of the SN9C10x controllers, where one unit
273 corresponds to 32 pixels.
275 [1] The frame header has been documented by Bertrik Sikken.
278 9. Supported devices
279 ====================
280 None of the names of the companies as well as their products will be mentioned
281 here. They have never collaborated with the author, so no advertising.
283 From the point of view of a driver, what unambiguously identify a device are
284 its vendor and product USB identifiers. Below is a list of known identifiers of
285 devices mounting the SN9C10x PC camera controllers:
287 Vendor ID Product ID
288 --------- ----------
289 0x0c45 0x6001
290 0x0c45 0x6005
291 0x0c45 0x6009
292 0x0c45 0x600d
293 0x0c45 0x6024
294 0x0c45 0x6025
295 0x0c45 0x6028
296 0x0c45 0x6029
297 0x0c45 0x602a
298 0x0c45 0x602b
299 0x0c45 0x602c
300 0x0c45 0x6030
301 0x0c45 0x6080
302 0x0c45 0x6082
303 0x0c45 0x6083
304 0x0c45 0x6088
305 0x0c45 0x608a
306 0x0c45 0x608b
307 0x0c45 0x608c
308 0x0c45 0x608e
309 0x0c45 0x608f
310 0x0c45 0x60a0
311 0x0c45 0x60a2
312 0x0c45 0x60a3
313 0x0c45 0x60a8
314 0x0c45 0x60aa
315 0x0c45 0x60ab
316 0x0c45 0x60ac
317 0x0c45 0x60ae
318 0x0c45 0x60af
319 0x0c45 0x60b0
320 0x0c45 0x60b2
321 0x0c45 0x60b3
322 0x0c45 0x60b8
323 0x0c45 0x60ba
324 0x0c45 0x60bb
325 0x0c45 0x60bc
326 0x0c45 0x60be
328 The list above does not imply that all those devices work with this driver: up
329 until now only the ones that mount the following image sensors are supported;
330 kernel messages will always tell you whether this is the case:
332 Model Manufacturer
333 ----- ------------
334 HV7131D Hynix Semiconductor, Inc.
335 MI-0343 Micron Technology, Inc.
336 PAS106B PixArt Imaging, Inc.
337 PAS202BCB PixArt Imaging, Inc.
338 TAS5110C1B Taiwan Advanced Sensor Corporation
339 TAS5130D1B Taiwan Advanced Sensor Corporation
341 All the available control settings of each image sensor are supported through
342 the V4L2 interface.
344 Donations of new models for further testing and support would be much
345 appreciated. Non-available hardware will not be supported by the author of this
346 driver.
349 10. How to add plug-in's for new image sensors
350 ==============================================
351 It should be easy to write plug-in's for new sensors by using the small API
352 that has been created for this purpose, which is present in "sn9c102_sensor.h"
353 (documentation is included there). As an example, have a look at the code in
354 "sn9c102_pas106b.c", which uses the mentioned interface.
356 At the moment, possible unsupported image sensors are: CIS-VF10 (VGA),
357 OV7620 (VGA), OV7630 (VGA).
360 11. Notes for V4L2 application developers
361 =========================================
362 This driver follows the V4L2 API specifications. In particular, it enforces two
363 rules:
365 - exactly one I/O method, either "mmap" or "read", is associated with each
366 file descriptor. Once it is selected, the application must close and reopen the
367 device to switch to the other I/O method;
369 - although it is not mandatory, previously mapped buffer memory should always
370 be unmapped before calling any "VIDIOC_S_CROP" or "VIDIOC_S_FMT" ioctl's.
371 The same number of buffers as before will be allocated again to match the size
372 of the new video frames, so you have to map the buffers again before any I/O
373 attempts on them.
375 Consistently with the hardware limits, this driver also supports image
376 downscaling with arbitrary scaling factors from 1, 2 and 4 in both directions.
377 However, the V4L2 API specifications don't correctly define how the scaling
378 factor can be chosen arbitrarily by the "negotiation" of the "source" and
379 "target" rectangles. To work around this flaw, we have added the convention
380 that, during the negotiation, whenever the "VIDIOC_S_CROP" ioctl is issued, the
381 scaling factor is restored to 1.
383 This driver supports two different video formats: the first one is the "8-bit
384 Sequential Bayer" format and can be used to obtain uncompressed video data
385 from the device through the current I/O method, while the second one provides
386 "raw" compressed video data (without frame headers not related to the
387 compressed data). The compression quality may vary from 0 to 1 and can be
388 selected or queried thanks to the VIDIOC_S_JPEGCOMP and VIDIOC_G_JPEGCOMP V4L2
389 ioctl's. For maximum flexibility, both the default active video format and the
390 default compression quality depend on how the image sensor being used is
391 initialized (as described in the documentation of the API for the image sensors
392 supplied by this driver).
395 12. Video frame formats [1]
396 =======================
397 The SN9C10x PC Camera Controllers can send images in two possible video
398 formats over the USB: either native "Sequential RGB Bayer" or Huffman
399 compressed. The latter is used to achieve high frame rates. The current video
400 format may be selected or queried from the user application by calling the
401 VIDIOC_S_FMT or VIDIOC_G_FMT ioctl's, as described in the V4L2 API
402 specifications.
404 The name "Sequential Bayer" indicates the organization of the red, green and
405 blue pixels in one video frame. Each pixel is associated with a 8-bit long
406 value and is disposed in memory according to the pattern shown below:
408 B[0] G[1] B[2] G[3] ... B[m-2] G[m-1]
409 G[m] R[m+1] G[m+2] R[m+2] ... G[2m-2] R[2m-1]
410 ...
411 ... B[(n-1)(m-2)] G[(n-1)(m-1)]
412 ... G[n(m-2)] R[n(m-1)]
414 The above matrix also represents the sequential or progressive read-out mode of
415 the (n, m) Bayer color filter array used in many CCD/CMOS image sensors.
417 One compressed video frame consists of a bitstream that encodes for every R, G,
418 or B pixel the difference between the value of the pixel itself and some
419 reference pixel value. Pixels are organised in the Bayer pattern and the Bayer
420 sub-pixels are tracked individually and alternatingly. For example, in the
421 first line values for the B and G1 pixels are alternatingly encoded, while in
422 the second line values for the G2 and R pixels are alternatingly encoded.
424 The pixel reference value is calculated as follows:
425 - the 4 top left pixels are encoded in raw uncompressed 8-bit format;
426 - the value in the top two rows is the value of the pixel left of the current
427 pixel;
428 - the value in the left column is the value of the pixel above the current
429 pixel;
430 - for all other pixels, the reference value is the average of the value of the
431 pixel on the left and the value of the pixel above the current pixel;
432 - there is one code in the bitstream that specifies the value of a pixel
433 directly (in 4-bit resolution);
434 - pixel values need to be clamped inside the range [0..255] for proper
435 decoding.
437 The algorithm purely describes the conversion from compressed Bayer code used
438 in the SN9C10x chips to uncompressed Bayer. Additional steps are required to
439 convert this to a color image (i.e. a color interpolation algorithm).
441 The following Huffman codes have been found:
442 0: +0 (relative to reference pixel value)
443 100: +4
444 101: -4?
445 1110xxxx: set absolute value to xxxx.0000
446 1101: +11
447 1111: -11
448 11001: +20
449 110000: -20
450 110001: ??? - these codes are apparently not used
452 [1] The Huffman compression algorithm has been reverse-engineered and
453 documented by Bertrik Sikken.
456 13. Contact information
457 =======================
458 The author may be contacted by e-mail at <luca.risolia@studio.unibo.it>.
460 GPG/PGP encrypted e-mail's are accepted. The GPG key ID of the author is
461 'FCE635A4'; the public 1024-bit key should be available at any keyserver;
462 the fingerprint is: '88E8 F32F 7244 68BA 3958 5D40 99DA 5D2A FCE6 35A4'.
465 14. Credits
466 ===========
467 Many thanks to following persons for their contribute (listed in alphabetical
468 order):
470 - Luca Capello for the donation of a webcam;
471 - Joao Rodrigo Fuzaro, Joao Limirio, Claudio Filho and Caio Begotti for the
472 donation of a webcam;
473 - Carlos Eduardo Medaglia Dyonisio, who added the support for the PAS202BCB
474 image sensor;
475 - Stefano Mozzi, who donated 45 EU;
476 - Bertrik Sikken, who reverse-engineered and documented the Huffman compression
477 algorithm used in the SN9C10x controllers and implemented the first decoder;
478 - Mizuno Takafumi for the donation of a webcam;
479 - An "anonymous" donator (who didn't want his name to be revealed) for the
480 donation of a webcam.