sn9c102.txt 21 KB

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  1. SN9C1xx PC Camera Controllers
  2. Driver for Linux
  3. =============================
  4. - Documentation -
  5. Index
  6. =====
  7. 1. Copyright
  8. 2. Disclaimer
  9. 3. License
  10. 4. Overview and features
  11. 5. Module dependencies
  12. 6. Module loading
  13. 7. Module parameters
  14. 8. Optional device control through "sysfs"
  15. 9. Supported devices
  16. 10. Notes for V4L2 application developers
  17. 11. Video frame formats
  18. 12. Contact information
  19. 13. Credits
  20. 1. Copyright
  21. ============
  22. Copyright (C) 2004-2006 by Luca Risolia <luca.risolia@studio.unibo.it>
  23. 2. Disclaimer
  24. =============
  25. SONiX is a trademark of SONiX Technology Company Limited, inc.
  26. This software is not sponsored or developed by SONiX.
  27. 3. License
  28. ==========
  29. This program is free software; you can redistribute it and/or modify
  30. it under the terms of the GNU General Public License as published by
  31. the Free Software Foundation; either version 2 of the License, or
  32. (at your option) any later version.
  33. This program is distributed in the hope that it will be useful,
  34. but WITHOUT ANY WARRANTY; without even the implied warranty of
  35. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  36. GNU General Public License for more details.
  37. You should have received a copy of the GNU General Public License
  38. along with this program; if not, write to the Free Software
  39. Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  40. 4. Overview and features
  41. ========================
  42. This driver attempts to support the video interface of the devices assembling
  43. the SONiX SN9C101, SN9C102, SN9C103, SN9C105 and SN9C120 PC Camera Controllers
  44. ("SN9C1xx" from now on).
  45. The driver relies on the Video4Linux2 and USB core modules. It has been
  46. designed to run properly on SMP systems as well.
  47. The latest version of the SN9C1xx driver can be found at the following URL:
  48. http://www.linux-projects.org/
  49. Some of the features of the driver are:
  50. - full compliance with the Video4Linux2 API (see also "Notes for V4L2
  51. application developers" paragraph);
  52. - available mmap or read/poll methods for video streaming through isochronous
  53. data transfers;
  54. - automatic detection of image sensor;
  55. - support for built-in microphone interface;
  56. - support for any window resolutions and optional panning within the maximum
  57. pixel area of image sensor;
  58. - image downscaling with arbitrary scaling factors from 1, 2 and 4 in both
  59. directions (see "Notes for V4L2 application developers" paragraph);
  60. - two different video formats for uncompressed or compressed data in low or
  61. high compression quality (see also "Notes for V4L2 application developers"
  62. and "Video frame formats" paragraphs);
  63. - full support for the capabilities of many of the possible image sensors that
  64. can be connected to the SN9C1xx bridges, including, for instance, red, green,
  65. blue and global gain adjustments and exposure (see "Supported devices"
  66. paragraph for details);
  67. - use of default color settings for sunlight conditions;
  68. - dynamic I/O interface for both SN9C1xx and image sensor control and
  69. monitoring (see "Optional device control through 'sysfs'" paragraph);
  70. - dynamic driver control thanks to various module parameters (see "Module
  71. parameters" paragraph);
  72. - up to 64 cameras can be handled at the same time; they can be connected and
  73. disconnected from the host many times without turning off the computer, if
  74. the system supports hotplugging;
  75. - no known bugs.
  76. 5. Module dependencies
  77. ======================
  78. For it to work properly, the driver needs kernel support for Video4Linux and
  79. USB.
  80. The following options of the kernel configuration file must be enabled and
  81. corresponding modules must be compiled:
  82. # Multimedia devices
  83. #
  84. CONFIG_VIDEO_DEV=m
  85. To enable advanced debugging functionality on the device through /sysfs:
  86. # Multimedia devices
  87. #
  88. CONFIG_VIDEO_ADV_DEBUG=y
  89. # USB support
  90. #
  91. CONFIG_USB=m
  92. In addition, depending on the hardware being used, the modules below are
  93. necessary:
  94. # USB Host Controller Drivers
  95. #
  96. CONFIG_USB_EHCI_HCD=m
  97. CONFIG_USB_UHCI_HCD=m
  98. CONFIG_USB_OHCI_HCD=m
  99. The SN9C103, SN9c105 and SN9C120 controllers also provide a built-in microphone
  100. interface. It is supported by the USB Audio driver thanks to the ALSA API:
  101. # Sound
  102. #
  103. CONFIG_SOUND=y
  104. # Advanced Linux Sound Architecture
  105. #
  106. CONFIG_SND=m
  107. # USB devices
  108. #
  109. CONFIG_SND_USB_AUDIO=m
  110. And finally:
  111. # USB Multimedia devices
  112. #
  113. CONFIG_USB_SN9C102=m
  114. 6. Module loading
  115. =================
  116. To use the driver, it is necessary to load the "sn9c102" module into memory
  117. after every other module required: "videodev", "v4l2_common", "compat_ioctl32",
  118. "usbcore" and, depending on the USB host controller you have, "ehci-hcd",
  119. "uhci-hcd" or "ohci-hcd".
  120. Loading can be done as shown below:
  121. [root@localhost home]# modprobe sn9c102
  122. Note that the module is called "sn9c102" for historic reasons, althought it
  123. does not just support the SN9C102.
  124. At this point all the devices supported by the driver and connected to the USB
  125. ports should be recognized. You can invoke "dmesg" to analyze kernel messages
  126. and verify that the loading process has gone well:
  127. [user@localhost home]$ dmesg
  128. or, to isolate all the kernel messages generated by the driver:
  129. [user@localhost home]$ dmesg | grep sn9c102
  130. 7. Module parameters
  131. ====================
  132. Module parameters are listed below:
  133. -------------------------------------------------------------------------------
  134. Name: video_nr
  135. Type: short array (min = 0, max = 64)
  136. Syntax: <-1|n[,...]>
  137. Description: Specify V4L2 minor mode number:
  138. -1 = use next available
  139. n = use minor number n
  140. You can specify up to 64 cameras this way.
  141. For example:
  142. video_nr=-1,2,-1 would assign minor number 2 to the second
  143. recognized camera and use auto for the first one and for every
  144. other camera.
  145. Default: -1
  146. -------------------------------------------------------------------------------
  147. Name: force_munmap
  148. Type: bool array (min = 0, max = 64)
  149. Syntax: <0|1[,...]>
  150. Description: Force the application to unmap previously mapped buffer memory
  151. before calling any VIDIOC_S_CROP or VIDIOC_S_FMT ioctl's. Not
  152. all the applications support this feature. This parameter is
  153. specific for each detected camera.
  154. 0 = do not force memory unmapping
  155. 1 = force memory unmapping (save memory)
  156. Default: 0
  157. -------------------------------------------------------------------------------
  158. Name: frame_timeout
  159. Type: uint array (min = 0, max = 64)
  160. Syntax: <0|n[,...]>
  161. Description: Timeout for a video frame in seconds before returning an I/O
  162. error; 0 for infinity. This parameter is specific for each
  163. detected camera and can be changed at runtime thanks to the
  164. /sys filesystem interface.
  165. Default: 2
  166. -------------------------------------------------------------------------------
  167. Name: debug
  168. Type: ushort
  169. Syntax: <n>
  170. Description: Debugging information level, from 0 to 3:
  171. 0 = none (use carefully)
  172. 1 = critical errors
  173. 2 = significant informations
  174. 3 = more verbose messages
  175. Level 3 is useful for testing only, when only one device
  176. is used. It also shows some more informations about the
  177. hardware being detected. This parameter can be changed at
  178. runtime thanks to the /sys filesystem interface.
  179. Default: 2
  180. -------------------------------------------------------------------------------
  181. 8. Optional device control through "sysfs" [1]
  182. ==========================================
  183. If the kernel has been compiled with the CONFIG_VIDEO_ADV_DEBUG option enabled,
  184. it is possible to read and write both the SN9C1xx and the image sensor
  185. registers by using the "sysfs" filesystem interface.
  186. Every time a supported device is recognized, a write-only file named "green" is
  187. created in the /sys/class/video4linux/videoX directory. You can set the green
  188. channel's gain by writing the desired value to it. The value may range from 0
  189. to 15 for the SN9C101 or SN9C102 bridges, from 0 to 127 for the SN9C103,
  190. SN9C105 and SN9C120 bridges.
  191. Similarly, only for the SN9C103, SN9C105 and SN9120 controllers, blue and red
  192. gain control files are available in the same directory, for which accepted
  193. values may range from 0 to 127.
  194. There are other four entries in the directory above for each registered camera:
  195. "reg", "val", "i2c_reg" and "i2c_val". The first two files control the
  196. SN9C1xx bridge, while the other two control the sensor chip. "reg" and
  197. "i2c_reg" hold the values of the current register index where the following
  198. reading/writing operations are addressed at through "val" and "i2c_val". Their
  199. use is not intended for end-users. Note that "i2c_reg" and "i2c_val" will not
  200. be created if the sensor does not actually support the standard I2C protocol or
  201. its registers are not 8-bit long. Also, remember that you must be logged in as
  202. root before writing to them.
  203. As an example, suppose we were to want to read the value contained in the
  204. register number 1 of the sensor register table - which is usually the product
  205. identifier - of the camera registered as "/dev/video0":
  206. [root@localhost #] cd /sys/class/video4linux/video0
  207. [root@localhost #] echo 1 > i2c_reg
  208. [root@localhost #] cat i2c_val
  209. Note that "cat" will fail if sensor registers cannot be read.
  210. Now let's set the green gain's register of the SN9C101 or SN9C102 chips to 2:
  211. [root@localhost #] echo 0x11 > reg
  212. [root@localhost #] echo 2 > val
  213. Note that the SN9C1xx always returns 0 when some of its registers are read.
  214. To avoid race conditions, all the I/O accesses to the above files are
  215. serialized.
  216. The sysfs interface also provides the "frame_header" entry, which exports the
  217. frame header of the most recent requested and captured video frame. The header
  218. is always 18-bytes long and is appended to every video frame by the SN9C1xx
  219. controllers. As an example, this additional information can be used by the user
  220. application for implementing auto-exposure features via software.
  221. The following table describes the frame header exported by the SN9C101 and
  222. SN9C102:
  223. Byte # Value or bits Description
  224. ------ ------------- -----------
  225. 0x00 0xFF Frame synchronisation pattern
  226. 0x01 0xFF Frame synchronisation pattern
  227. 0x02 0x00 Frame synchronisation pattern
  228. 0x03 0xC4 Frame synchronisation pattern
  229. 0x04 0xC4 Frame synchronisation pattern
  230. 0x05 0x96 Frame synchronisation pattern
  231. 0x06 [3:0] Read channel gain control = (1+R_GAIN/8)
  232. [7:4] Blue channel gain control = (1+B_GAIN/8)
  233. 0x07 [ 0 ] Compression mode. 0=No compression, 1=Compression enabled
  234. [2:1] Maximum scale factor for compression
  235. [ 3 ] 1 = USB fifo(2K bytes) is full
  236. [ 4 ] 1 = Digital gain is finish
  237. [ 5 ] 1 = Exposure is finish
  238. [7:6] Frame index
  239. 0x08 [7:0] Y sum inside Auto-Exposure area (low-byte)
  240. 0x09 [7:0] Y sum inside Auto-Exposure area (high-byte)
  241. where Y sum = (R/4 + 5G/16 + B/8) / 32
  242. 0x0A [7:0] Y sum outside Auto-Exposure area (low-byte)
  243. 0x0B [7:0] Y sum outside Auto-Exposure area (high-byte)
  244. where Y sum = (R/4 + 5G/16 + B/8) / 128
  245. 0x0C 0xXX Not used
  246. 0x0D 0xXX Not used
  247. 0x0E 0xXX Not used
  248. 0x0F 0xXX Not used
  249. 0x10 0xXX Not used
  250. 0x11 0xXX Not used
  251. The following table describes the frame header exported by the SN9C103:
  252. Byte # Value or bits Description
  253. ------ ------------- -----------
  254. 0x00 0xFF Frame synchronisation pattern
  255. 0x01 0xFF Frame synchronisation pattern
  256. 0x02 0x00 Frame synchronisation pattern
  257. 0x03 0xC4 Frame synchronisation pattern
  258. 0x04 0xC4 Frame synchronisation pattern
  259. 0x05 0x96 Frame synchronisation pattern
  260. 0x06 [6:0] Read channel gain control = (1/2+R_GAIN/64)
  261. 0x07 [6:0] Blue channel gain control = (1/2+B_GAIN/64)
  262. [7:4]
  263. 0x08 [ 0 ] Compression mode. 0=No compression, 1=Compression enabled
  264. [2:1] Maximum scale factor for compression
  265. [ 3 ] 1 = USB fifo(2K bytes) is full
  266. [ 4 ] 1 = Digital gain is finish
  267. [ 5 ] 1 = Exposure is finish
  268. [7:6] Frame index
  269. 0x09 [7:0] Y sum inside Auto-Exposure area (low-byte)
  270. 0x0A [7:0] Y sum inside Auto-Exposure area (high-byte)
  271. where Y sum = (R/4 + 5G/16 + B/8) / 32
  272. 0x0B [7:0] Y sum outside Auto-Exposure area (low-byte)
  273. 0x0C [7:0] Y sum outside Auto-Exposure area (high-byte)
  274. where Y sum = (R/4 + 5G/16 + B/8) / 128
  275. 0x0D [1:0] Audio frame number
  276. [ 2 ] 1 = Audio is recording
  277. 0x0E [7:0] Audio summation (low-byte)
  278. 0x0F [7:0] Audio summation (high-byte)
  279. 0x10 [7:0] Audio sample count
  280. 0x11 [7:0] Audio peak data in audio frame
  281. The AE area (sx, sy, ex, ey) in the active window can be set by programming the
  282. registers 0x1c, 0x1d, 0x1e and 0x1f of the SN9C1xx controllers, where one unit
  283. corresponds to 32 pixels.
  284. [1] The frame headers exported by the SN9C105 and SN9C120 are not described.
  285. 9. Supported devices
  286. ====================
  287. None of the names of the companies as well as their products will be mentioned
  288. here. They have never collaborated with the author, so no advertising.
  289. From the point of view of a driver, what unambiguously identify a device are
  290. its vendor and product USB identifiers. Below is a list of known identifiers of
  291. devices assembling the SN9C1xx PC camera controllers:
  292. Vendor ID Product ID
  293. --------- ----------
  294. 0x0471 0x0327
  295. 0x0471 0x0328
  296. 0x0c45 0x6001
  297. 0x0c45 0x6005
  298. 0x0c45 0x6007
  299. 0x0c45 0x6009
  300. 0x0c45 0x600d
  301. 0x0c45 0x6011
  302. 0x0c45 0x6019
  303. 0x0c45 0x6024
  304. 0x0c45 0x6025
  305. 0x0c45 0x6028
  306. 0x0c45 0x6029
  307. 0x0c45 0x602a
  308. 0x0c45 0x602b
  309. 0x0c45 0x602c
  310. 0x0c45 0x602d
  311. 0x0c45 0x602e
  312. 0x0c45 0x6030
  313. 0x0c45 0x603f
  314. 0x0c45 0x6080
  315. 0x0c45 0x6082
  316. 0x0c45 0x6083
  317. 0x0c45 0x6088
  318. 0x0c45 0x608a
  319. 0x0c45 0x608b
  320. 0x0c45 0x608c
  321. 0x0c45 0x608e
  322. 0x0c45 0x608f
  323. 0x0c45 0x60a0
  324. 0x0c45 0x60a2
  325. 0x0c45 0x60a3
  326. 0x0c45 0x60a8
  327. 0x0c45 0x60aa
  328. 0x0c45 0x60ab
  329. 0x0c45 0x60ac
  330. 0x0c45 0x60ae
  331. 0x0c45 0x60af
  332. 0x0c45 0x60b0
  333. 0x0c45 0x60b2
  334. 0x0c45 0x60b3
  335. 0x0c45 0x60b8
  336. 0x0c45 0x60ba
  337. 0x0c45 0x60bb
  338. 0x0c45 0x60bc
  339. 0x0c45 0x60be
  340. 0x0c45 0x60c0
  341. 0x0c45 0x60c8
  342. 0x0c45 0x60cc
  343. 0x0c45 0x60ea
  344. 0x0c45 0x60ec
  345. 0x0c45 0x60fa
  346. 0x0c45 0x60fb
  347. 0x0c45 0x60fc
  348. 0x0c45 0x60fe
  349. 0x0c45 0x6130
  350. 0x0c45 0x613a
  351. 0x0c45 0x613b
  352. 0x0c45 0x613c
  353. 0x0c45 0x613e
  354. The list above does not imply that all those devices work with this driver: up
  355. until now only the ones that assemble the following image sensors are
  356. supported; kernel messages will always tell you whether this is the case (see
  357. "Module loading" paragraph):
  358. Model Manufacturer
  359. ----- ------------
  360. HV7131D Hynix Semiconductor, Inc.
  361. MI-0343 Micron Technology, Inc.
  362. OV7630 OmniVision Technologies, Inc.
  363. OV7660 OmniVision Technologies, Inc.
  364. PAS106B PixArt Imaging, Inc.
  365. PAS202BCA PixArt Imaging, Inc.
  366. PAS202BCB PixArt Imaging, Inc.
  367. TAS5110C1B Taiwan Advanced Sensor Corporation
  368. TAS5130D1B Taiwan Advanced Sensor Corporation
  369. Some of the available control settings of each image sensor are supported
  370. through the V4L2 interface.
  371. Donations of new models for further testing and support would be much
  372. appreciated. Non-available hardware will not be supported by the author of this
  373. driver.
  374. 10. Notes for V4L2 application developers
  375. =========================================
  376. This driver follows the V4L2 API specifications. In particular, it enforces two
  377. rules:
  378. - exactly one I/O method, either "mmap" or "read", is associated with each
  379. file descriptor. Once it is selected, the application must close and reopen the
  380. device to switch to the other I/O method;
  381. - although it is not mandatory, previously mapped buffer memory should always
  382. be unmapped before calling any "VIDIOC_S_CROP" or "VIDIOC_S_FMT" ioctl's.
  383. The same number of buffers as before will be allocated again to match the size
  384. of the new video frames, so you have to map the buffers again before any I/O
  385. attempts on them.
  386. Consistently with the hardware limits, this driver also supports image
  387. downscaling with arbitrary scaling factors from 1, 2 and 4 in both directions.
  388. However, the V4L2 API specifications don't correctly define how the scaling
  389. factor can be chosen arbitrarily by the "negotiation" of the "source" and
  390. "target" rectangles. To work around this flaw, we have added the convention
  391. that, during the negotiation, whenever the "VIDIOC_S_CROP" ioctl is issued, the
  392. scaling factor is restored to 1.
  393. This driver supports two different video formats: the first one is the "8-bit
  394. Sequential Bayer" format and can be used to obtain uncompressed video data
  395. from the device through the current I/O method, while the second one provides
  396. "raw" compressed video data (without frame headers not related to the
  397. compressed data). The compression quality may vary from 0 to 1 and can be
  398. selected or queried thanks to the VIDIOC_S_JPEGCOMP and VIDIOC_G_JPEGCOMP V4L2
  399. ioctl's. For maximum flexibility, both the default active video format and the
  400. default compression quality depend on how the image sensor being used is
  401. initialized (as described in the documentation of the API for the image sensors
  402. supplied by this driver).
  403. 11. Video frame formats [1]
  404. =======================
  405. The SN9C1xx PC Camera Controllers can send images in two possible video
  406. formats over the USB: either native "Sequential RGB Bayer" or compressed.
  407. The compression is used to achieve high frame rates. With regard to the
  408. SN9C101, SN9C102 and SN9C103, the compression is based on the Huffman encoding
  409. algorithm described below, while the SN9C105 and SN9C120 the compression is
  410. based on the JPEG standard.
  411. The current video format may be selected or queried from the user application
  412. by calling the VIDIOC_S_FMT or VIDIOC_G_FMT ioctl's, as described in the V4L2
  413. API specifications.
  414. The name "Sequential Bayer" indicates the organization of the red, green and
  415. blue pixels in one video frame. Each pixel is associated with a 8-bit long
  416. value and is disposed in memory according to the pattern shown below:
  417. B[0] G[1] B[2] G[3] ... B[m-2] G[m-1]
  418. G[m] R[m+1] G[m+2] R[m+2] ... G[2m-2] R[2m-1]
  419. ...
  420. ... B[(n-1)(m-2)] G[(n-1)(m-1)]
  421. ... G[n(m-2)] R[n(m-1)]
  422. The above matrix also represents the sequential or progressive read-out mode of
  423. the (n, m) Bayer color filter array used in many CCD or CMOS image sensors.
  424. The Huffman compressed video frame consists of a bitstream that encodes for
  425. every R, G, or B pixel the difference between the value of the pixel itself and
  426. some reference pixel value. Pixels are organised in the Bayer pattern and the
  427. Bayer sub-pixels are tracked individually and alternatingly. For example, in
  428. the first line values for the B and G1 pixels are alternatingly encoded, while
  429. in the second line values for the G2 and R pixels are alternatingly encoded.
  430. The pixel reference value is calculated as follows:
  431. - the 4 top left pixels are encoded in raw uncompressed 8-bit format;
  432. - the value in the top two rows is the value of the pixel left of the current
  433. pixel;
  434. - the value in the left column is the value of the pixel above the current
  435. pixel;
  436. - for all other pixels, the reference value is the average of the value of the
  437. pixel on the left and the value of the pixel above the current pixel;
  438. - there is one code in the bitstream that specifies the value of a pixel
  439. directly (in 4-bit resolution);
  440. - pixel values need to be clamped inside the range [0..255] for proper
  441. decoding.
  442. The algorithm purely describes the conversion from compressed Bayer code used
  443. in the SN9C101, SN9C102 and SN9C103 chips to uncompressed Bayer. Additional
  444. steps are required to convert this to a color image (i.e. a color interpolation
  445. algorithm).
  446. The following Huffman codes have been found:
  447. 0: +0 (relative to reference pixel value)
  448. 100: +4
  449. 101: -4?
  450. 1110xxxx: set absolute value to xxxx.0000
  451. 1101: +11
  452. 1111: -11
  453. 11001: +20
  454. 110000: -20
  455. 110001: ??? - these codes are apparently not used
  456. [1] The Huffman compression algorithm has been reverse-engineered and
  457. documented by Bertrik Sikken.
  458. 12. Contact information
  459. =======================
  460. The author may be contacted by e-mail at <luca.risolia@studio.unibo.it>.
  461. GPG/PGP encrypted e-mail's are accepted. The GPG key ID of the author is
  462. 'FCE635A4'; the public 1024-bit key should be available at any keyserver;
  463. the fingerprint is: '88E8 F32F 7244 68BA 3958 5D40 99DA 5D2A FCE6 35A4'.
  464. 13. Credits
  465. ===========
  466. Many thanks to following persons for their contribute (listed in alphabetical
  467. order):
  468. - Luca Capello for the donation of a webcam;
  469. - Philippe Coval for having helped testing the PAS202BCA image sensor;
  470. - Joao Rodrigo Fuzaro, Joao Limirio, Claudio Filho and Caio Begotti for the
  471. donation of a webcam;
  472. - Dennis Heitmann for the donation of a webcam;
  473. - Jon Hollstrom for the donation of a webcam;
  474. - Nick McGill for the donation of a webcam;
  475. - Carlos Eduardo Medaglia Dyonisio, who added the support for the PAS202BCB
  476. image sensor;
  477. - Stefano Mozzi, who donated 45 EU;
  478. - Andrew Pearce for the donation of a webcam;
  479. - John Pullan for the donation of a webcam;
  480. - Bertrik Sikken, who reverse-engineered and documented the Huffman compression
  481. algorithm used in the SN9C101, SN9C102 and SN9C103 controllers and
  482. implemented the first decoder;
  483. - Mizuno Takafumi for the donation of a webcam;
  484. - an "anonymous" donator (who didn't want his name to be revealed) for the
  485. donation of a webcam.
  486. - an anonymous donator for the donation of four webcams.