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authorMichael Krufky <mkrufky@linuxtv.org>2006-04-02 01:14:11 -0500
committerMauro Carvalho Chehab <mchehab@infradead.org>2006-04-02 03:55:56 -0400
commit1864cfb1537e108c2fe7a8e178b28bffde5a5439 (patch)
treef25083dd3fb3781670ee4a37b52240a34dbfb67f /Documentation/usb/sn9c102.txt
parentcc33668b1eed1eac43f00cec639066047323b01d (diff)
V4L/DVB (3653h): Move usb v4l docs into Documentation/video4linux
- Move documentation for usb v4l devices from Documentation/usb to Documentation/video4linux. - Removed trailing whitespace. - Update Kconfig help text links to reflect the new file locations. Signed-off-by: Michael Krufky <mkrufky@linuxtv.org> Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
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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.