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Linus Torvalds1da177e2005-04-16 15:20:36 -07001README for Linux device driver for the IBM "C-It" USB video camera
2
3INTRODUCTION:
4
5This driver does not use all features known to exist in
6the IBM camera. However most of needed features work well.
7
8This driver was developed using logs of observed USB traffic
9which was produced by standard Windows driver (c-it98.sys).
10I did not have data sheets from Xirlink.
11
12Video formats:
13 128x96 [model 1]
14 176x144
15 320x240 [model 2]
16 352x240 [model 2]
17 352x288
18Frame rate: 3 - 30 frames per second (FPS)
19External interface: USB
20Internal interface: Video For Linux (V4L)
21Supported controls:
22- by V4L: Contrast, Brightness, Color, Hue
23- by driver options: frame rate, lighting conditions, video format,
24 default picture settings, sharpness.
25
26SUPPORTED CAMERAS:
27
28Xirlink "C-It" camera, also known as "IBM PC Camera".
29The device uses proprietary ASIC (and compression method);
30it is manufactured by Xirlink. See http://www.xirlink.com/
31http://www.ibmpccamera.com or http://www.c-itnow.com/ for
32details and pictures.
33
34This very chipset ("X Chip", as marked at the factory)
35is used in several other cameras, and they are supported
36as well:
37
38- IBM NetCamera
39- Veo Stingray
40
41The Linux driver was developed with camera with following
42model number (or FCC ID): KSX-XVP510. This camera has three
43interfaces, each with one endpoint (control, iso, iso). This
44type of cameras is referred to as "model 1". These cameras are
45no longer manufactured.
46
47Xirlink now manufactures new cameras which are somewhat different.
48In particular, following models [FCC ID] belong to that category:
49
50XVP300 [KSX-X9903]
51XVP600 [KSX-X9902]
52XVP610 [KSX-X9902]
53
54(see http://www.xirlink.com/ibmpccamera/ for updates, they refer
55to these new cameras by Windows driver dated 12-27-99, v3005 BETA)
56These cameras have two interfaces, one endpoint in each (iso, bulk).
57Such type of cameras is referred to as "model 2". They are supported
58(with exception of 352x288 native mode).
59
60Some IBM NetCameras (Model 4) are made to generate only compressed
61video streams. This is great for performance, but unfortunately
62nobody knows how to decompress the stream :-( Therefore, these
63cameras are *unsupported* and if you try to use one of those, all
64you get is random colored horizontal streaks, not the image!
65If you have one of those cameras, you probably should return it
66to the store and get something that is supported.
67
68Tell me more about all that "model" business
69--------------------------------------------
70
71I just invented model numbers to uniquely identify flavors of the
72hardware/firmware that were sold. It was very confusing to use
73brand names or some other internal numbering schemes. So I found
74by experimentation that all Xirlink chipsets fall into four big
75classes, and I called them "models". Each model is programmed in
76its own way, and each model sends back the video in its own way.
77
78Quirks of Model 2 cameras:
79-------------------------
80
81Model 2 does not have hardware contrast control. Corresponding V4L
82control is implemented in software, which is not very nice to your
83CPU, but at least it works.
84
85This driver provides 352x288 mode by switching the camera into
86quasi-352x288 RGB mode (800 Kbits per frame) essentially limiting
87this mode to 10 frames per second or less, in ideal conditions on
88the bus (USB is shared, after all). The frame rate
89has to be programmed very conservatively. Additional concern is that
90frame rate depends on brightness setting; therefore the picture can
91be good at one brightness and broken at another! I did not want to fix
92the frame rate at slowest setting, but I had to move it pretty much down
93the scale (so that framerate option barely matters). I also noticed that
94camera after first powering up produces frames slightly faster than during
95consecutive uses. All this means that if you use 352x288 (which is
96default), be warned - you may encounter broken picture on first connect;
97try to adjust brightness - brighter image is slower, so USB will be able
98to send all data. However if you regularly use Model 2 cameras you may
99prefer 176x144 which makes perfectly good I420, with no scaling and
100lesser demands on USB (300 Kbits per second, or 26 frames per second).
101
102Another strange effect of 352x288 mode is the fine vertical grid visible
103on some colored surfaces. I am sure it is caused by me not understanding
104what the camera is trying to say. Blame trade secrets for that.
105
106The camera that I had also has a hardware quirk: if disconnected,
107it needs few minutes to "relax" before it can be plugged in again
108(poorly designed USB processor reset circuit?)
109
110[Veo Stingray with Product ID 0x800C is also Model 2, but I haven't
111observed this particular flaw in it.]
112
113Model 2 camera can be programmed for very high sensitivity (even starlight
114may be enough), this makes it convenient for tinkering with. The driver
115code has enough comments to help a programmer to tweak the camera
116as s/he feels necessary.
117
118WHAT YOU NEED:
119
120- A supported IBM PC (C-it) camera (model 1 or 2)
121
122- A Linux box with USB support (2.3/2.4; 2.2 w/backport may work)
123
124- A Video4Linux compatible frame grabber program such as xawtv.
125
126HOW TO COMPILE THE DRIVER:
127
128You need to compile the driver only if you are a developer
129or if you want to make changes to the code. Most distributions
130precompile all modules, so you can go directly to the next
131section "HOW TO USE THE DRIVER".
132
133The ibmcam driver uses usbvideo helper library (module),
134so if you are studying the ibmcam code you will be led there.
135
136The driver itself consists of only one file in usb/ directory:
137ibmcam.c. This file is included into the Linux kernel build
138process if you configure the kernel for CONFIG_USB_IBMCAM.
139Run "make xconfig" and in USB section you will find the IBM
140camera driver. Select it, save the configuration and recompile.
141
142HOW TO USE THE DRIVER:
143
144I recommend to compile driver as a module. This gives you an
145easier access to its configuration. The camera has many more
146settings than V4L can operate, so some settings are done using
147module options.
148
149To begin with, on most modern Linux distributions the driver
150will be automatically loaded whenever you plug the supported
151camera in. Therefore, you don't need to do anything. However
152if you want to experiment with some module parameters then
153you can load and unload the driver manually, with camera
154plugged in or unplugged.
155
156Typically module is installed with command 'modprobe', like this:
157
158# modprobe ibmcam framerate=1
159
160Alternatively you can use 'insmod' in similar fashion:
161
162# insmod /lib/modules/2.x.y/usb/ibmcam.o framerate=1
163
164Module can be inserted with camera connected or disconnected.
165
166The driver can have options, though some defaults are provided.
167
168Driver options: (* indicates that option is model-dependent)
169
170Name Type Range [default] Example
171-------------- -------------- -------------- ------------------
172debug Integer 0-9 [0] debug=1
173flags Integer 0-0xFF [0] flags=0x0d
174framerate Integer 0-6 [2] framerate=1
175hue_correction Integer 0-255 [128] hue_correction=115
176init_brightness Integer 0-255 [128] init_brightness=100
177init_contrast Integer 0-255 [192] init_contrast=200
178init_color Integer 0-255 [128] init_color=130
179init_hue Integer 0-255 [128] init_hue=115
180lighting Integer 0-2* [1] lighting=2
181sharpness Integer 0-6* [4] sharpness=3
182size Integer 0-2* [2] size=1
183
184Options for Model 2 only:
185
186Name Type Range [default] Example
187-------------- -------------- -------------- ------------------
188init_model2_rg Integer 0..255 [0x70] init_model2_rg=128
189init_model2_rg2 Integer 0..255 [0x2f] init_model2_rg2=50
190init_model2_sat Integer 0..255 [0x34] init_model2_sat=65
191init_model2_yb Integer 0..255 [0xa0] init_model2_yb=200
192
193debug You don't need this option unless you are a developer.
194 If you are a developer then you will see in the code
195 what values do what. 0=off.
196
197flags This is a bit mask, and you can combine any number of
198 bits to produce what you want. Usually you don't want
199 any of extra features this option provides:
200
201 FLAGS_RETRY_VIDIOCSYNC 1 This bit allows to retry failed
202 VIDIOCSYNC ioctls without failing.
203 Will work with xawtv, will not
204 with xrealproducer. Default is
205 not set.
206 FLAGS_MONOCHROME 2 Activates monochrome (b/w) mode.
207 FLAGS_DISPLAY_HINTS 4 Shows colored pixels which have
208 magic meaning to developers.
209 FLAGS_OVERLAY_STATS 8 Shows tiny numbers on screen,
210 useful only for debugging.
211 FLAGS_FORCE_TESTPATTERN 16 Shows blue screen with numbers.
212 FLAGS_SEPARATE_FRAMES 32 Shows each frame separately, as
213 it was received from the camera.
214 Default (not set) is to mix the
215 preceding frame in to compensate
216 for occasional loss of Isoc data
217 on high frame rates.
218 FLAGS_CLEAN_FRAMES 64 Forces "cleanup" of each frame
219 prior to use; relevant only if
220 FLAGS_SEPARATE_FRAMES is set.
221 Default is not to clean frames,
222 this is a little faster but may
223 produce flicker if frame rate is
224 too high and Isoc data gets lost.
225 FLAGS_NO_DECODING 128 This flag turns the video stream
226 decoder off, and dumps the raw
227 Isoc data from the camera into
228 the reading process. Useful to
229 developers, but not to users.
230
231framerate This setting controls frame rate of the camera. This is
232 an approximate setting (in terms of "worst" ... "best")
233 because camera changes frame rate depending on amount
234 of light available. Setting 0 is slowest, 6 is fastest.
235 Beware - fast settings are very demanding and may not
236 work well with all video sizes. Be conservative.
237
238hue_correction This highly optional setting allows to adjust the
239 hue of the image in a way slightly different from
240 what usual "hue" control does. Both controls affect
241 YUV colorspace: regular "hue" control adjusts only
242 U component, and this "hue_correction" option similarly
243 adjusts only V component. However usually it is enough
244 to tweak only U or V to compensate for colored light or
245 color temperature; this option simply allows more
246 complicated correction when and if it is necessary.
247
248init_brightness These settings specify _initial_ values which will be
249init_contrast used to set up the camera. If your V4L application has
250init_color its own controls to adjust the picture then these
251init_hue controls will be used too. These options allow you to
252 preconfigure the camera when it gets connected, before
253 any V4L application connects to it. Good for webcams.
254
255init_model2_rg These initial settings alter color balance of the
256init_model2_rg2 camera on hardware level. All four settings may be used
257init_model2_sat to tune the camera to specific lighting conditions. These
258init_model2_yb settings only apply to Model 2 cameras.
259
260lighting This option selects one of three hardware-defined
261 photosensitivity settings of the camera. 0=bright light,
262 1=Medium (default), 2=Low light. This setting affects
263 frame rate: the dimmer the lighting the lower the frame
264 rate (because longer exposition time is needed). The
265 Model 2 cameras allow values more than 2 for this option,
266 thus enabling extremely high sensitivity at cost of frame
267 rate, color saturation and imaging sensor noise.
268
269sharpness This option controls smoothing (noise reduction)
270 made by camera. Setting 0 is most smooth, setting 6
271 is most sharp. Be aware that CMOS sensor used in the
272 camera is pretty noisy, so if you choose 6 you will
273 be greeted with "snowy" image. Default is 4. Model 2
274 cameras do not support this feature.
275
276size This setting chooses one of several image sizes that are
277 supported by this driver. Cameras may support more, but
278 it's difficult to reverse-engineer all formats.
279 Following video sizes are supported:
280
281 size=0 128x96 (Model 1 only)
282 size=1 160x120
283 size=2 176x144
284 size=3 320x240 (Model 2 only)
285 size=4 352x240 (Model 2 only)
286 size=5 352x288
287 size=6 640x480 (Model 3 only)
288
289 The 352x288 is the native size of the Model 1 sensor
290 array, so it's the best resolution the camera can
291 yield. The best resolution of Model 2 is 176x144, and
292 larger images are produced by stretching the bitmap.
293 Model 3 has sensor with 640x480 grid, and it works too,
294 but the frame rate will be exceptionally low (1-2 FPS);
295 it may be still OK for some applications, like security.
296 Choose the image size you need. The smaller image can
297 support faster frame rate. Default is 352x288.
298
299For more information and the Troubleshooting FAQ visit this URL:
300
301 http://www.linux-usb.org/ibmcam/
302
303WHAT NEEDS TO BE DONE:
304
305- The button on the camera is not used. I don't know how to get to it.
306 I know now how to read button on Model 2, but what to do with it?
307
308- Camera reports its status back to the driver; however I don't know
309 what returned data means. If camera fails at some initialization
310 stage then something should be done, and I don't do that because
311 I don't even know that some command failed. This is mostly Model 1
312 concern because Model 2 uses different commands which do not return
313 status (and seem to complete successfully every time).
314
315- Some flavors of Model 4 NetCameras produce only compressed video
316 streams, and I don't know how to decode them.
317
318CREDITS:
319
320The code is based in no small part on the CPiA driver by Johannes Erdfelt,
321Randy Dunlap, and others. Big thanks to them for their pioneering work on that
322and the USB stack.
323
324I also thank John Lightsey for his donation of the Veo Stingray camera.