README for Linux device driver for the IBM "C-It" USB video camera INTRODUCTION: This driver does not use all features known to exist in the IBM camera. However most of needed features work well. This driver was developed using logs of observed USB traffic which was produced by standard Windows driver (c-it98.sys). I did not have data sheets from Xirlink. Video formats: 128x96 [model 1] 176x144 320x240 [model 2] 352x240 [model 2] 352x288 Frame rate: 3 - 30 frames per second (FPS) External interface: USB Internal interface: Video For Linux (V4L) Supported controls: - by V4L: Contrast, Brightness, Color, Hue - by driver options: frame rate, lighting conditions, video format, default picture settings, sharpness. SUPPORTED CAMERAS: IBM "C-It" camera, also known as "Xirlink PC Camera" The device uses proprietary ASIC (and compression method); it is manufactured by Xirlink. See http://www.xirlink.com/ http://www.ibmpccamera.com or http://www.c-itnow.com/ for details and pictures. The Linux driver was developed with camera with following model number (or FCC ID): KSX-XVP510. This camera has three interfaces, each with one endpoint (control, iso, iso). This type of cameras is referred to as "model 1". These cameras are no longer manufactured. Xirlink now manufactures new cameras which are somewhat different. In particular, following models [FCC ID] belong to that category: XVP300 [KSX-X9903] XVP600 [KSX-X9902] XVP610 [KSX-X9902] (see http://www.xirlink.com/ibmpccamera/ for updates, they refer to these new cameras by Windows driver dated 12-27-99, v3005 BETA) These cameras have two interfaces, one endpoint in each (iso, bulk). Such type of cameras is referred to as "model 2". They are supported (with exception of 352x288 native mode). Quirks of Model 2 cameras: ------------------------- Model 2 does not have hardware contrast control. Corresponding V4L control is not used at the moment. It may be possible to implement contrast control in software, at cost of extra processor cycles. This driver provides 352x288 mode by switching the camera into quasi-352x288 RGB mode (800 Kbits per frame) essentially limiting this mode to 10 frames per second or less, in ideal conditions on the bus (USB is shared, after all). The frame rate has to be programmed very conservatively. Additional concern is that frame rate depends on brightness setting; therefore the picture can be good at one brightness and broken at another! I did not want to fix the frame rate at slowest setting, but I had to move it pretty much down the scale (so that framerate option barely matters). I also noticed that camera after first powering up produces frames slightly faster than during consecutive uses. All this means that if you use videosize=2 (which is default), be warned - you may encounter broken picture on first connect; try to adjust brightness - brighter image is slower, so USB will be able to send all data. However if you regularly use Model 2 cameras you may prefer videosize=1 which makes perfectly good I420, with no scaling and lesser demands on USB (300 Kbits per second, or 26 frames per second). The camera that I had also has a hardware quirk: if disconnected, it needs few minutes to "relax" before it can be plugged in again (poorly designed USB processor reset circuit?) Model 2 camera can be programmed for very high sensitivity (even starlight may be enough), this makes it convenient for tinkering with. The driver code has enough comments to help a programmer to tweak the camera as s/he feels necessary. WHAT YOU NEED: - A supported IBM PC (C-it) camera (model 1 or 2) - A Linux box with USB support (2.3/2.4; 2.2 w/backport may work) - A Video4Linux compatible frame grabber program such as xawtv. HOW TO COMPILE THE DRIVER: You need to compile the driver only if you are a developer or if you want to make changes to the code. Most distributions precompile all modules, so you can go directly to the next section "HOW TO USE THE DRIVER". The driver consists of two files in usb/ directory: ibmcam.c and ibmcam.h These files are included into the Linux kernel build process if you configure the kernel for CONFIG_USB_IBMCAM. Run "make xconfig" and in USB section you will find the IBM camera driver. Select it, save the configuration and recompile. HOW TO USE THE DRIVER: I recommend to compile driver as a module. This gives you an easier access to its configuration. The camera has many more settings than V4L can operate, so some settings are done using module options. Typically module is installed with command 'modprobe', like this: # modprobe ibmcam framerate=1 Alternatively you can use 'insmod' in similar fashion: # insmod /lib/modules/2.x.y/usb/ibmcam.o framerate=1 Module can be inserted with camera connected or disconnected. The driver can have options, though some defaults are provided. Driver options: (* indicates that option is model-dependent) Name Type Range [default] Example -------------- -------------- -------------- ------------------ debug Integer 0-9 [0] debug=1 flags Integer 0-0xFF [0] flags=0x0d framerate Integer 0-6 [2] framerate=1 hue_correction Integer 0-255 [128] hue_correction=115 init_brightness Integer 0-255 [128] init_brightness=100 init_contrast Integer 0-255 [192] init_contrast=200 init_color Integer 0-255 [128] init_color=130 init_hue Integer 0-255 [128] init_hue=115 lighting Integer 0-2* [1] lighting=2 sharpness Integer 0-6* [4] sharpness=3 videosize Integer 0-2* [2] videosize=1 Options for Model 2 only: Name Type Range [default] Example -------------- -------------- -------------- ------------------ init_model2_rg Integer 0..255 [0x70] init_model2_rg=128 init_model2_rg2 Integer 0..255 [0x2f] init_model2_rg2=50 init_model2_sat Integer 0..255 [0x34] init_model2_sat=65 init_model2_yb Integer 0..255 [0xa0] init_model2_yb=200 debug You don't need this option unless you are a developer. If you are a developer then you will see in the code what values do what. 0=off. flags This is a bit mask, and you can combine any number of bits to produce what you want. Usually you don't want any of extra features this option provides: FLAGS_RETRY_VIDIOCSYNC 1 This bit allows to retry failed VIDIOCSYNC ioctls without failing. Will work with xawtv, will not with xrealproducer. Default is not set. FLAGS_MONOCHROME 2 Activates monochrome (b/w) mode. FLAGS_DISPLAY_HINTS 4 Shows colored pixels which have magic meaning to developers. FLAGS_OVERLAY_STATS 8 Shows tiny numbers on screen, useful only for debugging. FLAGS_FORCE_TESTPATTERN 16 Shows blue screen with numbers. FLAGS_SEPARATE_FRAMES 32 Shows each frame separately, as it was received from the camera. Default (not set) is to mix the preceding frame in to compensate for occasional loss of Isoc data on high frame rates. FLAGS_CLEAN_FRAMES 64 Forces "cleanup" of each frame prior to use; relevant only if FLAGS_SEPARATE_FRAMES is set. Default is not to clean frames, this is a little faster but may produce flicker if frame rate is too high and Isoc data gets lost. framerate This setting controls frame rate of the camera. This is an approximate setting (in terms of "worst" ... "best") because camera changes frame rate depending on amount of light available. Setting 0 is slowest, 6 is fastest. Beware - fast settings are very demanding and may not work well with all video sizes. Be conservative. hue_correction This highly optional setting allows to adjust the hue of the image in a way slightly different from what usual "hue" control does. Both controls affect YUV colorspace: regular "hue" control adjusts only U component, and this "hue_correction" option similarly adjusts only V component. However usually it is enough to tweak only U or V to compensate for colored light or color temperature; this option simply allows more complicated correction when and if it is necessary. init_brightness These settings specify _initial_ values which will be init_contrast used to set up the camera. If your V4L application has init_color its own controls to adjust the picture then these init_hue controls will be used too. These options allow you to preconfigure the camera when it gets connected, before any V4L application connects to it. Good for webcams. init_model2_rg These initial settings alter color balance of the init_model2_rg2 camera on hardware level. All four settings may be used init_model2_sat to tune the camera to specific lighting conditions. These init_model2_yb settings only apply to Model 2 cameras. lighting This option selects one of three hardware-defined photosensitivity settings of the camera. 0=bright light, 1=Medium (default), 2=Low light. This setting affects frame rate: the dimmer the lighting the lower the frame rate (because longer exposition time is needed). The Model 2 cameras allow values more than 2 for this option, thus enabling extremely high sensitivity at cost of frame rate, color saturation and imaging sensor noise. sharpness This option controls smoothing (noise reduction) made by camera. Setting 0 is most smooth, setting 6 is most sharp. Be aware that CMOS sensor used in the camera is pretty noisy, so if you choose 6 you will be greeted with "snowy" image. Default is 4. Model 2 cameras do not support this feature. videosize This setting chooses one if three image sizes that are supported by this driver. Camera supports more, but it's difficult to reverse-engineer all formats. Following video sizes are supported: videosize=0 128x96 (Model 1 only) videosize=1 176x144 videosize=2 352x288 videosize=3 320x240 (Model 2 only) videosize=4 352x240 (Model 2 only) The last one (352x288) is the native size of the sensor array, so it's the best resolution camera (Model 1) can yield. The best resolution of Model 2 is 176x144, and larger images are produced by stretching the bitmap. Choose the image size you need. The smaller image can support faster frame rate. Default is 352x288. WHAT NEEDS TO BE DONE: - The box freezes if camera is unplugged after being used (OHCI). Workaround: remove usb-ohci module first. - On occasion camera (model 1) does not start properly (xawtv reports errors), or camera produces negative image (funny colors.) Workaround: reload the driver module. Reason: [1]. - The button on the camera is not used. I don't know how to get to it. I know now how to read button on Model 2, but what to do with it? [1] - Camera reports its status back to the driver; however I don't know what returned data means. If camera fails at some initialization stage then something should be done, and I don't do that because I don't even know that some command failed. This is mostly Model 1 concern because Model 2 uses different commands which do not return status (and seem to complete successfully every time). VIDEO SIZE AND IMAGE SIZE Camera produces picture X by Y pixels. This is camera-specific and can be altered by programming the camera accordingly. This image is placed onto larger (or equal) area W by H, this is V4L image. At this time the driver uses V4L image size (W by H) 352x288 pixels because many programs (such as xawtv) expect quite specific sizes and don't want to deal with arbitrary, camera-specific sizes. However this approach "hides" real image size, and application always sees the camera as producing only 352x288 image. It is possible to change the V4L image size to 128x96, and then if camera is switched to 128x96 mode then xawtv will correctly accept this image size. But many other popular sizes (such as 176x144) will not be welcomed. This is the reason why all camera images are at this time placed onto 352x288 "canvas", and size of that canvas (V4L) is reported to applications. It will be easy to add options to control the canvas size, but it will be application- specific because not all applications are ready to work with variety of camera-specific sizes. CREDITS: The code is based in no small part on the CPiA driver by Johannes Erdfelt, Randy Dunlap, and others. Big thanks to them for their pioneering work on that and the USB stack.