324 lines
14 KiB
Plaintext
324 lines
14 KiB
Plaintext
README for Linux device driver for the IBM "C-It" USB video camera
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INTRODUCTION:
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This driver does not use all features known to exist in
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the IBM camera. However most of needed features work well.
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This driver was developed using logs of observed USB traffic
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which was produced by standard Windows driver (c-it98.sys).
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I did not have data sheets from Xirlink.
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Video formats:
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128x96 [model 1]
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176x144
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320x240 [model 2]
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352x240 [model 2]
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352x288
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Frame rate: 3 - 30 frames per second (FPS)
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External interface: USB
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Internal interface: Video For Linux (V4L)
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Supported controls:
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- by V4L: Contrast, Brightness, Color, Hue
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- by driver options: frame rate, lighting conditions, video format,
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default picture settings, sharpness.
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SUPPORTED CAMERAS:
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Xirlink "C-It" camera, also known as "IBM PC Camera".
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The device uses proprietary ASIC (and compression method);
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it is manufactured by Xirlink. See http://xirlinkwebcam.sourceforge.net,
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http://www.ibmpccamera.com, or http://www.c-itnow.com/ for details and pictures.
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This very chipset ("X Chip", as marked at the factory)
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is used in several other cameras, and they are supported
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as well:
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- IBM NetCamera
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- Veo Stingray
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The Linux driver was developed with camera with following
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model number (or FCC ID): KSX-XVP510. This camera has three
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interfaces, each with one endpoint (control, iso, iso). This
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type of cameras is referred to as "model 1". These cameras are
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no longer manufactured.
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Xirlink now manufactures new cameras which are somewhat different.
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In particular, following models [FCC ID] belong to that category:
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XVP300 [KSX-X9903]
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XVP600 [KSX-X9902]
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XVP610 [KSX-X9902]
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(see http://www.xirlink.com/ibmpccamera/ for updates, they refer
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to these new cameras by Windows driver dated 12-27-99, v3005 BETA)
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These cameras have two interfaces, one endpoint in each (iso, bulk).
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Such type of cameras is referred to as "model 2". They are supported
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(with exception of 352x288 native mode).
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Some IBM NetCameras (Model 4) are made to generate only compressed
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video streams. This is great for performance, but unfortunately
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nobody knows how to decompress the stream :-( Therefore, these
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cameras are *unsupported* and if you try to use one of those, all
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you get is random colored horizontal streaks, not the image!
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If you have one of those cameras, you probably should return it
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to the store and get something that is supported.
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Tell me more about all that "model" business
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--------------------------------------------
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I just invented model numbers to uniquely identify flavors of the
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hardware/firmware that were sold. It was very confusing to use
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brand names or some other internal numbering schemes. So I found
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by experimentation that all Xirlink chipsets fall into four big
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classes, and I called them "models". Each model is programmed in
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its own way, and each model sends back the video in its own way.
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Quirks of Model 2 cameras:
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-------------------------
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Model 2 does not have hardware contrast control. Corresponding V4L
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control is implemented in software, which is not very nice to your
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CPU, but at least it works.
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This driver provides 352x288 mode by switching the camera into
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quasi-352x288 RGB mode (800 Kbits per frame) essentially limiting
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this mode to 10 frames per second or less, in ideal conditions on
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the bus (USB is shared, after all). The frame rate
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has to be programmed very conservatively. Additional concern is that
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frame rate depends on brightness setting; therefore the picture can
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be good at one brightness and broken at another! I did not want to fix
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the frame rate at slowest setting, but I had to move it pretty much down
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the scale (so that framerate option barely matters). I also noticed that
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camera after first powering up produces frames slightly faster than during
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consecutive uses. All this means that if you use 352x288 (which is
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default), be warned - you may encounter broken picture on first connect;
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try to adjust brightness - brighter image is slower, so USB will be able
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to send all data. However if you regularly use Model 2 cameras you may
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prefer 176x144 which makes perfectly good I420, with no scaling and
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lesser demands on USB (300 Kbits per second, or 26 frames per second).
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Another strange effect of 352x288 mode is the fine vertical grid visible
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on some colored surfaces. I am sure it is caused by me not understanding
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what the camera is trying to say. Blame trade secrets for that.
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The camera that I had also has a hardware quirk: if disconnected,
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it needs few minutes to "relax" before it can be plugged in again
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(poorly designed USB processor reset circuit?)
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[Veo Stingray with Product ID 0x800C is also Model 2, but I haven't
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observed this particular flaw in it.]
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Model 2 camera can be programmed for very high sensitivity (even starlight
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may be enough), this makes it convenient for tinkering with. The driver
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code has enough comments to help a programmer to tweak the camera
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as s/he feels necessary.
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WHAT YOU NEED:
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- A supported IBM PC (C-it) camera (model 1 or 2)
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- A Linux box with USB support (2.3/2.4; 2.2 w/backport may work)
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- A Video4Linux compatible frame grabber program such as xawtv.
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HOW TO COMPILE THE DRIVER:
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You need to compile the driver only if you are a developer
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or if you want to make changes to the code. Most distributions
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precompile all modules, so you can go directly to the next
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section "HOW TO USE THE DRIVER".
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The ibmcam driver uses usbvideo helper library (module),
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so if you are studying the ibmcam code you will be led there.
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The driver itself consists of only one file in usb/ directory:
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ibmcam.c. This file is included into the Linux kernel build
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process if you configure the kernel for CONFIG_USB_IBMCAM.
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Run "make xconfig" and in USB section you will find the IBM
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camera driver. Select it, save the configuration and recompile.
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HOW TO USE THE DRIVER:
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I recommend to compile driver as a module. This gives you an
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easier access to its configuration. The camera has many more
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settings than V4L can operate, so some settings are done using
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module options.
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To begin with, on most modern Linux distributions the driver
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will be automatically loaded whenever you plug the supported
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camera in. Therefore, you don't need to do anything. However
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if you want to experiment with some module parameters then
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you can load and unload the driver manually, with camera
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plugged in or unplugged.
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Typically module is installed with command 'modprobe', like this:
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# modprobe ibmcam framerate=1
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Alternatively you can use 'insmod' in similar fashion:
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# insmod /lib/modules/2.x.y/usb/ibmcam.o framerate=1
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Module can be inserted with camera connected or disconnected.
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The driver can have options, though some defaults are provided.
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Driver options: (* indicates that option is model-dependent)
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Name Type Range [default] Example
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-------------- -------------- -------------- ------------------
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debug Integer 0-9 [0] debug=1
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flags Integer 0-0xFF [0] flags=0x0d
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framerate Integer 0-6 [2] framerate=1
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hue_correction Integer 0-255 [128] hue_correction=115
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init_brightness Integer 0-255 [128] init_brightness=100
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init_contrast Integer 0-255 [192] init_contrast=200
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init_color Integer 0-255 [128] init_color=130
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init_hue Integer 0-255 [128] init_hue=115
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lighting Integer 0-2* [1] lighting=2
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sharpness Integer 0-6* [4] sharpness=3
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size Integer 0-2* [2] size=1
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Options for Model 2 only:
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Name Type Range [default] Example
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-------------- -------------- -------------- ------------------
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init_model2_rg Integer 0..255 [0x70] init_model2_rg=128
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init_model2_rg2 Integer 0..255 [0x2f] init_model2_rg2=50
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init_model2_sat Integer 0..255 [0x34] init_model2_sat=65
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init_model2_yb Integer 0..255 [0xa0] init_model2_yb=200
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debug You don't need this option unless you are a developer.
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If you are a developer then you will see in the code
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what values do what. 0=off.
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flags This is a bit mask, and you can combine any number of
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bits to produce what you want. Usually you don't want
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any of extra features this option provides:
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FLAGS_RETRY_VIDIOCSYNC 1 This bit allows to retry failed
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VIDIOCSYNC ioctls without failing.
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Will work with xawtv, will not
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with xrealproducer. Default is
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not set.
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FLAGS_MONOCHROME 2 Activates monochrome (b/w) mode.
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FLAGS_DISPLAY_HINTS 4 Shows colored pixels which have
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magic meaning to developers.
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FLAGS_OVERLAY_STATS 8 Shows tiny numbers on screen,
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useful only for debugging.
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FLAGS_FORCE_TESTPATTERN 16 Shows blue screen with numbers.
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FLAGS_SEPARATE_FRAMES 32 Shows each frame separately, as
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it was received from the camera.
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Default (not set) is to mix the
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preceding frame in to compensate
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for occasional loss of Isoc data
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on high frame rates.
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FLAGS_CLEAN_FRAMES 64 Forces "cleanup" of each frame
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prior to use; relevant only if
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FLAGS_SEPARATE_FRAMES is set.
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Default is not to clean frames,
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this is a little faster but may
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produce flicker if frame rate is
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too high and Isoc data gets lost.
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FLAGS_NO_DECODING 128 This flag turns the video stream
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decoder off, and dumps the raw
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Isoc data from the camera into
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the reading process. Useful to
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developers, but not to users.
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framerate This setting controls frame rate of the camera. This is
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an approximate setting (in terms of "worst" ... "best")
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because camera changes frame rate depending on amount
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of light available. Setting 0 is slowest, 6 is fastest.
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Beware - fast settings are very demanding and may not
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work well with all video sizes. Be conservative.
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hue_correction This highly optional setting allows to adjust the
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hue of the image in a way slightly different from
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what usual "hue" control does. Both controls affect
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YUV colorspace: regular "hue" control adjusts only
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U component, and this "hue_correction" option similarly
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adjusts only V component. However usually it is enough
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to tweak only U or V to compensate for colored light or
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color temperature; this option simply allows more
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complicated correction when and if it is necessary.
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init_brightness These settings specify _initial_ values which will be
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init_contrast used to set up the camera. If your V4L application has
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init_color its own controls to adjust the picture then these
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init_hue controls will be used too. These options allow you to
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preconfigure the camera when it gets connected, before
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any V4L application connects to it. Good for webcams.
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init_model2_rg These initial settings alter color balance of the
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init_model2_rg2 camera on hardware level. All four settings may be used
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init_model2_sat to tune the camera to specific lighting conditions. These
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init_model2_yb settings only apply to Model 2 cameras.
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lighting This option selects one of three hardware-defined
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photosensitivity settings of the camera. 0=bright light,
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1=Medium (default), 2=Low light. This setting affects
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frame rate: the dimmer the lighting the lower the frame
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rate (because longer exposition time is needed). The
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Model 2 cameras allow values more than 2 for this option,
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thus enabling extremely high sensitivity at cost of frame
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rate, color saturation and imaging sensor noise.
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sharpness This option controls smoothing (noise reduction)
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made by camera. Setting 0 is most smooth, setting 6
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is most sharp. Be aware that CMOS sensor used in the
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camera is pretty noisy, so if you choose 6 you will
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be greeted with "snowy" image. Default is 4. Model 2
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cameras do not support this feature.
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size This setting chooses one of several image sizes that are
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supported by this driver. Cameras may support more, but
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it's difficult to reverse-engineer all formats.
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Following video sizes are supported:
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size=0 128x96 (Model 1 only)
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size=1 160x120
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size=2 176x144
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size=3 320x240 (Model 2 only)
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size=4 352x240 (Model 2 only)
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size=5 352x288
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size=6 640x480 (Model 3 only)
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The 352x288 is the native size of the Model 1 sensor
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array, so it's the best resolution the camera can
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yield. The best resolution of Model 2 is 176x144, and
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larger images are produced by stretching the bitmap.
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Model 3 has sensor with 640x480 grid, and it works too,
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but the frame rate will be exceptionally low (1-2 FPS);
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it may be still OK for some applications, like security.
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Choose the image size you need. The smaller image can
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support faster frame rate. Default is 352x288.
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For more information and the Troubleshooting FAQ visit this URL:
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http://www.linux-usb.org/ibmcam/
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WHAT NEEDS TO BE DONE:
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- The button on the camera is not used. I don't know how to get to it.
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I know now how to read button on Model 2, but what to do with it?
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- Camera reports its status back to the driver; however I don't know
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what returned data means. If camera fails at some initialization
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stage then something should be done, and I don't do that because
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I don't even know that some command failed. This is mostly Model 1
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concern because Model 2 uses different commands which do not return
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status (and seem to complete successfully every time).
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- Some flavors of Model 4 NetCameras produce only compressed video
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streams, and I don't know how to decode them.
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CREDITS:
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The code is based in no small part on the CPiA driver by Johannes Erdfelt,
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Randy Dunlap, and others. Big thanks to them for their pioneering work on that
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and the USB stack.
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I also thank John Lightsey for his donation of the Veo Stingray camera.
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