drivers/usb/media/pwc/philips.txt

   1 This file contains some additional information for the Philips and OEM webcams.
   2 E-mail: webcam@smcc.demon.nl                        Last updated: 2004-01-19
   3 Site: http://www.smcc.demon.nl/webcam/
   4
   5 As of this moment, the following cameras are supported:
   6  * Philips PCA645
   7  * Philips PCA646
   8  * Philips PCVC675
   9  * Philips PCVC680
  10  * Philips PCVC690
  11  * Philips PCVC720/40
  12  * Philips PCVC730
  13  * Philips PCVC740
  14  * Philips PCVC750
  15  * Askey VC010
  16  * Creative Labs Webcam 5
  17  * Creative Labs Webcam Pro Ex
  18  * Logitech QuickCam 3000 Pro
  19  * Logitech QuickCam 4000 Pro
  20  * Logitech QuickCam Notebook Pro
  21  * Logitech QuickCam Zoom
  22  * Logitech QuickCam Orbit
  23  * Logitech QuickCam Sphere
  24  * Samsung MPC-C10
  25  * Samsung MPC-C30
  26  * Sotec Afina Eye
  27  * AME CU-001
  28  * Visionite VCS-UM100
  29  * Visionite VCS-UC300
  30
  31 The main webpage for the Philips driver is at the address above. It contains
  32 a lot of extra information, a FAQ, and the binary plugin 'PWCX'. This plugin
  33 contains decompression routines that allow you to use higher image sizes and
  34 framerates; in addition the webcam uses less bandwidth on the USB bus (handy
  35 if you want to run more than 1 camera simultaneously). These routines fall
  36 under a NDA, and may therefor not be distributed as source; however, its use
  37 is completely optional.
  38
  39 You can build this code either into your kernel, or as a module. I recommend
  40 the latter, since it makes troubleshooting a lot easier. The built-in
  41 microphone is supported through the USB Audio class.
  42
  43 When you load the module you can set some default settings for the
  44 camera; some programs depend on a particular image-size or -format and
  45 don't know how to set it properly in the driver. The options are:
  46
  47 size
  48    Can be one of 'sqcif', 'qsif', 'qcif', 'sif', 'cif' or
  49    'vga', for an image size of resp. 128x96, 160x120, 176x144,
  50    320x240, 352x288 and 640x480 (of course, only for those cameras that
  51    support these resolutions).
  52
  53 fps
  54    Specifies the desired framerate. Is an integer in the range of 4-30.
  55
  56 fbufs
  57    This paramter specifies the number of internal buffers to use for storing
  58    frames from the cam. This will help if the process that reads images from
  59    the cam is a bit slow or momentarely busy. However, on slow machines it
  60    only introduces lag, so choose carefully. The default is 3, which is
  61    reasonable. You can set it between 2 and 5.
  62
  63 mbufs
  64    This is an integer between 1 and 10. It will tell the module the number of
  65    buffers to reserve for mmap(), VIDIOCCGMBUF, VIDIOCMCAPTURE and friends.
  66    The default is 2, which is adequate for most applications (double
  67    buffering).
  68
  69    Should you experience a lot of 'Dumping frame...' messages during
  70    grabbing with a tool that uses mmap(), you might want to increase if.
  71    However, it doesn't really buffer images, it just gives you a bit more
  72    slack when your program is behind. But you need a multi-threaded or
  73    forked program to really take advantage of these buffers.
  74
  75    The absolute maximum is 10, but don't set it too high!  Every buffer takes
  76    up 460 KB of RAM, so unless you have a lot of memory setting this to
  77    something more than 4 is an absolute waste.  This memory is only
  78    allocated during open(), so nothing is wasted when the camera is not in
  79    use.
  80
  81 power_save
  82    When power_save is enabled (set to 1), the module will try to shut down
  83    the cam on close() and re-activate on open(). This will save power and
  84    turn off the LED. Not all cameras support this though (the 645 and 646
  85    don't have power saving at all), and some models don't work either (they
  86    will shut down, but never wake up). Consider this experimental. By
  87    default this option is disabled.
  88
  89 compression (only useful with the plugin)
  90    With this option you can control the compression factor that the camera
  91    uses to squeeze the image through the USB bus. You can set the
  92    parameter between 0 and 3:
  93      0 = prefer uncompressed images; if the requested mode is not available
  94          in an uncompressed format, the driver will silently switch to low
  95          compression.
  96      1 = low compression.
  97      2 = medium compression.
  98      3 = high compression.
  99
 100    High compression takes less bandwidth of course, but it could also
 101    introduce some unwanted artefacts. The default is 2, medium compression.
 102    See the FAQ on the website for an overview of which modes require
 103    compression.
 104
 105    The compression parameter does not apply to the 645 and 646 cameras
 106    and OEM models derived from those (only a few). Most cams honour this
 107    parameter.
 108
 109 leds
 110    This settings takes 2 integers, that define the on/off time for the LED
 111    (in milliseconds). One of the interesting things that you can do with
 112    this is let the LED blink while the camera is in use. This:
 113
 114      leds=500,500
 115
 116    will blink the LED once every second. But with:
 117
 118      leds=0,0
 119
 120    the LED never goes on, making it suitable for silent surveillance.
 121
 122    By default the camera's LED is on solid while in use, and turned off
 123    when the camera is not used anymore.
 124
 125    This parameter works only with the ToUCam range of cameras (720, 730, 740,
 126    750) and OEMs. For other cameras this command is silently ignored, and
 127    the LED cannot be controlled.
 128
 129    Finally: this parameters does not take effect UNTIL the first time you
 130    open the camera device. Until then, the LED remains on.
 131
 132 dev_hint
 133    A long standing problem with USB devices is their dynamic nature: you
 134    never know what device a camera gets assigned; it depends on module load
 135    order, the hub configuration, the order in which devices are plugged in,
 136    and the phase of the moon (i.e. it can be random). With this option you
 137    can give the driver a hint as to what video device node (/dev/videoX) it
 138    should use with a specific camera. This is also handy if you have two
 139    cameras of the same model.
 140
 141    A camera is specified by its type (the number from the camera model,
 142    like PCA645, PCVC750VC, etc) and optionally the serial number (visible
 143    in /proc/bus/usb/devices). A hint consists of a string with the following
 144    format:
 145
 146       [type[.serialnumber]:]node
 147
 148    The square brackets mean that both the type and the serialnumber are
 149    optional, but a serialnumber cannot be specified without a type (which
 150    would be rather pointless). The serialnumber is separated from the type
 151    by a '.'; the node number by a ':'.
 152
 153    This somewhat cryptic syntax is best explained by a few examples:
 154
 155      dev_hint=3,5              The first detected cam gets assigned
 156                                /dev/video3, the second /dev/video5. Any
 157                                other cameras will get the first free
 158                                available slot (see below).
 159
 160      dev_hint=645:1,680:2      The PCA645 camera will get /dev/video1,
 161                                and a PCVC680 /dev/video2.
 162
 163      dev_hint=645.0123:3,645.4567:0     The PCA645 camera with serialnumber
 164                                         0123 goes to /dev/video3, the same
 165                                         camera model with the 4567 serial
 166                                         gets /dev/video0.
 167
 168      dev_hint=750:1,4,5,6       The PCVC750 camera will get /dev/video1, the
 169                                 next 3 Philips cams will use /dev/video4
 170                                 through /dev/video6.
 171
 172    Some points worth knowing:
 173    - Serialnumbers are case sensitive and must be written full, including
 174      leading zeroes (it's treated as a string).
 175    - If a device node is already occupied, registration will fail and
 176      the webcam is not available.
 177    - You can have up to 64 video devices; be sure to make enough device
 178      nodes in /dev if you want to spread the numbers (this does not apply
 179      to devfs). After /dev/video9 comes /dev/video10 (not /dev/videoA).
 180    - If a camera does not match any dev_hint, it will simply get assigned
 181      the first available device node, just as it used to be.
 182
 183 trace
 184    In order to better detect problems, it is now possible to turn on a
 185    'trace' of some of the calls the module makes; it logs all items in your
 186    kernel log at debug level.
 187
 188    The trace variable is a bitmask; each bit represents a certain feature.
 189    If you want to trace something, look up the bit value(s) in the table
 190    below, add the values together and supply that to the trace variable.
 191
 192    Value  Value   Description                                      Default
 193    (dec)  (hex)
 194        1    0x1   Module initialization; this will log messages       On
 195                   while loading and unloading the module
 196
 197        2    0x2   probe() and disconnect() traces                     On
 198
 199        4    0x4   Trace open() and close() calls                      Off
 200
 201        8    0x8   read(), mmap() and associated ioctl() calls         Off
 202
 203       16   0x10   Memory allocation of buffers, etc.                  Off
 204
 205       32   0x20   Showing underflow, overflow and Dumping frame       On
 206                   messages
 207
 208       64   0x40   Show viewport and image sizes                       Off
 209
 210      128   0x80   PWCX debugging                                      Off
 211
 212    For example, to trace the open() & read() fuctions, sum 8 + 4 = 12,
 213    so you would supply trace=12 during insmod or modprobe. If
 214    you want to turn the initialization and probing tracing off, set trace=0.
 215    The default value for trace is 35 (0x23).
 216
 217
 218
 219 Example:
 220
 221      # modprobe pwc size=cif fps=15 power_save=1
 222
 223 The fbufs, mbufs and trace parameters are global and apply to all connected
 224 cameras. Each camera has its own set of buffers.
 225
 226 size and fps only specify defaults when you open() the device; this is to
 227 accommodate some tools that don't set the size. You can change these
 228 settings after open() with the Video4Linux ioctl() calls. The default of
 229 defaults is QCIF size at 10 fps.
 230
 231 The compression parameter is semiglobal; it sets the initial compression
 232 preference for all camera's, but this parameter can be set per camera with
 233 the VIDIOCPWCSCQUAL ioctl() call.
 234
 235 All parameters are optional.
 236