patch-2.4.5 linux/Documentation/usb/philips.txt

• Lines: 142
• Date: Tue May 22 10:25:36 2001
• Orig file: v2.4.4/linux/Documentation/usb/philips.txt
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.4/linux/Documentation/usb/philips.txt linux/Documentation/usb/philips.txt
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+This file contains some additional information for the Philips webcams.
+E-mail: webcam@smcc.demon.nl                        Last updated: 2001-04-25
+
+The main webpage for the Philips driver is http://www.smcc.demon.nl/webcam/.
+It contains a lot of extra information, a FAQ, and the binary plugin
+'PWCX'. This plugin contains decompression routines that allow you to
+use higher image sizes and framerates; in addition the webcam uses less
+bandwidth on the USB bus (handy if you want to run more than 1 camera
+simultaneously). These routines fall under an NDA, and may therefor not be
+distributed as source; however, its use is completely optional.
+
+You can build this code either into your kernel, or as a module. I recommend
+the latter, since it makes troubleshooting a lot easier. The built-in
+microphone is supported through the USB Audio class.
+
+(Taken from install.html)
+
+When you load the module you can set some default settings for the
+camera; some programs depend on a particular image-size or -format. The
+options are:
+
+size
+   Can be one of 'sqcif', 'qsif', 'qcif', 'sif', 'cif' or
+   'vga', for an image size of resp. 128x96, 160x120, 176x144,
+   320x240, 352x288 and 640x480 (of course, only for those cameras that support these resolutions).
+
+fps
+   Specifies the desired framerate. Is an integer in the range of 4-30.
+
+palette
+   Specifies the desired colour order that should be delivered by read() and
+   mmap(). The string can be one of bgr24, rgb24, rgb32, bgr32, yuyv,
+   yuv420, yuv420p. If the tool you use produces odd colours (more
+   specificly, red and blue are swapped), try palette=bgr24 or
+   palette=rgb24.
+
+fbufs
+   This paramter specifies the number of internal buffers to use for storing 
+   frames from the cam. This will help if the process that reads images from 
+   the cam is a bit slow or momentarely busy. However, on slow machines it 
+   only introduces lag, so choose carefully. The default is 3, which is 
+   reasonable. You can set it between 2 and 5.
+
+mbufs
+   This is an integer between 1 and 4. It will tell the module the number of
+   buffers to reserve for mmap(), VIDIOCCGMBUF, VIDIOCMCAPTURE and friends.
+   The default is 2, which is adequate for most applications (double
+   buffering).
+      
+   Should you experience a lot of 'Dumping frame...' messages during
+   grabbing with a tool that uses mmap(), you might want to increase if. 
+   However, it doesn't really buffer images, it just gives you a bit more
+   slack when your program is behind. But you need a multi-threaded or
+   forked program to really take advantage of these buffers.
+
+   The absolute maximum is 4, but don't set it too high!  Every buffer takes
+   up 1.22 MB of RAM, so unless you have a lot of memory setting this to
+   something more than 2 is an absolute waste.  This memory is only
+   allocated during open(), so nothing is wasted when the camera is not in
+   use.
+
+power_save
+   When power_save is enabled (set to 1), the module will try to shut down
+   the cam on close() and re-activate on open(). This will save power and
+   turn off the LED. Not all cameras support this though (the 645 and 646
+   don't have power saving at all), and some models don't work either (they
+   will shut down, but never wake up). Consider this experimental. By
+   default this option is disabled.
+
+compression (only useful with the plugin)
+   With this option you can control the compression factor that the camera
+   use to squeeze the image through the USB bus. You can set the 
+   parameter between 0 and 3:
+     0 = prefer uncompressed images; if the requested mode is not available
+         in an uncompressed format, the driver will silently switch to low
+         compression.
+     1 = low compression.
+     2 = medium compression.
+     3 = high compression.
+      
+   High compression takes less bandwidth of course, but it could also
+   introduce some unwanted artefacts. The default is 2, medium compression. 
+   See the FAQ on the website for an overview of which modes require
+   compression.
+      
+   The compression parameter only applies to the Vesta & ToUCam cameras.
+   The 645 and 646 have fixed compression parameters.      
+
+trace
+
+   In order to better detect problems, it is now possible to turn on a
+   'trace' of some of the calls the module makes; it logs all items in your
+   kernel log at debug level.
+
+   The trace variable is a bitmask; each bit represents a certain feature.
+   If you want to trace something, look up the bit value(s) in the table 
+   below, add the values together and supply that to the trace variable.
+
+   Value  Value   Description					   Default
+   (dec)  (hex)
+       1    0x1   Module initialization; this will log messages       On
+                  while loading and unloading the module
+
+       2    0x2   probe() and disconnect() traces                     On
+
+       4    0x4   Trace open() and close() calls                      Off
+
+       8    0x8   read(), mmap() and associated ioctl() calls         Off
+
+      16   0x10   Memory allocation of buffers, etc.                  Off
+
+      32   0x20   Showing underflow, overflow and Dumping frame       On
+                  messages
+
+      64   0x40   Show viewport and image sizes                       Off
+
+
+   For example, to trace the open() & read() fuctions, sum 8 + 4 = 12,
+   so you would supply trace=12 during insmod or modprobe. If
+   you want to turn the initialization and probing tracing off, set trace=0.
+   The default value for trace is 35 (0x23).
+
+   Example:
+     
+     # modprobe pwc size=cif fps=15 power_save=1
+
+The fbufs, mbufs and trace parameters are global and apply to all connected
+cameras. Each camera has its own set of buffers.
+
+size, fps, palette only specify defaults when you open() the device; this is
+to accommodate some tools that don't set the size or colour palette. You can
+change these settings after open() with the Video4Linux ioctl() calls. The
+default of defaults is QCIF size at 10 fps, BGR order.
+
+The compression parameter is semiglobal; it sets the initial compression
+preference for all camera's, but this parameter can be set per camera with
+the VIDIOCPWCSCQUAL ioctl() call.
+
+All parameters are optional.
+
+