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
+ 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.
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
+ 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
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.
+ 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.
compression (only useful with the plugin)
With this option you can control the compression factor that the camera
- uses to squeeze the image through the USB bus. You can set the
+ uses 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.
+ 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
this is let the LED blink while the camera is in use. This:
leds=500,500
-
+
will blink the LED once every second. But with:
leds=0,0
when the camera is not used anymore.
This parameter works only with the ToUCam range of cameras (720, 730, 740,
- 750) and OEMs. For other cameras this command is silently ignored, and
+ 750) and OEMs. For other cameras this command is silently ignored, and
the LED cannot be controlled.
Finally: this parameters does not take effect UNTIL the first time you
format:
[type[.serialnumber]:]node
-
+
The square brackets mean that both the type and the serialnumber are
optional, but a serialnumber cannot be specified without a type (which
would be rather pointless). The serialnumber is separated from the type
by a '.'; the node number by a ':'.
-
+
This somewhat cryptic syntax is best explained by a few examples:
dev_hint=3,5 The first detected cam gets assigned
- /dev/video3, the second /dev/video5. Any
- other cameras will get the first free
- available slot (see below).
+ /dev/video3, the second /dev/video5. Any
+ other cameras will get the first free
+ available slot (see below).
dev_hint=645:1,680:2 The PCA645 camera will get /dev/video1,
- and a PCVC680 /dev/video2.
-
- dev_hint=645.0123:3,645.4567:0 The PCA645 camera with serialnumber
- 0123 goes to /dev/video3, the same
- camera model with the 4567 serial
- gets /dev/video0.
+ and a PCVC680 /dev/video2.
+
+ dev_hint=645.0123:3,645.4567:0 The PCA645 camera with serialnumber
+ 0123 goes to /dev/video3, the same
+ camera model with the 4567 serial
+ gets /dev/video0.
- dev_hint=750:1,4,5,6 The PCVC750 camera will get /dev/video1, the
- next 3 Philips cams will use /dev/video4
- through /dev/video6.
+ dev_hint=750:1,4,5,6 The PCVC750 camera will get /dev/video1, the
+ next 3 Philips cams will use /dev/video4
+ through /dev/video6.
Some points worth knowing:
- - Serialnumbers are case sensitive and must be written full, including
+ - Serialnumbers are case sensitive and must be written full, including
leading zeroes (it's treated as a string).
- - If a device node is already occupied, registration will fail and
+ - If a device node is already occupied, registration will fail and
the webcam is not available.
- You can have up to 64 video devices; be sure to make enough device
- nodes in /dev if you want to spread the numbers (this does not apply
- to devfs). After /dev/video9 comes /dev/video10 (not /dev/videoA).
+ nodes in /dev if you want to spread the numbers.
+ After /dev/video9 comes /dev/video10 (not /dev/videoA).
- If a camera does not match any dev_hint, it will simply get assigned
the first available device node, just as it used to be.
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
+ 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
+ while loading and unloading the module
2 0x2 probe() and disconnect() traces On
16 0x10 Memory allocation of buffers, etc. Off
32 0x20 Showing underflow, overflow and Dumping frame On
- messages
+ messages
64 0x40 Show viewport and image sizes Off
Example:
-
+
# modprobe pwc size=cif fps=15 power_save=1
The fbufs, mbufs and trace parameters are global and apply to all connected
git://git.onelab.eu / linux-2.6.git / blobdiff