dummy_camera is a Video4Linux driver that
fakes a simple Webcam. It is implemented as a completely
independent loadable kernel
module, and does not require any kernel modifications to use.
It is intended to be used to assist in
testing and develping video-conferencing
setups. It requires no hardware, so problems can be
isolated from hardware and network configuration, etc. Like a real Webcam,
dummy_camera generates low resolution images
(128x128) at low frame rates (3 fps). It does not, therefore,
suport the `mmap' interface to V4L drivers (see below)
which may be a limitation for some clients. The driver
generates a simple test pattern, as shown below (this
screenshot is from the Xawtv application).
dummy_camera responds to instructions from the client to
change brightness and colour, so if you tweak these
on the client you should see the display change in
real time.
make clean make make installThe most important file created by this process is the loadable module itself,
dummy_camera.o. make install
puts this in the misc subdirectory of the modules
directory. You can load the module like this:
modprobe videodev modprobe dummy_cameraThe dummy camera module has a depedency on the
videodev
module, so that must be loaded first.
If you get `unresolved symbol' messages from modprobe,
please contact me.
dummy_camera emulates a
primitive Webcam. There is no sound support, because primitive
Webcams don't have their own sound devices. There is no support
for the `mmap' interface to V4L drivers, which many modern
devices benefit from. The `mmap' scheme allows the client application
to get direct access to the driver's buffers, which is faster than
making explicit `read' operations for each frame. This is only a
limitation if the software you want to test insists on using
mmap: some does.
Although brightness and colour changes are supported, the other adjustable display properties are not (hue, contrast, etc). There did not seem to be much point in implementing these.