Re: Handling multiple video devices

On Wednesday 07 March 2007, Nigel Henry wrote:
On Wednesday 07 March 2007 21:13, Anne Wilson wrote:
I have three video devices that may be in use at any time on this box.
One is a pci video-capture card, so always present. The other two are
webcam and usb tv tuner. The problem is that every package that can
handle either the webcam or the tv tuner looks for video0.

tvtime's menu has an entry for changing the input, and I thought that
should do it, but absolutely nothing happens if I click on that. I
haven't had any more luck with amsn + webcam either - as long as it gets
video0 it is happy, but it won't talk to anything else.

There must be some way to configure these to talk to video*. I've had
some luck with getting udev to track the webcam connection, so if I could
point amsn to /dev/webcam, that would be solved. Similarly I could build
a rule for the tuner, but it's no good if I can't get the software to use
it.

Has anyone managed this sort of situation?

Anne

Hi Anne. This probably going to be a totally useless reply, but, how are
the 3 devices setup at the moment? I think you have Xawtv. Try running
xawtv -hwscan to see how the video devices are setup in /dev.

With xawtv I can specify which device to use when I launch it. For example
my TV tuner card uses /dev/video0, so that is just launched as xawtv. If I
want to use xawtv to access the webcam, I set the command on the desktop
launcher as, xawtv -device /dev/video1, and then get the webcam showing on
xawtv. I don't know much about TVtime, but it may be worth launching it
specifying the device it should use.

Amsn is a problem, as it just looks in /dev/video. If you mess with udev,
and create symlinks (/dev/webcam) Amsn is totally lost. Can't see the wood
for the trees.

My TVtuner card uses /dev/video0, and the webcam (ov511) uses /dev/video1,
except on FC5 with the 2.6.18 kernel, where it's a bit hit and miss in
which order they are loaded. I've used the webcam using /dev/video1 while
talking to you on Amsn, so I don't think there is a problem with Amsn, as
long as it can find a webcam device in /dev/video, whether that's
/dev/video0, 1, 2, or 3.

I don't if this is any help, but on FC2 the USB webcam was being
given /dev/video0, and the TVtuner card wasn't being loaded. The TVtuner
card should be loaded as /dev/video0, and the webcam as /dev/video1, but
that was an FC2 problem. USB starts early in the boot process, and USB
devices were loaded before PCI stuff.

This is what I did on FC2 in /etc/rc.d/rc.local to fix it.

/sbin/modprobe -r ov511 (remove webcam using /dev/video0)

/sbin/modprobe tda9887 port2=0 pal=I (load TVtuner card to /dev/video0)
/sbin/modprobe bttv tuner=38 automute=0 (more TVcard stuff)
#install bttv /sbin/modprobe tda9887 port2=0 pal=I; /sbin/modprobe
--ignore-install bttv

/sbin/modprobe ov511 force-palette=15 (load webcam to /dev/video1)

It may be worth trying something like this. I don't think there is a
problem with the webcam, so that can be loaded last, as Amsn is just
looking in /dev/video for a webcam device. The TVtuner card I don't know
about, but may be worth loading this first so that it grabs /dev/video0,
especially as you have problems with TVtime. Load the driver for the PCI
video-capture card second, and the driver for the webcam third.

If all 3 drivers are already loaded you will have to do a modprobe -r for
each one in /etc/rc.d/rc.local before modprobing them in the order you want
to have them loaded.

Personally I think this is a bit of a hack, but it has worked to get the
TVtuner card, and the webcam driver loaded in the correct order on FC2.

Thanks, both Nigel and Sander. I haven't had time to look into this any
further today, but I'll take another look at it tomorrow.

Anne


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