Handling multiple video devices

[Nigel Henry]

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.

All the best.

Nigel.