Re: [GnomeMeeting-devel-list] Re: [OpenH323]VIDEO ISSUE SOLVED:Reg Latest Openh323 compilation in Linux

On Thu, 2004-09-02 at 15:19, Damien Sandras wrote:
> Do you think that a good GUI should present :
> "Philips ToUCam Pro 2"
> "BTTV card"
> "Quickcam USB"
> or 
> "/dev/video0"
> "/dev/video1"
> "/dev/video2"
> to users?

To users of a GUI application, such as gnome-meeting, you want to
present the long names.  (Eg, a mouse click on a drop down is easy).

To users of a command line application, or utility, it is not as cut and
dried as always wanting the full name.  I don't want to go through all
my code to add '-d Philips WebCamera 740K #2' for my second webcam
instead of '-d /dev/video1'.

Finally, for a library-handle to identify a device, the unique
identifier is the /dev/video* name on linux.  The user-string name of
the device isn't guaranteed to be unique.[#]

Possible compromise ?

1. Return from the V4L plugin as available devices something like:

 "/dev/video0 : Philips ToUCam Pro 2"
 "/dev/video1 : BTTV card"
 "/dev/video2 : Philips ToUCam Pro 2"
 "/dev/video3 : Unknown Video Device"

2. Let GM/gui apps do whatever lazy matching of user-input for camera
selection what they want to.  List-boxes, etc.

3. Pass back the /dev/video* part to pwlib/openh323, as it is the only
guaranteed unique identifier.  It's backwards compatible with existing
command line applications.

Some random musings from the sidelines,


PS. Obviously the list of names returned from the V4L plugin needs to be
well defined and documented if all the apps are going to be able to
present the appropriate unique identifier back to whatever syslem
library is handling the device - be that openh323/v4w/ddraw, etc.

[#] If you try to have the V4L plugin automatically return a list of
'friendly strings', you have the '2 identical cameras connected' case to
deal with...

If you suffix duplicates, and one is removed, you can't renumber/rename
the existing devices, at which point you end up with the V4L module
needing long-term state to map back to (unique) /dev/video* from the
(potentially transient) 'user friendly' name.

Also, how do you identify a camera that doesn't have anything printable
in that field, either by design or mistake, etc ?

Mark Cooke <mpc star sr bham ac uk>
University Of Birmingham

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