Re: [GnomeMeeting-list] IBM Ultraport II Cam and gnomemeeting 0.85.1, RH 7.3, kernel 2.4.18-3

[Damien Sandras <dsandras seconix com>]

On Mon, Jul 01, 2002 at 12:25:36PM -0500, Kurt Stephens wrote:
> Not to be a pain in the ... but gnomemeeting should handle any device 
> image size.  Or is there something about V4L that I dont understand?  Is 

The H.323 protocol specifies that if a H323 software is able to do video
(ie Netmeeting, GnomeMeeting, ...), it has to support the QCIF size.
QCIF size is 176x144, it is not an obligation to support other sizes.
GnomeMeeting also supports 352x288 (ie CIF size). Netmeeting also supports
QCIF and CIF.

> it policy that videodev clients specify the image size they want and the 
> device driver must resample?  What if someone wants to use a HW NTSC 

No, the device driver should not resample. But if the device driver doesn't
support 176x144 as video size, it should report an error and not say "it is
ok" but send a broken picture. The Philips Vesta Pro Scan for example only 
supports 160x1?? but works in 176x144 with a black border. In that case,
GnomeMeeting can ask to the driver to send the 160x size, and send QCIF
as requested by H.323. But your driver has a bug, apparently.

> frame grabber at 640x480 with gnomemeeting?  Does the restriction of 
> 176x144 or 352x288 lie in the H.261 protocol?
> 
> I tend to think that device drivers should be as dumb as possible.  I'd 
> be willing to contribute wherever help is needed, but I've never hacked 
> linux kernel code.  Put the image scaling code in reusable library 
> instead, that could be embedded later in drivers that *absolutely* need 
> it or other apps that have nothing to do with /dev/video.  Less code in 
> the kernel makes the kernel smaller and more reliable.  I vaguely 
> remember someone open-sourcing some image scaling routines, used in OGLE.
> 

I agree. Even if image scaling is not implemented, you can add a black border,
or simply cut parts of the image. That is what would happen if your driver
had no bug.

> One less reason to run VMWARE is always a good thing.
> 
> Yours,
> Kurt Stephens
> 


Damien