Re: [GnomeMeeting-list] H261PixelEncoder : H.261 bad geometry: 320x240

[Miguel Rodríguez <migrax terra es>]

I think the best solution here would be to have pwlib[1] return the
unmodified image and make GnomeMeeting do the scaling. Maybe we can use
XVideo or the SDL library to show the image in the GUI, having the
scaling possible hardware accelerated in that case.

Sadly I don't have the necessary skills/time to do that myself soon.

[1] For the logitech camera this also means fixing the driver to not
return sizes not supported by the hardware.

El mié, 07-01-2004 a las 12:03, Damien Sandras escribió:
> Hi,
> 
> Le mer 07/01/2004 à 10:04, Van Duc Uy a écrit :
> > Hi all,
> > I use gnomemeeting-0.98.5 on Mandrake linux 9.2.
> > camera is Logitech Quickcam Pro 4000. 
> > 
> > it's because gnomemeeting always display the picture with a
> > BIG "Gray border" (as i know GM_QCIF_HEIGHT/WIDTH). 
> > 
> > so i want to choose another mode GM_SIF_WIDTH/HEIGHT that
> > displayed at 320/240 pixels. 
> > After i modified the gnomemeeting code, and rebuilt it, 
> > the video can display very well without border anymore. ..
> > 
> > But, when i try to make a connection to another host (Netmeeting 3.0),
> > at the console i saw the message :
> > 
> > H261PixelEncoder : H.261 bad geometry: 320x240
> > Segmentation fault
> > 
> > and then gnomemeeting crashed.
> > 
> > Can anyone explain for me about the problem ?
> 
> You modified things without understanding. If it was possible to do it
> so easily, it would already be a feature ;)
> 
> > why H.261 can not encoder with 320/240 pixel ?
> 
> Actually, the H.323 standard specified that at least H.261 QCIF must be
> supported by endpoints. So, if you are sending SIF or QSIF, there is no
> guarantee that the remote endpoint will be able to decode it. The
> OpenH323 H.261 encoder, which is the vic encoder, only supports QCIF and
> CIF.
> 
> > If i don't want to see the "Gray border", how can i do ?
> > 
> 
> There are 2 possibilities :
> - Buy a camera that supports exactly QCIF and CIF
> - Modify vconvert.cxx in pwlib so that it supports image scaling.
> Currently, pwlib will ask to the driver to capture in QCIF, if the
> driver supports it, it will work. If the driver doesn't support QCIF,
> pwlib will try the next size and surround it with borders. So it will
> try QSIF, for example, and surround it with borders so that it becomes
> QCIF. You could extend the methods so that the QSIF is scaled in QCIF
> instead of surrounded by borders. However, that won't work with the
> logitech quickcam, because when you request QCIF, the driver will itself
> send QSIF surrounded by borders, without the intervention of the
> library, there are thus 2 things to do :
> 	* extend pwlib colour converters so that they support scaling 	instead
> of cropping/borders
> 	* fix the driver so that it fails when QCIF is asked, instead of
> 	adding itself the borders
> 
> Good luck!