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

[Van Duc Uy <uyvd sunyard net tw>]

Hi Damien,
It's very nice of you to explain my mail very clearly.

actually i never know this before.
I want to make Gnomemeeting with *FIX* resolution (320x240) and i don't want 
to use GConf. i  modified the source code and right now all are very well.
And i think if the image can display more beautiful with my camera is 
excellent. ;-) 

Thank you very much.
Michael

On Wednesday 07 January 2004 06:03 pm, Damien Sandras wrote:
> 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!