Re: ATI card (was Re: tomorrow's meeting)

[Jeff Licquia <jeff@licquia.org>]

On Tue, 2002-09-24 at 12:36, Erich Schroeder wrote:
> On Tue, 24 Sep 2002, Steven Pritchard wrote:
> > Which ATI card?
> 
> Its a All-in-wonder Radeon 7500. I picked it because it showed as having 
> good support under the GATOS project, but their pages don't really explain 
> the steps well.
> 
> I also got this because I will be working on providing streaming video 
> content, both live and canned, and I wanted to use gnomemeeting. I don't 
> have gnomemeeting working yet (can't find the video device) but it does 
> work under xawtv.

I have some experience in ATI All-in-Wonder cards.  I wouldn't call the
GATOS project "good support", at least not at this point.

The GATOS idea of the video4linux API isn't quite the same as the
video4linux project's idea. :-)  Part of this isn't their fault.  The
AIW shares video memory between the graphics card and the video
subsystem; this means that the XFree86 driver, DRI, and the v4l driver
have to coordinate for video memory.  There currently isn't a spec for
doing such coordination, so GATOS just moved some of the v4l API into
the DRI/XF86 drivers that initializes the v4l device to accomplish this.

This translates into the v4l driver not supporting certain calls in the
v4l API that have to do with initializing the card.  Some v4l programs
(like xawtv) don't seem to mind this as long as you use the card in
"preview mode" and use the Xvideo extension to get the video on your
screen.

You'll also find that you can't stream video to disk, or do anything
else besides watch the video on your screen, unless you use avview, the
GATOS-written video program.  Again, this is because of the
aforementioned problem with video memory coordination; video programs
have to dance the rhumba a little too, and only avview does it right. 
Avview, in turn, requires that you use ALSA instead of the default sound
drivers.  Avview is written in Tcl/Tk with some C extension modules that
talk to the hardware.

To sum up, it seems to me that you have a few options:

 - Get a budget and hire the DRI and GATOS people, stuff them in a
conference room, and don't let them out until they hammer out a protocol
for shared video memory arbitration.

 - Start writing a H.323-conformant voice protocol stack in Tcl.

 - Get a Hauppage WinTV card and some other VGA card for the video
server, and use that.

 - Use a USB QuickCam to do your video streaming.

 - Switch to Windows.

My information is current as of a few months ago, by the way.


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