Re: Why Only Standard resolution ?

Jason Williams (streak@ccwf.cc.utexas.edu)
Sun, 23 Aug 1998 04:50:18 -0500 (CDT)


On Sun, 23 Aug 1998, Tim3D wrote:
> Why not to make available to change resolution(320x240 ...) and aspect (3/4)
> to any values users want ?
> This can solve many problems with non standard video capture devices.

You didn't mention which version of CU-SeeMe you're in reference to, but I
believe the Enhanced Versions DO work with other resolutions (I think I've
seen 3.1.1 work with the Quickcam VC using QCIF resolution).

There's two different things to consider though...Enhanced CU may work
with other resolutions, but it doesn't send the different resolution. It
scales whatever resolution the capture card gives it to 160x120. That
allows it to work with other resolutions, but doesn't allow you to
actually send/receive at that resolution. My understanding of CU isn't
complete of course, but as far as I know, there's isn't anything in the
protocol to allow for dynamically chosen resolutions. I believe seeing
somewhere in the protocol (possibly while testing the Cornell 1.0 version)
that there's the ability to send two resolutions: normal (160x120) and
hi-res (320x240). I believe that's sent along with the Open Continue (OC)
packets. Only the Cornell versions allow you to display 320x240 vid as
320x240/640x480.

So I guess the short answer is...it's not part of the protocol. I suppose
the protocol could be changed to allow fields for the dimensions of the
vid, but that could get really messy. Imagine someone advertising a
dimension of 10,000x10,000 which would blow up anyone who opens their vid.
I believe Netmeeting is the same way with three different predetermined
resolutions. You also have to consider the bandwidth. To send 320x240
grayscale eats up four times as much bandwidth as 160x120. If most people
are on modems, they wouldn't be able to handle 1024x768 vid. The Enhanced
CU client (3.X) gets around this by allowing you to scale the 160x120 vid
to any size you want. 3.X also doesn't handle the extra data from 320x240
vids.

--
streak@ccwf.cc.utexas.edu    * Jason Williams -- Austin, Tx.  |     |
streak@mail.utexas.edu       * University of Texas at Austin  | ___ |
streak@cs.utexas.edu         * BS Computer Science             \_|_/
*************** http://ccwf.cc.utexas.edu/~streak/ **************|