[AG-TECH] bridging H.323 to AG questions

Markus Buchhorn Markus.Buchhorn at anu.edu.au
Thu Nov 20 15:54:50 CST 2003

At 10:34 20/11/2003 -0500, Gurcharan S. Khanna wrote:
>seems likes taking h.323 output and feeding into an AG box means encoding
>a pre-encoded signal which must reallly degrade the image.
>also, taking the AG output and feeding it into an H.323 box must not look
>very good.

 From h.323 to AG as an analogue signal is reasonable, but not great. Going the other way is much harder, since the AG display is somewhat larger than your typical PAL video frame :-) So you could just point a camera at your AG display, or scan convert from VGA->PAL, and/or do some stream selection. Ugly.

H.323 is (currently) based around h.261 with limited video frame sizes (CIF max). h.263 can go higher, as can h.264 (the default codec for mpeg4). So it also depends on your H.323 clients.

You can use vrvs today to do some digital bridging, and I gather insors has a solution as well. So do we, once the students working on it finish their exams :-) and we'll release the code for that then. It allows you to select a set of streams from the AG videos, and lay them out in whatever style suits you (ok, some constraints) as a single video feed for h.323 terminals to dial into. All of the audio is passed on. Basically it's a software MCU, with a web interface for control where necessary (you can ignore that though and use the defaults, which is what we'll do for telephony bridging).


Markus Buchhorn, ANU Internet Futures Project,      | Ph: +61 2 61258810
Markus.Buchhorn at anu.edu.au, mail: Bldg #108 - CS&IT |Fax: +61 2 61259805
Australian National University, Canberra 0200, Aust.|Mob: 0417 281429

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