[AG-TECH] AG Grid dream system

Markus Buchhorn Markus.Buchhorn at anu.edu.au
Thu Sep 26 19:38:01 CDT 2002

At 11:21 AM 26/09/2002 -0500, Robert Olson wrote:
>At 11:59 AM 9/26/2002 -0400, Douglas Baggett wrote:
>>Just starting a discussion for thinking of how to get the video REALLY good. I'm competing with H.323 devices that companies like Polycom make, and at 2 Mb/s the Polycom video is broadcast quality and looks very good. The AG has so much more to offer, broadcast video quality can't be that far behind concidering how fast PC's and devices are lateley....
>Do you know what protocol the polycom is speaking at that rate? is it h.261 or h.263? Also, does it spec what resolution?

I think it'd have to be h.263, at 4CIF (VGA). h.261 is limited to CIF/QCIF, at N*64kb, and maxes at 1.5Mb/s (and you don't get much beyond about 1.1Mb/s). h.263 has a lot more going for it, including much larger and more flexible image sizes (multiples of 8x8 I believe, to almost any size). Polycom and Tandberg both support h.263 at 4CIF (at the high end of the product range).

"broadcast quality" is an interesting term :-). I'm not aware if anybody has actually developed an analyser that looks at a video signal and measures delivered colour depth, frame rate, contrast/fractal dimension, etc. I see claims for h.263 (and mpeg4, which uses one flavour of it) of 'broadcast' quality or 'dvd quality'. 

>(the difference is that the polycom gets to use a hardware h26X codec with full motion estimation, etc. the vic h261 encoder doesn't do motion est. Anyone know an opensource h26x encoder with that?)

Not that I've seen. I haven't looked at the ITU sample code for h.263 - has anybody here? It's meant to be freely downloadable if you can work your way through the ITU registration system. I've used it to download the written specs, but not the software.


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.  |Mobile: 0417 281429

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