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FYI: Comcast digital TV in Cambridge

Jarod Wilson wrote:
> Are we talking h.264 here or mpeg2? I can tell you from first-hand
> experience, you can NOT stream 1080i mpeg2 hdtv content over 802.11g
> with any sort of reliability. Too much packet loss, and while g claims
> 54Mbps throughput, I've never seen better than a sustained 2.4MB/s
> transfer, which is about what most 1080i mpeg2 streams require.

I was thinking of ATSC content which is 18Mbps maximum, or about 
2.25MB/s; a clean 801.11g connection can just about manage that, though 
you had better not have much else happening on the network. HD from 
cable uses substantially lower bit rates, making the problem easier; I 
don't know of any cable company that sends HD at more than 10Mbps, and 
the systems that are using H.264 are probably using even less. (FIOS may 
be an exception; they've got bandwidth to burn.) There is a tradeoff 
between quality and channel capacity, and the cable guys always choose 
the latter because it's a stronger marketing point. People using cable 
for HD... trying hooking up an antenna and watching some broadcast ATSC, 
especially from WGBH, and see how much better it looks than the same 
stations on cable.

Blu-Ray 1080p content may need higher bit rates, and therefore 802.11n. 
Home-encoded 1080i might also need more bandwidth; your encoder isn't as 
good as the ones the broadcasters have so you need to throw more bits at 
the problem to compensate. Remember, the network people can throw a LOT 
of money at the problem; they send the MPEG2 transmission streams on 
their satellites now so they only need one really good encoder for the 
entire network! Yes, that means that the local programming generally 
won't look as good as the prime time shows.

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