[opendtv] Re: Food for thought
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 20 Feb 2007 20:47:18 -0500
Craig Birkmaier wrote:
> Can you provide a reference for this position from the BBC.
http://www.bbc.co.uk/info/policies/pdf/dtt_hdtrial.pdf
And here is the specific quote, in the conclusions section:
"Each HD channel is likely to need bandwidth equivalent to that required
by three or four standard definition channels even when using more
advanced MPEG-4 technology."
They quote 19.5 Mb/s as their max rate.
In short, H.264 when transmitted in practical transmissions might not
give you the theoretical best compression people talk about. As we
discussed in the past, more than once. If one HD channel, to look good,
takes up the space occupied by 3 or 4 SD channels, that is just what
H.262 requires. In fact, some stations transmit 3 SDs *and* and HD
channel, with H.262.
My guess is that you can degrade the HD channel more gracefully with
H.264, or you can tell the users to just sit tight while the station
syncs up.
Bert
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