[opendtv] Re: Food for thought
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Thu, 22 Feb 2007 09:25:08 -0500
At 3:42 PM -0500 2/21/07, Manfredi, Albert E wrote:
"Essentially equal," in the practical tests, is the key. Not identical,
not in degraded modes, not squeezing them to the limit, perhaps, but
essentially equal as implemented.
This is an unsupportable conclusion that flies in the face of real
world experience.
It is a Bertclusion drawn out of the thin air.
You have all the information you need:
1. Freeview uses 16-QAM, 2/3 FEC, 8 MHz channels, or roughly 15 to 16
Mb/s per multiplex. (I'm not sure of the GI, assume 1/16.)
2. Freeview assigns 4 to 5 program streams per multiplex, or on average
anywhere between 3 and 4 Mb/s per SD stream.
http://www.dgtvi.it/stat/Europa/Gran_Bretagna/Page1.html
3. HDTV in H.264 takes up the same capacity as 3 to four SDTV programs,
which means 9 to 16 Mb/s at the lower and upper limits of that estimate.
4. They tested to a max of 19.5 Mb/s, for HDTV.
Read it again Bert. Some of the UK multiplexes have up to 8 programs.
But all of this is totally irrelevant to the discussion.
The BBC tested four different encoding parameters with 1080i and 720p
at low and high bit rates. They were concerned with ONE THING - how
to deliver HIGH QUALITY HDTV. Any dolt understands that to deliver
the full quality of HDTV you'll need the equivalent of the bits
required for about 4 SD services (both vary with the type of content,
especially as it relates to fast action). We are dealing with
information content and entropy here, not sorcery.
You know a lot. Okay, maybe not 12 to 20 Mb/s as I had estimated, which
gave each SD stream 4 to 5 Mb/s avg, but still within the range of what
HDTV using H.262 can do, from 24p to 60p, for good HDTV.
Spend a little time studying the h.264 standard and comparative tests
before spouting off on this list again Bert. You are not enhancing
your credibility.
Regards
Craig
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