[opendtv] Re: Food for thought

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Wed, 21 Feb 2007 15:42:31 -0500

John Shutt wrote:

> How you can jump to the conclusion that MPEG-2 and MPEG-4 are
> essentially equal in bitrate requirements when use in HD is
> beyond me, beyond logic, and not supported by any data.

"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.

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.

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.

Bert
 
 
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