[opendtv] Re: ITV calling for temporary spectrum for transition to HDTV
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Mon, 28 May 2007 12:24:10 -0400
At 5:43 PM -0400 5/25/07, Manfredi, Albert E wrote:
Craig Birkmaier wrote:
My guess is that they would use the new multiplex to develop
an HDTV service using higher power and more advanced modulation
techniques to increase the total bit rate for the multiplex.
Agreed. The multiplexes they have now are good for 15.6 Mb/s or so. If
they go to 64-QAM, they will be able to increase that to 22 Mb/s,
assuming they want to go with the SFN idea (still 2/3 FEC, but reducing
the GI to 1/8).
These numbers are not correct. The 16QAM multiplexes deliver 18 Mbps
and the 64QAM multiplexes deliver 24 Mbps:
\http://en.wikipedia.org/wiki/Digital_terrestrial_television_in_the_United_Kingdom#Multiplex_1
These numbers will increase when the system converts to 8K carriers
and higher power levels.
They seem to offer typically 4 or 5 program streams per multiplex now,
maybe occasionally 6. So if they went up to 64-QAM, kept the SD channels
as MPEG-2 compression, and avoided simulcasting, they could set aside
about 11 Mb/s for one HDTV program in each multiplex. Or they could
apply H.264 to all their programs, and get a few more b/s for the HD
channel. Maybe enough for two HD channels per multiplex.
You can be certain that everything will convert to H.264. All new
receivers will require it as well as the ability to deal with
improved modulation techniques. There would be no reason to continue
using MPEG-2 after the switch over.
Regards
Craig
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