[opendtv] Re: 7% penetration for UK HD-DTT by 2012: report

At 6:19 PM -0400 4/25/08, Manfredi, Albert E wrote:


Craig, you are confusing two different posts, and a couple of different
topics mentioned in each one. And that is why you are concluding 8 Mb/s
for an HD stream, which is not anything stated in any of the posts. (And
anyway, is not completely out of the question with H.262, e.g. in 720 at
24p mode.)


NO. I am talking about the story I quoted.


And that's where they are referring to DVB-T2 or the Ofcom MIMO scheme
(or maybe the MIMO scheme is also classified under "DVB-T2"). And BTW,
much of this fretting is caused by the fact that these new HD streams
have to be simulcast over and above the existing SD service. It would
otherwise be very simple to just replace one existing SD stream with an
HD stream, in each multiplex, and offer at least as many HD channels as
there are multiplexes.
MIMO is not an Ofcom scheme. It is a possible option for future DVB-T2 deployments. It IS NOT going to be used in the UK for the Freeview service. 


So, Ofcom mentioning "new technologies and standards" suggests probably
the MIMO scheme, since that was THEIR proposal. In which case, four HD
streams over 44 Mb/s means 11 Mb/s avg per stream.
You're reaching again. To the best of my knowledge Ofcom has never recommended any technology - they have simply said you can't have more spectrum for an HDTV transition. The BBC - the MAIn Freview "partner" has taken the lead with testing of new technologies for the HDTV multiplex. I spoke with the people who did this at NAB. There is NO PLAN to use MIMO because they are leveraging installed antennas now and will continue to do so in the future.
There is the possibility of a new service using SFNs with MIMO, in different spectrum, for a mobile DTV service in the future, but this in not going to be part of the Freview service. 

As I showed previously, some HD channels in the US are already down to
something close to that bit rate. And worse, using 1080i, which is
supposed to compress less efficiently than 720p.


Yup, and it looks like it too.

You really need to give it up Bert. MPEG-2 is legacy technology.
There is nothing left to wring out of it. The only way to make any further improvements would be to go outside the MPEG-2 toolbox for an encoder that could do a better job of motion compensated prediction, as this is where MPEG-2 gets it biggest compression kick. In the end, however, the compressed bit stream would have to conform to the MPEG-2 spec, and the tools are simply too crude to gain any additional benefit. It is far more productive to put any further engineering effort into h.264, where there are new tools to exploit that offer far better precision for motion compensated predictions. 



So you see, Craig, H.264 does not appear to be carrying any huge amount
of responsibility in the European introduction of HDTV, other than the
fact that it is being mandated. But sure, H.264 at 11 Mb/s is likely to
give better results than H.262 at 11 Mb/s. H.264 is however not
absolutely essential in this.

So let's not make a bigger deal out of it than it deserves.
It deserves the attention I gave it. The Europeans are fully embracing h.264 for HDTV. 

End of story.

Regards
Craig


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