[opendtv] Re: Food for thought
- From: "Bob Miller" <robmxa@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 21 Feb 2007 14:04:31 -0500
On 2/21/07, Manfredi, Albert E <albert.e.manfredi@xxxxxxxxxx> wrote:
John Shutt wrote:
> If you want to play quote games, then I hope you didn't miss
> this quote from the BBC presentation:
The quote was so simple and straightforward that I really am astounded
by this level of spin, John. Let me put it really simply: if the quote
had said, "One SD program in MPEG-2 can be replaced by one HD stream in
H.264," THEN the hype would have been justified.
I agree that the quote was "so simple and straightforward that I
really am astounded
by this level of spin" Albert. To me the quote says that EVEN if
using MPEG-4 the trade off between SD and HD is STILL "three or four
standard definition channels".
They don't say anywhere what the trade off would be if they used
MPEG-2. I beleive it is implied that with MPEG-2 six SD programs would
have to be displaced or the entire channels worth for one HD program
and that with MPEG-4, while it might be possible to squeeze 2 HD
programs in, that they would STILL displace at least 3, or 4 SD
programs, that is half or more of its SD MPEG-2 capacity.
Of course you can read it your way but you have to put a lot of spin
on it IMO. Seems pretty obvious what they mean to me.
Bob Miller
As it is, no one should pretend that it's H.264 or bust. It simply is
not borne out by the facts. Neither the US nor the Aussie versions of
HDTV are heavily compromised by their use of H.262, until some future
codec comes along.
In any case, nothing in your preferred quote, below, disputes anything I
said or the BBC wrote. Your quote states the obvious. Which is, if the
HDTV program uses H.264, you need an STB with H.264 to decode it.
> "HD set-top boxes were specifically commissioned and developed
> for the trial by Humax and ADB. These operated using the
> MPEG-4 compression standard rather than the MPEG-2 used in
> standard DTT boxes, allowing more efficient encoding of the
> broadcast signal. This was essential to the successful delivery
> and decoding of the HD signals used in the trial, and meant
> that any households with standard DTT boxes were not able to
> view the HD services."
>
> Digital encoding is not a cliff edge, it is a continuum. As you
> vary the bitrate, you subtly vary the amount of video
> impairment according to the scene being encoded.
So tell me something I don't know. Once again, had they claimed that
each SD program can be replaced at the same bit rate by an HD program,
the value of H.264 would have been undisputable.
Every change in a deployed standard comes at a price. If you have to
pick a time when an upgrade is to be implemented, you're better off
making sure the upgrade is an obvious improvement. In the case of the
BBC, introducing HDTV in a market with no HDTV and no deployed MPEG-2 MP
at HL boxes at all, it's no big shakes to go to H.264. In countries
where HDTV is deployed and working just fine, I would wait until
something more efficient comes along.
Bert
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