[opendtv] Re: Half Truths - Was More 1080p@60
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 4 Dec 2007 15:54:28 -0500
Craig Birkmaier wrote:
> The EBU studies provide the correct technical basis to justify
> this, and their conclusion is that we should use 720P for
> emission.
Not quite that simple.
The EBU studies I think you're referring to said that 1080 at 50p would
be the best emission option as long as bit rates could be above 10 to 13
Mb/s, using H.264 compression. They said that below that channel
capacity, 720 at 50p was preferable. And they said that 1080i was never
the best choice.
The real conclusion, wrt 1080 at 50p as emission format, was:
http://www.ebu.ch/en/technical/trev/trev_308-hdtv.pdf
"1080p/50 provides more information in the spatio-temporal domain and
encoders can conduct the compression more efficiently. However, at the
lower bitrates (i.e. <10...13 Mbit/s) the 1080p/50 encoder becomes more
overloaded with information, depending on the content, and this
information overload appears to become the dominant factor affecting
quality. The impairments with high compression are not as bad as those
for 1080i/25 but more visible than 720p/50. 1080p/50 has the potential
to be a future HDTV format for emission, particularly if higher
resolution displays are available, but further studies are required."
So, the way I read this Ambarella paper is that maybe they are tweaking
H.264 efficiency to the point that the future the EBU was talking about
is now. The numbers they claimed seemed way optimistic, but on the other
hand, the numbers in the EBU report did not seem subsanttially different
from what MPEG-2 compression can do (namely, they used 18, 16, 13, 10, 8
and 6 Mb/s). So the truth probably lies somewhere in the middle.
If the Arambella numbers represent some sort of real breakthrough in
H.264 tweaking, then I would think H.264 and a 1080 at 60p transmission
format would also make sense for the ATSC to consider.
On a side note, I noticed the small (19" and even less) LCD TVs on store
shelves are now no longer SD or even 1366 X 768. They are now 1440 X
900. This says that large TVs beyond 1080p are just around the corner.
That's when a 1080p transmission format may well start making sense, for
displays of, say, 50" and greater anyway.
This stuff is not going to remain static. The CE companies have to have
something new to sell you, after you've owned your set for three or four
years.
Bert
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