[opendtv] Re: 1080p @ 60 is Next?
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Fri, 11 May 2007 07:59:41 -0400
At 10:36 PM +0200 5/10/07, Olivier Houot wrote:
Those relatively small flat screens used in the EBU tests may be
very trendy, but any self-respecting HD geek would only contemplate
a picture with at least a 2.5 meter base.
Also, consider that some "live" events might be retransmitted in
digital theaters on a cinema-sized screen.
I understand it would have been difficult to set up a demo with
three 10 meters wide screens, but at least 2 x 2.5 m above one
another could have been considered.
Big screens would be more revealing of resolution deficiencies, and
the conclusions would have offered some security margins when
applied to smaller ones.
I seriously doubt the results would have been much different, EXCEPT
for the uncompressed comparisons. Big Screens also make it much
easier to see the compression artifacts, which would make the
advantages of 720p emission even more noticeable.
But Olivier does raise an important issue. The resolution of the
display IS important as the screen size increases, and there is a
point where 1080P (or higher) will show an advantage or 720P as a
display format. We have discussed this many times over the years.
Bottom line, the point where 1080P display becomes important -
assuming the same viewing distance measured in picture heights - is
somewhere in the range of 70 inch to 100 inch diagonal, depending on
the visual acuity of the viewer.
Or another way to state this, display oversampling can be a good
thing, but only in a narrow range of applications. For example, a 70
inch 1080P display may produce visibly superior results to a 70 inch
720P display, but there will be no visible difference at normal
viewing distances between a 40 inch 1080p display and a 40 inch 720P
display.
I don't think the choice of the more appropriate standard should be
based on the present market trends, especially in an industry where
things can change so quickly.
True. We are now in a digital world where acquisition, transmission
and display are decoupled. It is easy to understand and to project
that we will keep seeing improvements on the acquisition side of the
equation, including 1080@60P cameras and production.
It is far less clear that there are any advantages to 1080@60P
emission. Actually just the opposite appears to be true based on the
EBU tests. As I have said MANY TIMES BEFORE, what is important in
emission is the delivered quality of the samples. As long as we are
dealing with progressive rasters, up and down conversions are
relatively simple and the quality can be very good. The introduction
of interlace is a major problem for both the acquisition/production
and transmission components of the chain. Interlacing at the display
is a cheap and easy cost reduction technique, and may persist as long
as we are building boxes to feed legacy interlaced displays.
Watching a 1.27 m screen (diagonal), even in high definition, does
not fundamuntally change the TV experience. With a 2.5 m screen
(width), it really begins to fell like you're at the movies.
YUP. HD has more to do with screen size than delivered resolution.
NTSC delivers a very sharp picture on the 19" display for which it
was designed.
A sizeable fraction of the early HD adopters have opted for a big
picture (which means front projectors at the moment), and EBU should
not make a choice that would clearly expose limitations in such
viewing conditions.
They did not. Emisiion and display are decoupled. Enlarging any image
via projection is going to make the flaws more visible. From personal
experience, corroborated by the EBU study, it is the artifacts of
compression that are the primary determinant of delivered image
quality. Feel free to blow them up to any size you want. After you
see the results you will better understand why a nearly artifact free
720P encoding is superior to an artifact riddled 1080P emission.
Perhaps the final conclusions would not be very different, but at
least the test should be made.
I believe that such a test would only help to confirm the work that
Hans and the EBU have done.
Regards
Craig
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