[opendtv] Re: Samsung Rep admits HDMI won't support 1080p until v.1.3
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 9 Nov 2005 09:55:28 -0500
At 11:30 PM -0500 11/8/05, Tom Barry wrote:
>Craig -
>
>Curiously I've had a chance to test this assertion in the last couple
>days. Over the weekend I bought a $900 XGA front projector at CostCo to
>replace my dying RPTV. This is a DLP with a 4:3 1024x768 native
>resolution. Since it automatically switches to 16:9 with an HD signal
>that means it's really using a 1024x576 (wide-PAL) resolution for movies.
>
>Now everyone on this list has probably heard my laments that very few
>broadcast shows seem to have an effective resolution much more than this
>anyway. And since I equally will use this projector as an easy-eye
>computer monitor it seemed an economical choice.
>
>It has been so far.
>
>I'm currently projecting on a white wall about 9-10' from my eyes,
>watching an image about 3' high (when 16:9) so I'm about 3 screen
>heights away. And I don't notice any loss of detail compared to my
>previous 1080i RPTV. However I'm just on the edge of being able to see
>the pixel structure at that distance. For instance in computer mode as
>I type this I can see the slight jagginess of the computer fonts. But
>for HD video images that is much harder.
I did similar tests almost a decade ago with LCD projectors. This is
a perfect example of display scalability. What you are seeing at ~9
feet is virtually identical to what your eyes see when looking at a
17" 1024 x 768 computer screen at ~30 inches. As you would expect you
can just see the jaggies of the NON-NYQUIST limited imagery generated
by your computer. And you are doing exactly what most human observers
would do when viewing such a large screen...you chose a viewing
distance where the raster disappeared and you could perceive a sharp
image.
>
>However when I first set it up I had the projector set back a bit
>further because it was temporarily convenient. That made the image
>about 10-20% larger, probably just over the size/distance threshold
>where I could pretend it was pixel free. For my vision and seating
>distance I would personally need a bit more display resolution if I
>wanted to keep a 4' high 16:9 image.
Yup. It is relatively easy to determine the resolution requirements
of a display if you know the screen size and viewing distance. This
is why 1080P is only relevant on very large screens viewed at about 3
picture heights.
>
>I'm not sure whether that would also mean a higher transmission
>resolution for current HD broadcast. But I am certain sure I'd need it
>if I was really watching full resolution 1080p, say with possible new
>HD/DVD's of some flavor.
Forget 1080P. 1280 x 720 has more than adequate resolution (as an
emission container) to deliver any kind of TV content.
With all of the posts to this list about the sorry quality of MPEG
compressed video, one would THINK that people would wake up and
understand that this IS NOT an ANALOG transmission system. We are
delivering bits that represent anything...audio, video, still images,
web pages, etc.
An analog system is limited by the bandpass. You can deliver any
level of quality up to the bandpass limits of the system.
A digital system is NOT limited by the bandpass of the transmission
network, except for the peak bit rate at any moment in time. This is
the same issue that we confront with DVDs, where the peak bit rate
limits the quality of what can be encoded. We can use the available
bits to deliver a high quality file at lower spatial/temporal
resolution, or we can try to squeeze harder, and deliver content that
falls apart when the peak bit rate is insufficient. The RIGHT
approach is to resample to a lower resolution and NOT squeeze so
hard. You get two benefits from this approach:
Greatly improved MTF;
More headroom to handle the peak bit rate requirements.
>I also notice with the very large screen size that I do NOT want a full
>field of vision for web browsing. It makes me more aware of why reading
>a magazine with separate narrower columns seems easier, not zooming my
>eyes back and forth across 80 some inches of wall to read each line.
>Luckily Windows can make windows where this is needed.
You have discovered what HDTV is all about. Direct eye movement. With
small screens it is not necessary to track motion - the entire image
is captured by your foveal receptors. When increase the viewing angle
the eye is forced to track motion, and this is what causes the
induction effect that is critical for the immersive HD viewing
experience. we use direct eye movement all the time when we work with
an up close and personal computer display. But the close distance to
the screen means that we don't need to move far; it also means that
we can reduce the viewing distance by about half by simply moving our
head closer to the screen. With the big screen 9 feet or more,
moving our head does virtually nothing to change the viewing
distance, and we will necessarily move our eyes more to track motion
than with a small TV display.
I also suspect that you found navigation of web pages to be quite
easy on your big screen, if you have a good surface for the keyboard
and mouse. To the brain there is no difference as the same samples
are being presented at the same level of detail.
>
>All in all I'm pretty happy here, and do still tend to believe that 576p
>can indeed match most current HD as a delivery format, even if I know we
>could theoretically do better.
>
>- Tom (who still expects to buy a 1080p display when it's priced right)
My 50 inch 1280 x 720 screen is also quite adequate as a computer
display, WHEN I can get a 1280 x 720 raster to the screen. My current
notebook cannot output this format, so the set resamples the 1024 x
768 output, which adds considerable blur from the resampling of the
non-Nyquist limited imagery.
1080@60P consumer displays are mostly an appeal to those who have
more money than sense.
Regards
Craig
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