[opendtv] 1080i vrs 720P
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: OpenDTV Mail List <opendtv@xxxxxxxxxxxxx>
- Date: Wed, 28 Sep 2005 10:39:27 -0400
Last Saturday we had a surprise party for my Father-in--Law, who was
celebrating his 80th birthday. The part took place while Florida was
playing Kentucky - the game was in HD on CBS.
The room was filled with Florida fans, and I was forced to sit in a
chair about three feet from the 50" screen, to the side. At normal
viewing distances the pictures looked very good. I think CBS has
improved their production processes, and their HD sports no longer
look like a compromise between the SD and HD audience. But at three
feet, i was amazed at how bad the pictures looked.
Since my display is 720P, I expected so artifacts from the
inter-format conversion from the 1080i source. But I was amazed at
how pronounced the interlace artifacts were at this distance. The
small area twitter was quite pronounced, and I would often see
tearing and hash in graphics. But this was not as bad as the
compression artifacts.
There were three major types of video that fell apart into visible
blocking artifacts:
1. Anything with a dissolve in and out of replays with DVE zoom
effects would fall apart. And any other dissolve would fall apart.
2. Any close-ups with players moving through the field of view would
fall apart. This was especially noticeable on tight close-ups, even
if slightly out of focus.
3. Many graphics would fall apart, especially when they were being
flown in and out.
What was most annoying was the huge differences in quality; sometime
the pictures would be sharp, and at other times they would just fall
apart.
Just now I pulled up a game from ESPN-HD that was recorded on the
PVR. The game was the FSU Boston College game of two weeks ago. An
interesting side story with this one. The game was supposed to be in
HD, but "due to technical difficulties" the first half was presented
in 4:3. What was interesting is that it looked like 4:3 HDTV. They
managed to get things working during half-time and the second half
was in 16:9 at 720P - the images were not sharper, they just filled
the screen.
So I sat in the same chair at the same distance and watched some of
the game in 720P. The difference was remarkable. First, there were no
interlace artifacts. Second, the pictures rarely if ever showed
blocking artifacts. What did happen was the SNR would spike up during
more difficult scenes - the picture would become a bit noisy, but did
not break up. All of the problems I had seen with the CBS 1080i feed
were MUCH less pronounced with the 720P feed.
This is the first time I have had the luxury to compare formats on my
HD display, thanks to the PVR. It was quite revealing. Now if our
local ABC affiliate would get their DTV station on the air...
Regards
Craig
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