[opendtv] Re: Receiver costs too expensive in the Brazilian DTV system:
- From: "Albert Manfredi" <bert22306@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Mon, 10 Sep 2007 21:04:25 -0400
Cliff wrote:
I've seen macroblocking and mosquito noise on every digital cable
channel, DirecTV and Dish as well as OTA, digital tape and DVDs.
No system is immune to the unadvertised and whispered problems
of digitized television images. If it were just an ATSC problem why
are the artifiacts visible in all digital sources, no matter how they
get to my TV?
Certainly, a problem with digital compression would not appear *only* in
ATSC.
So just for grins, I just now conducted a close inspection of the WETA-DT
multiplex, which is the most densely populated that I receive so far. One HD
and three SD channels. I was standing no more than 2' from the 26" screen.
Sure enough, compared with stations that only transmit HD and one SD, like
WUSA-DT for instance, which is CBS 9 and therefore also 1080i, the WETA HD
was not quite as sharp.
Then I carefully inspected scenes during quick cuts and during fades, with
fast motion in most of the scene or with fast motion in only small parts of
the scene.
The cuts seemed artifact-free to me, completely.
They showed a closeup of the legs of many individuals on treadmills, filling
the screen. From that close viewing distance, yes, I could see macroblocking
on the legs as they moved quickly back and forth. But that was the only time
I noticed anything that obvious, and I'm sure it would have been less
obvious from a normal viewing distance.
In one fade, a man's head came on while it was moving to one side. I got an
instantaneous macroblocking event, and then it was fine.
Okay, I wasn't watching football, but what I saw, to me, was very
acceptable. And no comparison at all with NTSC. And remember, I was right up
close to the screen.
The SD channels were probably well pre-filtered, because they seemed to lack
any obvious artifacts. And from up close, they were certainly not as sharp
as the HD channel, but again, no comparison at all with NTSC, which is
essentially unwatchable that close up.
It's not about better quality images, its ALL about more channels
in less bandwidth to make more money. That's all it is about.
I think it is about both. People are demanding and will continue to demand
better quality simply because they are buying plasmas and LCDs in droves, in
sizes far bigger than their old CRTs. And I, for one, welcome the greater
choice as well.
My conclusion is that with MPEG-2, while more perfect 1080i might require an
average 16 Mb/s, this is by no means a hard number. I'm not saying that a
comparison with H.264 would show no difference. I'm simply saying that these
are soft numbers. Yeah, if we try squeezing that down to less than 1.5 or so
Mb/s, MPEG-2 will fall apart completely, and H.264 will not. But those
images would not be so great on most TV-size screens anyway.
Bert
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