[opendtv] Re: Case for 720p60
- From: "Hunold, Ken" <KRH@xxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 20 Apr 2010 10:32:40 -0400
While ATSC may "support" only certain sampling structures, I'm sure you
know that the FCC specifically left out the ATSC format tables when they
adopted the ATSC standard. From what I read at the time, certain groups
within the industry thought that having (only) 18 formats would stifle
development and advancement of new formats. Program
producers/providers/distributors could use any sampling structure they
wish. It was always known that any new format might not be receivable
on all receivers, but it was assumed that the almighty marketplace would
ensure that popular sampling formats would be supported. Even so, just
to be safe, many TV manufacturers made sure that they supported at least
the ATSC's 18 formats. Some closed-system providers provided "non-ATSC"
formats, but always provided the receivers to go with them.
Maybe "everything we predicted has come to pass," but other things have
come to pass that were *not* predicted. The broadcast proponents of 720p
correctly "predicted" that future displays would be natively
progressive, but I don't think they thought that these displays would be
capable of 1920x1080 resolution. "Too many pixels," they said. Now we
have 1920x1080 display panels, so why not 60 (progressive) frames per
second on those? Limits of MPEG2 compression, we are told.
Interest has been low for 1080/60p, but now 3-D HDTV is all the rage.
Side-by-side distribution is the most predominant method of
distribution, but is 720p60 the best choice for it? Side-by-side cuts
the horizontal resolution in half, so is 640x720 really HD? Remember,
720x576 is commonly considered SD.
I'll avoid the temptation to further decimate the SD line count because
it is interlaced, because that's not the point. 3-D sports is a big
motivator here, and even 60 Hz is too slow for sports programs. A
blurry replay of a 60 Hz field or frame is *still* blurry, regardless of
how it is scanned. 90-100 Hz is more like it.
Regards,
Ken
-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx]
On Behalf Of Craig Birkmaier
Sent: Tuesday, April 20, 2010 7:37 AM
To: opendtv@xxxxxxxxxxxxx
Subject: [opendtv] Re: Case for 720p60
At 11:09 AM -0500 4/19/10, Manfredi, Albert E wrote:
>Craig Birkmaier wrote:
>
>> What is lacking here is any discussion of the fact that most folks
>> are still watching, and most stations are still broadcasting
>> interlaced SDTV...
>
>In ATSC-land, where there are no MPEG-2 MP at ML restrictions, in
>principle at least, broadcasters could begin to transmit SDTV as
>480p24 or 480p60. So why don't they?
The only 480p format that could be used is square pixel 640 x 480 with a
4:3 aspect ratio. The ATSC does not support 854 x 480p or 704/720x480p.
These formats are supported by MPEG-2 at various levels, but there is no
guarantee that all ATSC receivers will display them, so broadcasters do
not use them.
>
>One of the NBC4 subchannels is Universal Sports, now using 480i. It
>probably doesn't make sense to try using 480p24 for sports, so they
>would have to use 480p60. If it's true that MPEG-2 compression is so
>much more efficient in progressive mode, are the advocates of
>progressive saying that the US subchannel could be transmitted as
>480p60 over the same ~2.5 Mb/s channel now used for 480i?
Sure, but only using ATSC approved formats as described above.
Regards
Craig
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