[opendtv] Re: Redefining anamorphic
- From: Ron Economos <w6rz@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Fri, 07 Mar 2008 13:00:56 -0800
DVD is not a good example. DVD only allows 720x480, 704x480 and 352x480 for
NTSC and 720x576, 704x576 and 352x576 for PAL. It's more limited than ATSC.
A better example would be cable, satellite or the now defunct HD DVD where
all the "standard" sub-sampled horizontal resolutions are allowed and at
least for
cable and satellite, in use.
Vertical resolutions that don't match the uncompressed input/output
format are
a non-starter. Too difficult to scale in a *commodity* decoder
(especially for interlace).
Same is true for oddball horizontal resolutions, since the polyphase
up/sub-sampling
filters are not that extravagant.
So just specifying MP@ML and MP@HL doesn't get you unlimited resolutions
in the real world of hardware encoders and decoders.
Ron
Craig Birkmaier wrote:
At 9:09 AM -0800 3/7/08, John Willkie wrote:
Funny that after criticizing the 'table 3" format restrictions, you
are now
advocating a new one. That is a very bad idea.
Let's just call it a "recommended practice."
If broadcasters had stuck to the deal they struck with CICATS to drop
Table 3 , which the FCC endorsed, AND we had simply said decoders must
conform to the MPEG-2 levels and Profiles that are specified in the
ATSC standard, NONE of this would matter. A broadcaster could deliver
1024 x 576, 640 x 360, 1440 x 1080, etc. It simply would not matter
because the decoder could handle it and it would be scaled to fill at
least one dimension of the screen, as is the case today with movies on
DVD, which use more or less vertical lines to support ALL aspect ratios.
None of this matters anymore, outside of the world of the TV in the
family room. We just encode the source as faithfully as possible.
There is no "format" for video distributed via the Internet. You can
optimize any way you want, and EXPECT that the browsers and media
players will do the right thing. Then again, people work with multiple
windows on a computer, so not using the entire display for video is
also an accepted part of the experience (although most media players
can fill the screen in several ways, just like a TV.
Regards
Craig
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