[opendtv] Re: Redefining anamorphic
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 5 Mar 2008 10:27:50 -0500
At 9:29 AM -0500 3/5/08, John Shutt wrote:
Since both 1280x720p and 1920x1080 i or p video is always 16:9, it
is not standard industry practice to refer to it as "anamorphic."
The term "anamorphic" is reserved for those formats that have more
than one "native" aspect ratio, such as 720(704)x480.
Good explanation John, but one caveat.
Much of the HD content we see today is ALSO anamorphic, just not the
stuff that you broadcast using the ATSC standard. It is VERY common
to resample 1920 x 1080 to 1440 x 1080 or even 1280 x 1080. And it is
also common to resample 1280 x 720 to 960 x 720. This is all
supported by the MPEG-2 standard.
It really has nothing to do with anamorphic lenses anymore. It's just
an artifact of the reality that every fully conformant MPEG-2 decoder
can scale the samples back up to the full raster size for display.
The resampling reduces entropy and allows the source to be compressed
to a lower bit rate.
Regards
Craig
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