[opendtv] Re: Definition of Anamorphic
- From: Kilroy Hughes <Kilroy.Hughes@xxxxxxxxxxxxx>
- To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
- Date: Fri, 9 Oct 2009 20:13:31 +0000
Yep, and specs weren't clear whether 720, 708, or 704 were the 4:3 width, and
whether that corresponded to 486, 483, or 480 lines. Production Aperture,
Display Aperture weren't accurate enough to matter in an analog world where 3 -
5% of your picture was cropped off in the CRT and there was no hope of a D1
sample lining up with a hole in a shadow mask.
Now we have to encode in blocks of a fixed size and want the sample grid to
align with the pixel grid in the display exactly, whenever possible. Scaling
704 to fill a 720w display, or 480 to 486 lines is unnecessarily ugly, but
common. Most TV inputs will even scale up 1280x720 input a few percent just so
they can throw away the edges.
Insane ritual homage to the CRT.
Kilroy
-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] On
Behalf Of Mark Schubin
Sent: Wednesday, October 07, 2009 12:33 PM
To: opendtv@xxxxxxxxxxxxx
Subject: [opendtv] Re: Definition of Anamorphic
Kilroy Hughes wrote:
> Just to complicate things ...
> Everyone is using "720" as the width, but the display width and 4:3/16:9
> display aperture is actually supposed to be 704 (implying a Sample Aspect
> Ratio in an MPEG codec too dumb to specify it as 11/10 H/W, 1.10), and it can
> be encoded at 704 or 720.
No question that it's 704 in ATSC (and probably some other systems), but there
are also 720, 708, and other values.
TTFN,
Mark
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