[opendtv] Re: Popular screen aspect ratios

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
  • Date: Fri, 7 Jan 2011 19:36:52 -0600

Cliff Benham wrote:

> Attached are two screen shots of a 16:9 TV displaying the MGM Logo
> from a Blu-Ray disk of a 4:3 film.
>
> When the BD Player's DVD aspect ratio is set to 'Letterbox' the 4:3
> film frame is expanded [distorted] horizontally and is letterboxed
> on the 16:9 TV screen 'postage stamp' sized surrounded on all four
> sides by black bars.

This is exactly what I had suspected. By setting the BD player to "letterbox," 
you are implicitly telling it, "this STB is connected to a 4:3 display." So, 
the decoder letterboxes the pillarboxed image (where the pillars are actually 
part of the image itself).

When you instead connect the STB to the 16:9 display, as you just did, the 
image becomes horizontally stretched. It was intended for a 4:3 display, and 
now each horizontal scanning line is stretched out (in the same amount of time 
it took to scan the 4:3 display), to fill the width of the 16:9 display. Ergo, 
stretch.

> When the BD Player's DVD aspect ratio is set to 'Pan and Scan' the
> 4:3 film frame is displayed Pillar boxed on the 16:9 screen.

And in your previous shot, this looked compressed horizontally.

Under normal, correct circumstances, when sending a 16:9 or a 4:3 image to a 
16:9 display, "pan and scan" should be irrelevant. There's no reason for the 
decoder to do such processing, no matter what, if the display is 16:9. So 
something doesn't jive.

The picture you posted is basically a normal wide screen TV rendition of the 
4:3 image. John Shutt suspected that this was happening because the disc was 
not encoded to permit pan and scan, so it simply sends out the 16:9 pillarboxed 
image as a 16:9 frame.

Perhaps, when a disc does not permit pan and scan, the STB simply transmits the 
entire image.

Bert
 
 
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