[opendtv] Re: Popular screen aspect ratios

  • From: "John Shutt" <shuttj@xxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Mon, 3 Jan 2011 07:34:54 -0500

Both Blu-Ray players, Cliff's 350 and his friend's 370, have a "Pan and Scan" mode that would have zoomed the image to fill the screen of a 4:3 display while throwing away some image area to the left and right of the displayed information. In Cliff's particular case, that image area would just be the black pillar box information.


However, DVD and Blu-Ray authors can override the selection of Pan and Scan in the player, and force the letterbox mode. This is what is happening to Cliff's Blu-Ray discs.

There is no fault other than stupidity on the part of the Blu-Ray disc authors.

John


----- Original Message ----- From: "Albert Manfredi" <albert.e.manfredi@xxxxxxxxxx>
To: <opendtv@xxxxxxxxxxxxx>
Sent: Monday, January 03, 2011 2:40 AM
Subject: [opendtv] Re: Popular screen aspect ratios



Cliff Benham wrote:

Hi John,

I got a friend to drag his BD-S370 over and we tried 3 different 1.33:1
films on Blu-Ray with a 4:3 display.

No success in making any of the films fill a 4:3 screen.

I believe this is because the 4:3 image on the disk is set into a 16:9
frame.

When played on the 4:3 screen in 'pan and scan' mode the image is 1:1
with black bars on all sides.

When played on a 4:3 screen in 'letter box' mode the image is a postage
stamp size 4:3 again with black bars on all sides.

It is apparently impossible to play a 1.33:1 film on Blu-Ray with the
correct full screen 4:3 aspect ratio on a 4:3 screen.

See the two attachments demonstrating the problem.

Cliff, here's my take on your JPEG shots.

The first shot you attached is actually the correct one, as far as I can tell. No distortion. I think that's what you describe as "letterbox mode." Letterbox mode must assume the display is 4:3, otherwise why would anyone need to letterbox? It does exactly what Ron described yesterday.

(Out of curiosity, what does this mode look like on a 16:9 display? My guess, it looks horizontally stretched.)

Problem seems to be, your display does not have the necessary zoom mode. The 16:9 frame is letterboxed to fit as it should in a 4:3 display, when viewing widescreen HD letterboxed, and the pillarboxing was always in the image as recorded on the disc. A zoom feature would fill the frame, just like when you zoom a 16:9 set into a postage stamped 16:9 SD frame.

The second frame is the image as it should be sent to a 16:9 display, but it's compressed horizontally because you're sending it to a 4:3 screen without tewlling the decoder. This is what I was describing. I don't see but the slightest amount of black bars top and bottom, just as I would have expected. The thin bars may be the academy ratio thing.

Remember the ATSC STBs? They had no trouble with any of this. In our two STBs, HD shows sent to 4:3 displays seemed always to be set by default to fill the 4:3 frame, so I suppose they had to be full screen height pan and scan. Letterboxing was an option. SD 4:3 shows had no problem either, and they filled the screen undistorted.

My take is, the BluRay players must assume that you would use letterbox mode when sending to any 4:3 display, and that modern 4:3 display can zoom into postage stamp images, just like modern 16:9 displays can? Instead, ATSC STBs were meant to be usable with older 4:3 sets that cannot zoom?

Would be real interesting to see what happens in these two modes, when connected to a 16:9 display.

Bert


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