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Difference between i and p

post #1 of 3
8/26/08 at 11:22pm
Thread Starter 
I just purchased a BR player and want to get this title:

Return to Balance by Sterling Johnson and Ron Kauk - Blu-ray HD - 7156020

1.) Just curious what it means by 1080i High Definition rather than 1080p?
I know this means it is interlaced, though how much of a difference would it be if it was p?

2.) Is this not a good BR disc to use as an example of what it is capable of?

Thanks.
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post #2 of 3
8/27/08 at 5:32am

Re: Difference between i and p

i means interlaced and [i]p[/] means progressive. TV displays (especially the CRT variety) all used to scan every other line on each pass—the next scan was for other set of lines. The phosphors on the screen (they remained illuminated) and your eye translated this to your brain so that you saw moving pictures. This type of display is called interlaced.

Progressive scan displays refresh every line on the display on every scan.

So to begin, if your display is a 720p or a 1080i display, you won’t benefit from a 1080p encoded disk. Chances are you won’t be able to tell the difference between 1080p and 1080i. Even if you can, a 1080i disk will look spectacular.

I know nothing about that particular disk, so I can’t comment.
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post #3 of 3
8/28/08 at 6:51am

Re: Difference between i and p

Blue Ray disks contain enough material to make:
1. 60 half pictures (fields) per second as 1080i, or
2. 30 (24 for film source) frames per second as 1080p

Most DVD's come only one way, namely say if it is 1080i, you have no choice in the matter.

The video is typically output from the player as 1080i at 60 fields per second or as 1080p at 24 frames per second regardless of "disk encoding format". Non film source encoded at 1080i comes out better if you do not select 24 fps (one of the 1080p output choices). Other choices for output such as 480p@60 and sometimes 1080p@60 are available too with the player doing conversions.

Most TV's display only one format, usually 720p or 1080p at 60 frames per second. They'll all accept almost all of the traditional video formats including 480i but will convert the video signal as needed.

HDTV CRT sets usually display 1080i only or 1080i/480p and sometimes do not accept 720p. They may have a switch setting that juxtaposes/staggers the alternate fields producing 540p/960i respectively. The change is optical only and does not depend on whether the incoming video was i or p.

Video hints: Video Technicalia Made Easy
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