Re: 3D Anaglyphic Movies Online

[P3D Greg Marshall <greg.marshall@xxxxxxxxxxxxxxx>]

P3D Andrew Woods writes:

>To my understanding it isn't possible to make an MPEG or Quicktime
>movie which would be compatible with field sequential (Liquid Crystal)
>glasses.

>The problem relates to the fact that a left and right image stream
>must be reproduced separately and distinctly and not be mixed.
>For LC glasses, this would involve either (1) interlacing the image stream
>(i.e. odd and even lines in the image are from the left and right
>image) or (2) using alternate images as left and right image.

>MPEG and Quicktime would probably be too slow for (2) to work successfully.

>With regards to method (1) the nature of the compression used in MPEG and 
>Quicktime would mean that alternate lines would be somewhat mishmashed 
>together therefore left and right images would be mixed (separation
>would be lost).

The obvious way to make a stereo MPEG sequence for LC goggles would be
the 
same way it's done in video, assigning left and right views to alternate
fields (half
of an interlaced frame).  There are two reasons this doesn't work well:
(1) MPEG
compression relies on the uniformity of the image (yes, even within one
frame), so
image quality and/or compression ratio would suffer.  (2) The field
sequence would
have to play back flawlessly to avoid *very annoying* glitches in the
stereo effect.
Few, if any, systems can play an MPEG sequence without occasionally
missing
a frame.  These problems are (technically) easy to solve, but would
require some
changes to fairly well established standards.

Greg Marshall


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