P3D Re: Anaglyph 3-D Video

[Greg Kintz <gkintz@xxxxxxxx>]

"JMarc" <desvalsjm@xxxxxx> wrote:
> Hi 3DMens,
>
> Sorry if what i ask sounds stupid :
> Is there any specific problem known about converting
> anaglyphs pictures from computer-graphic-files to Videotape?
> We tried to make a kind of '3Dslide show' on TV screen using
> anaglyph method, it was a disaster...Horrible ghosting effect,
> unbelievable flickering on the screen, ... however, the same
> files view on computer screen were good.


Anaglyph 3-D video is a *very* fragile format, and can easily
be degraded by a number of factors. Using the United States
NTSC format, (w/Europe's PAL format being slightly different)
video starts out as pure red green and blue signals (RGB). These
signals are most often converted from their component form (RGB)
into a joined "composite" video signal. Composite video alone
degrades the original color bandwidth quite a bit and is used for
broadcast television, 12" laserdiscs, and VHS. However DVD
and DSS store video in a component form, so if the original source
material was kept component throughout the transfer and the
consumer uses an S-Video or component connector, a component
anaglyph 3-D video will have better cancellation over a composite
anaglyph 3-D sourced one. Another problem with composite video
is the NTSC color decoders found in consumer sets. TV manufactures
can "tweak" the decoding matrix to favor certain colors, and of
course many do. The VHS format adds further degradation to the
color by reducing the color bandwidth (again) and recording it at
a much lower frequency than found in a standard composite signal.

One other small part of the VHS format worth mentioning is
that the color and black and white information are separated
for recording, then combined for playback. When the S-VHS
format was introduced, JVC engineers recognized that if the
color and B&W information weren't separated and combined
so many times, a better copy would be the result. So if you have
access to a S-VHS VCR and if your PC has a Y/C S-Video
output, try using that method to record your computer images
over to video. The VHS/S-VHS format will still degrade the
color resolution, but at least it will never have been mixed with
the black & white information. (A S-video equipped monitor
will also be needed for best results as well.)

I think the PAL systems often use a SCART connection.
..Does anyone know if this carries siginals in a Y/C S-video
or component video form?

> How to calibrate colors in this way?

Of course the proper red and blue (or cyan) colors must
be picked for maximum cancellation.

> We used files build with WONDERFUL's Dave 3Dsif software,
> PAL format (768x576), tga graph files, Red-eye choice.

Again the PAL format is slightly different than NTSC, but not
much. One benefit of PAL is that there is no chance (in theory)
of color drift, which is why almost none of the PAL sets have a
"Tint" or "Hue" control.

As we slowly move towards component digital video, many of
these problems will (hopefully) go away. But of course there will
always be limitations. How good are the monitors phosphors?
Can color anaglyph be perfected? Will we keep the "tint' control?

> Any help appreciated, especially in french =)
>
> Amicalement a tous.
> JMarc

 I hoped this helped!

   -Greg Kintz-

PS: Dan Symmes of "D3" may already be working on
component anaglyph content for the new digital formats.
His website makes mention of a new anaglyph format
called "DIGITAL NATURAL VISION 3DĘ."  And to
quote his web page "With advances in video technology,
Symmes was able to get past the limitations of composite
video."   http://www.3dcompany.com/3dtvintro.html



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