P3D Re: standards conversion of field-sequential 3D video

[Andrew Woods <andrew@xxxxxxxxxxxxxxxxxxxxx>]

Alexander Klein <klein@xxxxxxxxxxxxxxxxx> wrote:
> FWIW: I'm using a Toshiba 3D-camcorder which records the images in NTSC 
> format. Here in Germany, we use PAL as TV-standard, and I am using a 
> Panasonic VCR to playback the NTSC tape on my very old (>15 years) TV-set. 

Your VCR probably has a label on it which says "NTSC playback on PAL TV".
Such VCRs only partially convert the NTSC signal to PAL - in fact it is
converted to 60Hz-PAL.

NTSC and PAL differ in three respects: 
  colour carrier frequency (3.58Mhz vs. 4.43Mhz), 
  number of lines per frame (525 vs. 625), and
  number of fields per second (60Hz vs. 50Hz).

Converting the colour frequency is simply & cheaply done with linear 
analog electronics.  Converting line and field rate must be done
digitally at considerably more expense.

Consumer VCRs which state "NTSC playback on a PAL TV" are only 
converting the colour carrier frequency therefore producing 60Hz PAL.
This relies on your TV being able accept the 60Hz field rate 
(as opposed to the 50Hz rate it is used to).  Some TVs don't like
this and won't display a stable picture (like my home TV).

> Works fine, although (obviously) more flicker is noticeable due to 50 Hz 
> used in Germany vs. 60 Hz in the USA.

As explained above, you'll probably find that the display is at 60Hz
for your Toshiba tapes.  Try playing a 50Hz tape to see whether you
can detect the difference.

> I have, however, not tried to record the image on a PAL VCR and play it 
> back from there...

You'll find that it won't work since a PAL standard VCR will only accept
50Hz PAL.  A PAL VCR is very finely tuned to the 50Hz field rate
and won't accept 60Hz-PAL.

This is probably explained a bit more clearly in my paper:
  http://info.curtin.edu.au/~iwoodsa/spie96/spie96pa.html

Cheers,
Andrew Woods.         http://info.curtin.edu.au/~iwoodsa


------------------------------