Posted by Roderick Stewart on 10/11/06 12:56

On Wed, 11 Oct 2006 11:42:48 GMT, Jan Panteltje
<pNaonStpealmtje@yahoo.com> wrote:

>There are a few basic differences between UV and IQ, here it is described
>rather well:
> http://en.wikipedia.org/wiki/YIQ
>In NTSC the vectors are rotated 33 degrees.
>As for representation of where all the colors are relative to R-Y and B-Y see
>the 'vectorscope':
> ftp://panteltje.com/pub/vectorscope.gif.

Maybe I didn't explain very well, but the point I was trying to make
is that R-Y and B-Y are the same for all three systems, and colours
should appear in the same places on a vectorscope for all of them.
Although NTSC is officially *encoded* with different bandwidths along
a pair of axes at 33deg wrt the R-Y and B-Y axes, it is perfectly
possible to *decode* along any axes, including R-Y and B-Y, just as
for PAL (which doesn't use the different bandwidth trick).

Strictly speaking an NTSC decoder should have it's demodulator phases
aligned with the I and Q axes, and the resultant signals matrixed to
produce R-Y and B-Y, but it is quite common for the phases to be
aligned with the R-Y and B-Y axes. You don't get the advantage of
extra chroma bandwidth in one of the signals (can't remember which
one), but it works and most people can't tell the difference.

Rod.

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