[Tig] Combined measurement of Luminance plus Chrominance
Wed Oct 23 20:43:30 BST 2002
Thanks to Dave and Bill for the technical reasons for limiting p/p
luminance plus chrominance. Again thanks to Bill for debunking "vector
chroma" as some standard to evaluate chroma levels. I would like to
add that in the DC area facilities, combined levels are kept to 110 IRE
(770mv) for most broadcasters with a strict 100 IRE (700mv) for
luminance. PBS technically accepts 120 IRE but prefers a lower figure.
For DTV delivery the norm is to monitor transcoded YBR to RGB and keep
a strict 0 to 100 IRE levels. It doesn't work for dual delivery
(analog/ DTV) so we use a "legalizer", for both RGB and encoded video
to control excessive chroma. Most of the rest of the world wants the
combined levels kept to 770mv.
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