|
|
Posted by Roderick Stewart on 10/11/06 10:47
On Wed, 11 Oct 2006 03:48:36 +0300, "Jukka Aho" <jukka.aho@iki.fi>
wrote:
>> "Compatible" color is called that because it is built on the base of
>> the original black&white video image. If you know that
>> "white" is made of 11% blue and 30% red, you can calculate
>> the green as the remainder. Note that this is the proportion
>> for NTSC, dunno that PAL/SECAM are exactly the same?
>
>PAL uses YUV, NTSC uses YIQ, and SECAM uses YDbDr.
These are effectively different notation for the same things, i.e.
luminance and two colour-difference signals based on R-Y and B-Y.
The one minor qualification is that broadcast NTSC is supposed to be
encoded with a higher chrominance bandwidth along one encoding axis
which doesn't exactly align with either of the two colour-difference
axes, but I understand this is often ignored by TV receiver designers
and nobody notices. You can demodulate an NTSC signal in R-Y and B-Y
phases (instead of I and Q phases) and matrix the resultant signals
with Y to produce R G and B in exactly the same way as for PAL The R-Y
and B-Y signals from a SECAM decoder will be exactly the same too.
Signals are often transcoded between all three standards without any
change to the R-Y and B-Y derived signals other than to adjust their
amplitudes to conform to the appropriate standards.
Rod.
Navigation:
[Reply to this message]
|