🚀 go-pugleaf

In article <1992Nov17.161717.2694@acri.fr>, pjhicks@hard03.acri.fr (Peter J. Hicks) writes:
|>  Is there anybody out there that knows how to transcode Secam to Pal ?
|>  
|>  Are there chips available that do this function or is it a matter of building a mass of logic 
|> 
|>  if  so,  hows about a circuit diagram.
|> 
|>   Final question  What is the difference between  Secam and Pal ?
|> 

NTSC	Never Twice the Same Colour
SECAM	Something Essentially Contrary to the American Method
PAL	Practical Alternative to the Losers

But seriously:

The PAL system attempts to overcome the limitations of NTSC colour phase shift by
reversing the phase of the colour subcarrier signal on successive lines. So any
phase distortion tends to average out: one line might be a little too red, while
the next, a little too green. The eye is nowhere near as sensitive to colour
perturbations as it is to brightness, so the whole thing works. PAL also uses
(R-Y) and (B-Y) colour difference signals, rather than the more complex I and Q
chrominance signals of NTSC.

SECAM transmits one colour difference signal during one scan line, and the other
during the succeeding line. The receiver must delay the first difference signal
by one line period, so as to have both available for processing. So, in total,
only half the colour information of the other two systems is available. Hence the
name behind the acronym: syste`m e'lectronique couleur avec me'moire.

Provided you are referring to conversion between two systems with identical line
rates, there is no particular reason why you should not be able to generate PAL
from SECAM, given the caveat of only having half the colour information of a
regular PAL signal. In fact, Philips/Signetics have done it for you in their
TDA3592A SECAM/PAL transcoder chip.

JohnH

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