On 2/11/2012 1:35 AM, Vladimir Ivanov wrote:
yes, anywhere, including in the middle of a scan line. And because then
the color PLL is not locked you will get off colors for few lines until
it locks.
Actually in most cases the PLL locking on the color burst is exactly what
turns the color on.
The circuit is quite simple: a phase detector is fed with the burst and the
local oscillator shifted by 90 degrees. If there is no lock, the output will
change polarity and average to zero. After the oscillator locks, there is a a
full signal of one polarity whenever there is a burst present. This voltage
is filtered and becomes the color enable.