PAL TV Syncro generator, few problems occured

[System.out]

Hello,

I am thinking on building a syncro generator for PAL TV signal, when syncro is supressed. I want the circuit to generate syncro lines taking as a reference when color burst isn't detected, so taking the time from last color burst we can trigger the syncro for the first line. It also needs to filter or do something attending that syncro line could be inverted, so I would use a limitator to trim the signal generated.

For the circuit I was thinking on using a PLL to follow color burst.

TV Signal -----------> Adder (+) --------------> Trimmer
..........|.............................^.....................................................TV
......... -..............................|.........................................|_ > Signal
Syncro -----------> Syncro Generator
Detector

I hope that diagram comes clear.


Problems:

* Syncro Generator -------> ¿VCO, NCO, XTAL, memory table?
* Insert syncro generated ----->
1) No detection of color burst.
2) Follow the fileds.
3) Think about something else?
* I would work with a signal form TV, a base band signal form euroconector, would that cause any problem ?
* I need trimmer in case syncro was partialy supressed to no saturate the signal.

What do you think? Any recomendation ? Any chip ?

Thanks :roll: 8)

 

[Wizzard]

Sounds to me like you are trying to recreate sync signals on an encoded signal like on an SSAVI system or something like that

If that is the case most of these systems have fake color burst to prevent you from being successful

It is simpler for you to synchronize on the front porch of the regular sync even if it is suppressed because the flank of the line sync is still there just measure it with a comparator and ignore any signal that is not correct in time
for example in a PAL system you will have sync pulses on the 21st first line of the frame after that they are suppressed so make a "windows from 63 to 65 us that toy accept a new sync pulse and you will find it even if it is suppressed

/Wizzard

 

[System.out]

.

I guess what I want to do is that a syncro system for SSAVI, but only with educational purposes. As you said sometimes it comes a fake burst, so I am thinking on how to avoid that. So, do you think I should syncronized taking as a reference 'front porch' ? I'll think about it. But what's wrong if I detect color burst, and when I dont detect it for a while I would know that I am crossing the field, so I can calculate when to star triggering sync.

Many thanks !