Sync restoration (how) ?
Ken Parkyn email (remove spam text)
>> I have a composite video signal (PAL) with *no* sync pulses at all.
>>I would like to build a simple circuit to put the sync back (a sync
>>restorer). Ideally, vertical & horizonal phase (and frequency -- slight
>>changes) would be adjustable.
>Although there're a variety of timebase chips that would do this cheaply,
>still going to need a reference to lock on to... eg you can't just re-insert
>syncs from a free running timebase - (you could try locking to colour
>and dividing down - but it's not too easy in PAL..
If the colour burst (or even a remnant of it) is present, it should be
possible to detect this & then at least generate sync pulses for the
following lines, meaning you'd miss one line sync. Once this has been locked
on to, you'd then need to look for a missing pulse at the vertical interval
and derive the vertical serration sequence. around line 8 or 9 the colour
burst starts again. This again could be detected and your insertion sequence
initiated. (Perhaps this is where the missing line could be tolerated, as
it's already in the vertical area.)
The lion and the calf shall lie down together, but the calf won't get much
See also: www.piclist.com/techref/index.htm?key=sync+restoration
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