[LEAPSECS] TV frame-rate in 60Hz countries

[Peter Vince]

On 18 January 2014 23:11, Stephen Scott <stephenscott at videotron.ca> wrote:


> Is there any attempt to maintain the PAL 8-field sequence when aligning

> the timestamps with clock time?

>

> Yes. The specification defines which seconds start with a "field 1",

however, the time code signal must also be accurately phased to the TV
field sync timing (so you can unambiguously identify each frame).  So when
resetting the time code generator ("jamming" or "jam-locking"), the
generator only sets itself within plus of minus 2 frames of the time
reference, so that its output is correctly phased to the sync pulses, and
as close as possible to the time reference.  Historically the TV sync-pulse
generator had an accurate frequency reference, but its timing was
completely random with respect to UTC.  I'm not sure if that is still the
case - modern generators that have a GPS receiver built in could well phase
themselves, but we don't have of those :-(

     Peter
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