[time-nuts] Time Signals on TV signals

[Lux, James P]

I think you're talking about the VITC, which is on lines 19  and 20 (so you
get it on both fields with interlacing).  VITC carries
hour/minute/second/frame (same as LTC), but I don't know if it's "program
time" (since start of program) or "real time).


There's a bunch of flavors of vertical interval time code, too.. Some put
different info on each line, and use up to 4 lines.  And don't forget the
complexities introduced by 3/2 pulldown.

As for what's actually broadcast (as opposed to put on a VTR or distributed
in the editing suite) that's a whole 'nother ballgame.

On 5/25/09 2:07 PM, "Glenn Little WB4UIV" <glennmaillist at bellsouth.net>
wrote:

> It appears that the time information is transmitted in line 21 of the
> analog TV signal.
> This is the same line that carries Close Captions in an analog signal.
> It further appears that PBS is the major carrier of these time signals.
> See :
> http://simson.net/ref/autoclock/Interface-June-01.pdf#search=%27PBS%20time%20s
> ignal%20auto%20VCR%20set%27
> 
> This may explain why you are having problems.
> 
> I do not know how this is handled in the DTV world.
> 
> We translate line 21 captions to CEA-608 and CEA-708 captions for out
> DTV transmissions.
> 
> See:
> http://ncamftp.wgbh.org/DTV/CEA%20test%20material/Iteration_1/It1.2ReadMe.pdf
> 
> This explains a little about the conversion of analog line 21 to DTV captions.
> 
> It is possible that you can set your recorder to read 608 captions?
> 
> Hope this helps.
> 
> 73
> Glenn
> WB4UIV
> CE WCIV TV
> 
> At 12:52 PM 5/25/2009, Bill Hawkins wrote:
>> Aficionados of accurate time,
>> 
>> I have two Panasonic DVD TV recorders, a DMR-EZ27 and 28. They were set to
>> automatically sync time to a TV station. This worked fine until a few months
>> ago. Now they are on manual time, but, of course, they drift.
>> 
>> Tried to turn automatic time setting back on this morning. The screen says,
>> "This may take a few minutes." It still said that 10 minutes later, as the
>> busy indicator continued to rotate through three spots.
>> 
>> Gave up on automatic and asked the only group I know that might know.
>> 
>> Why did TV stations stop broadcasting time signals? HDTV requirements?
>> 
>> Could a cable company interfere with the time signals?
>> 
>> Thanks,
>> Bill Hawkins
>> 
>> 
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