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Discussion Starter · #1 ·
The ATSC Recommended Practice "PSIP Implementation Guidelines for Broadcasters" clearly states in section 5.1 that "The STT time should be checked daily and locked to house time."


Section 6.6, which expounds on the System Time Table, also states: "The System Time data is required to be no less accurate than plus or minus four seconds, but by locking it to the station master clock, the DTV receiver could be one of the most accurate timepieces in the household." An accompanying footnote also states the ATSC Implementation Subcommittee has recommended the tolerance be reduced to +/- 1 second.


Almost every TV station in the US synchronizes their studio facility master clock to their network (if they have one) or GPS. Sometimes they use both.


There is no reason for the PSIP generator to not be connected to a source of valid time.


ATSC standards can be found here:
http://www.atsc.org/standards.html
 

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Thank you for your post. There are some on this forum who seem to believe that the problem lies with the manufacturers of STBs, and not with the TV stations. These are the same people who demand absolutely flawless performance from their equipment, yet are willing to accept mediocre performance from those TV stations who have seen it fit to not comply with all of the ATSC standards. Granted, no one should expect absolute perfection from the broadcasters at this stage of the DTV transition, but adherence to MINIMUM standards (such as transmitting static PSIP data at all times and keeping the clock info accurate) would enable the STBs to do their job properly. A battery operated $20 clock tuned to the radio signals from the atomic clock in Colorado would do the trick as far as the time issue is concerned. Is that too much to ask?
 

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Would an email blitz by everyone, referencing the above standards, sent to their local stations be appropriate?


Comments.
 

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Discussion Starter · #5 ·
Quote:
Originally posted by spwace
Our $100,000+ encoder has no provision for locking the clock to an external reference.
Interesting. Can you tell us the brand and model of this encoder, or is that proprietary information?
 

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Quote:
Originally posted by FrankV
Interesting. Can you tell us the brand and model of this encoder, or is that proprietary information?
I would rather not name names, but ours is an early model. This oversight has probably been corrected in later models. Also, we rely on the static PSIP generated within the encoder, which provides the required data minus the program guides. When we upgrade to the full PSIP generator, soon, all of this data, including the clock, will be inserted downstream of the encoder.


We do check the clock from time to time, but it is fairly low on the priorty list. I have never found it to be off.


As mentioned in an earlier thread, the correct display of time does depend on the proper set up of the STB. The data we transmit is Universal Coordinated Time and will only be correct if the time zone and daylight savings time are properly configured in the STB.


I have also noticed PSIP clocks that are incorrectly set.
 

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Quote:
Originally posted by spwace
Our $100,000+ encoder has no provision for locking the clock to an external reference.
Like I said previously in another thread, the people responsible for our current DTV standards should've gotten a lot more input from the people in the real world.....the TV engineers and the viewing public.


Anyway, I've faxed notes to our local DTV stations advising them of the problems, and all but one have corrected their PSIP time data. The sole remaining station is having a meeting on the matter today to try to figure out how to ensure there are no future glitches. Everyone I've spoken to has been very courteous and even thankful for the feedback I gave them.
 

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Discussion Starter · #11 ·
Quote:
Originally posted by [email protected]
Our GI encoder operates via a PC running NT and has no provision for external time code input.
There are several different ways to keep computer system clocks, even systems running Windows, synchronized to external sources. We do it all the time.


As long as the GI software uses the system clock for the time, that should be sufficient. You might ask your GI rep....
 

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The PC's clock works well. We've had no complaints. GI no longer supports their early encoders. They are now supported by /\\/\\otorola.
 

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I have no idea what this is about, but for the really correct Eastern Standard time, look at:

http://tycho.usno.navy.mil/rc.html


Allow a couple of seconds for transmission time. It can be adjusted for other time zones.
 

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Discussion Starter · #16 ·
Quote:
Originally posted by kippjones
Wow, the clock on my Nextel was within 1 second. I am impressed.
Folks, the cell phone systems are synchronized to GPS. GPS time, in turn, is directly traceable to the U S Naval Observatory, the official source of both US civil time and military time, via the Alternate Master Clock co-located with the GPS Master Control Station at Falcon (Schriever) Air Force Base.


Companies like EndRun Technologies make receivers that can decode the time in cellular CDMA system and present it to a computer or network for synchronization.
 

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I called the local WTNH-8 and they had no idea what I was talking about. :rolleyes:
 

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Quote:
Originally posted by spwace
Our $100,000+ encoder has no provision for locking the clock to an external reference.
That's because you didn't buy the $101,500+ encoder. I knew FOX affiliates were cheap :D


Eric
 
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