[opendtv] Re: XDS and ATSC
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Mon, 21 May 2007 12:52:41 -0400
John Shutt wrote:
> If a station is blasé about their PSIP time, call the station and
> tell them about it.
Well, sure, except that I'd essentially have to call all of them. The 10 minute
example was just the worst one. In other cases, it seemed like 4-5 minutes, or
more, was common. But perhaps I'm being unfair, because I have not checked
lately. (You only get so many opportunities to screw up my recordings.)
> The thing that drives me nuts is the ATSC standard regarding PSIP
> time is flawed.
>
> The ATSC standard expects stations to broadcast GPS time, and
> broadcast a GPS offset to UTC time.
They have a reason for that. It's that GPS time is continuous, whereas UTC is
not. UTC has these periodic leap-second corrections, to account for the slowing
down of the earth's rotational speed. So if the ATSC box has to program for
future events, and UTC were used, that box would have to anticipate the
discontinuities. (Seems a bit obsessive, IMO, but it does make some sense.)
There's a discussion in A/69 Annex E.
> Some stations simply broadcast UTC with an offset value of zero,
That sounds like a great pragmatic approach to me.
Bert
----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:
- Using the UNSUBSCRIBE command in your user configuration settings at
FreeLists.org
- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
unsubscribe in the subject line.
Other related posts:
