[opendtv] Re: XDS and ATSC
- From: "John Shutt" <shuttj@xxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 22 May 2007 17:09:06 -0400
----- Original Message -----
From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
If not, get UTC from your already-corrected GPS clock, add the offset,
and use that higher time value and the offset for the PSIP time table. I
don't see anything tricky about any of this.
Actually, our PSIP generator takes in local time (as UTC -5 during DST), and
I believe it creates GPS time to transmit via ATSC, which along with the GPS
offset value results in UTC again in the receiver. A roundabout way of
doing business, and defeats the theoretical discontinuity when a leap second
occurs, because we have to manually enter in the offset value when and if it
changes again.
That's what had John so confused. He writes PSIP generators, so he had to
write the code to take local time (or UTC time) and derive GPS time for
transmission. Therefore his entire mindset has been what *he* had to do in
software to make things work properly, not what the ATSC requires to be
transmitted.
You're probably longing for DVB-SI, because they use UTC. I see it as
tomato and tomahto.
We have DVB already, for our satellite uplink, and for our PBS programming.
PBS has abandoned Digicipher II in favor of DVB-S for delivery of
programming to member stations.
I say Patatoe (with apologies to a former Vice-President.)
John
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