[opendtv] Re: XDS and ATSC
- From: "Kon Wilms" <kon@xxxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Mon, 21 May 2007 14:03:27 -0700
On 5/21/07, John Willkie <johnwillkie@xxxxxxxxxxxxx> wrote:
BTW, stattions get fined for not having accurate time in their STT. ATSC A/65
requires an accuracy within one second. I should also note that time of day
from the phone company is not an accurate time reference: it can be up to 10
seconds off, in my experience. I've checked hundreds, if not thousands of
times.
I remember back to iBlast days where every station in LA we tested had
bogus STT. The station blamed the manufacturer who blamed us,
eventually resulting in one of those 'see here, here is your packet,
and your time is always midnight' pie-in-the-face responses.
For datacasting clock sync between transmission and local PC time is
required so that a socket can be opened at the correct time to receive
content (depending on how the system works, usually the end PC is
offset from UTC and the clock modified by the receiver application). I
ended up writing an app that pulled NTP time from nist and converted
it to a multicast stream. So much for relying on STT. In fact we still
use such a system for datacasting since when you're jumping over
disparate networks it is easier to forward a PID or IP multicast
stream than it is to do time conversion all over the place. What a
joke that was...
BTW you are aware our multiplexer can restamp STT using an add-in GPS
module? Does that get me the $100? Maybe $50 for effort? (make check
payable to Steve Jones) :-)
Cheers
Kon
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