[mythtv] NTP config

[Steve Adeff]

On Thursday 20 October 2005 11:38, Rudy Zijlstra wrote:
> Steve Adeff wrote:
> >On Thursday 20 October 2005 11:03, Rudy Zijlstra wrote:
> >>Daniel Kristjansson wrote:
> >>>On Thu, 2005-10-20 at 09:57 -0400, Steve Adeff wrote:
> >>>>On Thursday 20 October 2005 09:25, Ivor Hewitt wrote:
> >>>>>Daniel Kristjansson wrote:
> >>>>>>DVB/ATSC time can never be as accurate as ntpd time because the
> >>>>>>transmission, buffering, and capture delays can not be measured.
> >>>>>>But it should always be within a few seconds of the correct time,
> >>>>>>so it is more than good enough for a MythTV backend.
> >>>>>
> >>>>>Actually you might say for mythbackend purposes it might be more
> >>>>>accurate, since it's the current time that should match the start
> >>>>> times of programs accurately.... even if it is delayed slightly.
> >>>>
> >>>>is this why so many shows don't start "on time"? If the TV stations
> >>>>follow their own time code then it would make more sense for
> >>>> mythbackend to run on this time. I guess the only issue is if two
> >>>> stations are running on their own, differing time...?
> >>>
> >>>In the US companies using the public airwaves are supposed to use GPS
> >>>to set their clocks, so a program should always start a little late,
> >>>and never early. This regulation doesn't apply to cable, and I don't
> >>>know what the laws are in DVB countries. But this is what pre-roll
> >>>and post-roll are for. If you add 5 seconds on each end you should get
> >>>the entirety of any program when you don't have a recording scheduled
> >>>before or after the program, at that point MythTV ignores the pre-roll
> >>>and post-roll settings on the assumption that you would rather get the
> >>>other program than apply this extra safety buffer.
> >>>
> >>>There is some controversy over whether MythTV should have a pre-roll
> >>>and post-roll which is never ignored. But this is mostly due to
> >>>channels in Australia which don't adhere to their published schedule
> >>>and air programs up to 20 minutes later than scheduled. This would
> >>>be illegal in the other countries unless they transmitted updated
> >>>EIT data or the government activated some sort of emergency broadcast
> >>>override, say in the case of global thermonuclear war.
> >>>
> >>>-- Daniel
> >>
> >>In the Netherlands, Belgium, France, Germany - those i am certain of -
> >>programs can start more than 20 minutes later than announced. Not on all
> >>channels, some are worse than others, yet most channels are "late" by
> >>23:00 or later. Which is why i am using a hard "end-late" setting on all
> >>recordings, and enough tuners so that recordings do not need to be
> >>back-to-back on the same tuner.
> >>
> >>It does not matter whether the broadcast is analog or digital (DVB), the
> >>behaviour is the same. And EIT-schedule, even EIT-next/now is not always
> >>modified....
> >>
> >>Cheers,
> >>
> >>Rudy
> >
> >wow, thats so weird. why do they do this?
>
> optimistic sheduling? Ask the broadcasters, we simply have to put up
> with it. Its not the cable operators, its really the broadcasters that
> cause this.
>
> Regards,
>
> Rudy

Right, but why would they? Do they sell ads by physical time and not by the 
show they will be playing in? I know in the u.S. if shows did this even less 
people would watch, causing advertising revenue to go down, sharply affecting 
the $$ a broadcaster would get for an ad spot on a show.

Steve