[mythtv] NTP config

Steve Adeff adeffs at gmail.com
Thu Oct 20 15:27:37 UTC 2005

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?

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