[mythtv] NTP config

[Rudy Zijlstra]

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