[mythtv] mythTV ... recording watching TV with VPS (germany) ...videotext

Erik Arendse erik_nospam.arendse at bigfoot.com
Thu Feb 12 06:18:14 EST 2004


At 11:17 12-2-2004, you wrote:
>I would love to have VPS/PDS support in myth. 

Don't forget one thing: VPS/PDS is only usable if you have the _original_ 
broadcast data of the program. The most important reason for VPS was 
recording programs even if they were moved, so the VPS code tranmitted 
tells when the program was supposed to start.

If you use Teletext in most European countries to look up the 
programschedule, usually the original program times are available as 
'hidden' information (shows with the '?' button).

It happens quite often this data is _very_ different (think very often 5-10 
minutes of, quite often 30 or worse in times when major sport events take 
place), as the PDS codes are assigned before they finalize their broadcast 
schedules.

If you don't get the PDS time 100% correct when using a PDS-enabled 
hardware VCR, the recording will _not_ be made.

Unfortunately all XMLTV like EPG data available on the internet does _not_ 
have the original program times. They only have the most recent times 
provided by the broadcaster. Even worse: due to tracing illegal use of 
program data quite a few provides change at random some program times a 
single minute. If the same 'errors' show up at another place they have a 
good argument in court... But even a 1-minute deviation is enough to spook 
a traditional (VCR-hardware) VPS implementation.

I guess with software you could use a few minutes slack for the PDS code to 
start the program. But then again: If a program has been replaced (say a 
movie you wanted at 21:00 is replaced by a tennis-match at 21:00) the 
original PDS time for the movie will be 21:00, but the tennis match will 
use PDS time 21:01 to indicate the original program has been dropped, even 
though it will be broadcast and publicised at 21:00...

And finally: to detect early starting programs you must have the tuner 
available... How could the scheduler handle that, say you are recording a 
low-priority show running until 21:00, and want to record a high-priority 
show from 21:00 onwards using PDS on a channel from another company. With 
only one tuner you can't receive the PDS code telling you the high-priority 
show runs early...

All in all there are so many disadvantages to PDS with grabbed EPG data, I 
stopped thinking about ever using it in a PVR.

Only Germany maybe has a source with PDS codes which can be grabbed: the 
analog nexTView guide. For other countries I don't know of any way to get 
them except scraping the individual teletext pages for each station. Which 
is a pain in the *** and only gives line programinfo for at most a few days 
ahead.

Erik






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