Digital Markers in broadcasts?

[time_lord]

Hi, just a general question...
I was wondering if there are any digital markers in a broadcast (DVB-T) that relate to the program currently playing.
I could guess that there aren't, at least during ad breaks in the show, because then people could easily use these for cutting out ads. It seems this is why comskip goes to such lengths to try to remove ads (why it's such a tricky thing to do well).
What about markers at the very start and end of the program? Are these available so that we can get clean starting and ending points, or again are there no markers so that the leading and trailing ads are hard to distinguish from the main program?
If there are no markers (in this high-tech digital age ) what has gone on here - do broadcasters 'homogenise' the stream so that it's continuous? So there are no variations in the type of stream that is being broadcast? I would have thought normally there there would have been a variation in encoded materials. (Ignoring the fact that the broadcast has to be in format(s) everyone understands.)

Just curious (and interested in the content of the streams)...

[sub]

The stream contains info like the currently playing show etc, but this is still marked as the current show even when the adverts are playing. Its also seems this info is from the programming schedule (at least here in NZ), not what is really being played, so it can be out a little at the beginning and end of a show.

I dont think they'd want to clearly identify adverts in the stream, for obvious reasons.

[time_lord]

The stream contains info like the currently playing show etc, but this is still marked as the current show even when the adverts are playing. Its also seems this info is from the programming schedule (at least here in NZ), not what is really being played, so it can be out a little at the beginning and end of a show.

There are markers but they aren't reliable... bugger!

I dont think they'd want to clearly identify adverts in the stream, for obvious reasons.

Exactly.

Other than trimming unwanted fat of the ends of a recording, I was initially concerned over what happens if my computer clock is out by a few minutes (not that it should be ordinarily)... I'll miss bits of a recording. Just as likely that a broadcaster isn't running on time (but that's also pretty rare these days!).

The other reason to only record what is absolutely necessary: I do have the 1 minute pre-padding and 2 mins post-padding set for recordings. But what does gbpvr do (I have not tried this yet) if both my tuners are busy until 19:00 (which with the padding becomes 19:02) and I have another channel I want to record at 19:00 (which will start at 18:59)? There is an overlap, so how does gbpvr handle it?
In the case where the 19:00 recording is on the same channel as one of the previous recordings, there doesn't need to be any loss between recordings. But there are still two separate recordings requests, so how does gbpvr handle this situation?

[sub]

Padding is always considered "nice to have but optional". If the tuner is required for something else then the padding will be dropped.

[erik]

Some broadcasts do contains XDS data that is supposed to deliver all kind of useful data such as show name, duration, time in the show, program rating.

I have added the decoding to comskip so it can be used when available.
But its not containing much useful actual data.......
I have only one (out of many) example that does give the time in the show.

[time_lord]

Padding is always considered "nice to have but optional". If the tuner is required for something else then the padding will be dropped.

Thanks for answering that... a pretty reasonable strategy ;-)

Thanks for the comments also erik