I just spent a number of hours on a pleasant saturday morning trying to work out exactly why MythTV doesn't get program info for Channel Nine (in Sydney, Australia). I already knew this was because Mythtv was failing to parse the EIT data, and in particular, the SDT wasn't being found.
After a fair bit of poking around, re-learning the fragments of DVB that I have long since forgotten, compiling various hacks into mythbackend, I eventually worked out that it was looking for the SDT in the wrong transport ID.
Because mythtv (being the bastion of stunning design that it is), stores a NIT/TID (network id, transport id) per channel, and _also_ stores a TID into the multiplex table. So the channel table has lots of very fine NIT/TIDs which I checked until the cows came home, before eventually discovering that the code was also reading from the dtv_multiplex table.
One "update dtv_multiplex set transportid = 1056 where mplexid=24;" and I now have program schedules for channel 9. w00t!
Ok, this is a pretty trivial thing, and I don't actually care about the data: It's just that this has been non-working for many months, and every time I noticed it it irritated me that I didn't know why it was broken.
Now I do. So now I'm happy :)