[mythtv] SI/PSIP Parser

[Daniel Thor Kristjansson]

]On my set top ATSC box I have to re-scan from time to time because they
]are always changing what minor channels exist and what not, so I
]suspect there may be a need for some sort of Auto-PID code instead of
]caching PIDs in the DB (Which I don't like the idea of caching PIDs
]since it takes almsot no time to get and parse the PAT and PMT).

I've done some timings on this and it only takes a few milliseconds to
get the PAT & PMT, while it takes 200-300 ms to get the first GOP.
Unfortunately if you wait for the TVCT that also seems to take 200-300
ms to come in. This argues for caching the TVCT info in the database.
We don't want to wait 600 ms just to BEGIN writing the recording to
disk.

But caching the TVCT isn't so bad since the broadcasters are discouraged
from changing the subchannel<->programID mapping very often.

-- Daniel