A few years ago I remember reading that the first generation
commercial detectors were able to do their magic because of the
practice TV broadcasters used of always blanking the signal for just
a fraction of a second, and then having the commercial come in at a
(much) higher average volume..
This could be sensed algorithmically, and combined with a formula
which conversely also sensed when the level went back down
again..(especially if it was one of several standard lengths of time
later) it was better than 90% effective.
I wouldn't be surprised if this was still the case. I am sure there
is more to this story..
The existence of these devices was and is pretty politically charged.
Just as they are arguing that the airwaves are not public property,
but the government's to buy and sell, with community relevance being
irrelevant, some would argue that we have no legal right to expect
'programming' between the *real* programming.. i.e. 'commercials'.
;)
-Chris
