Comment Re:"almost certainly" (Score 1) 160
SETI isn't necessarily looking for an intentional signal (though if one weren't intentional it would be unlikely to reach us), just anything that demonstrates artifice. It doesn't have to be something like an alien soap-opera perfectly displayed in NTSC format, but the kind of noise generated by that kind of broadcast is generally different than natural noise.
For one, since we can't test every signal for every kind of imaginable modulation, format, encryption or whatever, we have to look instead for a pattern between what could be real information. Every IP broadcast has plainly readable headers and part of them always begin a certain way, no matter how the information they help deliver is formatted. Every NTSC signal has within them the defining characteristics of the 60 Hertz frequency the information carries.
Whether digital or analog, there always has to be some kind of reliable pattern for the receiver to interpret, but all we can see is "Pattern-noise-pattern-noise". This is why SETI's problem is more of processing power than space to point telescopes at, they use Fourier transformations to attempt to find individual frequencies in a spectrum and then each of those frequencies need to be tested for potential data containers.