(Not necessarilly true, I beleive for instance TVO sends a different feed to the rest of the province transmitters and they use shaw direct for that)
when I said source I meant the local channel i.e. in the example I gave earlier it would be CBC 5 Toronto not CBC as a network. Right, if you watch on cable or sat CBC it will be the CBC of an area. For example my sister in Ottawa has Bell Sat and so when I am there watching CTV Montreal, I am watching what CFCF is broadcasting, not what Toronto is broadcasting or Vancouver or some generic CTV out there, and that means they are limited by what CTV Montreal sends out. An even better example would be Videotron here and VPT-33 in the US. Videotron shows what plays onmn 33.1, they don’t show 33.2, 33.3 ,33.4 but because they get the same feed as I get OTA their signal cannot be of higher quality than mine and my antenna.
(Not OTA , it is limited by the bandwitdh of an ATSC channel , that is 6 Mhz, sat/cable could change those internally).
what I meant is that theoretically the high quality feed could be mixed with the ads and sent as is (uncompressed further) to the BDUs instead of the BDUs getting the same OTA feed and quality that I do, if they would do the former rather than the later they could technicaly have higher quality. But that does not tend to happen which is why OTA is the best quality since it is the first limiting factor in the chain.
As for the 6mhz you are right that is the definition of a channel since NTSC but ATSC is ~20Mbps because of the modulation done on that 6mhz if one day there is ATSC* with a different modulation it might technically be higher. (the same way dial-up modems kept increasing until 56k modems, also in 2008 ATSC added h.264 to the specs so if stations used that even if the BW did not increase we would technically get better video (on the other hand most tuners don't support it so that won't happen any time soon.)
(from the arena it goes to CBC master control , I would assume, and then it gets "produced" and distributed),
you most likely got me there, but in my defence I was trying to be precise.
it depends on so many factors actually, and yes everyone should care