said by ArthurS:
Broadcasters in North America have 19 Mbit/s to play with per channel, and depending on the compression schemes they use, can squeeze multiple sub channels in along with their main broadcast.
Scroll to the bottom of this page to see all the different combinations:
This. It is all basically bandwidth at this point. 19mbit/s total per transmitter and MPEG2 video. Divy up into how many subchannels you want based on bandwidth usage.
I've seen some with about 4 or 5 subchannels including the main. If someone desired to do solely music they could probably do like how Music Choice is operated on cable networks and fit in some ~40 channels with the right bitrate setup.
Where I used to live up in the Youngstown area, WKBN (at last check) runs both their channel (CBS) and WYFX (Fox, they own the channel as well) at 720p each on the same transmitter with a good encoder setup that does well keeping the quality up on both channels and squeezing them in the 19mbps allotment.
And with the development of Mobile DTV you now also have what is essentially an IP stream run OTA that feeds a youtube-like H264/AAC video feed meant for mobile devices and it runs in that same 19mbps limit.
All bits now flying through the air.
EDIT: One good site I would recommend looking at if you want to see some of the technical details: »www.rabbitears.info/market.php
Drill down to a market and station and hit the TSReader data and it will show you the core details of the complete transmission.--
I swear, some people should have pace-makers installed to free up the resources. Breathing and heart beat taxes their whole system, all of their brain cells wasted on life support.-two bit brains, and the second bit is wasted on parity! ~head_spaz