The other thing you can do, and some people don't realize this, is map the exact same stream of video to multiple audio feeds. So if I had a slide that listed what was on the 12 different audio subchannels, I could show the same slide, using the 1.5 Mbps or so of bandwidth once rather than duplicating it for each subchannel.
A few stations already do something like this. If you look at any of the Bahakel stations, they have a primary network feed on xx-1, and then air the same
HD video on xx-2 but with SAP audio. Here's WCCB, for example:
http://www.rabbitears.info/screencap.../49157-0_0.htm (I know it's called WCCB-SD but it's actually the same 720p video feed if you examine it. That capture is actually about a year out of date; it's now WCCB-DV.)
Technically speaking, I think you're supposed to be able to transmit AC3 audio without any video, but a lot of receivers don't support it, thus the addition of the static slide. Most stations which transmit audio-only subchannels have a static slide (see WMVT, KAET, KRCB, and others), while only a few do not (NJN AudioVision is the only one I can think of).
I'd still like to see channels 5 and 6 deleted to expand the FM band, using FMeXtra for its digital technology rather than the massive failure that is IBOC.
- Trip
