AudioBob

Does anyone know what percentage of a given DTV channel is given to the Dolby Digital 5.1 audio? I'd think that one DTV station slot could carry a slew of FM Stations. Could be very useful for outlying and "shadow" areas. HDRadio is nice, but this scenario would sound much better!

HTNut

Hey, there's a business idea for TV stations! I'm not sure if FM and TV broadcast on the same digital spectrum, it might be a completely seperate type of broadcast transmitter.

Aaron62

I don't think it's possible.....they are on different parts of the spectrum.

From North American broadcast television frequencies - Wikipedia, the free encyclopedia

AudioBob

I don't think spectrum is an issue. For example KRCB DTV channel 22.3 shows a "card" saying "You are listening to KRCB Radio 91." and the FM station is simulcast on that sub-channel. Since most serious FM listeners probably connect their TVs to decent amps and speakers anyway, why not extend the "listening" environment to the DTV spectrum. In fact, you could use a converter box and a very small "handheld" TV propped up on top. And what about low power licenses for that very purpose?

Piggie

WJCT does the same thing on 7.5. They show community calendar events and play their sister station's sound WJCT-FM

Trip would know the rules surrounding transmitting audio without video, but if a simple card is up it doesn't take much bandwidth.

One could put up a card and music with about 1.5 mbps, which could fit 12 of those in a video channel. Most of the bandwidth would be video.

If you didn't need to add video (not sure how the rules deal with this), it only takes about .20 to .40 mbps. This leaves room for a LOT of audio programs. At .2 you would but up to 90 stations on one TV carrier.

You could put about 45 5.1 Dolby audio programs on a TV channel if nothing else were there.

If you wanted to compare it to FM radio, 3.3 channel would be the same size as the FM band we have now.

It was hoped by a few, very very few that mattered that maybe CH6 could have been used to expand the FM radio band, adding about 30% more room. It would have been nice. But as it turned out of all the lowband channels occupied with DTV, CH6 is one of the most popular.

Trip

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

Piggie

Never thought of it but that makes since. Send the data once, but map it over and over.

I started a HD Radio thread here, but I know nothing about it, which is basically what I said. You just gave me a clue to search between those two standards.

So is FMeXtra robust enough for the noise 76 to 88 MHz? Or is the shear fact Radio is narrow band make digital work that low?

Trip

FMeXtra works the same way FM Stereo does, only it carries digital bits instead of an extra audio channel. Anywhere you have stereo, you have digital. It replaces reading services, RDS, etc. in the feed.

Not so with IBOC. (I refuse to use their marketing name as it is misleading.)

- Trip

1inxs

HD Radio on my antenna would be icing on the cake. This is just one of many reasons I'm excited for the future of OTA DTV. The possibility's are endless.