I stumbled across this article which talks about a drive-in theatre in the USA offering digital sound to drive-in theatre patrons.

here

What puzzles me is that it appears that all they are doing is just mixing the sound down to 2 channels. Most of our drive-ins here in Melbourne already have stereo fm sound so what is the advantage of what they are offering?

cheers Peter

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Originally posted by Peter Berrett:
Most of our drive-ins here in Melbourne already have stereo fm sound so what is the advantage of what they are offering?

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Practically nothing but perceived marketing advantage. They can say they have digital sound.

Note that they mention it right at the top of the page here

FM, stereo or otherwise is a lot better than a 4 inch window speaker, but it doesn't have the noise floor that a reasonably well-installed (and much less expensive) SR system can produce. Unless you have an expensive, recently made FM exciter (transmitter), good theatre components feeding it and an interference-free clear shot to your customers' cars, you'd be lucky to see noise floors down more than -30 to -40db or so at the output of a car radio. With all the "activity" going on in and around most cars in a drive-in, (read that one any way you want), you're not going to hear much sound below that level, even if it was there... which is part of why broadcasters use a lot of compression-based processing to REMOVE those dynamics!!!

Stereo separation can vary widely, too, which really defeats the quality that digital film systems produce.

The stereo generator in an FM transmitter contains an audio filter which removes everything above 15kHz. This prevents interference with the signals that "tell" your radio how to make stereo out of a single-channel analog transmission. This pretty much brings the FM transmission process down to a level, maybe somewhat better than consumer-grade analog tape. Sure, you can get better results in a controlled environment... (that + "drive-in" = oxymoron).

Now, add the uncontrolled dynamics of the car itself. Every car in the field is a small auditorium with unknown acoustics that would be impossible to equalize for.

So... what will you get by running digital? Probably not much more than click-free splices and the ability to say you're digital. Unfortunately, a lot of drive-ins are not the first to play a print.
I wonder how how consistently a digital system would work, considering the reliability of receiving DTS discs or a readable digital track once a print's been out there for a while (unless of course, Filmguard is being used!).

American broadcasters are able to operate in digital all the way to the transmitter, if they choose. However, as our radios are still analog, the signal has to be converted before it leaves the transmitter site... as it would at a drive-in.

Also, you are right about the channel limitation. Any system (digital or not) that generates more than two channels would have to mix them down before they hit the subsequent components of the drive-in's audio chain, or they'd be lost.

The point of a DTS drive-in sounds more like a marketing ploy. Not a bad idea though, most people wouldn't notice anyway.

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3% Body Fat. 1% Brain Activity.

...A projectionist without a theatre...

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Better Projection Pays!

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Originally posted by Scott Norwood:
WRT digital radio broadcasts: Is this the satellite radio thing or something different? Is the sound quality decent, or is it some nasty form of compression at a low bitrate?

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It's not satellite based, but a method whereby existing broadcasters can add a digital audio stream to their signal. Dan and Tim are correct... the FCC did authorize the process recently, and those radio stations that had a jump on equipment installation were able to begin using it immediately. As with color tv and the early days of FM, there aren't any receivers out there to speak of... but someone had to be first, so it looks like this it is.

Here's a story on the subject you can read here... printed just before the FCC voted on the authorization.

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As with color tv and the early days of FM, there aren't any receivers out there to speak of...

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Someone on WOR was just talking about this. They're broadcasting to no one on the digital channel.

(Hello there, Jack. Welcome!)

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Better Projection Pays!

Technologically speaking, it would be pretty easy to do 5.1 digital and simultaneous 2 channel FM analog audio broadcasts to a drive-in theater audience. However, the infrastructure is currently not in place.

If the music industry could get over its war with the Internet and actually back some next-generation audio formats like DVD-A and SACD with some worthwhile music content --and not the same damned 10 songs Clearchannel keeps payola-playing over and over and over again-- we might see a wider proliferation of 5.1 surround equipped car stereo systems.

With digital radio broadcasting now set to hit the airwaves, that could help out in the process of building up car surround sound infrastructure. What needs to happen is the digital broadcast receivers need to be able to recognize an incoming Dolby Digital or even DTS audio bitstream and process it.

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As for compression rates, etc... what makes this a possible issue of interest to drive-ins is the fact that in the end, the car only has 2 channels to begin with, so 5.1 or otherwise, it's not an issue for us. DAB would provide a silent digital pathway from our booths to our customers' cars, something many drive-in owners do not currently have, when considering interference for real, licensed broadcasters (darn their hides!) AM skip interference and the low power levels used in the "transmitters" drive-ins use.

The following bit was from here

"Television stations are required by federal law to add the higher-quality digital signal to their broadcasts by May 2003.

Although standard televisions can't receive digital signals, consumers won't have to run out and buy new sets anytime soon. Stations must continue to broadcast the standard analog signals until 85 percent of consumers in a market have bought digital televisions, Petrowich said."

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edit: I just watched the Toronto hockey game and the picture was severely messed up about 4 times due to 'digital problems'.