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Discussion Starter · #1 ·
Just noticed while watching "Touched by an angel " on CBS 2.1, over the air. I thought most HD broadcasted shows came in as dolby digital- ac3? It shows as prologic. Is this normal? Does the broadcasting companies only send Dolby Digital to HD broadcasted movies? If anyone has noticed this please let me know.

Thanks.


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PeterDz
 

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I don't know much, but here is what I do know:

All ASTC digital transmissions are done in Dolby Digital. This doesn't mean 5.1 sound. CBS broadcasts only in Dolby Digital 2.0. Many of their programming is encoded in Pro Logic, and either the encoder at the station's end or your receiver may detect this and cause the display you are seeing. However, no matter what you see on your receiver or hear from your speakers, the sound you get from OTA digital is always Dolby Digital.


--Andrew
 

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Discussion Starter · #3 ·
Thanks Andrew,

Cause I made sure that my Denon reciever and Sony sathd100's

audio digital setting is on Dolby Digital setting. So just making sure that nothing's wrong with my setup.

Thanks again.


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PeterDz
 

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I asked the chief engineer at the local CBS affiliate about 5.1 and he intimated that the equipment necessary to receive and pass through "full" Dolby Digital sound was not yet available to them. I guess I should be happy that we have a CBS station that broadcasts HD. I read here that some cities, Phoenix, for example, have CBS stations that are not going to do HD, let alone 5.1 sound anytime soon. Art
 

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Quote:
Originally posted by jdiehl:
Most HD broadcasting is still in DD 2.0

The only channel that I've found alot of DD 5.1 is on HBO HD.
Almost all Sho HD is DD5.1 if it was around when the movie was released or subsequently made availble in that format.


Some OTA, primarily movies on ABC, are DD5.1. Actually the ABC track record is pretty good since the release of Jaws (about an hour in in Boston), to have DD5.1.


Tim
 

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Hello DTV pals!


All audio delivered in a digital television transmission, whether via terrestrial, cable or satellite, is encoded into a Dolby Digital data stream and decoded through your set-top box or external decoder or home theatre integrated amplifier. Just remember that Dolby Digital and "5.1" are not the same thing. Dolby Digital is scalable and can carry a single mono program as well as a 5.1 presentation, and anywhere in between.


In the case of a full blown home theatre 5.1 presentation, the vast majority of providers are performing a "pass through" of a network feed, since local affiliates have limited ability to create their own 5.1 audio content. While the Dolby Digital professional encoders and reference decoders are not that expensive for a local affiliate to buy, other equipment like HD recorders, file servers, master control switchers, etc. are very pricey and out of the question for most local broadcasters at this point. That's a big reason for the lack of HD programming. Rest assured however that if you are receiving a 5.1 Dolby Digital broadcast either through a cable, satellite or terrestrial transmission, the broadcaster is using a Dolby Digital professional encoder (Model #DP569) and reference decoder (Model #DP562).


In nearly all cases when receiving an upconverted broadcast, the audio will be a stereo (2/0) Dolby Digital data stream. Dolby Digital also carries what's called "metadata" that allows the broadcaster to flag or identify this stereo broadcast as a Pro Logic encoded stereo presentation. When this flag is received by your decoder at home, it automatically performs a Pro Logic decode on the audio after the Dolby Digital data stream has been decoded to baseband digital audio. In this way you will receive and enjoy a surround broadcast, even though it may not be full 5.1 theatrical presentation.


There are a host of other parameters that encompass the library of flags and controls that are collectively called "metadata". You can find more comprehensive explanations of metadata on our web site at www.dolby.com.


Best regards,

Mike Babbitt

Dolby Laboratories
 
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