Proper Dolby Digital mode question

Discussion in 'Archived Threads 2001-2004' started by Nick Senger, Jul 23, 2002.

  1. Nick Senger

    Nick Senger Stunt Coordinator

    Joined:
    Jun 17, 2002
    Messages:
    192
    Likes Received:
    0
    First, let me apologize about the length of this post, but I couldn't describe my problem in any other way. I have a question about selecting the proper listening mode for a dvd. I have a Kenwood VR-507 that normally does a good job selecting the automatic surround mode for a dvd. But I recently bought Better Off Dead and was surprised at how bad it sounded, even for a dvd that says on the box: Dolby Digital: English Stereo.

    I thought it was the dvd until I read a review of the movie that said be sure to listen to it in Pro Logic II. I went back to the movie and sure enough, it sounded much better in that mode. I had been listening to it in my receiver's Dolby Digital mode. Now here is my question: Can someone help me to understand which mode goes with which box description?

    I have read the faq on Dolby Digital, and I thought I understood it pretty well, but here is what I face:

    Better Off Dead: Dolby Digital-English Stereo
    Henry V (w/Kenneth Branagh) - English: Stereo Surround
    Real Genius - English (Dolby Surround)
    The Man from Snowy River - English Stereo Surround

    Now, it appears from this that as long as the box says "Surround" (assuming, of course that the box is correct, which I know is not always true), then I should use the Dolby Digital selection on my receiver. And if the box says simply "Stereo," then I should use Pro Logic II Movie. Is this correct?

    Also, adding to my confusion is the listing for these movies on DVD Profiler:

    Better Off Dead: Stereo
    Henry V: Stereo
    Real Genius: Dolby Surround (3 Channels)
    The Man from Snowy River: Pro-logic (4 Channels)

    Should I be watching The Man from Snowy River in a Pro-Logic mode? It sounded ok when I watched it in Dolby Digital mode, but maybe it could have been better. I realize that these entries are made by users and could be incorrect.

    I'm sorry if this seems like a dumb question. I'm sure I must be missing something obvious, but I would like to avoid what happened with Better Off Dead in the future. Thanks.
     
  2. Vince Maskeeper

    Vince Maskeeper Producer

    Joined:
    Jan 18, 1999
    Messages:
    6,499
    Likes Received:
    0
    Nick,
    This is actually a somewhat complex question. I will try my best to explain it, but if this doesn't make sense, feel free to follow up!
    The most important first step is to realize that "Dolby Digital" is an audio format that is available to encode any number of channels. DVD can feature a full 5.1 surround soundtrack, but it can also include a simple 2 channel soundtrack (or it can contain a mono 1 channel, and any possible channel configurations inbetween)-- and all these various configurations can be written using the same audio format: Dolby Digital.
    So, the audio for most of 2 channel DVDs is written in this "dolby digital" format-- which some people see the name and assume it means 5.1. Just because a disc has DOLBY DIGITAL soundtrack does not indicate how many channels it uses, rather only stipulates the audio encoding format...
    On your receiver, the "Dolby Digital Mode" appears to simply leave the disc in its native channel configuration- for example if it is 5.1, you will get 5.1. If it is 2 channel, you will simply get 2 channel. This is true for most receivers- if you see the mode as "DOLBY DIGITAL", it simply means it has detected a DD type audio stream and will produce that audio stream as it was presented...
    Now, Any soundtrack that is 2 channel (whether it be presented in DD format, or even PCM format like you find on audio CDs or MP3 format you find on the internet-- heck even stereo material from a Record or Cassette tape)- it can have additional processing applied to "simulate" surround, even though it is only stereo.
    Most receivers have the popular DSP mode PRO LOGIC and PRO LOGIC II included which can be applied to these 2 channel signals to create a surround effect, but many offer other surround simulation programs like "HALL" and "ARENA" DSPs. These modes are simply "special effects" that can be applied to 2 channel soundtracks to achieve surround effects.
    Now, some soundtracks can be specifically designed with PRO LOGIC type processing in mind. These sound tracks are often denoted as you mentioned above "Stereo Surround", "Dolby Surround", etc. These soundtracks were encoded on the disc as 2 channel stereo soundtracks, but were specifically designed to work well with Pro Logic processing-- thus creating a pleasing surround effect.
    However, a soundtrack does NOT have to be specifically designed with Pro Logiic in mind to have Pro Logic applied to them. Many sound tracks achieve very pleasing results with pro logic processing applied to them, without having been specifically design to do so (on the other hand, some soundtracks sound bad in Pro Logic).
    The bottom line is really this:
    The "Dolby Digital" mode on your receiver will present soundtracks exactly in the channel configuration they are encoded. If it is 2 channel, you will get just that: 2 channel audio from the Left and Right speaker-- if it is 5.1, you will get 5.1.
    On any soundtracks that are 2 channel, you might then try to processes them with DPL or DPL2 (or any of the other DSP modes on your receiver). They do not have to say "Surround" on them in order to use DPL or DPL2- as again these modes are simply special effects which create a surround sound output from a 2 channel input.
    So if it's 5.1 leave the receiver in DOLBY DIGITAL mode. If it is 2 channel, then you can try applying the DPL or DPL2 processing modes to it, and see if you find it "better".
    In the case of Better off Dead, you initially left your receiver to the DD mode, which presented exactly what was there: a stereo 2 channel soundtrack. Upon revisiting the title, you applied DPL2 processing to that 2 channel soundtrack and found that it provided a more pleasing experience for you when processed using DPL2.
    Hope that helps
    Vince
     
  3. Nick Senger

    Nick Senger Stunt Coordinator

    Joined:
    Jun 17, 2002
    Messages:
    192
    Likes Received:
    0
    Thanks, Vince, that was extremely helpful. I think I only have one more question. Are there titles that have more than 2 native channels but less than 5.1 (such as Man from Snowy River and Real Genius, or Jesus of Nazareth)? On some boxes I see the Dolby Digital diagram with two front speakers and one surround speaker, or two front speakers and two surrounds. Are these native 3 and 4 channel soundtracks that my receiver will pick up in Dolby Digital, or are they 2-channel soundtracks designed to be processed? Thanks again for your help.

    Nick
     
  4. Vince Maskeeper

    Vince Maskeeper Producer

    Joined:
    Jan 18, 1999
    Messages:
    6,499
    Likes Received:
    0
    Good question. Short answer: It depends.
    Man from Snowy River is 2.0 (with a mono mix available I believe), Real Genius is also 2.0, Jesus of Nazareth I'm not sure about- but I think it was a made for TV series so it is likely 2.0 as well (IMDB confirms this). All 3 are listed as 2.0 surround on IMDB- so they are stereo 2 channel soundtracks which were designed to have Pro Logic applied.
    There are some titles encoded as 4.0 (L/R/C/MonoSurround) and although I've never seen a 3.0 disc, I'm sure someone, somewhere has done one... But these are few and far between.
    Usually when you see this 3 dot logo, it means that it is Dolby Surround (2 channel designed for use with ProLogic Processing). Here is the explaination from Dolby's site:
    [​IMG]
    Here's another which might be helpful:
    [​IMG]
    I'll say this, and I might be wrong in your case- but in most cases the receiver will ONLY let you apply Dolby PL to a 1 or 2 channel source... so if DPL is shown as available on your receiver- chances are that it is a 1 or 2 channel soundtrack. YOu can try this yourself, using any disc which has a 5.1 track and see if it allows you to select Pro Logic processing.
    Also, some processors can read a flag that tells it if the disc is just 2.0 stereo or 2.0 surround, and turn on DPL automatically. I have never owned a processor that could do it (and several discs are flagged incorrectly)- but this might also be a possibility which will help you...
    Also- you can check the audio menu on the disc- most will not use the dolby logos and will instead use text to describe the available audio options. If it says Stereo, Dolby Stereo, Dolby Surround- then it's a 2 channel soundtrack. Any disc that has an out of the ordinary configuration (like 3.0 or 4.0) should have this outlined in the audio menu.
    -Vince
    PS: Here are a few other discussions related to this topic you might find useful:
    http://www.hometheaterforum.com/htfo...threadid=30453 (Roger Dressler from Dolby popped up in that one).
    http://www.hometheaterforum.com/htfo...threadid=52915
    http://www.hometheaterforum.com/htfo...threadid=51550
     
  5. Nick Senger

    Nick Senger Stunt Coordinator

    Joined:
    Jun 17, 2002
    Messages:
    192
    Likes Received:
    0
    I've been experimenting and have discovered that my receiver will indicate with an extra red light when it is automatically playing in a DPL mode that it has picked up from a disc. When a dvd box indicates surround sound and the DPL light does not come on, then I can choose to use DPL or not. And, as you thought, if my receiver picks up anything beyond 1 or 2 channels it will not let me process with DPL, as I discovered with my Gettysburg Dolby 5.0 disc.

    Well you've answered some HUGE questions about Home Theater that I have had for a while. I'll really be able to enjoy my movies now. Thank you very much, Vince.

    Nick
     

Share This Page