Stereo vs Prologic on DVD Season sets

Discussion in 'TV on DVD and Blu-ray' started by Cliff C, Jun 3, 2004.

  1. Cliff C

    Cliff C Extra

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    This has been bugging me for a while. How come on some shows like Smallville, the audio is encoded as stereo, but on others like Buffy they are encoded as dolby prologic.

    Everytime I watch Smallville I have to manually adjust the audio output on my receiver to prologic, but on the buffy dvd's it's automatic.

    Everytime I skip ahead in an episode on my Smallville dvds the audio shifts back to stereo so I have to manually adjust my receiver again...

    Is it just how the show elements were created originally? I personally prefer prologic because it seems to sound more "natural"
     
  2. Yee-Ming

    Yee-Ming Producer

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    IIRC, nothing is actually "encoded" as Prologic per se, it's still basic stereo and works as stereo on non-Prologic equipment. Dolby Prologic processes a stereo source to "extract" diffuse sound and send it to the surround speakers, and of course sends anything that was "dead-centre" in the stereo feed to the centre speaker.

    So you need to check how your receiver works and what it defaults to, e.g. if I leave my receiver in "auto" mode, when it encounters a Dolby 2.0 source it automatically goes to Prologic II, whereas a Dolby 5.1 source goes to Dolby 5.1.


    (Of course, that's an oversimplification, stereo on TV can be processed in a way to work with a Prologic decoder better in sending ambient sounds to the surrounds, but the point is it isn't specifically "flagged as Prologic", if you take my meaning, it's just plain Dolby 2.0 or sterero.)
     
  3. Herschel

    Herschel Stunt Coordinator

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    I think the 2.0 audio track can still have a flag that indicates whether there's any matrixed surround information in there. PowerDVD, for example, sometimes shows a 2.0 audio track as "Dolby Digital 2.0", and other times as "Dolby Digital 2.0 Surround."

    My uneducated guess is that your receiver is using that flag to decide how to process it. From seeing where that shows up in PowerDVD, though, it's not very consistently used, and lots of movies and TV shows that are definitely matrixed surround show up without that "surround" tag in PowerDVD.
     
  4. Yee-Ming

    Yee-Ming Producer

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  5. Michael Reuben

    Michael Reuben Studio Mogul

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    Excellent guess! That's exactly how it works. The problem here is that Cliff's receiver is slavishly obeying the flag instead of sticking with his manual setting. I don't care for that design in receivers and processors, and I hope it doesn't become common.

    M.
     

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