dolby pro logic

Discussion in 'Archived Threads 2001-2004' started by Mikey L, Apr 1, 2002.

  1. Mikey L

    Mikey L Agent

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    I have a Yamaha RXV-620 and was wondering about watching my cable (digital) in dolby pro logic. Doby Pro Logic Normal/Enhanced are part of the DSP programs, but do I need these activated to get a pro logic signal? If I understand correctly, many programs don't broadcast in pro logic, but when I set my DSP to either Normal or Enhanced, the Pro Logic indicator lights up and stays on no matter what channel I have on (QVC, C-SPAN, etc.). Also, since Pro Logic only utilizes 2 channels, do I need to turn off my center and surrounds?
     
  2. Bob McElfresh

    Bob McElfresh Producer

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    If you want to decode the ProLogic signal, you want to leave at least the "Normal" turned on.

    Your indicator lights are inconsistant.

    It will say "ProLogic" to mean "I am looking for ProLogic encoding". This happens even with no signal, mono signal, and stereo signals.

    But it will flip to say "Dolby Digital" when it detects a Dolby Digital signal.

    Try watching some of the prime-time shows like CSI or ER - these usually announce the "Surround Sound" feature at the begining. (Another name for ProLogic is "Dolby Surround").

    Hope this helps.
     
  3. Dave Nibeck

    Dave Nibeck Stunt Coordinator

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    Also, DPL extracts 4 channels of info from 2 L+C+R+Rear.

    A great test is Saturday Night Live. They put the laugh track on rear and it sounds like crap. The effect is much better with DPL II.
     
  4. Mikey L

    Mikey L Agent

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    When the "Dolby Digital" light is on, isn't that only refering to 5.1? That's what I get on 5.1 DVD'S (my cable provider doesn't carry a 5.1 signal)....I am just looking for Dolby Pro Logic, and that indicator stays on regardless of the program when I have that particular DSP turned on.
     
  5. Michael Reuben

    Michael Reuben Studio Mogul

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  6. Mikey L

    Mikey L Agent

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    Thanks, I will look for that indicator then....I take it I do not have to shut off any of my speakers (i.e. center, surrounds) to get the Pro Logic decoded?
     
  7. Michael Reuben

    Michael Reuben Studio Mogul

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  8. Vince Maskeeper

    Vince Maskeeper Producer

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    1) Pro logic is a processing mode that can be applied to any signal-- if it is specifically "encoded" for pro logic or not. You could apply PRO LOGIC mode to you favorite CD, or even to material from a cassette tape if you wanted to.

    In your case, you applying it to the cable signal. Again- even if the broadcast is or is not encoded specifically with PRO LOGIC processing in mind, you can apply this processing to it and see what happens.

    This processing will not turn on/off when a prologic encoded signal is detected-- it has no way of sensing if a program was created with prologic in mind... Instead it is simply a processing mode- like any of the DSP modes in your receiver- that creates a "4 channel" output from a 2 channel input.

    Really, all/most DSP modes are simply there to create a "surround" output from a simple stereo input-- Some do so by creating reverby ambience modes (Stadium mode for example)-- while Prologic or Prologic 2 have their own methods to trying to create a multichannel output from a 2 channel input.

    2) You do not need to disconnect anything for Prologic- in fact, quite to opposite-- you need 6 speakers to properly experience pro logic. Pro logic simply looks at the stereo signal coming in, figures out what elements of that signal are being sent equally to right and left, and uses that audio to create a "center" channel feed. It thn finds material that is out of phase and sends that to the rear channels. If you have your speakers set to small- it then takes bass material in each speaker and reroutes that to the sub. Thus you need all 6 speakers to experience a real prologic processed signal.

    Hope that helps you understand it.

    -Vince
     
  9. Mikey L

    Mikey L Agent

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    thanks for the thorough response, I get it now....there is nothing on my reciever that would tell me if a specific show is being broadcast in dolby surround...I appreciate the explanation, I am relatively new to these forums (surprise, surprise) and am finding them a very useful resourse....this new hobby of mine is great for the ears and eyes, not so for the wallet!
     
  10. Oliver_RN

    Oliver_RN Auditioning

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    Bob McElfresh said:

     
  11. Michael Reuben

    Michael Reuben Studio Mogul

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    Oliver, the difference between Dolby Surround and Dolby ProLogic is strictly on the decoder side, not the broadcast side. In fact, you could apply Dolby Surround or ProLogic decoding to a Dolby Digital broadcast, if the DD broadcast is 2 channels, as many of them are.
    M.
     
  12. Adam J

    Adam J Stunt Coordinator

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    Harold_C Stunt Coordinator

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