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DPL and Nicam clearups

Discussion in 'AV Receivers & Amplifiers' started by John R Baker, Jan 25, 2002.

  1. John R Baker

    John R Baker
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    It seems that there are a few questions about DPL and NICAM. I hope the following helps, although it is not the only answer.

    NICAM (near instantaneous companding audio multiplex) is a method of delivering near CD (35KHz 12 Bit ) stereo audio.

    DPL (Dolby Pro Logic www.dolby.co.uk) is a method of encoding 4 channels of audio into 2 by using an audio phasing encoding system. See Dolby for a technical breakdown. You can listen to the broadcast as normal in stereo but a DPL decoding circuit can be used to extract the 2 other channels.

    So a NICAM broadcast can be used to send a DPL soundtrack.

    Do not assume that all stereo audio has been process in DPL.


    Please do not flame this post, as it is only to help.
     
  2. LV426

    LV426
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    Exactly right, but often not understood by many. Many people believe that there is some "magic" in a DPL signal. In truth, it is nothing more than a simple stereo signal, the contents of which have been manipulated at the recording/mixing stage.

    The clever stuff is done in the DPL decoder to extract four channels of information from the two in the stereo signal using differences in phase to steer the sound.

    It is also worth mentioning that this decoding WILL, in all cases, result in some rear channel presence from all stereo signals, whether they have been specifically mixed for the purpose or not. Only fully mono signals (ie those where the L & R are identical) will give no rear presence.

    It is also probably worth mentioning that it is likely to be impossible to strip surround information out of a DPL mixed stereo signal, except by mixing the two channels together (to get mono).
     
  3. Confucius

    Confucius
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    An easy, though not always 100% reliable, method of checking whether DPL is encoded into stereo is to engage the DPL function on an AV amp/prcessor. Normally if it's plain old stereo (and especially 2 channel mono) the sound will collapse to the centre speaker.

    This is effectively the same as what happens when non-EX/ES(matrix) material is processed using EX/ES, instead of sound coming from all 3 (or 4) surround channels it will again collapse to the rear channel(s).
     

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