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Regarding "true" and "fake" surround

Discussion in 'AV Receivers & Amplifiers' started by Zacabeb, Mar 1, 2005.

  1. Zacabeb

    Zacabeb
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    The more I read comments about systems like Dolby Pro Logic II only producing "fake" surround, I feel following needs to be stressed:
    Systems like Dolby Pro Logic, Dolby Pro Logic II, DTS Neo:6, Logic7 et al, do produce "true" surround so long as the source is surround encoded.

    While matrix-encoded sound does not compare to discrete multichannel in quality, and there is always leakage between channels in decoding, it does permit deliberate surround. This method has been used in movie theaters for 30 years and is still used today if/when the digital sound fails, and in theaters that for one reason or another aren't equipped with digital sound. Home theater was also dependent on this for surround sound for almost a decade and a half before digital multichannel was introduced for home use, and it is still a vital method for surround program delivery today.

    Sounds can be forced to decode into the surround channels by using an encoder to create the necessary phase and level relationships in the mix. The encoding and decoding are matched for this purpose, and the sound is monitored through the decoder to ensure it's mixed with respect to decoder behavior. So, matrix surround encoded material is controlled as tightly as possible given the inherent limitations of the system. It's flawed, but not random.

    This is the reason the newest matrix decoders like Dolby Pro Logic II and DTS Neo:6 have separate Movie/Cinema and Music modes - the former is intended for decoding material that is deliberately surround encoded, the latter for material which is not, and as the name suggests optimized for music.

    Edit: Made a change as per Reiner's suggestion below. :)
     
  2. Reiner

    Reiner
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    You should stress the part marked in bold:
    The named formats can indeed produce "true" surround from such sources, but the formats (with the exception of DPL) can also produce "fake" surround from e.g. plain old stereo by applying some clever processing.

    Thus you need to determine first to what kind of source signal you are applying the processing or decoding - the former could be called "fake" while the latter would qualify as "true" surround.
     

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