Why does SPDIF/PCM = no DD output and SPDIF/RAW = DD output for DVD player?

Discussion in 'Archived Threads 2001-2004' started by Paul Spurgeon, Nov 6, 2001.

  1. Paul Spurgeon

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    I finally noticed today (10 days after getting my new receiver) that I was not truly getting Dolby Digital output from my receiver. Any time I would try to set the DVD output to DD, it would only allow me to set PLII. I remembered having to change a setting in my DVD player setup menu in order to get digital sound at all, and I went back to that menu. After changing the setting from PCM to RAW, DD kicked in immediately.
    My question is this: what is the difference in the bitstream between PCM and RAW, and if there are other differences, what are they? I'm assuming the answer to this question will explain why PCM = no DD... if it doesn't, then could someone explain this also?
     
  2. Kevin P

    Kevin P Screenwriter

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    In the SPDIF/RAW mode, the DVD player sends an unaltered (e.g. "raw") bitstream to your receiver. In other words, if you select a Dolby Digital track, a Dolby Digital bitstream is sent to your receiver; a DTS track is sent as a DTS bitstream to your receiver, PCM is sent as PCM, etc. The player doesn't alter the bitstream, it just passes it "as is" to your receiver or decoder.
    SPDIF/PCM mode tells the DVD player to convert Dolby Digital tracks to PCM format. In doing so, it gets converted to 2-channel (ProLogic matrix encoded) through downmixing. The only reason to use this mode is if you have a receiver that's not Dolby Digital capable but has a digital input that accepts PCM (say for a CD player, DAT/MD deck, etc.)
    If you have a Dolby Digital capable receiver/pre-pro (most of us do nowadays), you'd select the SPDIF/RAW mode. By the way, SPDIF is just a techie term for the digital output (coaxial or optical) on your DVD player.
    KJP
     
  3. Paul Spurgeon

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    cool, thanks for the info
     

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