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QUESTIONS: S/PDIF, 5.1, CPU utilization, etc.

Discussion in 'Soundcards' started by DJ, Sep 28, 2003.

  1. DJ

    DJ Guest

    In general, I'm pretty knowledgeable about this stuff, but on this issue,
    I'm stuck.

    Question 1: When referring to "digital" speakers, it simply means that the
    speakers have a S/PDIF input and can handle the Dolby Digital (and DTS or
    whatever else) decoding themselves. (Usually they have a break-out box for
    this.) True/False?

    Question 2: I have the RealTek ALC650 on-board audio on my computer. I can
    get a NON-digital 5.1 speaker package and hook it up via the 3 mini-jacks
    and get full 5.1 surround sound. The decoding would be handled by the
    ALC650 chip, the signals to the speakers would be analog, and I would take a
    CPU utilization hit for it. True/False?

    Question 3: If I get a digital 5.1 speaker package and hook them up via the
    S/PDIF output, then it bypasses the ALC650 in terms of 5.1 decoding and all
    of that is done by the speaker package. Do I still incur the CPU
    performance hit? Does the audio still come out of the mini-jacks? If I do
    and it does, is there any way to stop it? Does the ALC650 do any work to
    the signal coming out of the S/PDIF connector? If I disable on-board sound,
    does signal still come out of the S/PDIF connector?

    Question 4: If I buy an Audigy 2 with all the on-board 5.1 (or 6.1 or 7.1)
    decoding built in, and then used the S/PDIF output, was there any point to
    buying the audio card in the first place?

    Thanks in advance... I've spent a full day searching online for these
    answers to no avail.

    DJ, Sep 28, 2003
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  2. DJ

    Arny Krueger Guest

    Generally true. If there's a digital input, then the digital/analog decoding
    is done in the speakers because there is noplace else it could happen and be
    It depends on how the application software is written. Most DVD player
    software operates in either/or mode. Any software that activated the analog
    and digital sound cards concurrently would still incur the CPU utilization
    Up to the application software and/or the user.
    Test it yourself and see.
    I don't see any.
    Arny Krueger, Sep 29, 2003
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  3. DJ

    DJ Guest

    Thank you so much for your replies. You pretty much confirmed everything I

    Just to follow up... I don't see any way (in the drivers) to stop the audio
    from being processed by the ALC650 while still letting the bits go through
    the S/PDIF port. If certain software applications provide that, cool, but I
    don't see it in any that I use. I'm primarily looking at games.

    Also, as you suggested, I confirmed for myself that if I turn off on-board
    audio in the BIOS, the S/PDIF link goes dead as well. (It's optical, so it
    was pretty easy to tell. ;-)

    Thanks again!
    DJ, Sep 30, 2003
  4. Games are another issue : the sound is CREATED on-the-fly, so here the
    sound card is more important for performance because the sound has to be
    altered to be heard as coming from whereever someone is fragging you ;-)
    And in that case I don't think you can use the S/PDIF digital out to plug
    it to a external receiver (only the nforce2 chipset can encode the 3d
    sound in Dolby to ouput it digitally).

    Emmanuel Allaud, Sep 30, 2003
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