Optical output / bit transparency / external clocking.

Discussion in 'MacBook Pro' started by theaero, Jun 3, 2010.

  1. theaero macrumors 6502

    Mar 5, 2008
    I am trying to hook up the Macbook Pro's optical output to a Crane Song Avocet.

    I have a few questions and concerns:

    First of all, I am using a mini-toslink to toslink cable going into a toslink optical to spdif coaxial converter (said to be bit-transparent).

    Now, my concerns are regarding real time sample rate conversion on output, digital attenuation causing distortion, word length truncation, etc. Bit transparency is crucial.

    My other concern is whether or not I will be able to sync to an external clock.

    Any insight on this would be very helpful. Thanks.
  2. theaero thread starter macrumors 6502

    Mar 5, 2008
  3. theaero thread starter macrumors 6502

    Mar 5, 2008
  4. apbsignal macrumors newbie

    Jun 5, 2010
    The Macbook Pro hardware is capable of bit-perfect output. Of course, your software must also be capable of bit-perfect playback. iTunes is capable of bit-perfect playback if properly configured.

    Bit-perfect output can be verified by playing a DTS encoded audio file.

    You can download a DTS encoded WAV file here:
    See Multichannelcheck at bottom of page. The unzipped file name is SURROUNDTEST_011212.wav

    DTS audio cannot be decoded if it has been modified by sample rate conversion, lossy compression or Digital Signal Processing. If using iTunes for playback, all Digital Signal Processing must disabled as described in Apple article "Playing DTS audio files with iTunes":

    DTS audio playback requires a digital connection to a DTS decoder. Connect the Macbook Pro's optical output, or an Airport Express Base Station's optical output, to an audio receiver or processor that has a DTS decoder. Set up the receiver or processor to automatically detect the format of the digital audio signal.

    If the bitstream is unmodified, the receiver or processor will automatically engage its DTS decoder and correctly reproduce the 5.1 channel audio signal. If the bitstream is corrupted, the receiver will indicate the source is digital PCM and will produce noise that sounds like static.
  5. theaero thread starter macrumors 6502

    Mar 5, 2008
    I don't have a receiver, or anything to test multichannel decoding. as I'm not doing anything like that. I figured I could to some recording back into my computer, and doing null tests.

    My main concern is how the MBP clocks. Can it sync to an external device?

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