QT says 6 channel AAC, but AppleTV outputs in 2ch. VLC baffled.

Discussion in 'Apple TV and Home Theater' started by toypadlock, Nov 30, 2010.

  1. toypadlock macrumors member

    Joined:
    May 17, 2010
    Location:
    UK
    #1
    so yeah, i downloaded a 720p mp4 file that plays great on my appleTV (2010), except that surround doesn't work.

    i understand that this is probably to do with its audio track being a 6ch AAC, which my awful old receiver probably can't handle (it's connected via optical).

    how do i get it to output in 5.1?

    (also, VLC seems to think the file is stereo, which is weird).

    thanks in advance!
     
  2. peterjcat macrumors 6502

    Joined:
    Jun 14, 2010
    #2
    AppleTV can't handle 6-channel AAC, so you'll only get the stereo downmix.

    The only way to get multichannel out of an AppleTV is Dolby Digital (AC3).

    You should be able to re-encode the audio with MKVTools.
     
  3. williedigital macrumors 6502

    Joined:
    Oct 4, 2005
    #3
    Technically True

    But in the old Apple TV (and the current from what I can tell), the device would convert 6-channel AAC to Dolby Pro Logic Surround. I can certainly hear it doing something "surroundy", depending on the file. I can't tell if the conversion is to "old" DPL or DPLII, but there is some understanding of the multichannelness to my ears.
     
  4. toypadlock thread starter macrumors member

    Joined:
    May 17, 2010
    Location:
    UK
    #4
    this didn't light up the surround light on the receiver, it was definitely 2ch. thanks for the help though, I foolishly assumed MKVtools would only work with .mkv files.
     
  5. peterjcat macrumors 6502

    Joined:
    Jun 14, 2010
    #5
    Yeah it's maybe not the best name for the package (though much better than the old name!).
     
  6. williedigital macrumors 6502

    Joined:
    Oct 4, 2005
    #6
    it wouldn't

    A DPL/DPLII mode stays on regardless of what the receiver is being fed. It will even attempt to simulate surround effects on stereo audio.

    Subjectively I would say that, on a scale of surround "perception" by the user where stereo is a 1 and proper 5.1 ac3 is a 10, stereo audio run through a DPL system is a 2, stereo run though a DPLII system is a 3, DPL encoded stereo run through a DPL system is a 4, and DPLII encoded stereo run through a DPLII system is just below a 7.

    The only question for me is whether the apple TV decoded 5.1 aac as DPL stereo or DPLII stereo. My ears would say DPLII, but I can't say for certain.
     

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