Apple TV2 / 5.1 AAC->5.1 LPCM?

Discussion in 'Apple TV and Home Theater' started by amarcus, Apr 9, 2011.

  1. amarcus macrumors 6502

    Joined:
    Feb 26, 2008
    Location:
    London, UK
    #1
    Can anyone with an Apple TV gen. 2 connected via HDMI to a receiver that supports 5.1 LPCM test to see if a file with 5.1 AAC plays with surround sound?

    All the information I've found so far seems to be either: dated (before gen. 2), from someone using a receiver that doesn't support LPCM, or from someone who doesn't have their receiver connected via HDMI (as optical doesn't have the bandwidth for it).

    Thanking you all in anticipation!

    Adam


    In case you were wondering: I own an apple tv and have lots of 5.1 AAC files. Looking to by an expensive receiver if it will get the job done...
     
  2. spacepower7, Apr 9, 2011
    Last edited: Apr 9, 2011

    spacepower7 macrumors 68000

    Joined:
    May 6, 2004
    #2
    From what I have read, which may be outdated too...

    The AppleTV 2 will output 5.1-AAC as stereo, not 5.1 LPCM. I think that there may be a muxer that converts that 5.1 AAC into 5.1 AC-3 (Dolby Digital).

    The problem is that the your sources are encoded for PS3 and WDTV (maybe?) and HTPCs.

    The PS3 can't deal with the AC-3 (DD) or the m4v container. The people making these files usually encode the 5.1 AAC at the same bit-rate (448 or 480, i forget) that the original 5.1 AC-3 (DD) was encoded, therefore they are not really shrinking the files by choosing AAC, just making them PS3 compatible.

    MKVtools, written by one of our forum members.

    MP4 with 5.1 AAC to MP4 (video pass-thru, untouched) with sound converted to 5.1 AC-3 (DD) with a 2 channel AAC to maintain ipad/iphone/ios compatibility.

    I'm testing for you right now ;)

    UPDATE

    I just did the conversion, took 17 minutes on my 2GHZ Core2Duo Mac Mini with 4GB of RAM

    MKVtools
    Gobbled up about 1.5 GB of RAM (speeds up muxing)
    -Ran 2 mencoder processes, i think one for converting the 5.1 AAC to 5.1 AC-3, and the other for converting to 2 Channel AAC (for iOS compatibility)
    These processes ran at 55-70% of 1 cpu each.

    Then mp4box runs through 4 sequential steps, the first 2 using 20-30% of one cpu
    The steps 3 and 4 using 8% or less of one cpu

    When it was all done 17 minutes later, MKVtools promptly freed up 1.5GB of RAM that it needed

    Now for the file details

    Original
    MP4
    Video Stream
    Codec (Human Name)................................AVC
    Codec (FourCC)....................................avc1
    Codec Profile.....................................High@L4.1
    Frame Width.......................................1 280 pixels
    Frame Height......................................688 pixels
    Frame Rate........................................23.976 fps
    Total Frames......................................132932
    Display Aspect Ratio..............................1.860
    Scan Type.........................................Progressive
    Color Space.......................................YUV
    Codec Settings (Summary)..........................CABAC / 4 Ref Frames
    QF (like Gordian Knot)............................0.134
    Codec Settings (CABAC)............................Yes
    Codec Settings (Reference Frames).................4
    Video Stream Length...............................1h 32mn 24s 381ms
    Video Stream BitRate..............................2 825 Kbps
    Video Stream BitRate Mode.........................VBR
    Bit Depth.........................................8 bits
    Video Stream Size.................................1.82 GiB (87%)

    Audio Stream #1
    Codec.............................................AAC
    Codec (FourCC)....................................40
    Audio Stream Length...............................1h 32mn 24s 533ms
    Audio Stream BitRate..............................425 Kbps
    Audio Stream BitRate Mode.........................VBR
    Number of Audio Channels..........................6
    Audio Channel's Positions.........................Front: L C R, Side: L R, LFE
    Sampling Rate.....................................48.0 KHz
    Audio Stream Size.................................281 MiB (13%)
    Audio Stream Language.............................English

    New File:

    General / Container Stream #1
    Total Video Streams for this File.................1
    Total Audio Streams for this File.................2
    Video Codecs Used.................................AVC
    Audio Codecs Used.................................AC3 / AAC LC
    File Format.......................................MPEG-4
    Play Time.........................................1h 32mn
    Total File Size...................................2.22 GiB
    Total Stream BitRate..............................3 435 Kbps
    Video Stream #1
    Codec (Human Name)................................AVC
    Codec (FourCC)....................................avc1
    Codec Profile.....................................High@L4.1
    Frame Width.......................................1 280 pixels
    Frame Height......................................688 pixels
    Frame Rate........................................23.976 fps
    Total Frames......................................132932
    Display Aspect Ratio..............................1.860
    Scan Type.........................................Progressive
    Color Space.......................................YUV
    Codec Settings (Summary)..........................CABAC / 4 Ref Frames
    QF (like Gordian Knot)............................0.134
    Codec Settings (CABAC)............................Yes
    Codec Settings (Reference Frames).................4
    Video Stream Length...............................1h 32mn 24s 378ms
    Video Stream BitRate..............................2 825 Kbps
    Video Stream BitRate Mode.........................VBR
    Bit Depth.........................................8 bits
    Video Stream Size.................................1.82 GiB (82%)
    Audio Stream #1
    Codec.............................................AC-3
    Codec (FourCC)....................................ac-3
    Audio Stream Length...............................1h 32mn 24s 512ms
    Audio Stream BitRate..............................448 Kbps
    Audio Stream BitRate Mode.........................CBR
    Number of Audio Channels..........................6
    Audio Channel's Positions.........................Front: L C R, Side: L R, LFE
    Sampling Rate.....................................48.0 KHz
    Bit Depth.........................................16 bits
    Audio Stream Size.................................296 MiB (13%)
    Audio Stream Language.............................English
    Date of Original Encoding.........................UTC 2011-04-08 23:47:39

    Audio Stream #2
    Codec.............................................AAC
    Codec (FourCC)....................................40
    Audio Stream Length...............................1h 32mn 24s 448ms
    Audio Stream BitRate..............................157 Kbps
    Audio Stream BitRate Mode.........................VBR
    Number of Audio Channels..........................2
    Audio Channel's Positions.........................Front: L R
    Sampling Rate.....................................48.0 KHz
    Audio Stream Size.................................104 MiB (5%)
    Audio Stream Language.............................English



    Sorry I can't verify this works (AC-3) on the AppleTV 2 at this moment, but it transferred to my iPad 1 and is playing flawlessly.
     
  3. amarcus thread starter macrumors 6502

    Joined:
    Feb 26, 2008
    Location:
    London, UK
    #3
    Thanks for the testing, much appreciated. Spot on with the PS3 encodes! It's good to know that I have an option to get things working. Just wondering if theres a way around re-encoding. Anyone else got any recent info on this?

    Adam
     

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