"No accelerated IMDCT transform found"

Discussion in 'Apple TV and Home Theater' started by 3282868, Apr 18, 2011.

  1. 3282868 macrumors 603

    Jan 8, 2009
    Noticed this during a Handbrake encode of a DVD rip. None of my .m4v's are suffering from anything, but curious as to what it means. I've googled around but have had no luck.

    Thanks if any one can shed some light, no biggie, just curious :)
  2. blevins321 macrumors 68030

    Dec 24, 2010
    Winnipeg, MB
    I think that this is a code artifact from back in the processor emulator days. I might be wrong though. Pretty sure it means that there is no "shortcut" transcoding method found, so it's going about it the long way. In modern-day processors though, the difference isn't even noticeable.
  3. roidy macrumors 65816

    Dec 30, 2008
    Nottingham, UK
    IMDCT = Inverse Modified Discrete Cosine Transform.

    As far as I know it's a function used during the encoding of AAC audio. I get it on all my encodes as well. I think it basically means you don't have hardware support for the function so software will be used instead. Don't worry about it.
  4. 3282868 thread starter macrumors 603

    Jan 8, 2009
    Cool. I'm using AC3 6-Channel Discrete at 48 with 640 bitrate for audio track one, then AC3 Passthrough for Audio Channel two (defaults to Auto and 448), and the third track simple DD/Stereo for iDevices, etc (Overkill perhaps, but as I'm encoding full DVD rips I plan on chucking my DVD's so I need lossless quality).

    Playing through my Pioneer Elite VSX-33 with B&W speakers on my aTV 2 with XBMC is perfect! 1080P for Blu-Ray's and everything plays through in 7.1 and 5.1 (DTS) with no issues [knock on wood]. I've got an extra "Time Capsule" we weren't using extending our network with another "Time Capsule" and connected the "Time Capsule" to the aTV 2 via Ethernet, and it holds 1TB of movies for direct access using SMB in XBMC. GREAT setup if you can do it, and for almost nothing! :)

    Thanks guys for your help!
  5. The Mad Hatter macrumors 6502a

    The Mad Hatter

    Oct 12, 2004
    Forgive me, but I'm trying to figure out your need for track 1. If you are are doing this on DVDs, and the passthrough bitrate is maxing out at 448, why are you up-sampling to 640? I thought passthrough is as 'lossless' as youre going to get with DVDs. Correct me if I'm wrong, but isn't that akin to taking a MP3 and trying to make a lossless file out of it? Seems rather redundant to me, but to each their own. ;)
  6. 3282868 thread starter macrumors 603

    Jan 8, 2009
    The lossless only has 5.1, from research you can pass it through to 6-channel discrete when offered and up it to 7.1 (Got B&W 7.1 SSS's with my Pioneer Elite system). To be certain, I've encoded the first track with a higher bitrate and the second just passthrough (from what I have learned passthru/passthrough isn't necessarily "lossless", and newer systems can "upcode" the audio - somewhat similar to older DVD players that could "upcode" SD to 720P - not truly HD). Having the three audio tracks allows me to make certain I'm covering my bases and I don't care about size as I have tons of it :).

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