Encoding an audio stream with Dolby Digital

Discussion in 'Apple TV and Home Theater' started by ohsnap, Jul 4, 2011.

  1. ohsnap, Jul 4, 2011
    Last edited: Jul 4, 2011

    ohsnap macrumors regular

    Aug 5, 2004
    So I encode and transcode media to MP4 containers intended for use on my ATV2 and my DD 5.1 surround system. My audio system reports the audio streams that it's receiving as PCM using Dolby Pro Logic II. I understand that the ATV2 can send a Dolby Digital signal to the receiver but it depends on how the audio stream in the file is encoded. Today I somehow transcoded a documentary that had the standard AC-3 audio stream that I then converted to an AAC 5.1 format. This file is different though, it has somehow engaged the Dolby Digital on my receiver and sounds noticeably better than my other audio files. Does anyone know what I did right this time?
  2. DustinT macrumors 68000


    Feb 26, 2011
    Well, of course it will depend on having the source file posessing the DD 5.1 audio in the first place. But, assuming you have checked your source and it has this audio you'd want to load it into Handbrake and then check the 'Audio' tab. It should list the audio options. If you pop'd in a DVD you may see quite a few options, the DD 5.1, maybe an older Pro Logic mix, a director's commentary mix and\or some foreign language versions.

    You can add all tracks if you want, but that will waste space unless you plan on listening to the movie in French. If you want the DD 5.1 content you should make sure the top track listed is the DD 5.1 audio. Anything else should be added as the second track or lower. Then you'll choose AC3 Passthrough for the codec AND the mixdown. The Samplerate and Bitrate should be choosen automatically and can't be changed.

    Basically you are asking HB to just copy the audio and preserve it with no changes. Then your ATV 2 will be able to pull out what it needs, your receiver will light up with Dolby Digital and it will sound as the engineers intended it to.

    Bon Voyage!

    Attached Files:

  3. spacepower7 macrumors 68000

    May 6, 2004
    Please shoot me ;)

    You give absolutely no detail on your system or software used, nor your cable connections. I'd like to help but I'll probably forget this thread before you get around to giving me a detailed version of your issues if you respond soon, with details, we might actually be able to help.

    In general in the Apple world, I'd say to stay away from 5.1 aac since Apple doesn't use it. I only know of HTPC and PS3 people who use it. From what i have read, xbox360 can't use it but I may be wrong there.

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