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  1. Member
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    I want to convert .ac3 stereo 2.0 to .aac

    AC3 SPECS (MEDIAINFO): Bit Rate: 192kbps SR: 48.0 KHz

    In Megui, FDK-AAC:

    What is the difference between "mpeg 4" and "mpeg 2" AAC-LC profiles?

    Which is a good quality (1-5) for vbr?
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  2. I'm not a fan of fdkaac. you'd probably be better off using QAAC or Nero.

    I wrote a mini essay a while back explaining a bit about the various AAC encoders and where to find them. MeGUI supports QAAC, NeroAAC and FDKAAC.
    https://forum.videohelp.com/threads/370412-Looking-for-an-AAC-LC-encoder-from-Frauenhof...=1#post2376348

    The fourth paragraph mentions fdkaac's somewhat odd low pass filtering and how to change it. It's also explained here:
    http://wiki.hydrogenaud.io/index.php?title=Fraunhofer_FDK_AAC#Bandwidth

    What is the difference between "mpeg 4" and "mpeg 2" AAC-LC profiles?
    I'm not 100% sure about that one. Fdkaac is the only encoder that lets you choose, as far as I know.

    For "good" quality you probably want to use VBR 4 or 5, but maybe while also changing the low pass filtering, although you might find for 192kbps stereo AC3 it's not worth re-encoding because it doesn't reduce the bitrate enough. Look at it like this..... people once often used 128kbps for MP3 and your AC3 is 192kbps. For an encode of a 2 hour movie you're probably looking at about 110MB vs 170MB. Unless you're trying to squish a movie onto a 700MB CD does an extra 60MB over two hours matter that much?

    Of course if you're using a playback device that doesn't support AC3, ignore most of the last paragraph.
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  3. DECEASED
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    Originally Posted by Mildragon
    What is the difference between "mpeg 4" and "mpeg 2" AAC-LC profiles?
    http://www.mp3-tech.org/aac.html

    Originally Posted by hello_hello
    Fdkaac is the only encoder that lets you choose, as far as I know.
    faac and enc_aacplus can do the trick as well.
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  4. Member
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    Thanks for the information. I would like to check also QAAC 2.57. Could someone give me a simple example for using command line prompt with QAAC? Or maybe a GUI that supports QAAC 2.57.....
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  5. MeGUI supports it. Version 2.55 works fine and I'm not aware of a QAAC update breaking it. I haven't upgraded QAAC myself yet.
    You need to enable QAAC in Options/Settings/External Programs Configuration, and probably restart MeGUI.

    Foobar2000's converter includes a preset for VBR QAAC encoding, or you can create your own, modifying the commandline to suit.

    QAAC 2.77 was released pretty recently. If you're keen you can manually replace QAAC in MeGUI's Tools folder with a newer version but there's generally no need to rush. The Apple/Quicktime files do the encoding (and they're not updated often), so in that respect it doesn't matter too much if you don't upgrade QAAC in a hurry. I assume you're downloading the QuickTime installer and extracting the required files with makeportable (you'll find it at the QAAC web site).
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  6. Member
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    Ο.Κ. done!

    For 2.0 stereo anime sound I believe LC-AAC CVBR 128 Kbits will be fine.... or not?
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  7. It should be fine, although it's not something I'd generally do, given the bitrate reduction is only 64kbps.

    I re-encode DTS regularly as for a movie with 5.1ch audio, that can save you up to 1GB of hard drive space, but I don't bother re-encoding AC3. Each to their own though....
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  8. Member
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    Last question: For 192 Kbits AC3 stereo anime sound, what is the general "safe" level of bitrate in QAAC? Should I apply lower bitrate than 128 Kbits or not?
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  9. The AC3 bitrate really doesn't have anything to do with the required AAC bitrate. I can't answer the question exactly, because I always use higher bitrates. It seems though, below 128kbps you're heading into the territory where you can pick the AAC from the original audio in an ABX test.

    http://listening-test.coresv.net/results.htm

    It doesn't mean it'll sound bad, maybe just different when carefully compared to the original. I've no idea how much you can reduce the bitrate before you're in "sounds bad" territory. I've never tried it.
    Last edited by hello_hello; 4th Jan 2016 at 15:16.
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