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  1. Hello!

    I'm encoding a BRRip of 3GB to 700MB, I'm using VidCoder, I need to encode the Audio using AAC, in the settings I go to Audio and I don't know what to choose, AAC (avcodec), AAC (FDK) or HE-AAC (FDK).

    I searched all over the internet for help, could not find article that actually help me understand what I need.

    I know that I need the file to be compatible with mobile devices as well and not only on PC, I want my file to have the maximum compatibility, and I need to use AAC, so which one of the three to choose.

    Can you help me?

    And maybe on the way, you can explain in a basic language what each one of the three means and particularly what it is used for.


    Thanks in advance.
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  2. A Member since June, 2004 Keyser's Avatar
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    Originally Posted by yopmail View Post
    I'm encoding a BRRip of 3GB to 700MB, I'm using VidCoder, I need to encode the Audio using AAC, in the settings I go to Audio and I don't know what to choose, AAC (avcodec), AAC (FDK) or HE-AAC (FDK).
    Choose AAC (avcodec). FDK and avcodec are just different libraries used to encode the audio. HE-AAC is an extension of AAC LC.

    Originally Posted by yopmail View Post
    I searched all over the internet for help, could not find article that actually help me understand what I need.
    Really? I bet a google search will return a bunch of links in 5 seconds.

    Originally Posted by yopmail View Post
    I know that I need the file to be compatible with mobile devices as well and not only on PC, I want my file to have the maximum compatibility, and I need to use AAC, so which one of the three to choose.
    In that case why don't you just select the profile suited for your device and let VidCoder choose the appropriate settings.
    "The greatest trick the Devil ever pulled was convincing the world he didn't exist."
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  3. For max compatibility use AAC (avcodec) or AAC (FDK). For your purposes, it doesn't matter which.
    AAC (FDK) supposedly provides superior quality at the same bitrate than AAC (avcodec).
    HE-AAC is the best of all three at the same bitrate and although it is widely accepted, it is the newest and least compatible of the three.
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  4. Thanks.


    So if we leave the Quality issue aside, and we talk about compatibility ONLY, which to choose, avcodec or FDK?

    Cause if FDK is just as compatible as avcodec but it takes more time to encode, I dont mind it, I will use it to get higher quality, however if avcodec is compatible with certain devices that FDK does not, I will choose the avcodec even though it's supposedly lower quality.

    So the question is: Any device that support AAC (avcodec) MUST support AAC (FDK) as well? which is the most compatible between the two?
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  5. A Member since June, 2004 Keyser's Avatar
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    I don't think there are any compatibility issues with either one. As I said, they're just two different libraries to encode AAC.

    As for the quality, it is true that FDK tries to use as much bits as it can to encode lower frequencies which can result in a better sound to most people. However, this is done by "stealing" bits from higher frequencies that most people can't hear, but some can.
    "The greatest trick the Devil ever pulled was convincing the world he didn't exist."
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  6. For compatibility go with LC-AAC. In this case, AAC (avcodec) or AAC (FDK). For quality use AAC (FDK). Avcodecs AAC encoder is not as good as FDK yet.
    HE-AAC (FDK) should be used for very low bitrates, below 80kbs for stereo and below 256kbs for 5.1 audio. If your device does not support HE-AAC, which is LC-AAC + SBR, it will play just LC-AAC part. HE-AAC is backword compatible with LC-AAC decoders.
    Recent double-blind listening test on Hydrogenaudio showed that Apple AAC encoder and Fraunhoffer FDK AAC encoders are probably the best AAC encoders available to public and FAAC as the worst AAC encoder. Test was done at 96kbs.
    Last edited by Detmek; 2nd Feb 2015 at 00:45.
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  7. Originally Posted by Keyser View Post
    As for the quality, it is true that FDK tries to use as much bits as it can to encode lower frequencies which can result in a better sound to most people. However, this is done by "stealing" bits from higher frequencies that most people can't hear, but some can.
    Hmmmm.....

    Well in variable bitrate mode the default low pass filter frequencies might be a bit more aggressive than other encoders, but you can specify whatever low pass filter you like. In the highest quality VBR mode, no high pass filter is used.
    I found in VBR mode there's quite a bitrate jump between mode 4 and mode 5. I'd only use either of those modes but I found specifying a 18500 Hz low pass filter for mode 4 seemed to make the bitrate difference more balanced. The default for mode 4 is 15500 Hz.

    In constant bitrate mode the default low pass frequency for any decent bitrate is 17000 Hz. You can probably change it too, but unless you're using a fairly high bitrate it wouldn't be a good idea. Most people's hearing wouldn't go anywhere nearly as high as 17000 Hz anyway.

    Apparently these are the default low pass filter frequencies.
    http://wiki.hydrogenaud.io/index.php?title=Fraunhofer_FDK_AAC#Bandwidth

    All that's probably quite academic though, because I think Vidcoder only encodes in constant bitrate mode (could be wrong as I don't use it) and I doubt it'd let you specify a different low pass filter frequency.
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  8. yopmail,
    LC-AAC (low complexity) is probably what you want.
    HE-AAC is for low bitrates. It removes the higher frequencies then uses Spectral Band Replication (SBR) to reconstruct them. It's not unique to the FDK encoder. that's how HE-AAC works, but it's really only beneficial at low bit-rates and you may find many/most hardware players only support LC-AAC anyway. I'm not 100% sure there as I only use LC-AAC myself.

    And yes, use the FDK encoder.
    There's a lot of info about it here if you're interested. I don't use Vidcoder but I'd imagine it doesn't let you change the encoder settings all that much.
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  9. A Member since June, 2004 Keyser's Avatar
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    Originally Posted by hello_hello View Post
    I don't use Vidcoder but I'd imagine it doesn't let you change the encoder settings all that much.
    You can only choose the bitrate, nothing else. There are other settings like gain and DRC, but those are not codec specific.
    "The greatest trick the Devil ever pulled was convincing the world he didn't exist."
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  10. Hello guys and thanks for your answers, but...

    I already suspected from the begining, HE-AAC it's not for my use.

    However I wanted to know which is the most compatible with most devices, FDK or avcodec.

    Hope I will get an answer for this as well, thanks in advance.
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  11. Originally Posted by yopmail View Post
    However I wanted to know which is the most compatible with most devices, FDK or avcodec.
    Hope I will get an answer for this as well, thanks in advance.
    It doesn't matter. They're both AAC encoders. Any device capable of decoding AAC will be able to decode the audio regardless of the encoder used.
    Some devices might have a bitrate limit, but that's independent of the encoder. And some might only support stereo audio. For example most Apple devices support stereo LC-AAC up to 160kbps (specs for video files).
    http://www.apple.com/ipad-air-2/specs/
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