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  1. Member
    Join Date
    Feb 2010
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    Lithuania
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    I know that encoding a raw avi file with H264 and AAC is never recommended, but it works on computers and i am fine with it.

    So now, i need an encoder like AAC to encode my raw uncompressed avi file. It's audio is uncompressed 1500 kbps 2 channel stream. I need an encoder to make it 5.1 with lower bitrate, something like 500 kbps i guess, but it seems that AAC as an installation package is a decoder only, not encoder...

    What do i need to install into my PC, so that my virtual dub could use as a high bitrate encoder, that would work good with H264 video encoder?
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  2. VirtualDub only handles stereo audio. You'll need some other software to convert your stereo source to 5.1. You can't make real 5.1 from a stereo source.
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  3. Member
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    Feb 2010
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    Lithuania
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    Fine, let it be stereo, but i still need an audio encoder suitable for H264 that would work in vdub. AC3 filter did not work.
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  4. What video codec you use has no bearing on the what audio codec you use. You're free to use whatever audio codec you want. There must be a version of AC3 ACM that supports encoding. I have version 2.2 and it definitely encodes stereo up to 640 kbps with VirtualDub.
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  5. Member
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    Feb 2010
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    Lithuania
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    Yes, AC3 ACM was working.
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  6. Member
    Join Date
    Aug 2013
    Location
    Central Germany
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    VirtualDub itself will only create AVI containers.

    H.264 (AVC video) does not belong into an AVI container.
    AAC audio does not belong into an AVI container either.

    I don't want to say it is technically impossible to force them into it; it is indeed possible. But this container is obsolete, outdated, does not support many features of AVC and AAC streams (e.g. different handling of I and IDR frames, B frames in general and especially with multiple references, and VBR audio streams with so little support that there is hardly any certain 2CC). They belong into an MP4 container instead (or maybe MKV which can contain almost anything); but VirtualDub on its own won't be able to create that.

    At least, since version 1.10.0, VirtualDub supports external encoders and piping video and audio streams to them, it supports configuring a set of video encoder, audio encoder, and additional multiplexer. So you can export your result and have command line tools (e.g. x264.exe, qaac.exe, and MP4Box.exe) create an MP4 containing AVC and AAC.

    By the way, I remember that there are AC3 decoders which will choke on 640 kbps stereo AC3; this is a bitrate meant to be used for multi-channel, more than 2. Based on the "square root of channels" thumb rule for audio formats with good channel coupling, stereo AC3 (no matter if Pro-Logic or not) will sound great already with 192 or 224 kbps and be very compatible to most decoders too. No need to exaggerate. I believe Aften uses similar psycho-acoustic models as LAME, and MP3s encoded with LAME at 192 or 224 kbps will be "audibly transparent", usually.

    Regarding AAC, don't talk about bitrates; instead, rely on VBR quality levels. QAAC with TrueVBR level 81 or 90 should be satisfying.
    Last edited by LigH.de; 20th Oct 2014 at 14:12.
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