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  1. what is the minimum suitable bitrate for AC3 audio? is 256kbps is good enough? i want to convert some bluray movie DTS audio to AC3 without losing much data.
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  2. Minimum bitrate for AC3 5.1 is 384kbps, recommended is 448kbps or better, up to 640kbps.
    DVDs have 384kbps and 448kbps for AC3 5.1 - 256kbps is only suited for Stereo.

    For best quality you should convert to 640kpbs.
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  3. Member Skiller's Avatar
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    256 Kbit/s is way too low for 5.1 AC3 to sound acceptable.
    I agree 384 KBit/s is about the minimum you may use, but better go higher if you can.
    Note that for DVD 448 is the maximum allowed; 640 is not DVD compliant (although it should work fine in almost all cases anyway).
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  4. Originally Posted by firekid View Post
    what is the minimum suitable bitrate for AC3 audio? is 256kbps is good enough? i want to convert some bluray movie DTS audio to AC3 without losing much data.
    Transcoding from DTS to AC-3 may be sub-optimal (never found deeptrough analysis how DTS artifacts will affect DCT based codecs) - in your case i would do some tests and will try to find some sweet spot between bitrate and quality - it should be quite fast - ffmpeg and simple script should be fine.
    Afraid that there is no free (open source) AC-3 codec capable to provide quality (VBR) focused encoding - you may try to reduce bandwidth (low pass) in FC + surround channels - this may help in bitrate allocation for both Front channels so perhaps 256...320kbps will be quality acceptable.
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  5. thank you all, i think i will use 448.
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  6. Anything above 320kbps.
    Below this = MP3 quality not AC3.
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