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  1. Member
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    Jun 2007
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    Canada
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    Hi Everyone

    Just curious . . .

    what is the difference transcoding a 44,100 mp3 file to an 48,000 ac3 file?

    1. using ffmpeg or besweet i.e. decode -> mp3 then encode -> ac3

    2. using an avs file with either ffmpeg or besweet where the input is considered uncompressed
    decode wav/pcm ? then encode -> ac3

    On the surface it seems that transcoding from an avs "uncompressed" file would be better - and would apply to all compressed audio formats?

    TIA
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  2. Member
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    There shouldn't be any difference.

    On the decode side, FFmpeg (and I assume Besweet too) always first internally decompress the file to raw PCM.
    You cannot re-encode directly from mp3 to ac3.
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  3. Member AlanHK's Avatar
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    They're all the same, in that they decode/decompress, process (to resample) and reencode.

    However while the decoding will the same, there is a difference in quality of encoding.

    Besweet hasn't got a great rep for its AC3 encoding, and hasn't been updated for many years.

    I like to stream from an AVS file to Aften. This allows me to keep keep exact sync with video if I cut it (with "Trim()"), and there are some simple but powerful audio functions you can use to adjust volume, delay, sampling, downmix, etc. The newish function Soundout() gives you a direct export to AC3 from Avisynth.

    But anything fancy, like noise reduction, I export to wave (Soundout() is one good way) and use Audacity.
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  4. Member
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    Thanks for the info.

    @AlanHK - Besweet can use Aften - with the updated bsn.dll

    wiseant
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  5. Member AlanHK's Avatar
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    Originally Posted by wiseant
    Thanks for the info.

    @AlanHK - Besweet can use Aften - with the updated bsn.dll

    wiseant
    As far as I can see, that's just using Besweet to decode and piping it into Aften.
    It's not really integrated into it. Is it in any of the GUIs?

    I just use ffmpeg, like:
    Code:
    for %%I in (%1) do (
    ffmpeg -i "%%I" -ar 48000 -f wav -vn -y - | p:\aften\aften.exe -b 192 - "%%~nI.ac3"
    )
    for just about any audio format. (Or you can use ffmpeg to encode the AC3 if you prefer.)

    or use wavi on an AVS file:
    Code:
    for %%I in (%1) do (
    wavi %%I - | p:\aften\aften.exe -b 128 -s 1 -w 45 -dnorm 27 - "%%~nI.ac3"
    )
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