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Just annotations of little "how to's", so I know I can find how to do something I've already done when I need to do it again, in case I don't remember anymore, which is not unlikely. Hopefully they can be useful to others, but I can't guarantee that it will work, or that it won't even make things worse.
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Speeding up and reducing the quality of podcasts (saving disk space)

Posted 04-29-2017 at 10:49 PM by the dsc
Updated 09-15-2017 at 02:55 PM by the dsc

An interesting method I now realize is possible:

ffmpeg -i in-normal.mp3 -filter:a "atempo=1.4" -f wav - | lame -q 2 -v --vbr-new -V 9 -b8 -B 20 - out_speedup.mp3
A previous method I was using had sox and for some reason mpg123 or 321 I guess, to generate a "physical" temporary wav somewhere, this method use a pipe instead of an actual temporary file.

The input file isn't necessarily mp3, it can be m4a/aac at least, possibly also webm, I guess, whatever ffpeg can read, which I suppose is a lot of things.

In some cases you can do it all just with ffmpeg, but I just can't find clear documentation on how to achieve a comparable level compression, regardless of reencoding to mp3 or something else. The options are somewhat different, like, instead of specifying the variable bitrate range (given there by "-b 8 -B 20"), you chose just a "quality" level from 1 to 3 or to 5, and that would require to me at least a little bit of testing to see if quality 1 (worst) is simply unintelligible or unecessarily "higher" quality for this purpose.

(and once again I first close "code" with "quote")
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  1. Old Comment
    Thanks for the great tip!
    Posted 05-29-2017 at 06:08 AM by Kefijoo Kefijoo is offline


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