2

I have a big MP3 audio file, about 170 MB, which I'd like to check for clipping. In details I need to increase the audio volume but I don't want to push the volume too high and clip audio samples. I tried audacity to check samples visually but it hangs before I can view anything and — and my machine has 12GB RAM!

I know sox provides a visual indications when audio samples are clipped but I need to play the file. So is there any command line tool that can tell me whether samples are clipped without having to play it at normal speed?

5

sox doesn't need to play the file in order to gather statistics on it. Use -n to suppress sound output. Use the stat effect to find info on max levels:

$ sox mytest.mp3 -n stat
...
Maximum amplitude:     0.228743
Minimum amplitude:    -0.235424
...
Volume adjustment:        4.248

The above example file can have its volume increased by 4.2 to be normalised without clipping:

$ sox -v 4.24 mytest.mp3 norm.mp3
$ sox norm .mp3 -n stat 
...
Maximum amplitude:     0.921943
Minimum amplitude:    -0.951687
...
Volume adjustment:        1.051
  • Thanks @meuh, didn't know that. That's perfect. I had to increase the volume by at least 30db so get a sound close to normal listening conditions. – user86969 Aug 22 '15 at 20:10

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