Ubuntu – Is it possible to convert a 30 second clip of an .mp3 to .wav via the command line

The most appropriate command line tool is the ffmpeg utility available to be installed via the software center/synaptic manager.

A command line example would be something like this for Constant Bitrate Mode (CBR):

ffmpeg -i inputfile.m4a -c:a libmp3lame -ac 2 -b:a 190k outputfile.mp3

Or even better for Variable Bitrate Mode (VBR):

ffmpeg -i inputfile.m4a -c:a libmp3lame -ac 2 -q:a 2 outputfile.mp3

More information on mp3 encoding with FFmpeg can be seen here:

FFmpeg MP3 Encoding Guide

Note : What you want isn't directly possible with mpg123. I recommend using SoX instead -- the "Swiss Army Knife of sound processing".

Transcoding only a portion of an MP3 file to WAV and resampling it to a different rate

• Install SoX along with MP3 format support from the terminal with sudo apt-get install sox libfmt-sox-mp3

• You can then perform the transcoding you require via this command:

  sox -V3 input.mp3 -r 44100 output.wav trim 0:10 0:10
  

  • The -r option, inserted before the output file name, indicates that you want to resample the output to 44100 Hz.
  • The trim option, inserted after the output file name, indicates that you want to transcode only the portion beginning at 0 minutes and 10 seconds (first 0:10), for a length of 10 seconds from that point (second 0:10).
  • The -V3 is optional and simply tells sox to display the input/output parameters and transcoding progress for your information.