How to convert 22kHz mp3 to a CD playable in a CD player. Not the most spectacular task, but I had to do some digging to figure it out. And I might as well write it down for the next time :)

Problem:⌗

A relative asked me to convert some audio from some legal proceedings, given to him in mp3 format, to a CD so he could listem to it.

The audio files were in a different sample rate then what CD’s use.

$ file 12345678.mp3
12345678.mp3: RIFF (little-endian) data, WAVE audio, MPEG Layer 3, stereo 22050 Hz

(file name is obscured)

Solution:⌗

First we have to convert the file from MPEG to WAV. (apt-get install mp3-decoder)

$ mp3-decoder -w 12345678.pre.wav 12345678.mp3

Then we get a WAV file that is in the wrong bit rate:

$ file 12345678.pre.wav
12345678.pre.wav: RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, stereo 22050 Hz

This was the step that was a bit difficult to discover. I don’t use sox often, but I knew that sox was the right tool for this job. This is how to upsample the file:

$ sox -t wav 12345678.pre.wav -t wav -r 44100 12345678.wav resample -ql

Which gives us a CD-quality audio track:

$ file 12345678.wav 
12345678.wav: RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, stereo 44100 Hz

And now we can burn the file to CD and make a relative happy:

$ cdrecord -v -dao -audio -pad speed=24 12345678.wav

And that’s it.

See also…⌗

I have been told that you can use mplayer also (have not tried it)… here is something that you can investigate also:

$ mplayer -ao pcm:12345678.wav