Mp3

convert mp4a to mp3

ffmpeg -i inputfile.m4a -acodec libmp3lame -ab 93k outputfile.mp3

record mic on linux and convert it to mp3 with noise filter

arecord --device="hw:0,0" --format=S16_LE -c 2 rec.wav
ffmpeg -i rec.wav -acodec mp3 rec.mp3
ffplay rec.mp3