afconvert

Convert audio file to AAC

$ afconvert -f m4af -d aac [input.wav] [output.m4a]

$ afconvert -f m4af -d alac [input.wav] [output.m4a]

$ afconvert -f AIFF -d BEI16 [input.mp3] [output.aiff]

$ afconvert -f m4af -d aac -b [128000] [input.wav] [output.m4a]

afconvert [-f file-format] [-d data-format] [-b bit-rate] input output

afconvert is a macOS command-line tool for converting between audio file formats. It supports all audio formats handled by Core Audio, including WAV, AIFF, MP3, AAC, ALAC, CAF, and more.
The tool provides access to Apple's audio codecs and can perform sample rate conversion, bit depth conversion, and channel remapping along with format conversion.

-f format

Output file format: m4af, WAVE, AIFF, caff, etc.

Audio data format: aac, alac, BEI16, LEF32, etc.

Bit rate in bits per second for compressed formats

Sample rate for output file

Number of output channels

Encoder quality (0-127, higher is better)

Verbose output

Display available formats and help

This tool is macOS-only. Some format conversions may be lossy. AAC encoding quality varies with bit rate settings. Not all format combinations are valid.

afconvert has been part of macOS since Mac OS X, providing command-line access to the same audio conversion capabilities used by iTunes and other Apple applications.

ffmpeg(1), sox(1), lame(1)