afconvert

macOS audio file format converter

TLDR

Convert audio file to AAC

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

Convert to ALAC (Apple Lossless)

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

Convert to AIFF

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

Set bit rate for AAC encoding

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

Convert with VBR strategy

$ afconvert -f m4af -d aac -s 3 -b [128000] [input.wav] [output.m4a]

List supported formats

$ afconvert -hf

SYNOPSIS

afconvert [options] 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. If no output file is specified, the name is generated automatically and saved in the same directory as the input.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.

PARAMETERS

-f, --file format

Output file format (m4af, WAVE, AIFF, caff, etc.).

-d, --data format

Audio data format (aac, alac, BEI16, LEF32, etc.). Can include sample rate and format flags.

-b, --bitrate rate

Total bit rate in bits per second for compressed formats.

-c, --channels number

Number of output channels.

-l, --channellayout tag

Channel layout tag.

-q, --quality quality

Codec quality (0-127, higher is better).

-r, --src-quality quality

Sample rate converter quality (0-127, default: 127).

--src-complexity complexity

Sample rate converter complexity (line, norm, bats).

-s, --strategy strategy

Bitrate allocation strategy (0=CBR, 1=ABR, 2=VBR_constrained, 3=VBR).

-o filename

Specify output file path.

--dither algorithm

Dither algorithm (1 or 2).

--mix

Enable channel downmixing.

-v, --verbose

Display progress information.

-h, --help

Display help information.

-hf, --help-formats

List all supported file and data formats.

CAVEATS

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. Use -hf to see which formats are supported on your system.

HISTORY

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.