MacOS – What are the command line options for afconvert

audiomacosterminal

macOS includes a tool called afconvert which describes itself this way in the man page.

Audio File Convert will convert a source audio file to a new audio file with the specified file and data types

However, that's the entire man page. What are the command line options required and supported by afconvert? What are some basic examples of how to convert audio files back and forth?

Best Answer

Audio File Convert exports to 20 audio file formats and a multitude of codecs, all of which are shown with the -hf option.

Uncompressed Audio

File formats: AIFC AIFF NeXT Sd2f WAVE RF64

The original formats for storing audio files were all uncompressed because these are easy to work with, and can be played by even very early CPUs. However, uncompressed audio files are very large, easily going up to 10 MB/minute. These formats all share similar codec options like I8 BEI16 BEI24 BEI32 BEF32 BEF64. Smaller numbers give smaller files, but larger numbers give higher quality. If you're not sure what to choose, go with BEI32 or LEI32.

Compressed Audio

File formats: 3gpp 3gp2 adts ac-3 amrf m4af m4bf caff ec-3 flac mp4f

Not every codec is supported by every file format, but you can use this as a guide to get started choosing your codec. Once you've chosen a codec, you can look at the output of afconvert -hf to pick a suitable container file format.

aac MPEG-4 Low Complexity AAC
aace MPEG-4 AAC Enhanced Low Delay (without SBR)
aacf MPEG-4 AAC Enhanced Low Delay (with SBR)
aacg
aach MPEG-4 High Efficiency AAC
aacl MPEG-4 AAC Low Delay
aacp MPEG-4 High Efficiency AAC Version 2
ac-3 AC-3
alac Apple Lossless
alaw aLaw 2:1
drms Apple DRM
ec-3
flac Free Lossless Audio Codec
paac
pac3
pec3
samr
sawb
QDM2 QDesign2 Music
QDMC QDesign Music
Qclp QUALCOMM PureVoice
Qclq Qualcomm QCELP

(Note: I have excluded the MPG formats such as MPG3/MP3 from this list because they just do not work.)

Syntax

Once you've chosen a file format and codec, you run afconvert like this:

afconvert -f FORMAT -d CODEC SOURCEFILE [-o DESTINATIONFILE]

It is necessary to specify both the file format and the codec, otherwise an error is shown. If you omit the -o option, afconvert will pick a name and extension based on the other inputs.

Examples

If you have an audio file called MyAudio.m4a you could try these commands.

# AIFF
afconvert -f AIFF -d BEI32 MyAudio.m4a -o MyAudio.aiff

# WAVE
afconvert -f WAVE -d LEI32 MyAudio.m4a -o MyAudio.wav

# Apple Lossless
afconvert -f m4af -d alac MyAudio.m4a -o MyAudio.m4a

# FLAC
afconvert -f flac -d flac MyAudio.m4a -o MyAudio.flac

# AAC
afconvert -f mp4f -d aac MyAudio.m4a -o MyAudio.mp4

Related Solutions

MacOS – What are the afconvert settings for the iTunes Plus AAC encoding setting

I had the exact same obsession, and ended up creating a FLAC-to-iTunes importer that decodes FLAC files to WAV and imports them into iTunes using iTunes' own encoder: https://github.com/cbguder/FLAC2iTunes

It should be easy enough to modify FLAC2iTunes to support direct WAV input.

As for the soundcheck values, I compared iTunes, XLD and afconvert by encoding WAV files to AAC and decoding them back to WAV and comparing the decoded audio data. I also compared afinfo outputs for the encoded files. While the souncheck values are different for each file, the decoded WAVs are exactly the same, so even if you use XLD or afconvert, the chances are the resulting files will sound exactly the same.

For afconvert, I used the parameters suggested by Apple in the "Mastered for iTunes" guide, with an intermediate CAF file:

afconvert source.wav intermediate.caf -d 0 -f caff --soundcheck-generate
afconvert intermediate.caf -d aac -f m4af -u pgcm 2 --soundcheck-read -b 256000 -q 127 -s 2 final.m4a

For XLD, I used these settings:

Format: MPEG-4 AAC
Mode: VBR (Constrained)
Encoder Quality: Max
Sample Rate: Auto
Target bitrate: 256 kbps
Add gapless information for iTunes: checked
Write accurate bitrate information: checked

MacOS – What steps are needed to create a new user from the command line

Here is a shell script I wrote at work to handle this as part of the NetInstall process (creating a local administrator account automatically during imaging process).

#!/bin/sh
. /etc/rc.common
dscl . create /Users/administrator
dscl . create /Users/administrator RealName "Administrator Account"
dscl . create /Users/administrator hint "Password Hint"
dscl . create /Users/administrator picture "/Path/To/Picture.png"
dscl . passwd /Users/administrator thisistheaccountpassword
dscl . create /Users/administrator UniqueID 501
dscl . create /Users/administrator PrimaryGroupID 80
dscl . create /Users/administrator UserShell /bin/bash
dscl . create /Users/administrator NFSHomeDirectory /Users/administrator
cp -R /System/Library/User\ Template/English.lproj /Users/administrator
chown -R administrator:staff /Users/administrator

Some notes to mention:

I have this saved as an executable ".sh" file.
Since it executes during NetInstall it runs as root, and needs to run as root to work properly. You can also subtract the first two lines, add a "sudo" to the beginning of each subsequent line, and manually run these as individual commands in Terminal.
Modify UniqueID from 501 to a number that you will know is safe on all systems (501 is taken by the first account created on a Mac, generally something higher like 550 will probably be safe, depending on how many users you have on your system).
PrimaryGroupID of 80 creates an Admin user. Change to PrimaryGroupID of 20 to create a Standard user.
I've imaged well over 50 Macs this way with no issues. I use this account to run commands via SSH, to push out patches via ARD and to do local desk-side administration.