From the studio to everyone else
AIFF is what many Mac users have on their drives without thinking about it. Logic Pro and GarageBand bounce to AIFF by default, iTunes could import CDs as AIFF, and many sample packs and stems come in this format. The files sound perfect but are big, and outside the Mac world they cause trouble: some Windows programs, many phones, email services and upload forms reject them. Converting AIFF to MP3 is the quickest way to share a mix, send a demo or put an album on any device.
Picking the bitrate
AIFF is uncompressed, so the MP3 encoder starts from a perfect source. The bitrate decides how close the result stays to it:
| Use | MP3 bitrate | A 4-minute song |
|---|---|---|
| Sending a mix for feedback, DJ use | 320 kbps | about 9.6 MB |
| Music on headphones | 256 kbps | about 7.7 MB |
| General listening | 192 kbps | about 5.8 MB |
| Rough demo, voice | 128 kbps | about 3.8 MB |
The original AIFF at 16-bit and 44.1 kHz takes about 42 MB for the same song, and a 24-bit bounce at 48 kHz around 69 MB.
High-resolution bounces
MP3 works with 16-bit-equivalent resolution and sample rates up to 48 kHz. A 24-bit, 96 kHz AIFF is converted to a sample rate MP3 supports; no audible information is lost in that step. What matters more is headroom: if your mix peaks right at 0 dB, the MP3 encoder can create small overs that clip on playback. Leaving about 1 dB of headroom in the bounce, or using normalize with a peak target of -1 dB, prevents this.
Tags and file names
Many AIFF files have no tags, especially bounces from music software. If the AIFF contains an ID3 chunk, for example from an iTunes CD import, title, artist and album are copied to the MP3. Otherwise, add them afterwards in your music player. Keep the AIFF as the master: if you need another format later, convert again from the AIFF rather than from the MP3. For a smaller file with no loss at all, AIFF to FLAC is the right choice, and for Apple devices AIFF to M4A gives better quality at the same size.