AAC Export Options - Audacity Manual

# AAC Export Options

From Audacity Development Manual
AAC is a lossy, compressed audio format. It is the default audio format for Apple Music/iTunes\xc2\xae, iPhone\xc2\xae, iPad\xc2\xae and iPod\xc2\xae

| FFmpeg is not shipped with Audacity but you can download it and then export as AAC by following these instructions.

| Please be aware that there is a bug in Audacity whereby the bit rate setting that you make in an AAC export is not always honored by Audacity. See this logged bug for more details. For stereo all selected bit rates of 196kbps export at 196kbps - this includes the default bit rate setting of 160 kbps Settings in the range 200kbps to 224kbps are closely honored on export. On Mac higher bit rate settings are honored but not so on Windows where settings of 256kbps and 320kbps produce files of 233kbps and 235kbps.
| The workaround is to export as uncompressed WAV or AIFF and use iTunes/Music to make the AAC conversion, see this page for information regarding this.

  Accessed by: File > Export > Export Audio... then choosing M4A(AAC) Files FFmpeg from the Save as type dropdown menu

  Also accessed by: File > Export > Export Multiple... then choosing M4A(AAC) Files FFmpeg from the Save as type dropdown menu.

  In this case the options dialog will appear in the center of the Export Multiple dialog.

## Format Options

- Quality: This box controls the quality (bit rate in kbps) of the output AAC file. The Maximum bit rate (best quality) is 320 kbps (stereo) 160 kbps (mono) and the minimum is 98 kbps (mono).

  You can use the up/down arrow-heads to change the required value or you can simply type it in.

  The default quality setting of 160 typically produces a similar sized, but slightly higher quality file compared to an MP3 at Audacity's default 128 kbps constant bit rate. A stereo file is always produced, but a file exported from a mono track will have about half the bit rate (and hence half the file size) of one exported from a stereo track.

| On Mac please only use the up/down arrows to set your required bit rate as there is a bug whereby if you type a value Audacity will ignore that and use the last previously used value instead.

Like OGG, AAC encoding is a form of VBR or variable bit rate encoding, as opposed to the CBR or constant bit rate encoding used by default when exporting MP3 files.

This means that in order to maintain consistent quality throughout a track, a higher bit rate will be used when encoding a complex piece of audio (such as a full orchestral passage) than when encoding a solo voice or instrument. A recording which has more complex audio will produce a larger file. Increasing the sample rate in Audio Settings Preferences will increase the bit rate and so the file size (and vice versa).