MP3 bounce options in Logic Pro for Mac

You can bounce projects to MP3 (MPEG-2, Audio Layer 3) files. The MP3 file type, developed by the Fraunhofer Institute, allows high compression rates while maintaining reasonable audio quality. MP3 is a widely used standard for audio file exchange over the internet.

Because the MP3 file type involves a loss of audio quality, you shouldn’t use MP3 files during production if you have access to the same audio data in non-lossy file types such as AIFF or WAVE.

Bounced PCM files are also used for encoding to MP3/M4A. Note that this occurs before dithering takes place.

If PCM is unselected in the Destination area of the Bounce dialog, a temporary PCM file is created and used as a source for bouncing to MP3 or M4A, or for burning to a CD (depending on which options are selected).

Selecting the MP3 option in the Destination area automatically disables the PCM > Surround option. This is because the MP3 file type doesn’t support surround. However, Split Stereo format is possible, even if the encoded MP3 file is set to Joint Stereo mode.

When you click MP3 in the Destination area, the following options are available:

• Bit Rate (Mono/Stereo) pop-up menus: MP3 bit rates between 32 kbit/s and 320 kbit/s are available, but they default to 80 kbit/s mono and 160 kbit/s stereo. These rates offer acceptable quality and good file compression.

  For enhanced audio quality, you can choose:

  • 96 kbit/s for mono streams

  • 192 kbit/s for stereo streams

  You can choose higher rates, but the quality improvement afforded by bit rates above 96/192 kbit/s is nominal. Note that the higher the bit rate, the larger the size of the bounced file.

• Use Variable Bit Rate Encoding (VBR) checkbox: Variable Bit Rate encoding compresses simpler passages more heavily than passages that are (more) harmonically rich, generally resulting in better quality MP3 files.

  Because not all media players can accurately decode VBR-encoded files, this option is off by default. If you know that your target listeners can decode VBR-encoded files, you can turn this option on.

• Quality pop-up menu: Keep this set to Highest (the default) whenever possible. Reducing the quality shortens the conversion process, but at the expense of audio quality.

• “Use best encoding” checkbox: Like the Quality parameter, if you deselect this option, you shorten the time needed to bounce the file at the price of audio quality. This should always be selected, unless conversion time is an issue.

• “Filter frequencies below 10 Hz” checkbox: When this option is selected, frequencies below 10 Hz (which usually aren’t reproduced by speakers, and aren’t audible to human ears at any rate) are removed. This leaves slightly more data bandwidth for the frequencies that are audible, resulting in an improvement of the perceived quality. Only deselect this option if you’re experimenting with subsonic test tones.

• Stereo Mode pop-up menu: Choose Joint Stereo or Normal stereo mode. Depending on the original file, these settings may (or may not) offer any audible difference. Experiment with both settings to see which provides better results.

• “Write ID3 tags” checkbox: Writes ID3 tags to the file.

• ID3 Settings button: Opens a dialog where you can change ID3 tags.

  

  To edit an ID3 tag, double-click any of the Content column fields to the right of the corresponding ID3 Frame column entry, and enter your text.

  Select the “Use default values” checkbox to display default settings for certain Content columns, such as the Project Title and Tempo (Beats Per Minute) columns. Selecting “Use default values” also sets the Initial Key column to the first entry shown in the Signature track (This defaults to C if no key has been set for the project).

• “Add to Music” checkbox: Select this box if you want to add the .m4a file to your Music library.

  Note: If your Mac is running macOS Mojave or earlier, an “Add to iTunes” checkbox replaces the Add to Music checkbox.