The built-in MP3 File and MP3 for Audio Podcasting settings use the MP3 transcoding format. This format encodes MP3 files, which are often used for digital audio players. You can also create custom settings that use the MP3 transcoding format.

The properties of built-in and custom settings that use this transcoding format are located in the General inspector and Audio inspector. These properties are described below.

Important: When you add a setting (or a destination that includes settings) to a job, Compressor analyzes the source media and then automatically assigns the most appropriate setting properties (based on the setting’s transcoding format and the characteristics of your source media file). It’s recommended that you use the automatically assigned setting properties.

Setting summary

Displays the setting name and transcoding format, as well as an estimated output file size. When you add a setting to a job or change the setting’s properties, this summary automatically updates.

General properties

  • Name: Displays the name of the setting.

  • Description: Displays the description of the setting.

  • Extension: Displays the extension of the output file (.mp3).

  • Allow job segmenting: This checkbox is dimmed because job segmenting is not available for settings that output only an audio file.

  • Default location: Select an item from the pop-up menu to set the default save location for transcoded files.


This section contains one property:

  • Set duration to: Sets the processing algorithm used to adjust the frame rate during transcoding. Select either of the following options:

    • [Percentage] of source: Modifies the output clip’s speed by a percentage of the source clip’s speed. Enter a value in the percentage field or choose a preset value from the adjacent pop-up menu (with a downward arrow).

    • [Total duration]: Sets the duration of the clip. Enter a timecode duration in the field or click the arrows to increase or decrease the time.

    For more information, see Retime video and audio.

Audio properties

  • Channel layout: Use the pop-up menu to set the audio channel layout. For more information, see About audio channels.

  • Sample rate: Use this pop-up menu to set the number of times per second that music waveforms (samples) are captured digitally. The higher the sample rate, the higher the audio quality and the larger the file size.

  • Data rate: Use the slider to set the number of kilobits per second (kbps) required to deliver your audio file. Using a higher rate will produce a higher-quality audio file.

  • Use variable bit rate encoding: Select the checkbox to vary the number of bits used to store the music depending on the complexity of the music. Variable bit rate encoding can reduce the size of the output file.

  • Joint stereo: Select the checkbox to have one channel carry the information that’s identical on both channels, and another channel carry unique information. At bit rates of 160 kbps and below, this setting can improve the sound quality of your converted audio.

  • Smart encoding adjustments: Select the checkbox to have Compressor analyze the source file and the setting’s encoding properties to maximize the quality of the output file.

  • Filter frequencies below 10 Hz: Select the checkbox to have Compressor remove inaudible frequencies from the source file and output a smaller and more efficient file without perceptible loss of quality.

Audio effects

For a list of available audio effects and instructions on how to add an audio effect to a setting, see Add and remove effects.