MP3 Format Preferences allow setting up how output MP3 files are encoded. This tab allows specifying Constant or Variable Bit Rate, automatically or manually set Bit Rate value, Audio Quality, and Channels.

To open MP3 Format Preferences tab, choose 'Preferences' in Application Menu and select Format tab.

MP3 format settings, such as Bit Rate, Sample Rate, and Channels, are the most important aspects of conversion. Automatic Bit Rate and Sample Rate prevent degrading of audio quality or useless resampling. "As Source" Audio Channels for MP3 format wisely downmixes multi-channel songs into true-Stereo.

Optimal Constant Bit Rate value

Constant Bitrate settings in To MP3 Converter for Mac

Constant Bit Rate (CBR) means the Bit Rate is a constant, regardless of the complexity of the audio being encoded.

Advantages of Constant Bit Rate:

  • easy to control the size and quality of a file.
  • easy to stream.
  • full compatibility with hardware and software MP3 players.

Disadvantages of Constant Bit Rate:

  • use of high Bit Rate can result in the creation of large files.
  • unless high Bit Rate is in use, audio quality can suffer. 

Optimal value of Constant Bit Rate

The higher the Bit Rate, the better the quality, but higher Bit Rates create larger files.

Auto Bit Rate lets the application to calculate the best Bit Rate of encoded audio depending on the Bit Rate of source files. Automatical Bit Rate preserves audio quality and saves hard drive space. We recommend the use of automatical Bit Rate in a case when there are no requirements for the value of output Bit Rate, and if you don't want to get insights of audio conversion.

16-64 kbps are used primarily for voice, which does not require a high bandwidth.

128 kbps may be the only option for some car players. Many CD car players may not playback MP3 files with Bit Rates higher than 128 kbps.

128-256 kbps is deemed to be of ‘near CD quality’ and may give the best quality of encoded audio. The difference between 256 and 320 kbps is unnoticeable for a majority of listeners.  

Quality of Constant Bit Rate

Check "High Quality" option to encode audio with higher quality but at a lower speed of conversion.


Optimal Variable Bit Rate values

Variable bitrate settings in To MP3 Converter for Mac

Variable Bit Rate (VBR) means that Bit Rate varies throughout the audio, between low and high Bit Rates depending on the complexity of the audio at given moment. Variable Bit Rate is more efficient than CBR, and can, therefore, deliver audio of comparable quality in a smaller size.

Advantages of Variable Bit Rate:

  • easy to create high-quality audio with a smaller size.
  • high Bit Rates don't necessarily result in the creation of large files.

Disadvantages of Variable Bit Rate:

  • impossibility to stream.
  • partial compatibility with hardware and software MP3 players.
  • difficult to control the size of output audio. 

Low Bit Rate and High Bit Rate values for Variable Bit Rate.

Low Bit Rate and High Bit Rates are the minimal and the maximal allowed Bit Rate bounds. Variable Bit Rate can vary between the set of low and high Bit Rate values. The higher the Bit Rate, the better the quality, but higher Bit Rates create larger files. 

Quality of Variable Bit Rate

The quality of MP3 files, converted to Variable Bit Rates using To MP3 Converter, can vary from 0 (Best Quality, minimal quality losses after conversion) to 9 (Best Speed). Accordingly, you can set desired Quality value from 0 to 9 to select algorithm allowing to encode audio with better quality or higher conversion speed. 


Audio channels customisation in To MP3 Converter for Mac 

  • As Source - Mono or Stereo will be used depending on channels of a source audio. MP3 format does not allow to hold more than two channels, so source audio with more than two channels will be downmixed to stereo.

  • Stereo - the encoder makes no use of potentially existing correlations between the two input channels. It can, however, negotiate the bit demand between both channels, i.e. give one channel more bits if the other contains silence.

  • Joint - takes advantage on a similarity of two channels and uses the savings on the second channel to give higher quality compression. This method gives smaller files, but a stereo image can be distorted in encoded audio.

  • Dual - forces separate encoding of left and right channels. Each channel will have exactly half of the Bit Rate. This mode is designed for applications like dual languages encoding (for example, English in one channel and French in the other). Using this encoding mode for regular stereo audio will result in a lower quality encoding.

  • Mono  - this option will generate a mono audio. If the source audio has more than one channel, it will be downmixed to a mono. Mono is to be used automatically when the constant or minimal Bit Rate is less than 24 kbps.

Sample Rate

Select ‘As Source’ when encoded audio should have the same sample rate as source audio. This is the default preferred setting.

Sample Rate depends on Constant Bit Rate or Variable Bit Rate and can be changed to the best value corresponding to selected or automatically detected Bit Rate. To make sure the Sample Rate value will have an effect, please avoid using automatic Bit Rate and use a fixed Bit Rate instead. 

A fixed Sample Rate also can be set from 8000 to 48000 Hz. If the Sample Rate of source audio differs from fixed Sample Rate, the output audio will be resampled.

Cyclic Redundancy Check (CRC)

Check this option to enable CRC error protection. CRC code or checksum is added to each frame of encoded audio, allowing to detect transmission errors that could occur on the MP3 stream. It is the responsibility of player or receiver to check CRC codes, and many players just ignore them.