If you use AAC (Advanced Audio Coding) encoding, you can use custom settings for greater control over the quality and size of imported files.
To use custom settings with AAC encoding:
ChooseÂ iTunesÂ > Preferences, click General, and click Import Settings.
Choose AAC Encoder from the Import Using pop-up menu.
Choose Custom from the Setting pop-up menu.
In the dialog that appears, choose settings:
Stereo Bit Rate: The higher the Mono or Stereo kilobits per second (kbps), the higher the audio quality and the larger the file size. The most common bit rate for stereo AAC files is 128 kbps. Lower bit rates are more appropriate for sound files containing voice recordings (as opposed to music).
Sample Rate: The number of times per second the music waveforms are captured digitally. The higher the sample rate, the higher the quality and the larger the file size. Don’t choose a rate higher than the rate used to store the music originally or you’ll waste space. CD quality, for example, is 44.100 kHz, so choosing a higher rate when you’re encoding from a CD is unnecessary. In general, the best choice is Auto, which uses the same rate as the original music.
Channels: If you don’t have stereo speakers or if your audio files are monaural (mono files are about half the size of stereo files), choose Mono. If you’ll be listening through headphones or a stereo system, choose Stereo or Auto. Auto converts monaural tracks that into mono files and stereo files into stereo files.