MP3 (MPEG-1/2 Layer III)

MPEG-1/2 Layer III (MP3) is the name for the audio coding system within the MPEG-1 and MPEG-2 standard for video coding. MP3 can be used for:

• Single channel;
• Dual channel,
  • Two independent channels,
    (i.e. two different languages)
  • Stereo,
  • Joint stereo,
    (both mid/side stereo and , for lower bit rates intensity stereo);
• Multichannel signals, including 5.1 surround sound,
  (added in MPEG-2 Audio, not available in MPEG-1 Audio).

MPEG audio can use a number of sampling frequencies. MPEG-1 defines audio coding at sampling rates of 32 kHz, 44.1 kHz and 48 kHz. MPEG-2 added coding at lower sampling rates of 24 kHz, 22.05 kHz and 16 kHz. The resulting bit rate is somewhere in the range of 8 kbit/s (32 kbit/s for MPEG-1 Audio) up to 320 kbit/s. The bit rate can be both variable or fixed.

MP3 is based on perceptual coding. This means that the coding is based on the removal of tones that can not be heard by the human ear.