MP3Pro is a combination of MPEG 1/2 Layer III (MP3) and Spectral Band Replication (SBR) technology. The MP3 codec is used for the coding of the low frequencies of an audio signal. SBR is used at the decoder to recreate the higher frequencies out of the low frequencies together with some control information that is added by the encoder.
This combination can improve the coding efficiency of MP3 by more than 30% at lower bit rates. MP3Pro is able to deliver good-quality audio signals at bit rates of 64 kbit/s to 96 kbit/s for stereo audio signals.