Enhancing Audio Coding Efficiency of MPEG Layer-2 with Spectral Band Replication (SBR) for DigitalRadio (EUREKA 147/DAB) in a Backwards Compatible Way
Layer2 + SBR is an audio coding scheme which exceeds significantly the coding efficiency of MPEG-1/2 Layer2 especially for broadcasting applications like DAB (Digital Audio Broadcasting). Spectral Band Replication (SBR) is a technique to enhance the efficiency of perceptual audio codecs. High frequency parts of an audio signal are reconstructed on decoder side, so the audio encoder can focus on coding the low frequency part. Thus, a bitrate reduction can be achieved while maintaining subjective audio quality. Besides increasing the coding efficiency, the use of MPEG-Layer2 + SBR inside Eureka DAB would maintain backwards compatibility: Existing DAB receivers are capable of decoding the (bandwidth limited) Layer2 part of the bitstream. This paper describes the functionality of SBR and Layer2 + SBR and the achievable increase in coding efficiency. Furthermore, possible application and introduction scenarios are addressed.
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