Scelp: Lowdelay audio coding with noise shaping based on spherical vector quantization

In this contribution a new wideband audio coding concept is presented that provides good audio quality at bit rates below 3 bits per sample with an algorithmic delay of less than 10 ms. The new concept is based on the principle of Linear Predictive Coding (LPC) in an analysis-by-synthesis framework, as known from speech coding. A spherical codebook is used for quantization at bit rates which are higher in comparison to low bit rate speech coding for improved performance for audio signals. For superior audio quality, noise shaping is employed to mask the coding noise. In order to reduce the computational complexity of the encoder, the analysis-by-synthesis framework has been adapted for the spherical codebook to enable a very efficient excitation vector search procedure. The codec principle can be adapted to a large variety of application scenarios. In terms of audio quality, the new codec outperforms ITU-T G.722 [4] at the same bit rate of 48 kbit/sec and a sample rate of 16 kHz.