Ultra-low latency audio coding based on DPCM and block companding

A low delay audio coding scheme with good perceptual audio quality for a desired limited bit rate is presented. The proposed audio coding scheme is based on differential pulse code modulation (DPCM) and block companded (BC) quantization. Prediction is realized as a FIR filter in lattice structure. DPCM performs in feedback manner, therefore no transmission of prediction filter coefficients is needed. The incorporation of BC quantization in the DPCM relies on a prediction error recalculation scheme. The use of BC quantization in the DPCM allows to accurately follow the prediction error signal. This improves the perceptual audio quality significantly compared to a plain DPCM with an adaptive quantizer. An algorithmic delay below a half millisecond and an overhead of less than a half bit per sample is introduced due to the short fixed block length of the BC quantizer. Therefore, a real time bidirectional audio application is achievable.