ADPCM with Adaptive Pre- and Post-Filtering for Delay-Free Audio Coding

We propose an extension of ADPCM that includes adaptive pre-and post-filtering to achieve spectral shaping of the coding noise. The advantage of this coding scheme is that it allows a realization without algorithmic delay by making the filters backwards-adaptive. The measurements we present indicate that the addition of adaptive pre-and post-filtering to ADPCM results in a significant improvement in perceived audio quality. We therefore believe that the proposed system is a viable way to near-transparent lossy audio coding without algorithmic delay.