Warped Linear Prediction for Improved Perceptual Quality in the SCELP Low Delay Audio Codec
The SCELP (Spherical Code Excited Linear Prediction) audio codec, which has recently been proposed for low delay audio coding , is based on linear prediction (LP). It applies closed-loop vector quantization employing a spherical code which is based on the Apple Peeling code construction rule. Frequency warped signal processing is known to be beneficial especially in the context of wideband audio coding based on warped linear prediction (WLP). In this contribution, WLP is incorporated into the SCELP low delay audio codec. The overall audio quality of the resulting W-SCELP codec benefits from an improved perceptual masking of the quantization noise. Compared with existing standardized audio codecs with an algorithmic delay below 10 ms, the W-SCELP codec at a data rate of 48 kbit/sec outperforms the ITU-T G.722 codec at a data rate of 56 kbit/sec in terms of the achievable audio quality.