Low bit-rate quantization of LSP parameters using two-dimensional differential coding

A novel spectral coding method, two-dimensional differential line spectra pair coding (2DdLSP), is proposed. Taking advantage of the strong inter-frame, and intra-frame correlation of LSP parameters, a two-dimensional linear prediction technique is used to reduce the variance of the parameters to be quantized. One scalar quantization and two vector quantization schemes are designed to quantize the 2-D prediction residuals. Without further buffering delay, the spectral distortion of 1 dB² can be achieved at 19 b/frame when the frame period is 10 ms. Both within- and out-of-training tests show the robustness of the method to speech data variance