Signal transformation and interpolation based on modified DCT synthesis

This paper proposes a novel signal transformation and interpolation approach based on the modification of DCT (Discrete Cosine Transform). The proposed algorithm can be applied to any periodic or quasi periodic waveform for time scale and/or pitch modification purposes in addition to signal reconstruction, compression, coding and packet lost concealment. The proposed algorithm has two advantages:

• (i) 

  Since DCT does not have the explicit phase information, one does not need the cubic spline interpolation of the phase component of the sinusoidal model.

• (ii) 

  The parameters to be interpolated can be reduced because of the energy packing efficiency of the DCT. This is particularly important if signal synthesis is carried out on a remote location from the transmitted parameters.

The results are presented on periodic waveforms and on speech signal in order to appreciate the fidelity of the proposed algorithm. In addition, the proposed method is compared with TD-PSOLA, sinusoidal model and phase vocoder algorithms. The results are presented in objective PESQ scores for time scale modification and output files are provided as supplementary material,¹ for subjective evaluation, for packet lost concealment. Results prove that the proposed modification of the DCT synthesis provides a favorable algorithm for specialists working in the signal processing area.