An Approach to the Decoder Complexity Reduction in Waveform Interpolation Speech Coding

Since current Text-to-Speech (TTS) synthesizers are mostly based on a technique known as synthesis by concatenation, the implementation of a high quality TTS requires huge storage space for a large number of speech segments. In order to compress the database in the TTS system, the use of speech coders would be an efficient solution. Waveform Interpolation (WI) has been shown to be an efficient speech coding algorithm to provide high quality speech at low bit rates. However, its applications are constrained due to the high computational complexities. Especially, for the application of speech compression for the TTS database, the decoder complexity is one of the major factors in order to utilize the speech coder in the TTS system. In this paper, we describe an approach to the complexity reduction in WI speech decoder, which is used for compressing the database of the TTS system. The proposed idea is able to reduce the complexity by removing the realignment process from the decoder procedure in WI. Since the realignment factor obtained in the encoder should be transmitted to the decoder in order to realign the characteristic waveforms, overall bit rate is slightly increased. We can reduce the decoder complexity by 20 percent utilizing the new approach to the realignment procedure.