An Efficient Segment-Based Speech Compression Technique for Hand-Held TTS Systems

This paper proposes a novel segment-based speech coding algorithm to efficiently compress the database for concatenative text-to-speech (TTS) systems. To achieve a high compression ratio and meet the fundamental requirements of concatenative TTS synthesizers, i.e. partial segment decoding and random access capability, we adopt a modified analysis-by-synthesis scheme. The spectral coefficients are quantized by a length-based interpolation method and excitation signals are modeled with both non-predictive and predictive approaches. Considering that pitch pulse waveforms of a specific speaker show low intra-variation, the conventional adaptive codebook for pitch prediction is replaced by a speaker dependent pitch-pulse codebook. By applying the proposed algorithm to a hand-held Korean TTS system, we verify that the proposed coder provides a compression ratio of about 1/13, a low complexity of around 1.2 WMOPS, and random access capability.