This paper describes the design of a unified framework for a multilingual text-to-speech （TTS） synthesis engine - Crystal. The unified framework defines the common TTS modules for different languages and/or dialects. The interfaces between consecutive modules conform to the speech synthesis markup language （SSML） specification for standardization, interoperability, multilinguality, and extensibility. Detailed module divisions and implementation technologies for the unified framework are introduced, together with possible extensions for the algorithm research and evaluation of the TTS synthesis. Implementation of a mixed-language TTS system for Chinese Putonghua, Chinese Cantonese, and English demonstrates the feasibility of the proposed unified framework.
