Automatic Conversion from Phonetic to Textual Representation of Cantonese : The Case of Hong Kong Court Proceedings

Automatic Conversion from Phonetic to Textual Representation of Cantonese: The Case of Hong Kong Court Proceedings Benjamin K. Tsou, K.K. Sin, Samuel W K. Chan, Tom B. Y Lai, Caesar Lun, K. T Ko, Gary K. K. Chan, Lawrence Y L. Cheung Language Information Sciences Research Centre, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong SAR, China Fax: (852) 2788-9734 Email: rlbtsou@uxmail.cityu.edu.hk. ABSTRACT The resumption of sovereignty over Hong Kong by China and the implementation of legal bilingualism there have given rise to an urgent need for producing verbatim court records of proceedings conducted in Cantonese, the predominant Chinese dialect spoken by the majority of the population. This has created a challenge to build up the jurilinguistic infrastructure vital for the full implementation of bilingualism and the retention of the Common Law system in Hong Kong. While there are Computer-Aided Transcription (CAT) systems for processing English and Mandarin (Putonghua), none exists for processing Cantonese. This paper discusses the design of a Cantonese CAT system based on the special features of Cantonese speech sounds. The CAT system works on the conventional English-based keyboard to process Cantonese and meets the bilingual requirements of the Hong Kong courts. By utilizing primarily statistical techniques, the system is highly successful in handling the ambiguity resolution of homophonous Chinese characters, a tantalizing problem in the conversion from phonetic to textual representation of Chinese. Additional linguistic analysis and related processing are discussed which could further improve the performance of the system from about 92% to over 94% accuracy. 1. INTRODUCTION With the implementation of legal bilingualism in Hong Kong, Cantonese Chinese is increasingly used in the legal domain, particularly in court proceedings. Previously, when court proceedings were conducted exclusively in English, verbatim records were kept by court stenographers using the Pitman method and, more recently, the shorthand machine. The shorthand codes recorded by the machine were transcribed into English words via a Computer Aided Transcription (CAT) system. However, it is incapable of processing Cantonese, the dialect spoken by the predominant majority of Chinese litigants in Hong Kong. In the absence of an efficient and reliable device, the Judiciary of Hong Kong is confronted with the urgent problem of finding a way to maintain legally tenable records of court proceedings conducted in Cantonese Chinese. [1, 2, 3] Currently, the Judiciary has to resort to a primitive solution, i.e., transcribing the audio records of court proceedings into Chinese characters by means of audio-typing. This process is not only time-consuming but also error-prone. (b) Automated Transcription System (preliminary words in the target language) W ',,...,W'm (correct words in the target language) (a) Stenograph Machine (CAT codes) To remedy the situation, two supporting facilities are required, namely, a computer-compatible Cantonese shorthand method that allows court stenographers to make verbatim records of Cantonese speech, and a Cantonese CAT system that facilitates the transcription of Cantonese shorthand codes into Chinese characters. Both English- and Mandarin-based CAT systems have been available for some years. [4, 5] However, neither a computer-compatible Cantonese …

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