Transcribing Mandarin broadcast news

The paper describes improvements to the LIMSI broadcast news transcription system for the Mandarin language in preparation for the DARPA/NIST Rich Transcription 2003 (RT´03) evaluation. The transcription system has been substantially updated to deal with the varied acoustic and linguistic characteristics of the RT´03 test conditions. The major improvements come from the use of lightly supervised acoustic model training in order to benefit from unannotated audio data, the use of source specific language models, and MDI adaptation to tune the language models for sources with limited amounts of training data. The character error rate on the development data has been reduced from 34.5% with the baseline system to 22.6% with the evaluation system.