This paper describes the new ASR system developed by the LIUM and analyzes the various origins of the significant drop of the word error rate observed in comparison to the previous LIUM ASR system. This study was made on the test data of the latest evaluation campaign of ASR systems on French broadcast news, called ESTER 2 and organized in December 2008.

For the same computation time, the new system yields a word error rate about 38% lower than what the previous system (which reached the second position during the ESTER 1 evaluation campaign) did. This paper evaluates the gain provided by various changes to the system: implementation of new search and training algorithms, new training data, vocabulary size, etc. The LIUM ASR system was the best open-source ASR system of the ESTER 2 campaign.