Indexing and search of multimodal information

The Informedia Digital Library Project allows full content indexing and retrieval of text, audio and video material. The integration of speech recognition, image processing, natural language processing and information retrieval overcomes limits in each technology to create a useful system. In order to answer the question how good speech recognition has to be in order to be useful and usable for indexing and retrieving speech recognizer generated transcripts, some empirical evidence is presented that illustrates the degradation of information retrieval at different levels of speech accuracy. In our experiments, word error rates up to 25% did not significantly impact information retrieval and error rates of 50% still provided 85 to 95% of the recall and precision relative to fully accurate transcripts in the same retrieval system.