Automatic transcription of compressed broadcast audio

With increasing volumes of audio and video data broadcast over the Web, it is of interest to assess the performance of state-of-the-art automatic transcription systems on compressed audio data for media indexation applications. In this paper the performance of the LIMSI 10x French broadcast news transcription system is measured on a two-hour audio set for a range of MP3 and RealAudio codecs at various bit rates and the GSM codec used for European cellular phone communications. The word error rates are compared with those obtained on high quality PCM recordings prior to compression. For a 6.5 kbps. audio bit rate (the most commonly used on the Web), word error rates under 40% can be achieved, which makes automatic media monitoring systems over the Web a realistic task