Language and variety verification on broadcast news for Portuguese

This paper describes a language/accent verification system for Portuguese, that explores different type of properties: acoustic, phonotactic and prosodic. The two-stage system is designed to be used as a pre-processing module for the Portuguese Automatic Speech Recognition (ASR) system developed at INESC-ID. As the ASR system is applied everyday to transcribe the evening news from a Portuguese public TV channel, the presence of other languages (mainly English) and other varieties of Portuguese is very likely. In the first stage, for each automatically detected speaker, the system verifies if the spoken language is Portuguese, as opposed to nine other languages – English, Belgian Dutch, Croatian, Czech, Galician, Greek, Hungarian, Sloven and Slovak. The identified Portuguese speakers are then fed to the second stage which aims at identifying the Portuguese variety: European, Brazilian or African Portuguese from five countries. The identification results are then used either to mark the speech data as untranscribable or forward it to the European Portuguese ASR system, or a system tuned for other languages or varieties. The language verification system achieved an equal error rate for European Portuguese of 2.5%. In terms of variety identification, the overall rate of correct identification was 83.9%, when considering only the three broad varieties, and the best results were obtained for Brazilian Portuguese, also the variety that proved easiest to identify in perceptual experiments. The identification rate between African varieties themselves is relatively low, a fact that was also observed in the perceptual experiments.