The use of visual information in addition to acoustic can improve automatic speech recognition. In this paper we compare different approaches for audio-visual information integration and show how they affect automatic speech recognition performance. We utilize facial animation parameters (FAPs), supported by the MPEG-4 standard for the visual representation as visual features. We use both single-stream and multi-stream hidden Markov models (HMM) to integrate audio and visual information. We performed both state and phone synchronous multi-stream integration. Product HMM topology is used to model the phone-synchronous integration. ASR experiments were performed under noisy audio conditions using a relatively large vocabulary (approximately 1000 words) audio-visual database. The proposed phone-synchronous system, which performed the best, reduces the word error rate (WER) by approximately 20% relatively to audio-only ASR (A-ASR) WERs, at various SNRs with additive white Gaussian noise.
['Petar S. Aleksic', 'Aggelos K. Katsaggelos']
Product HMMs for audio-visual continuous speech recognition using facial animation parameters