Recognizing voice over IP: a robust front-end for speech recognition on the world wide web

The Internet Protocol (IP) environment poses two relevant sources of distortion to the speech recognition problem: lossy speech coding and packet loss. In this paper, we propose a new front-end for speech recognition over IP networks. Specifically, we suggest extracting the recognition feature vecto...

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Bibliographic Details
Published in:IEEE transactions on multimedia 2001-06, Vol.3 (2), p.209-218
Main Authors: Pelaez-Moreno, C., Gallardo-Antolin, A., Diaz-de-Maria, F.
Format: Article
Language:English
Subjects:
Automatic speech recognition
Codecs
Coding
Decoding
Distortion
Feature extraction
Internet Protocol
Internet telephony
IP (Internet Protocol)
IP networks
Networks
Protocols
Recognition
Robustness
Speech
Speech coding
Speech recognition
Voice
Voice recognition
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Summary:The Internet Protocol (IP) environment poses two relevant sources of distortion to the speech recognition problem: lossy speech coding and packet loss. In this paper, we propose a new front-end for speech recognition over IP networks. Specifically, we suggest extracting the recognition feature vectors directly from the encoded speech (i.e., the bit stream) instead of decoding it and subsequently extracting the feature vectors. This approach offers two significant benefits. First, the recognition system is only affected by the quantization distortion of the spectral envelope. Thus, we are avoiding the influence of other sources of distortion due to the encoding-decoding process. Second, when packet loss occurs, our front-end becomes more effective since it is not constrained to the error handling mechanism of the codec. We have considered the ITU G.723.1 standard codec, which is one of the most preponderant coding algorithms in voice over IP (VoIP) and compared the proposed front-end with the conventional approach in two automatic speech recognition (ASR) tasks, namely, speaker-independent isolated digit recognition and speaker-independent continuous speech recognition. In general, our approach outperforms the conventional procedure, for a variety of simulated packet loss rates. Furthermore, the improvement is higher as network conditions worsen.
ISSN:1520-9210
1941-0077
DOI:10.1109/6046.923820