High Performance Sequence-to-Sequence Model for Streaming Speech Recognition
Table 2: Latency and accuracy of the S2S model with bidirectional encoder on Hub5’00 test set.
['[BOLD] Method', '[BOLD] Beam Size', 'Δ', '[BOLD] WER', '[BOLD] Latency']
Using the immortal prefix condition, the final accuracy can be guaranteed as for the offline inference for large beam sizes, e.g., 8 and 4. For a smaller beam size, this condition is not strong enough to deal with unstable partial results – probably due to the changes of the encoder’s hidden states. In the 1st-ranked prefix approach, increasing Δ allows for a flexible trade-off between the accuracy and the latency. The offline accuracy can also be achieved if a very large Δ is applied. These results consolidate our findings in two aspects. First, the integration of Δ is reliable and crucial for the streaming inferences to work efficiently. And second, the use of the bidirectional LSTM for the encoder is possible and results in high accuracy.