Acoustic-To-Word Model Without OOV

Understand

Recently, the acoustic-to-word model based on the Connectionist Temporal Classification (CTC) criterion was shown as a natural end-to-end model directly targeting words as output units.

• However, this type of word-based CTC model suffers from the out-of-vocabulary (OOV) issue as it can only model limited number of words in the output layer and maps all the remaining words into an OOV output node.
• Therefore, such word-based CTC model can only recognize the frequent words modeled by the network output nodes.
• It also cannot easily handle the hot-words which emerge after the model is trained.