Finally, the decoder task, which predicts the target sequence probability at time t based on previous output and context information c t can be formulated: For speech recognition task, most common input x is a sequence of feature vectors like Mel-spectral filterbank and/or MFCC.
the local property helps our attention module focus on certain parts from the speech that the decoder wants to transcribe, and the monotonicity property strictly generates alignment left-to-right from beginning to the end of the speech.