Before revision:  However, FastSpeech has several disadvantages: 1) the teacher-student distillation pipeline is complicated  , 2) the duration extracted from the teacher model is not accurate enough, and the target mel-spectrograms distilled from teacher model suffer from information loss due to data simplification, both of which limit the voice quality.
After revision:  However, FastSpeech has several disadvantages: 1) the teacher-student distillation pipeline is complicated and time-consuming , 2) the duration extracted from the teacher model is not accurate enough, and the target mel-spectrograms distilled from teacher model suffer from information loss due to data simplification, both of which limit the voice quality.