Using Burg cepstrum for feature prediction

dnn/dump_data.c

dnn/freq.c

dnn/freq.h

dnn/lpcnet_plc.c

dnn/lpcnet_private.h

dnn/training_tf2/lpcnet_plc.py

dnn/training_tf2/plc_loader.py

dnn/training_tf2/train_plc.py