Empty array returned for feature_extraction_train_regression

[gardenia06]

I am trying to train a model with audio files but empty array is returned.
Here are my codes and the results, any help would be appreciated!

from pyAudioAnalysis import audioTrainTest as aT
aT.feature_extraction_train_regression("output/audio_temp/", 1, 1, aT.shortTermWindow, aT.shortTermStep, "svm", "data/svmSpeechEmotion", False)

Analyzing file 1 of 3: output/audio_temp/audio_full.wav
Analyzing file 2 of 3: output/audio_temp/audio_full_left.wav
Analyzing file 3 of 3: output/audio_temp/audio_full_right.wav
Feature extraction complexity ratio: 58.7 x realtime
([], [], [])