We used the audio and visual feature extractors pre-trained on YouTube videos and the Kinetics dataset (Kay et al., 2017) (Refer to  for the detail video features).
we used the 2048-dimensional I3D flow features from the "Mixed 5c" layer of the I3D network (Carreira and Zisserman, 2017) for visual features and 128dimensional Audio Set VGGish  for audio features.