Hi there,
First of all I would like to congratulate you for this great work and thank you for saharing the this awsome content publicly.
I am trying to run the demo.py after following all the steps described in the demo paragraph but unfortunately I am encountering problems and no visual results are generated in results folder except an empty results.txt file. Following is the terminal output that I am getting. The "Datalist len" is 0. I don't know why it is so. I have provided a total of 778 frames but I am not getting any output. Is there a minimum nunber of frames to be provided for detection?
Please help, Thanks.

python3 demo.py
Warning: If you want to use fp16, please apex with cuda support (https://github.com/NVIDIA/apex) and update pytorch to 1.0
Warning: If you want to use fp16, please apex with cuda support (https://github.com/NVIDIA/apex) and update pytorch to 1.0
Warning: If you want to use fp16, please apex with cuda support (https://github.com/NVIDIA/apex) and update pytorch to 1.0
Loading pretrain model from pretrained/ava_step.pth
Building I3D model...
Building I3D head for global branch...
Building I3D head for global branch...
Building I3D head for global branch...
Building I3D head for context branch...
Datalist len: 0