hello,I have tried 2 ways.Firstly,I put a video on the directory "/home/huiqiang/code/STEP-master/datasets/demo/frames/",the results like bellow.

[EllisHui]

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

[EllisHui]

Secondly, I put the video Frames on the directory "/home/huiqiang/code/STEP-master/datasets/demo/frames/",the results also are like bellow:
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

[EllisHui]

if you can give me some advice,i will be grateful.

[SanderHTNO]

Hi, I had this problem as well.
You need to put the framesXXXX.jpg into a subfolder of 'frames', e.g. 'video_id1'