You might accidently add a dot?

[Gassery]

I was importing the demux.py, and it gives me this error message:

from .decrypt import VideoDecrypter ImportError: attempted relative import with no known parent package

After I remove that '.' before decrypt it works fine.

To be honest, I don't know what '.decrypt' is, so this could be a result of my misuse, if this is the case, I apologize.

[BUnipendix]

maybe you put your script into cri_usm_demuxer you should treat this folder as module

[Gassery]

Cool, I think you're right.