MiemieMethod/PyCriUsm — reverse-engineered prompt

Build me a small Python tool for extracting Honkai Star Rail cutscene files.

I want to point it at an encrypted USM video file and choose an output folder, then have it decrypt and demux the file into separate video and audio outputs. It should use a fast Cython based decryption module like this project describes, and include a simple Python library function I can call from another script, something like passing in the video path and output folder and getting back the extracted videos and audios.

Please include the setup needed to compile the Cython extension, a requirements file, and a clear README with install, build, and usage instructions. A basic command line interface would be nice too, so I can run it without writing Python every time. Keep the scope focused on Honkai Star Rail USM files for now, but structure it so other encrypted USM files could maybe work later.