An spfx file extension is related to the Squeeze a video encoding app. An spfx file contains preset.
SPFX file extension - Squeeze preset
What is spfx file? How to open spfx files?
File type specification:
The spfx file extension is associated with the Squeeze, a video encoding application.
The spfx file contains saved parameters for video encoding.
The spfx file can be imported or exported from the application and shared on specialized Sorenson Media website.