OpenShot
From Just Solve the File Format Problem
OpenShot is an open-source video editor, originally written by Jonathan Thomas, and later maintained by company named "OpenShot Studios"[2]. Its project files have the extension ".osp". Its support for other formats comes from FFmpeg.[3]
Identification
OpenShot project files appear to be JSON files, or at least are heavily resemble them; assuming the terminology of the former, the file is a dictionary, with one key (never the first, in testing, and therefore unsuitable for use as a magic number) named "version", whose value is a dictionary with keys "openshot-qt" and "libopenshot", their values being version identifiers.