[Note: I am asking on behalf of an integrator. They are using the API’s, although I am unsure if it is Mobile Server specifically.]
JPEGGetAtOrAfter is actually RecorderCommandService SOAP protocol so if that is the one it is not mobile server.
Using the Image Server protocol you can get the raw recorded video.
Unfortunately there is no sample using raw video.
The TCPVideoViewer protocol sample could be used as a starting point and then modified to ask for raw video.
Working with raw video please read about the GenericByteData format - https://doc.developer.milestonesys.com/html/index.html?base=mipgenericbytedata/main.html&tree=tree_3.html