Using Adobe Premiere Pro you might be able to convert MJP2 file to FLV format.
Convert JPEG 2000 motion sequence format (ISO 15444-3) file to Flash video file.
We have found 2 software records in our database eligible for .mjp2 to .flv file format conversion.
Microsoft Windows software - convert mjp2 to flv on Windows
A timeline-based video editing software from Adobe
Convert from mjp2 file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned mjp2 to flv. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Apple macOS / Mac OS X software - convert mjp2 to flv on OS X
Mac version of Adobe's prime video editing software