If the file won't open, use VLC Media Player as it supports almost all MP4 encoding variations.
Use a trusted tool like VirusTotal to check the file before opening. Dod (309) mp4
In these contexts, the file might be a specific gameplay highlight or a cutscene archive shared on platforms like Niconico or community forums. 💡 How to Handle the File If the file won't open, use VLC Media