Registrator Viewer (DATAKAM Player) is the best player for dashcam video files. It known to be used in some DVR firmwares. Usually When format SD card using DVR menu RegistratorViewerX.X.exe apear in SD root folder. In case firmware not contain the player it still may be downloaded and used for most devices.
Currently URL http://download.registratorviewer.com/download/RegistratorViewer.exe reported by some browsers as insecure, but check with VirusTotal says it is ok. Other URL to DATAKAM Player Download page is http://datakam.ru/download/
Download from this site: