1) It is accessible through the app itself. There is a " Local file " section in its APP, all downloaded videos and photos are saved here. You can access to it without WiFi connection;
2) Or you can find it under this file path: My Files---Device storage---Samdv (or input "Samdv" to search );
Anyway, I think it should be easier to find the downloaded video in its APP " Local file " section.