Well, since the library returns the file as an input file, what you can do to save it without submitting it is using localStorage .
Since you did not leave more details about your code, I'll leave here a example of its use.
Now, to save it in "your project", as the browser runs on the client, it is not possible to save the file directly to your server, so you need to upload it to your application, sending it to the Controller. Follow example .
Note that the repository itself already has the implementation in MVC: RecordRTC-to- ASPNETMVC