See this thread about manually programming remotes made by UEI (typical brand: OneForAll)  to control the XV-DV313.  It seems to list the Surround mode function.

JP1 remotes can be programmed by computer using an interface cable, but you don't need that for the XV-DV313.  To manually program the remote, follow the 994 Command instructions after assigning setup code Audio 1384.

Here's an example of a remote that will work.  You need to get a remote that has Audio setup codes, so for example the URC-3920 won't work, even though it is a sister remote to the URC-3940 linked above.