SV4's are basically only used in CCTV/security systems, and they (the security system manufacturer) usually provide a player. Unless you have a compatible CODEC for that format, you're not going to be able to play them with 'standard' video players.
There are converters out there to convert SV4 files into standard formats, like AVI.
Here's one: The Surveillance Video Converter
*Note: I have no association with this software, nor have I used it.