Orginially, this was a feature in the beginning of RapidVideo, until more and more users abused it, which it slows our conversions down alot, we switched to one encoder completely."- Input MKV/MP4 with Subtitle support. We will hardcode the subs by default settings, you can change this setting in your user settings."
When it comes?
Today, we can still encode with subs efficently and faster than HandBrake. It will come soon, as it is under testing and bugfixing.