Sadly, there is currently no way how to convert DASH (Dynamic Adaptive Streaming over HTTP) files to the original, or any other video format, including RV (RealVideo) so dash to rv conversion is unlikely.
At best, you will be able to playback it using media player, however without audio track which is not included in .dash file.
DASH files are generally meant for watching purposes only (on Youtube for example) and not meant for downloading directly. Try to download the video in other format.
Updated: July 14, 2016