iFFmpeg is a graphical front-end for FFmpeg, an opensource command-line tool used to convert multimedia files between formats. There are many free GUIs written for FFmpeg that work on windows OS. To name a few: ffmpeg-gui, TEncoder, ffe, Avanti, Winff Among all TEncoder is a multi-threaded application. I am curious to see if you can replicate the results that you get from iFFmpeg, on a windows machine as they both seem to be using the same code. Feel free to share the footage (if you don't have access to windows) and I'd be more than happy to transcode on linux and windows and share the results.
Arash D got a reaction from MrTony in New iFFmpeg Samsung NX1 H.265 transcoding app for the Mac is the best yet