mBrowserX is supposed to be an advanced version of mBrowser. It uses ffmpeg to decode movies so that Auto shot can be used for a number of media formats beyond what mBrowser can handle. ffmpeg supports such media formats as AVI, DIVX, DV, FLV, MKV, MOV, MP4, MPEG, MTV, SWF, WMV (WMV7, WMV8, WMV9).
There is no User's Guide for mBrowserX as it's still under development. If necessary, please read mBrowser's User's Guide here.