remuxing ISM (Silverlight IIS smooth streaming) ??

[rubiohiguey]

I like ismdownloader for downloading and muxing IIS streams (ism file & manifest) but so far I have not been able to figure out how to select a particular stream (it always downloads the highest quality). I created a format file in Excel based on the manifest file that gives me an output of all fragments which I can then download separately. So I have audio and video chunks e.g. Fragments(video=20020000) Fragments(video=40040000) etc.

Does anybody know of a working tool that will allow me to remux these files together into a video file and audio file? Then can be standalone streams, I can then remux them into mkv with mkvtools. I tried merging the fragments with mkvtools but no luck (unsupported file/format error).