Ever heard of codec with fourcc WMVP? That is another Windows Media variant designed for slideshows, video albums, ets. Why I have got interested in it? WMV3 Complex Profile (aka Ye Olde Undocumented and Incompatible Advanced Profile) uses exactly the same coding method to store I-frames when flag RES_X8 is set (if it is not set then VC-1 Main Profile decoder may decode that movies).
While standard decoder output mostly garbage, some blocks are decoded correctly thus I hope it’ll be possible to add support for both WMVP and WMV3 CP.