From the link that you gave, first paragraph: FLV1:
'FFDShow is a DirectShow decoding filter for decompressing DivX, XviD,
H.264, FLV1, WMV, MPEG-1 and MPEG-2, MPEG-4 movies. It uses libavcodec
from ffmpeg project for video decompression, postprocessing code from
mplayer to enhance visual quality of low bitrate movies, and is based
on original DirectShow filter from XviD, which is GPL'ed educational
implementation of MPEG4 encoder'.
For my reference do you have the links for the FFDShow and Splitter
forums?
Best wishes.
'