I'm not sure it's FLVSplitter's fault, but I've found that when attempting to stream an FLV file from a website (such as Youtube) using both FLVSplitter and FFDShow, there are some major problems with buffering the data.
In fact, the video will not properly start playing until it has completely downloaded in the background.
Visually, you see a single frame and a fragment of audio, then it begins to buffer again. This continues, with a new frame appearing every 5-15 seconds, until all of a sudden the playback smooths out.
Do you have any idea what could be causing a problem like this?