If you download the Apple Quicktime AVC samples (for example Wildlife):
http://www.apple.com/quicktime/guide...ifehdreel.html
(Download is easy with new Versions of Quicktime Alternative)
And rename them to .mp4, the video plays well (if ffdshow takes care of AVC), but there is no AAC sound anymore... Seems the splitter has a problem there.
Every other mp4 files I had worked just fine though...