I have a corrupted MP4 file whose length is 25 minutes, but fter the first 4 minutes it jumps ahead to 20 minutes and one cannot playback the middle portion. It appears as though the index is corrupted. I re-encoded it as AVI using AVIDemux, with MPEG4-ASP as the output profile, but the resulting video was just 4 minutes long. I've gone through the list of repair tools at VideoHelp but there's nothing for an MP4 other than a couple of outrageously expensive tools listed there.
The file is encoded as H264, and the audio is AAC mono 128kbps, and I'm using Windows.