I am having some problems opening an mp4 file in Matlab (220.127.116.114 (R2011b) 64 bit, Windows 7). mminfo gives this error error "Could not get file information. System error: Impossible de lire le fichier. Le format n?est pas pris en charge". (I have Windows 7 in French, it means means "cannot read the file, the format is not handled"). VideoReader says "The file requires the following codec(s) to be installed on your system: Unknown Codec".
The video plays fine in VLC and Windows Media (v 12); the codec is called "H264 - MPEG-4 AVC (part 10) (avc1)" in VLC.