MediaInfo is a free and open source tool to get technical information and tags of a lot of multimedia files.
Supported formats :
Video: MKV, OGM, AVI, DivX, WMV, QuickTime, Real, MPEG-1, MPEG-2, MPEG-4, DVD (VOB)...
(Codecs: DivX, XviD, MSMPEG4, ASP, H.264, AVC...)
Audio: OGG, MP3, WAV, RA, AC3, DTS, AAC, M4A, AU, AIFF...
Subtitles: SRT, SSA, ASS, SAMI...
IDs: Audio/Video, C++, Developer Tools, LGPL, MediaInfo, MediaInfo 0.7.47, Multimedia, Sys Tool