With VLC, there is no need to continually update many different codec packs. VLC comes with nearly every codec built in!
And whats more, VLC can play back your files, even if the media is damaged! Missing or broken pieces wont stop VLC. All the video and audio information that remains can be played.
VLC is a media player, not converter, but if you're watching digital video, it's a must-have—plus VLC can indeed rip DVD's, as well as play ripped discs in ISO format (no actual optical media required.) VLC can also play FLV files downloaded from YouTube et al, no conversion to AVI required. Since there's a portable version, VLC's a nice choice for getting your DVD rips/saved YouTube video watching on wherever you go.
