Like all open source projects, VLC relies on community contribution for testing, developing, and financing. Unfortunately, at this point because of the lack of Mac developers helping the project, support for OS X is nearly dead. If a file has been damaged or improperly encoded, when QuickTime displays errors and does not play the file, VLC may be able to work. It has been a great alternative to QuickTime because of its support for a vast array of codecs and robust capability to play even corrupt videos. VideoLAN Client, or VLC, has been a popular media player for OS X that has developed and progressed over the years. Update (2x): VideoLAN has issued some clarification on this development (read below)
