I was recently given a keynote presentation which contained a movie. When I played the presentation the sound worked but the movie was blank. It turned out the movie was not in a format that Quicktime could play and it turns out there are many such formats. When I tried to play the movie in Quicktime I got an error saying ‘The document could not be opened. The movie is not in a format that QuickTime Player understands.You may need to install additional software to open this type of file.’ The tell me more option was next to useless, but there is a solution.

Perian is a handy free program that allows your mac to play almost any movie format including AVI files from a Windows computer. In fact it claims to play all the following movie formats: AVI, DIVX, FLV, MKV, GVI, VP6, and VFW, MS-MPEG4 v1 & v2, DivX, 3ivx, H.264, Sorenson H.263, FLV/Sorenson Spark, FSV1, VP6, H263i, VP3, HuffYUV, FFVHuff, MPEG1 & MPEG2 Video, Fraps, Snow, NuppelVideo, Techsmith Screen Capture and DosBox Capture.

You can download it for free from perian.org.

Then simply click on the icon and it will install itself as a Preference Pane. It sits in the background – you don’t need to do anything. Your normal programs such as keynote and quicktime will now be able to play any movie format.