Always make sure you choose the right video format, we offer the following formats:

MKV  @ 50 fps - For more info: http://en.wikipedia.org/wiki/Matroska
WMV @ 25 fps - For more info: http://en.wikipedia.org/wiki/Windows_Media_Video

Both are the same resolution 768 x 576, but the MKV format offers a more smooth and sharper playback than WMV.
The MKV video format is more CPU-demanding than WMV.

A MKV  video sample to test playback can be downloaded >HERE<
A WMV video sample to test playback can be downloaded >HERE< 

MKV 1080P @ 25/29,97 fps resolution 1920 x 1080 - More info: http://en.wikipedia.org/wiki/Matroska

WMV  720P @ 25/29,97 fps resolution 1280  x  720 - More info: http://en.wikipedia.org/wiki/Windows_Media_Video

A MKV 1080P video sample to test playback can be downloaded >HERE<

A WMV  720P video sample to test playback can be downloaded >HERE<

MKV  downloads for Windows : Matroska Windows | CCCP | Media Player Classic

MKV  downloads for Mac OS X: Matroska OS X

WMV downloads for Windows : Windows Media Player | Media Player Classic
WMV downloads for Mac OS X: Flip4Mac