inverted video?

When capturing video on the iphone 4 in landscape mode, why should it matter which side the home button is on? If I view a video on the phone, it will correctly show the video, but if I copy it to my comptuer and show it on something other than quicktime (such as windows media player), it will correctly show the video if the home button was on the right. But if the video was recorded with the home button on the left, the video is upside down. Why?