Aspect ratio: Please be sure your aspect ratio is "16:9". Aspect ratio is the proportional relationship between the video's width and its height. HD is 16:9 and that's the ratio we use on your site. More on aspect ratios here.
High quality: Record videos in the highest quality setting you can.
Size: Make sure the size is set to “ Full HD” or “1080p”. 1080p (aka Full HD) is characterized by 1080 horizontal lines of vertical resolution. The term usually assumes a widescreen aspect ratio of 16:9, implying a resolution of 1920×1080 (2.1 megapixel).
Frame rate: The frame rate for your videos should be 30 fps. If you are interested in learning a little more about frame rates, have a look at this brief but very explanatory article: http://www.steves-digicams.com/knowledge-center/video-frame-rates-24p-25p-30p-60i.html#b