Most of the people think that video in 1080i quality is better then 720p ,and this because most of them think that 1080i is bigger number or they mix up 1080i and 1080p.
In reality there is a huge difference between 1080i and 1080p or 720p.The alphabet "i" means  interlaced video and if this is 1080i ,it means interlaced video in 1080i mode. Now the second one is "p" that means progressive,this video quality make video in progressive video quality(explained below).
When we deal with interlaced video,the viewer actually saw the half resolution because the video frame is divided in two fields,one is even and other is odd field.Both together make a frame that we call the interlaced frame.This video technique was useful in early days when there were bandwidth limitations.But now with help of  new technology we can see Full image in single frame with high quality i:e 720p and 1080p.
Now the question is How 720p works ? Answer is quite simple,In 720p there are 720 horizontal lines in each frame but in 1080i ,you only see half of the line that are 540 lines.So this means 720p is better then 1080i.In interlaced resolution when object is moving fast and if you abruptly stop the video,you will see the fast moving object looks is smearing across the screen instead of looking natural.
This is the sequence of high Resolution
1080p

720p

1080i

480p

480i

and others...

Motion Capture is the process of recording movement and translating that movement on to a digital model Usually used in military, entertainment, sports, and medical applications, and for validation of computer vision and robotics and mostly in filmmaking.