Your videos were most often framed to miss ball contact. Don't frame areas of court below your feet and miss the ball impact.
With regular speed video you cannot catch the final arm & racket acceleration to the ball impact because it is much too fast (<20 milliseconds). See comments on optimizing video for the serve this thread.
Improve the video framing. If you want to understand the serve consider a high speed video camera from Santa.
One way to show your serve's ball impacts with the camera located behind -- If you can find any frames with impact use the MS Windows "Snipping Tool" to capture part of that frame and make a jpeg. Upload the jpeg file to a free photo hosting site such as Snapfish or Tinypics. On the site, right click on the picture and select "Copy Image Location". When composing a reply select the icon above that looks like mountains. Paste the 'image location' into the box that appears.
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