Film one serve from two phones, one beside the server and one behind the baseline, and Serve Lab draws a stick figure over each video. It then joins the two views into a 3D figure you can turn around. You get measurements at the trophy position, racquet drop and contact: how far the hips and shoulders turn, how deep the knees bend, and the order in which the body uncoils.
Keep the court lines in the picture. Serve Lab measures everything against the painted lines of the court, so each video needs to show the baseline and at least one other line clearly, such as the center mark, a sideline or the service line. If the lines are cut off or hidden, the measurements can't be worked out.
Get a code to share with the person filming the other angle. It works for 3 hours.
Enter the code from the other phone, or open the join link it sent you.
Clips pair up when the two phones started recording within 6 seconds of each other at the same court.
These two clips are two different serves, recorded about 3 minutes apart. The 3D figure is stitched by lining the serves up at the toss, trophy, racquet drop and contact. That is close for a consistent server, but not exact. Film one serve with two phones at the same time and the same pipeline gives true 3D.
Measured on the 3D figure. Turn is how far the chest faces away from the net: 0° is square to the net, 90° is fully side-on.
Rule-based notes from the numbers. Check them against what you see on the video.
Each body segment should reach its top speed just after the one below it: hips, then shoulders, then the hitting arm.
Each phone's position was solved from the painted lines: baseline, center mark, service line and sidelines at their regulation distances. Joint positions from both views were then combined into one figure in court coordinates.