Watson - Wang early in the 1st set, a challenge.
They are starting to develop an ugly habit with the replay using RealBouce.
Yesterday and now today, they are stopping the replay BEFORE the ball has actually hit the surface and rebounded!
So when they pause RealBounce the ball is hovering over the line and looks in.
A few seconds later they continue the video, the ball bounces AND CHANGES DIRECTION.
That is when you decide if it is in or out! You must see that CHANGE OF DIRECTION.
The ball either caught a hair of the line or was out.
They were calling it in on the first pause.
The 'change of direction' applies only if a depression of the ball isn't seen.
If there is a complete depression of the ball, one can judge if it touched the line or not without needing to see the change of direction.