1 Topic by Chas Tennis (edited by Chas Tennis 2013-07-22 11:01:57)

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These composite pictures of selected video frames are being posted lately in the Tennis Talk Forum by Anatoly Antipin ("Toly"). 

In a Tennis Talk forum reply he says that he uses Kinovea to select single frames, convert and save as .jpeg. He then uses Photoshop and Powerpoint.  He uses the Photoshop multiple layers technique.  I don't produce these myself so I can't provide much more information on the process.

These pictures are one of the best ways that I've seen for showing athletic motions. I'm noticing things that I never noticed before. Especially, the rare Fuzzy Yellow Balls videos of the server taken from above show some very interesting details.   Also, where shown, the ball on its trajectory and the camera frame rate can provide timing. 

If anyone has samples of similar display methods, please post along with some of your techniques.


http://i1.ytimg.com/vi/QUwxiqFUi58/hqdefault.jpg

Youtube from Anatoly Anitipin showing composite of selected video frames as part of the video. 
http://www.youtube.com/watch?v=QUwxiqFUi58
Videos
http://www.youtube.com/channel/UCVtnV90bBCB50nkd8EQDFOQ


Some other composite pictures of video frames. 

http://i43.tinypic.com/2w3qibr.jpg
Stosur toss and impact location.


http://i46.tinypic.com/s3kmxx.jpg
Rare serves from above showing racket and hand movement.  See FYB Youtube videos. http://www.youtube.com/watch?v=2FpeYGG9XAg    and others from above.


http://i47.tinypic.com/x5y53s.jpg
Serve showing when racket goes from edge-on to the ball to impact, lasts ~ 0.02 second, and some of the follow through.  This is the internal shoulder rotation that contributes the most to racket head speed at impact.


http://i44.tinypic.com/jsdsgj.jpg
Composite picture of Roger Federer forehand.

2 Reply by Alexander

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A short commentary, Chas.

WOW!

big_smile

3 Reply by joan

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Great !

The sad thing is that there actually was a similar feature in the ancestor of Kinovea back in 2005 (screencap from the help files). You could interactively add/remove positions to the composite.

In all those years I never got around to reimplementing it (Massive limitation : it worked only for perfectly fixed camera views. I want it to work even when there is camera motion, but it's much more involved).

Particularly interesting in the first images you posted is that the composition is selective. You see all the ball's positions, but only a few of the racket's ones. This makes for a much clearer image if all you want to see is the ball trajectory.

4 Reply by Chas Tennis (edited by Chas Tennis 2013-07-28 21:22:35)

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joan wrote:

Great !

The sad thing is that there actually was a similar feature in the ancestor of Kinovea back in 2005 (screencap from the help files). You could interactively add/remove positions to the composite.

In all those years I never got around to reimplementing it (Massive limitation : it worked only for perfectly fixed camera views. I want it to work even when there is camera motion, but it's much more involved).

Particularly interesting in the first images you posted is that the composition is selective. You see all the ball's positions, but only a few of the racket's ones. This makes for a much clearer image if all you want to see is the ball trajectory.

The picture shows perfectly the toss by selecting the server in the two frames with the hand release and ball impact.   The kick serve trajectory and high bounce to the right also stand out.

I believe that the video for the first composite picture was taken on a tripod.  But I believe that having the camera absolutely stationary is incidental to making the composite pictures. 

Not a very rigorous treatment, I believe it's good for telephoto set ups but maybe not wide angle?? Needs work. -

If a camera is steady on a tripod, all frames should be spatially indexed pretty well.  If a camera is hand held, there are two movements:

1) translation X, Y, Z, and
2) variation in camera pointing angle. 

If the videographer with a hand held camera is in the same location, seated or standing, and some distance from the object, I believe that the variation of pointing angle is a much larger factor and that the translation is negligible.    For variations in pointing angle, the background objects in any frame can be used to align the frames.  (If the videographer moves, walks, then translation will not be negligible and the following won't work.) 

I don't use Photoshop or do much image processing, so I'm guessing on the details. 

1) Select and save complete frames as jpeg images using Kinovea. 

2) In Photoshop select objects from each frame, the ball, player, etc.. 

3) Paste selected objects into a master frame using background reference points to align.  Use Photoshop 'layering'?  I don't know the details of the Photoshop process.

Some of the composite pictures in Toly's Tennis Talk replies are not perfectly aligned, the tennis ball does not follow a smooth trajectory, etc.. I guess those might have been done more by eye than by indexing to a point in the frames. 

The composite pictures can also be placed back into videos as was done with the first composite picture in reply #1.  I assume that placing stills in a video is a standard process with Photoshop.

5 Reply by songtitle (edited by songtitle 2013-11-17 21:03:29)

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hugin might do some of this