1 Topic by jon

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Hi All,

I want to highlight the benefit to enable observational references (i.e. pictures) to remain on the screen during playback. One of my recent post asked this question. The idea allows comparison of the same athlete during different parts of the video. This idea is not new - Dartfish was the first to incorporate it into their software.

For example, in tennis, one could compare the position of the player when returning the ball. The original video is on youtube.
http://i53.tinypic.com/2hevk1y.jpg

Another example, in swimming the dive can be broken down into various positions. The original video is here.
http://i51.tinypic.com/2n1xe3d.jpg

To reproduce these videos in Kinovea, the camera will need to be in a fixed position. I think if this feature can be implemented, it could make Kinovea a very powerful program.

Jon

2 Reply by Phalanger

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You can actually create this effect with Microsoft's image composition editor with a moving video by getting the settings right.  Dartfish, PS too.  Would be nice to have it from video, even with a moving background (by recognising fixed points that are not moving).

3 Reply by joan

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Hi,
It is an extension of the Chronophotography type of effect that is scheduled for integration ASAP (but time is severely lacking these days).
(idea backlog ref: "Special effects - Chronophotography (kinogram merged into a common reconstructed background)")

The camera doesn't necessarily need to be fixed, if we can rebuild the background.

The steps would be
1. Find how images relate to each other spatially.
2. Rebuild the empty background by aligning and combining the images (if the athlete is moving relatively to the background, any given background position will be clear most of the video)
3. Compare each position with the rebuilt empty background to differenciate background pixels from athlete pixels.
4. Create an image or video with the total background and a few selected positions pasted on it.

Currently I have been focusing on steps 1 and 2, because I don't want this feature to be limited to fixed camera. You can see some results here.

4 Reply by jon

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Thanks for your responses. I did not know this special effect was planned for future releases tongue It would be great to see it in action.

I suppose using observational references is a very primitive form of Chronophotography. It allows common images to relate to each other using a fixed camera. I thought maybe it could be a short term solution. However, if Chronophotography is planned for future releases, that may not be necessary.


@Phalanger: How exactly do u create such a video using MS image composition editor? I've only had a brief look and it appears to focus mainly on still photos. Cheers.

5 Reply by Phalanger

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You can import video with it.  You can either hope it pulls it out right, or select key frames to work with.

Joan, when recreating the back ground, if it contains large spaces which are similar (lets say a snow/sky/water background) would it be possible to estimate the moving speed between known points.  So if it knows before it's moving at A pixels a second, and after at B pixels a second then it will presume it changed roughly from A to B during this period.