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Try to double tap the image to make it fit the screen.

Hi,
I would say this indicates that the dual recording is too CPU intensive and both playback and recording can't happen in real time.
Can you try with two webcams of different models ? There might be an additional complication with using two cameras of the same model.

More progress, almost done:

Fig1. Final coordinate system with perspective and distortion correction.

Fig 2. The camera calibration dialog. Here the coefficients correspond to a GoPro Hero 2 in Medium mode (127°).

Basically there are two ways to get the distortion coefficients. Both imply filming a checkerboard like pattern, then:

• In Kinovea, by creating several "Distortion grids", positionning them manually and then clicking "Calibrate camera" in this dialog.

• By using Agisoft Lens (freeware), importing the images and performing the (automated) calibration there. Then by importing the resulting XML file in Kinovea through this dialog.

This is a one-time-per-camera operation.

The "Image" tab shows a rectified version of the current image, however it is for ballpark verification, there is currently no plan to provide real time image rectification.

I'll describe in more details later how I verify that the lens distortion and perspective correction are correct.

The most probable cause is that the streaming format is not supported. At the moment the number of supported formats for network streams is rather limited: only MJPEG and JPEG.
If you want you can try to get it to work in "iSpy" and/or "VLC" and report which type of connection worked.

Hi,
Once you have done the calibration in the first video, you can save the corresponding KVA file from the save menu.
You can then import it to other videos from the "Load Key images data" menu. It will import the calibration.

Optional:
If the camera is completely fixed and you only work with videos from this camera, you can have this calibration file automatically imported on every video you open.
To do this you must rename the KVA to "playback.kva" and store it in the %appdata% directory. (For example : "C:\Users\joan\AppData\Roaming\Kinovea"). To stop using it, delete or rename the file.

Additional notes:
- You can safely delete the line that was used to create the calibration in the first place, it will not kill the calibration.
- It will work for plane calibration as well.
- When importing on a video of different resolution, the calibration is "adapted" to the target file.

"4. Usage of the distortion parameters to compute undistorted coordinates and usage of these coordinates to make all measurements in Kinovea."

Some measurements done filming the checkerboard pattern "roughly" orthogonal to the camera axis. Pictured lines, spanning 5 squares, are ±1% from each other in measured length (still true close to the border of the image).

For comparison, the same lines without lens distortion calibration :

(Lines at the edges of the image go down to 50% of their ground truth.)

For this test lens distortion coefficients were computed in an external (free) application and imported automatically. The geometric calibration used a grid spanning 10 squares and marked as 200% in length.

Hello,
Yes I did not add any new arrow tools in this version.
I want to focus on the quantitative analysis aspects for a while before returning to presentation features.
I keep them in mind though.

The first two topics I will likely work on for 0.8.23 are :
1. A "data analysis" window to review kinematics data : trajectory plots, projective view of points and lines on the plane, possibly a heatmap style plot, possibly an angle/angle or angle/angular velocity diagram for coordination analysis. With facilities to export the filtered values and the resulting plots.
2. Lens distortion compensation for measurements, with import/export of distortion profiles and distorted view of the coordinate systems.

I also want to do some research on time distortions (e.g: rolling shutter), camera pose estimation, frontal area computation, time of flight cameras, etc.