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1. A new drawing tool "distortion grid" allowing the user to place a grid on top of a checkerboard like pattern.
(The easy part).

(I have enlarged the width of the grid lines for the screenshot.)

At 6x zoom:

Manually placing the grid points might prove cumbersome. Many calibration tools have a function to automatically find corners in the image, we'll see.

I'm actually cautious with the very high framerates for now. During some experiments I have found that there seems to be "time noise", with the framerate variating around its nominal value. The higher the framerate, the higher the error. When digitizing coordinates, this is aggravated by the reduced resolution.

As the frame interval is used to compute the velocity of tracked objects, time bias on high framerate videos have a massive impact and introduce larger errors than for lower framerates. At 1000fps a 1/10px digitization error can be catastrophic for acceleration measurement, so if the frame time itself is not exact…

I haven't found much literature on the subject yet (contrary to spatial distortions), but I intend to explore the subject more when time permits. The time bias introduced by the rolling shutter is another time distortion I would like to experiment with.

Do you know how the framerate fidelity is assessed at the manufacturer level ?

Even the simplest experiments where I would film a high resolution stopwatch displaying miliseconds is not trivial to implement as these sort of stopwatches are not so common.

In addition to this, the things we see at 1000fps that we don't see at 300fps are probably for different analysis contexts. For evaluating limbs or implement movement in the context of sport technique, 300fps might be sufficient. Medical applications or "ball" analysis might benefit from higher framerates.

The synchronization mechanics has been rewritten and many issues should be fixed in 0.8.22.

You need to have a calibration reference in the video. Add a line drawing on top of something of a known length, right click the line and go into Calibrate measure to set the physical length of the object.

The accuracy of the measure will depend on several factors.

The line of known length should be on the plane of motion otherwise there will be perspective error.

The calibration object should be as large as possible and as close to the center of the image as possible to limit error due to camera lens distortion.

It should also be as close as possible to where the trajectory will take place. One idea would be to use the leg of the kicker if static points are clearly visible on it during the kick and assuming it doesn't deform (see also reservations about rotation).

To limit this camera lens distortion avoid using fisheye type lens by all means. With regular camera you will want to move back and then zoom in, this will flatten the scene and reduce perspective errors. Use a tripod and remote control the recording to minimize camera movement between calibration and measure. This is especially important if you take several attempts with the same calibration frame.

The camera optical axis should be perpendicular to the plane of motion to avoid perspective errors. At the least you will want to make sure it's parallel to the ground, with a small spirit level for example.

I'm not too familiar with how much rotation component is there during the kick. Not all of the motion will take place on a single plane of motion. You need to keep that in mind when comparing speed of several subjects if they have different kicking style.

The next version is coming along and will have several improvements on the topic. (sub pixel tracking, changing tracker parameters, acceleration, angular speed, etc.)

joan at kinovea dot org.

Pour les raccourcis claviers on peut les customiser depuis la version 0.8.21. Il faut aller dans Options > Préférences > Keyboard. L'onglet n'est pas traduit par contre. Recherchez la fonction (par ex: Catégorie "CaptureScreen", commande "TakeSnapshot" pour la capture d'image), cliquez dans la boîte de texte en bas à gauche, faire la combinaison de touche que l'on veut associer à la commande, puis finir par "Apply".

C'est à dire, depuis l'explorer Windows ? Oui ce serait intéressant.
Sinon une petite technique également depuis la version 0.8.21, le dossier de la vidéo en cours est automatiquement ajouté temporairement aux raccourcis. Pour l'ajouter définitivement il suffit donc de faire clic droit dessus.

Concernant le modificateur de vitesse, il est prévu un slider en échelle logarithmique avec beaucoup plus de précision dans les petits pourcentages que dans les grands. Il est déjà en place pour le délai sur le direct dans l'écran de capture.

Oui ça tourne sous Windows 8 / 8.1, mais sur les versions « normales », pas sur les versions qui n'ont que l'interface metro (type tablette Microsoft Surface RT.).