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Kinovea - Forums → Posts by joan
Super. Thanks for the follow-up.
For the record we continued the discussion off-line and I sent coachmattb a preversion of 0.8.25 with a bug-fix for testing purposes.
For others with this issue (any network camera should have the issue really), a workaround in 0.8.24 should be possible, by going to the global capture preferences in Options > Preferences > Capture, and in "Display synchronization strategy", select "Camera frame signal" instead of "Forced framerate".
In Kinovea you should use the direct URL to the MJPEG stream, something like http://192.168.0.45:8080/video for IP Webcam app.
There seems to be an issue with the display though, I also can't get a stable stream. Something must be broken…
If you install both using the installer they will share the application data directory and it could create conflicts as the preferences format is not the same.
The usual way to do this is to use the "portable" version for 0.8.24. This way it is completely self-contained and does not interfere.
No, Bluetooth is not involved. Wi-Fi should be turned on on both though.
Use the "Manual connection" button under the camera list and configure from there. The URL information should be found in the mobile app settings or documentation.
A web browser should also be able to connect to the stream, so you might want to test there to pinpoint the origin of the problem.
By default it will only "see" (as in create a thumbnail for) the cameras that are connected directly to the computer.
For network cameras you have to use the "Manual connection" button under the camera list and configure the camera IP and access URL there.
As far as I can see the camera streams H.264 which is not supported as an IP camera stream in Kinovea. Only MJPEG streams are supported.
Ok, that is strange and sounds like a bug. You should be able to see velocity as soon as a trajectory point has two neighbors, before and after, and acceleration as soon as it has four neighbors. So only the first and last points should be "###".
What happens when you display "Position" instead? Do you get anything?
Can you save to a KVA file and send it by mail please? (joan at kinovea dot org), thanks.
Can you right click the trajectory and go into "Data analysis" dialog. Do you get the position over time and other plots there?
The ELP has some advantages but it definitely has a lower image quality than the C920. There are some sample videos of the ELP at the bottom of the blog post, shot with not ideal lighting (as is often the case).
(I think you should be able to get the Logitech for less than 70€ now, as the price has dropped).
I can't really comment on whether 480p is enough for your application. Try to find someone with a cheap webcam and see for yourself if it's acceptable.
Regarding gait analysis, one aspect to keep in mind is the USB bandwidth. I have seen at a podiatrics setup a lot of USB peripherals (gait platform, other specific devices, etc.) and it can create issues for the cameras if you want to have two of them streaming at the same time in addition to all the other devices.
A C920 should give very decent results. You can configure stream, image size, framerate, exposure and gain directly in Kinovea. There is also special code to directly store the MJPEG stream to disk in order to reach peak performance during recording and avoid frame drops.
One drawback is that focus is built for room-scale and degrades a bit if the subject is at 5 meters or more.
I haven't personally tested the C930 but from all I've gathered there is no real advantage as far as filming sport is concerned.
Theoretically the Reflex would give a much better image but I'm not sure it will work at all. Does the HDMI output let you stream the live content seen by the sensor to a TV ? Or is it just to feed back videos previously recorded on the internal storage ? Also, video capture boxes haven't been tested and I haven't had any report that any of them work.
The only thing is that when you ask to show measure it shows position and displacement values, but for velocity, acceleration and their components it appear ### instead of numbers.
This usually happens when there aren't enough data points to compute the value. Since velocity and acceleration are derivatives and the data is filtered to remove noise, there is a minimum number of points that needs to be present before and after the position of interest in order to calculate the kinematic quantity at that point.
The white hand that moves during left button mouse clicked do not allow position the line on to the articular centre, it diminish digitizing precision. A cross or a transparent hand would be better.
Yes, fair point. Note that you can zoom in 600% with CTRL+mouse scroll, which should provide sub-pixel accuracy.
Ah, maybe it wasn't clear enough about what the feature is supposed to do.
The image will not be undistorted, it is the coordinate system that will now take the distortion into account. So if you add a planar or perspective coordinate system, the coordinates used for positions, distances, angles, speed, etc. will be distortion corrected.
If you add lines or grids, you will see them bend along the distortion field.
Rectifying the images in real-time is costly and Kinovea architecture is not suitable for this as it is.
Regarding accuracy there could be arguments in both directions, on one hand it is better to use the actual pixels captured by the sensor for digitizing points rather than use the rectified images that will be interpolated. On the other hand a circular marker will no longer be circular at the image periphery which could limit the accuracy of automated tracking. Currently the philosophy is to respect the original image from the sensor as much as possible.
Hi,
Yes they are UVC compliant and you can configure and drive them in Kinovea.
Note that there are a lot of models from this vendor, with a few baseline hardware and a lot of variations on top of them for lenses.
For the high framerate you'll be looking at the ones based on OV2710 sensor (ELP-USBFHD01M).
I wrote a review of this model on my personal blog here.
In my experiments it doesn't do 120fps but 100fps, and only at lower resolution (640x480). 1280×720 @ 60 fps is nice though but there are other shortcomings.
Bonjour,
Malheureusement à l'heure actuelle cette fonctionalité n'est pas supportée.
Si vous filmez avec un téléphone ou une tablette il faut tenir l'appareil en "paysage" pour éviter de faire des vidéos plus hautes que larges.
I reproduce a problem but I'm not sure it's the same.
For me it's the video that is 29.97 fps that is further along the timecodes, not the other way around.
It is running too fast by a bit less than 1% which is the expected error from the rounding issue mentioned earlier.
The issue only occurs during playback itself, as soon as I pause and restart playback the synchronization error is reset to zero. There is no issue when using the common slider to set the common time. It also has no impact on time-dependent computations like chronometer, kinematics, etc.
I ack the problem with timer precision. I'll have to think about the proper way to fix it.
Kinovea - Forums → Posts by joan