1 (edited by joan 2020-Jun-18 17:04:35)

Topic: Cannot see two USB cameras at the same time

Hi Folks...newbie here to Kinovea, retired and live in Tanilba Bay NSW Australia.
Need some help in settings if possible, please.
I wish to record golf swings in my shed - the area for this is 4m wide, 5m deep and have 3.5m of height. I have one 333fps Kayeton USB camera (set 120fps)  as well as a 120fps Global shutter usb camera. One camera is on a 1.5m cable, the other is on an active extension USB cable- connected to an older desktop gamer PC. Running W10. Both cameras into USB3 ports. I can see each camera separately under single camera capture and can switch between cameras.
My problem - when I set for two capture cameras, only one of the two images appears. The other image "appears" to be there, however there is just a boarder outline. No image. Previously I could see two cameras...however these were 30 and 60 fps units. As I purchased faster cameras, the issue of losing one of my two images arose.

The gaming desktop PC is probably 8 years old and is exclusively used for video capture. I had the same issue on my 2019 METABOX laptop (also a gaming machine) more about this brand search Metabox in West Australia metabox.com.au

Gotta be something simple I guess...I also have another question, how do you draw lines on a replay of an image. When I do a line it fades away after 1 second or so.

I have the latest version of Kinovea...I am now retired and spent most of my life in sales for various IT companies. I'm not a software/programmer person, more a "tin" person. I do need help...please...
Regards, Oscar mobile ***REDACTED***

Re: Cannot see two USB cameras at the same time

Hi,
When you can see each camera independently but not at the same time it's usually an issue of bandwidth or current at the USB level. Both cameras are ending up on the same USB root hub and have to share the bus bandwidth. If your laptop has other USB ports try switching around to find ports that are on different USB root hubs. The device manager might be of help to know if you have several root hubs or a single one serving all the ports. Put them on USB 3 ports if you have any.

Re: Cannot see two USB cameras at the same time

Hi Joan,
Thanks for the info...I woke up this morning and realised I purchased USB2 cameras...I had these plugged into the USB3 ports. Went to my setup, moved the ports into the USB2 slots and - there ya go...two screens...how silly was I. And I agree with you that it looked like a bandwidth issue. (That's why I specifically purchased a gaming machine - they generally have  good bandwidth.
Now...to start using Kinovea...any hints on how to draw a line on a replay of a video - and have that line stay there? Or do I have to save the file first. I generally record a video of a golf swing, then immediately replay it for examination...I draw lines to show the body movement levels...then essentially delete the file.
Maybe point me at a tutorial somewhere?
Thanks again...keep well. Best regards, Oscar

4 (edited by joan 2020-Jun-19 10:13:57)

Re: Cannot see two USB cameras at the same time

(The following is for version 0.9.2)

When you add a line or other object you can right click it and select the menu Visibility > Always visible. This way it will stop fading out after a few frames.

If you are only interested in having lines that are always visible, you can go to Options > Preferences > Drawings > Opacity > Default opacity of new drawings and check the box saying "Visible for the entire video". Now new drawings will be always visible by default, although you can still customize the fading option on a per-drawing basis by going to each drawing visibility menu.

If you are interested in having a specific set of lines to appear every time you open a video, you could create these lines, save them in a KVA file through File > Save > Save only the annotations, and then save this file as "playback.kva" and copy it in the application data directory. This directory can be found from menu Help > Open log folder. This way every video will load the KVA annotation file upon opening.

edit: I forgot to mention, and this is new in version 0.9.2, if you add the line directly in the capture screen, a KVA file should be saved automatically when you capture the sequence, and will be reloaded when you replay it. In this case the objects added at capture time should already be in "Always visible" mode.

Also if you are interested in these capture-replay scenarios there is also a way to automate the capture/playback loop so you don't have to attend the computer each time. This is done using File > Open replay folder observer and point it to your capture target folder.

5 (edited by obevz 2020-Jun-23 03:04:52)

Re: Cannot see two USB cameras at the same time

great thanks...generally the replay is once and delete...just for feedback to the golfer for practice. Sometimes that golfer is me...to check my swing etc.

Re: Cannot see two USB cameras at the same time

Hi again...wrt adding a drawing line on the capture screen (one capture/one replay)...I did come across that (by chance) and I noted the following: The lines on the capture screen are not the same when I replay the capture. For example, having a camera 2m behind a golfer's shoulder facing the direction of a golf shot, I draw a line from above a golfer's head down to the golf ball on the ground. When I view the replay...the line remains on the same angle, however it's shortened by about 30%...it does not "reach" the ball. I'm OK to test the "draw a line on the captured video. Great info BTW, thanks.

Re: Cannot see two USB cameras at the same time

obevz wrote:

great thanks...generally the replay is once and delete...just for feedback to the golfer for practice. Sometimes that golfer is me...to check my swing etc.

If you are sure you won't save the sequence, the simplest way to do instant feedback is to use the delay function. For example you can set the delay to 5 seconds.

obevz wrote:

The lines on the capture screen are not the same when I replay the capture.

I'm trying to reproduce the problem. Could you send a screenshot at joan at kinovea dot org? In particular what is the camera image size, whether the camera view is filling the capture screen, and same for the playback side.