2 or 3 cameras per hub
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Author:  MrKiii [ Thu Jul 19, 2018 1:42 pm ]
Post subject:  2 or 3 cameras per hub


After 7 years following the project, I finally have a good excuse to use iPi for a game I'm doing :) I got 6 PSeye cameras and I'm evaluating the software right now.

My question is what are the implications of using 3 cameras per controller instead of 2. I've connected 3 cameras in one of my computers (both computers I'll be using for evaluation only have 1 controller) and I've received the "more than 2 cameras connected to the same USB controller" warning.

However the statistics window state that the 3 cameras are running @ 60 FPS, and frame drops are minimal (like 1 frame drop per minute). Video mode on "setup" says 640x480 color @ 60HZ.

This data looks good to me, but I wanted to know if there are other parameters which I should be aware of, and which could influence a lower quality capture when using 3 cameras instead of 2, or if the warning is just to stay in the safe zone for most users and avoid troubles by suggesting only using 2 cameras.


Author:  vmaslov [ Fri Jul 20, 2018 5:46 am ]
Post subject:  Re: 2 or 3 cameras per hub

As soon as FPS is stable you should not worry about that warning.
2 cameras per USB controller is a rule of thumb from our experience to get stable 60 fps for PS Eye cameras. It's based on the bandwidth provided by a single USB 2.0 controller.
However, modern USB controllers mix USB 2.0 and USB 3.0 implementations in various ways. So devices which appear as connected to the same USB 2.0 controller may actually be provided with bandwidth exceeding USB 2.0 specs.
Also, 3 cameras can usually be connected to a "standard" USB 2.0 controller at lower frame rates because of reduced bandwidth requirements.

Author:  Snapz [ Fri Jul 20, 2018 11:15 am ]
Post subject:  Re: 2 or 3 cameras per hub


This warning appears as Maslov stated, due to shared USB 3.0 and 2.0 controller sharing, even when running 3 controllers (USB 2.0, 3.0 and 3.1) on the same machine, you will get this message, but since you only have one USB controller, connecting 3 cams to it makes sense it would show this warning too.

You will have to run through distributed recording method though of course.

You will have to see the results once you get all USB 2.0 active extension cables needed connected and then re-test while performing motions during recording, if it remains at 640 x 480 @ 60 fps, then great, but be aware if it drops at any point during recording the program will throw an error and auto-stop the recording on all cameras, showing a red banner error message on-screen with only video recorded up to that point can be saved.

This will also not include the use of any Move controllers, so test it with 2-3 of those connected in the recording if possible as well, these are recommended for best tracking animation outcomes.

You may also not be able to use the Background Removal setting and have to switch to JPG compression.

Just have to set it all up as if you would be actually making a recording for tracking use and see the results.

Good Luck, hope it works out well, please post any issues for information to other users in similar situations, Thanks.

Best Regards


Author:  MrKiii [ Fri Jul 20, 2018 3:52 pm ]
Post subject:  Re: 2 or 3 cameras per hub

thanks for the answers. I'll try 3 cameras per controller for the moment, and if a problem arises I'll try to get a second controller somehow or move to a 4 camera setup, at least to test.

Thanks again!

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