multiple image displays

[sikee]

Hi,

I plugged 2 USB3.0 cameras in LabVIEW, and displayed the images from both in the front panel seperately. One image display corresponds to one camera source. When I run the codes, the display windows are supposed to show separate image grabbed by the corresonding camera. However, the displays windows sometimes show the same image source from one camera and they are not stable. I guess the signals from both cameras are mixed sometimes. I have no idea how to solve this problem.Has anyone met with the same problem before?

Also, I'd like to confirm my calcultion of bandwidth. I want to plug 6 USB3.0 cameras in total eventually. They will all be set the same with resolution 1024x1280, mono8. The bandwidth of USB3.0 is 625 MB/s. Thus, the calculatin of maximum frame rate for each camera the setup could handle should be:

maximum frame rate = 625M / (1280 x 1024 x 6) = 79.4 fps.  Is this right? 

Thanks,

Olivia

[TiTou]

Hi,

Can you show the code you are using for that?

It seems quite surpring, I've made many applications with multiple cameras and I'm not having such issues. That said I've never used USB3 cameras yet.

[BlueCheese]

I'd guess your code is re-using the same image name for both cameras, causing them to overwrite each other's images in your loops.

As far as bandwidth, typically most USB3 interfaces see a practical limit around 350-400MB/s of real throughput, depending on many factors. When shared via a hub, the aggregate that is reliable may even be less due to peculiarities of how the hub manages bandwidth. A good solution would be to add ports via something like the PCIe 8244 card which adds 4 ports with dedicated bandwidth for each port.

Eric

[sikee]

Hi,

I attached my vi. file here.

Thanks,

Olivia

[BlueCheese · Accepted solution]

You are using the same image name everywhere.

You also have both cameras in the same loop, so the loop rate will be dictated by the slowest one.

[sikee]

Hi Eric,

Thanks for your help. I did choose different camera name, cam0 and cam1. The signals are not stable. Sometimes they display the same images, but sometimes they dispaly own image separately. I attached my vi. file.

As for the bandwidth, a good hub can save the bandwidth more or less, right? What kind of performance of the hub is required to look into?

Thanks again,

Olivia

[sikee]

You are right! I fixed those image names and it works well! Thanks!

As for the loop, I put 2 cameras in a loop bacause I want them to take images roughly at the same time.

Thanks!

Olivia