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upen24931251
April 14, 2015, 04:44:51
( sorry for my poor english )

Hi,
I encounter a problem about the FPS.
I was using two DMK 72AUC02 to show image on IC Capture.
When I set the FPS both are 20, then the Camera1 will show normal image, but
the Camera2 will show broken image.
When I set the FPS both are 13, then both Camera1 and Camera2 give me normal image.

I wonder about if this problem is caused by the bandwidth of USB2.0,
or cause by the CPU level(ex: i3, i7...), or cause by other reasons.

please help me, thanks!

Stefan Geissler
April 14, 2015, 10:40:59
If both cameras are connected to the same USB controller, then you must take care of the available bandwidth. Therefore, bith cameras can not run on full speed at the same time.

upen24931251
April 27, 2015, 01:55:35
Thank you for your reply.

But I still want to make sure the problem is caused by multiple camera connect to same USB controller.
Therefor, let me explain my experimental environment:
Environment 1:
i5 level computer X 1,
USB Hub X1,
USB2.0 Camera X 2,
both camera with FPS 19

I connect these two cameras to the USB Hub, then connect this hub to computer.
Then open the IC Capture2.3 program to see if these cameras work fine.
One of the camera randomly shows color block in the view.
https://drive.google.com/file/d/0B2yo8h5kPYdFN3NJNldnVHNRYUk/view?usp=sharing

Environment 2:
i5 level computer X 1,
USB2.0 Camera X 2,
both camera with FPS 19

I connect these cameras to the USB2.0 port on the mainboard of the computer.
And there is no color blocks anymore.


Please help me to confirm if the problem is cause by the USB controller, or not.
If not, please tell me your suggestions.

Thank you very much!

Stefan Geissler
April 27, 2015, 11:08:04
As you can see on your screen shot: You have set 19 fps per camera and IC Capture shows, only 7 fps are achieved. That means, you have many many frame drops.
You have 1280x960*19 = 23347200 bytes/s = 22MByte /s. (You need to add USB packets overhead.)
That means, running one camera with this resolution and frame rate must work. Even two of them in this situation, but this is hard to the limit of USB 2.0. But you see 7 fps only. Therefore, something blocks the image data transfer between USB Controller and memory.

In case you use an Intel CPU, you may try Processor Idle State Manager. It tries to prevent the CPU going into C3 state. The program can be downloaded from http://www.theimagingsource.com/en_US/support/downloads/

In case you use an AMD CPU, the only solution is using an USB 3.0 PCI Express board in your computer.

In very rare cases the USB 2.0 hub caused the loss of data packages.

Stefan Geissler
April 27, 2015, 11:08:04
As you can see on your screen shot: You have set 19 fps per camera and IC Capture shows, only 7 fps are achieved. That means, you have many many frame drops.
You have 1280x960*19 = 23347200 bytes/s = 22MByte /s. (You need to add USB packets overhead.)
That means, running one camera with this resolution and frame rate must work. Even two of them in this situation, but this is hard to the limit of USB 2.0. But you see 7 fps only. Therefore, something blocks the image data transfer between USB Controller and memory.

In case you use an Intel CPU, you may try Processor Idle State Manager. It tries to prevent the CPU going into C3 state. The program can be downloaded from http://www.theimagingsource.com/en_US/support/downloads/

In case you use an AMD CPU, the only solution is using an USB 3.0 PCI Express board in your computer.

In very rare cases the USB 2.0 hub caused the loss of data packages.

upen24931251
June 23, 2015, 06:10:25
Hello,

Thanks for your help, now I understand if i connect multiple cameras to a same USB port, that might cause some problems.

When I use IC Capture, this program can detect when should lower the FPS, when I connect multiple cameras to a same USB port.

May I ask you how to do this function?

Because our customer may connect cameras to the same USB port, so we want to do some protection.

Thank you very much!

Stefan Geissler
June 23, 2015, 14:32:34
I am very sorry, but IC Capture can not detect, whether you have connected your cameras to the very same controller or to different controllers. Therefore, it can not suggest frame rates.

upen24931251
June 25, 2015, 10:56:39
Hello:

Thank you for you help~