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BlazingForests / realsense_camera

use realsense camera in ROS
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Try to show images from multiple realsense devices #18

Open Wesley-Lin opened 8 years ago

Wesley-Lin commented 8 years ago

Hi BlazingForests,

I write a application to read realsense R200 via v4l2, it would be ok if launch single device. However, if I want to show two images from two devices, it only shows one image, the other app seems cannot get data. Have yo had any experience of showing multiple devices ? The other issue is that when I read RGB data from single device, in first time it can get data, but it cannot get data after that unless I physically replug and plug R200, do you have any idea for that ?

Thanks Regards

BlazingForests commented 8 years ago

Hi, @Wesley-Lin I don't have the R200 device yet. So i have on idea. Sorry.

Some time we need replug realsense device is still an issue.

What is the error information?

Maybe you can change the mmap buffer to 1 and test it.

Thx DD

wqf233333 commented 8 years ago

Hi BlazingForests and Wesley-Lin , I also get this problem. And there is someone do this but fail. https://github.com/PercATI/RealSense_ROS/issues/13 I want to connect six R200 to a NUC,but there are just two USB3.0 interface for each NUC.Can I use HUB to connect R200 to NUC? If not,How can I connect six R200 to a NUC? JUST like this:http://www.engadget.com/2015/01/06/intel-realsense-asctec-firefly-drone-ping-pong/

BlazingForests commented 8 years ago

Hi, I think this is an hardware limit problem.

We suppose each F200 work in RGB(1920x1080@30) + D(640x480@30) + I(640x480@30) mode

So there have 1920x1080x30x2 + 640x480x30x2 + 640x480x30x1 = 152064000Byte/s = 145.01953125MB/s

The USB3.0 port theoretical speed is 5Gb/s , by reason of some technical issue (eg. 8b/10b encoding ...), maybe 3.2Gb/s = 400MB/s , But actual speed maybe more lower.

So one USB3.0 port(NO hub) maybe support only one F200!

The intel Z97 chipset have only 6 USB3.0 port.(http://www.intel.com/content/www/us/en/chipsets/performance-chipsets/z97-chipset-diagram.html)

So.....

R200 even have three camera!!! so.....

You can check your hardware first.

thx DD

wqf233333 commented 8 years ago

Thanks BlazingForests, I notice that the bandwidth of the USB is the main problem, so I will test that once I get my realsense model.

TonderaiZR commented 7 years ago

Hello

You hope you got this to work looking to do some thing similar. Yes you can't have multiple cameras on the same usb bus because of bandwidth problems and other issues.

If you got it to work and have details please post.

Cheers.