Odroid U2/U3 multithreaded camera code

[Danodeth]

I just posted some C++ code I wrote to read from USB cameras and display the images to a monitor. Note that there is no "vision processing" going on here, so this isn't intended as a final solution to any particular problem. It's more of a test to see how fast I can capture and display images. It might be a nice starting place for someone who wants to do vision processing on a coprocessor, and in fact, team 696 may use it for that purpose in 2015, depending on the game.
This code has been run on Odroid U2 and U3 processors running Ubuntu, reading from either 1 or 2 Playstation Eye USB cameras, and displaying the images to a monitor attached to the Odroid via HDMI cable. I'm using 2 threads for each camera, 1 for reading in the image and one for sending the image to the display. The images are buffered in a queue in shared memory with pointers passed between threads to avoid unnecessary copying.
Here are the frame rates I've seen on Odroid U2:
1 camera 480 x 640 pixels: 43 fps
2 cameras 480 x 640 pixels: 15 fps
1 camera 240 x 320 pixels: 125 fps
1 camera 480 x 640 and 1 at 240x320: 30 fps
These are uncompressed images, and I expect we are limited by the speed of the USB connection.

The code is available here:
https://github.com/team696-public/2014_odroid_camera

Dependencies: Video4Linux, OpenCV.
The capture code accesses the cameras using the Video4Linux driver interfaces. OpenCV is used only to display the images.

[sparkytwd]

From those speeds it does sound like you're hitting USB bus limit. Not sure what the topology of U3's ports are, but on the XU, there were a few distinct end points, which means you can potentially have separate bandwidth for multiple cameras.

If you want to play around with cameras and compressed formats, give the C920 a shot. It supports both MJPEG and H264 compression. You can use gstreamer and v4l2loopback to convert the video to whatever format you'd like.