Hi list,

I've observed something surprising with a small UVC camera on the
gumstix overo. If I use the camera_node from uvc_camera, I get barely
2 fps in 640x480.
On the other hand, if I make a small application using the opencv
cvCapture function, I get close to 10fps at the same resolution.

Here is the cv code in all its complexity:

� � � � � �CvCapture* capture = 0;
� � � � � �capture = cvCaptureFromCAM( -1 );
� � � � � �IplImage *cv_image = NULL;
� � � � � �ros::Rate loop_rate(10);
� � � � � �while (ros::ok())
� � � � � �{
� � � � � � � �cv_image = cvQueryFrame(capture);
� � � � � � � �try {
� � � � � � � � � �image_pub_.publish(bridge_.cvToImgMsg(cv_image, "bgr8"));
� � � � � � � �} catch (sensor_msgs::CvBridgeException error) {
� � � � � � � � � �ROS_ERROR("error");
� � � � � � � �}
� � � � � � � �ros::spinOnce();
� � � � � � � �loop_rate.sleep();
� � � � � �}

� � � � � �cvReleaseCapture(&capture);

On the same camera on my laptop, both cv_capture and uvc_camera
publish at 10 fps.

I guess that means there is something that would need optimisation in
the uvc_camera/camera_node, but for now I'll be fine with just
reporting :-)

I've seen similar�discrepancies�in performance from the driver based on computer as well. See�http://code.ros.org/lurker/message/20110105.220655.b7e05812.en.html�(though in that situation, all of the computers in�question�had enough CPU horsepower to not drop the framerate).

Could you report which camera you are using? Also, no idea if you can get a monitor on the overo, but if you can, you could use guvcview to see if that also experiences a slow down in frame rate when you try to use similar settings to the uvc_camera driver.

- Eric

�

--
Cedric Pradalier
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