Converting from cv::VideoCapture to cs::VideoSource

[WilliamB]

Right now I’m attempting to use a pi 0 for some very lightweight vision processing and I have a camera connected to it using a ribbon cable. I am able to read frames from the camera but I want to be able to use camera server so I can easily display it on the smart dashboard

#include "cameraserver/CameraServer.h"
#include "opencv2/core.hpp"
#include "opencv2/videoio.hpp"

int main() {
    cv::VideoCapture cam(0);
    cv::Mat frame;
    cam >> frame;

    cs::MjpegServer srv("serve_USB Camera 0", 1706);
    srv.SetSource(cam);
}

but SetSource() only accepts cs::VideoSource objects

[Peter_Johnson]

I would recommend you not use OpenCV’s VideoCapture, use cs::UsbCamera (it will work for the Pi camera too) and cs::CvSink to get the frames as OpenCV Mat’s.

Regarding cs::MjpegServer, you need to create a cs::CvSource and provide the Mat to it.

This documentation will probably help (especially the example at the very end of the page).

Read and Process Video: CameraServer Class

Your code above will also just immediately exit. You’ll need to put in a loop to continuously process frames, similar to this example:

Using the CameraServer on the roboRIO

[WilliamB]

I know I’m missing the loop, I meant it as an example. so my only option i to refactor if I want to use wpilib’s mjpeg server? or is there a way I can display my own mjpeg source on shuffleboard?

[Peter_Johnson]

To send OpenCV images, you just need to create a CvSource to feed your cv::Mat to (in addition to the MjpegServer), e.g.

cs::CvSource cvsource("cv", VideoMode::kBGR, 320, 240, 30);
cs::MjpegServer srv("serve_cv", 1706);
srv.SetSource(cvsource);

...

cvsource.PutFrame(frame);

If you want to have it send the original camera stream directly, you will either need to pass through OpenCV as above, or use cs::UsbCamera.

Any mjpeg source can be shown on Shuffleboard using ShuffleboardContainer.addCamera().