Capturing 1080p at 30fps from logitech c920 with openCV 2.4.3

Question

I'm trying to capture the video stream off of my Logitech C920 in OpenCV. With Labview I can access an MJPG stream at 30fps 1080p. In opencv I am limited to either 5fps or 640x480.

Here is the code relevant to the camera settings:

this->camRef.set(CV_CAP_PROP_FRAME_WIDTH, 1920);
this->camRef.set(CV_CAP_PROP_FRAME_HEIGHT, 1080);
this->camRef.set(CV_CAP_PROP_FOURCC,CV_FOURCC('M','J','P','G'));

These all return 1, yet I get a 5fps stream of 1080p which corresponds to the YUY2 stream.
If I add the following line:

this->camRef.set(CV_CAP_PROP_FPS, 30);

This returns 0. I get a 30 fps stream at 640x480. To me it looks like the MJPG setting isn't be accepted but I don't know what to do or how to fix that.

EDIT: The following crashes the program.

 this->camRef.read(this->image);
 std::cout<< this->camRef.get(CV_CAP_PROP_FOURCC)                            << std::endl;
 std::cout<< this->camRef.set(CV_CAP_PROP_FRAME_WIDTH, config.width)         << std::endl;
 std::cout<< this->camRef.set(CV_CAP_PROP_FRAME_HEIGHT, config.height)       << std::endl;
 std::cout<< this->camRef.set(CV_CAP_PROP_FOURCC,CV_FOURCC('M','J','P','G')) << std::endl;
 std::cout<< this->camRef.get(CV_CAP_PROP_FOURCC)                            << std::endl;

Then in my run code I have the following:

void camera::run()
{
    while(true)
    {
        if(this->camRef.read(this->image) == 0)
        {
           if(this->capture)
            {
                cv::imwrite(fileName,this->image);
                this->count++;
            }
        }
        msleep(15);
    }
}

EDIT2: Solution is to set the fourCC codec before setting camera height and width.

Giorgia

if you want to set fps(must be supported by camera), you have to do it after codec setting, but before width/height settings – Fayalite

Sounds like your EDIT2 gave you 1080p at 30fps. Should be turned into an answer and accepted then to make the problem appear solved. – Battleax

Answer 1

As the author of the post already found the solution but didn't add it as an answer I will put the solution here.

You have to set the codec before you set the wanted resolution:

this->camRef.set(CV_CAP_PROP_FOURCC,CV_FOURCC('M','J','P','G'));
this->camRef.set(CV_CAP_PROP_FRAME_WIDTH, 1920);
this->camRef.set(CV_CAP_PROP_FRAME_HEIGHT, 1080);

Fez

Thanks! It worked as stated! On the other hand, I'd like to mention that although this will allow the fullHD@30 resolution, image quality may be very poor (compression rate has to be high in order to meet with the bandwidth restriction of USB 2.0) – Countryside

Answer 2

working with logitech c922, needed:

capture.open(CV_CAP_DSHOW);
capture.set(CV_CAP_PROP_FOURCC, CV_FOURCC('M', 'J', 'P', 'G'));
capture.set(CV_CAP_PROP_FRAME_WIDTH, 1920);
capture.set(CV_CAP_PROP_FRAME_HEIGHT, 1080);

Sup

Answer 3

Try to get first frame from capture before setting anything:

VideoCapture cap(0);
if(!cap.isOpened()) 
return -1;  

Mat frame;
cap >> frame;
double fps;
cap.set(CV_CAP_PROP_FRAME_HEIGHT, 1080.0);
cap.set(CV_CAP_PROP_FRAME_WIDTH, 1920.0);
//add the loop here

and check whether it will work without setting MJPG. If it will work, try with MJPG.

For me it's a bit weird that you have to get first frame before setting anything, but it's the only way it's working for me (windows 7 32bit).

//edit:
Yo may try to use different API - see second part of my answer here: https://mcmap.net/q/473671/-opencv-on-mac-is-not-opening-usb-web-camera OpenCV is trying to use the best API by default, but maybe in your case some other API will work better.

Concinnity

Thank you for the reply. I tried what you said and now my code crashes before displaying an image. cap.read returns 1 and then it crashes when it tries to read again from the camera. – Giorgia

I've updated the original question to show the code you requested. – Giorgia