slow framerate from camera in opencv+gstreamer (orange pi5)

Question

I have Orange Pi5 and ov13855 mipi camera module. Ubuntu 22.04, OpenCV 4.5.4, Gstreamer 1.20.3

I can capture video from /dev/video11 device via gstreamer:

gst-launch-1.0 v4l2src device=/dev/video11 ! video/x-raw,format=NV12,width=1920,height=1080,framerate=25/1 ! videoconvert ! xvimagesink

and it seems good.

But if i try to capture video via OpenCV it gets only 10 fps

#include <stdio.h>
#include <memory>
#include <sys/time.h>

#include "opencv2/core/core.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"

int main(int argc, char **argv)
{
    cv::namedWindow("Camera FPS");

    cv::VideoCapture capture("v4l2src device=/dev/video11 ! video/x-raw,format=NV12,width=1920,height=1080,framerate=25/1 ! videoconvert ! appsink drop=true", cv::CAP_GSTREAMER);

    if (!capture.isOpened())
        printf("ERROR: Device is not opened!\n");

    struct timeval time;
    struct timeval time2;

    gettimeofday(&time, nullptr);
    auto startTime = time.tv_sec * 1000 + time.tv_usec / 1000;

    int frames = 0;
    auto beforeTime = startTime;

    while (capture.isOpened())
    {
        cv::Mat img;

        gettimeofday(&time2, nullptr);
        auto startTime2 = time2.tv_usec;

        if (capture.read(img) == false)
            break;

        gettimeofday(&time2, nullptr);
        auto endTime2 = time2.tv_usec;

        cv::imshow("Camera FPS", img);

        if (cv::waitKey(1) == 'q') //Press q to exit
            break;
        frames++;

        if (frames % 30 == 0)
        {
            gettimeofday(&time, nullptr);
            auto currentTime = time.tv_sec * 1000 + time.tv_usec / 1000;
            printf("%f fps/s\n", 30.0 / float(currentTime - beforeTime) * 1000.0);
            printf("%lu us capture time\n", (endTime2-startTime2));
            beforeTime = currentTime;
        }
    }

    while (true)
    {
        cv::Mat img;

        cv::imshow("Camera FPS", img);
        if (cv::waitKey(1) == 'q') //Press q to exit
            break;
        frames++;
    }

    gettimeofday(&time, nullptr);
    auto endTime = time.tv_sec * 1000 + time.tv_usec / 1000;

    printf("Average:\t %f fps/s\n", float(frames) / float(endTime - startTime) * 1000.0);

    return 0;
}

I have a guess that ov13855 always sends full matrix resolution 4224x3136 and opencv sacale it to 1920x1080 and can't handle this but its only guess.

v4l2-ctl -d 11 -all

Driver Info:
        Driver name      : rkisp_v6
        Card type        : rkisp_mainpath
        Bus info         : platform:rkisp0-vir1
        Driver version   : 2.5.1
        Capabilities     : 0x84201000
                Video Capture Multiplanar
                Streaming
                Extended Pix Format
                Device Capabilities
        Device Caps      : 0x04201000
                Video Capture Multiplanar
                Streaming
                Extended Pix Format
Media Driver Info:
        Driver name      : rkisp0-vir1
        Model            : rkisp0
        Serial           :
        Bus info         :
        Media version    : 5.10.209
        Hardware revision: 0x00000000 (0)
        Driver version   : 5.10.209
Interface Info:
        ID               : 0x03000007
        Type             : V4L Video
Entity Info:
        ID               : 0x00000006 (6)
        Name             : rkisp_mainpath
        Function         : V4L2 I/O
        Pad 0x01000009   : 0: Sink
          Link 0x0200000a: from remote pad 0x1000004 of entity 'rkisp-isp-subdev' (Unknown V4L2 Sub-Device): Data, Enabled
Priority: 2
Format Video Capture Multiplanar:
        Width/Height      : 1920/1080
        Pixel Format      : 'UYVY' (UYVY 4:2:2)
        Field             : None
        Number of planes  : 1
        Flags             :
        Colorspace        : sRGB
        Transfer Function : Rec. 709
        YCbCr/HSV Encoding: Rec. 709
        Quantization      : Full Range
        Plane 0           :
           Bytes per Line : 3840
           Size Image     : 4147200
Selection Video Capture: crop, Left 0, Top 0, Width 4224, Height 3136, Flags:
Selection Video Capture: crop_bounds, Left 0, Top 0, Width 4224, Height 3136, Flags:
Selection Video Output: crop, Left 0, Top 0, Width 4224, Height 3136, Flags:
Selection Video Output: crop_bounds, Left 0, Top 0, Width 4224, Height 3136, Flags:

also i try use this code instead gst line:

    cv::VideoCapture capture(11);
    capture.open(11);

    capture.set(cv::CAP_PROP_BUFFERSIZE, 1);
    capture.set(cv::CAP_PROP_FPS, 25);
    capture.set(cv::CAP_PROP_FOURCC, cv::VideoWriter::fourcc('N','V','1','2'));
    capture.set(cv::CAP_PROP_FRAME_WIDTH, 1920);
    capture.set(cv::CAP_PROP_FRAME_HEIGHT, 1080);

but nothing changes still 10fps max.