Can't grab frames from an ip camera (rtsp) with a C++ dll using OpenCv 3.4.5

Question

I'm building a simple application in c++ (32-bits) that uses opencv to grab frames from a rtsp camera.

The function that grabs the camera frames run in a separated thread from the main program.

I've testes this application with a mp4 video, and it works fine. I was able to grab frames and process them. However when I use the rtsp link, although I was able to open a connection with the camera, whenever I tried to read both grab() and read() functions returns False.

First, i thought it was an issue with the rtsp link, but I made a simple Python application to test it, and it worked as well. So it was not the link.

This is the code that I'm using to grab the frames:

#ifndef _IMAGE_BUFFER_H_
#define _IMAGE_BUFFER_H_

#include <opencv2/core.hpp>
#include <opencv2/videoio.hpp>
#include <opencv2/highgui.hpp>

.
.
.

VideoCapture capture_;

string address_;
atomic<bool> keep_alive_;
thread thread_;
int fps_;
mutex mutex_;
list<FramePair> frames_;

int Run()
{

    capture_.open(address_, cv::CAP_ANY);

    if (!capture_.isOpened()) {
        printf("Could not open Camera feed! \n");
        return -1;
    }

    uint64_t period = uint64_t((float(1) / float(fps_)) * float(1000));

    period = period - (period / 20);

    uint64_t t0 = getCurrentTimeInMilli();
    while (keep_alive_) {

        uint64_t difftime = getCurrentTimeInMilli() - t0;
        if (difftime < period) {
            uint64_t sleep_time = period - difftime;
            if (sleep_time < period) {
                std::this_thread::sleep_for(std::chrono::milliseconds(sleep_time));
            }
        }

        t0 = getCurrentTimeInMilli();

        CaptureFrame();
    }

    return 0;
}

void CaptureFrame()
{
    Mat frame;

    bool ret = capture_.read(frame);
    if (!ret) {
        printf("Error in frame reading! \n");
    }

    vector<uint8_t> jpeg;
    cv::imencode(".jpg", frame, jpeg, vector<int>());

    mutex_.lock();

    frames_.push_back(FramePair(getCurrentTimeInMilli(), jpeg));

    if (frames_.size() > FRAME_QUEUE_SIZE)
        frames_.pop_front();

    mutex_.unlock();
}

The OpenCv version that I'm using is 3.4.5.

The link : rtsp://<user>:<pass>@<ip>:<port>/media

I appreciate any help on this matter.

Edit1:

What I have tried:

I`ve tried this this, but it didn't work
Also Tried with a pre-built opencv 3.4.0 version for 64 bits and still the same

Is your Python environment 64 or 32 bit. I'd look with procmon which dlls are/not loaded, (you might have a silent failure). Check maybe also the traffic with Wireshark to see if any communication occures for that protocol. — Damien LEFEVRE
I've made tests on both environments, and both worked. Right now i'm recompiling my opencv from source with the same flags from the python opencv. so at least I leave them with the same configuration. — MBoaretto

MBoaretto MBoaretto · Accepted Answer · 2020-06-10T13:40:02

Sorry for answering my own question.

But after a lot of trial and error, and reading various SO threads regarding the issue of using cv::VideoCapture in in Windows.

I found the issue,

I was trying to statically link OpenCv in my application, and due to license issues ffmpeg cannot be compiled statically along with the application.

I solved it by, copying the opencv_ffmpegxxx.dll, which can be found in /bin/ . And pasting it in my .exe folder as suggested in here.

There might be some workaround to embed ffmpeg dll in the application as suggested in here, but i haven't tried yet. I hope someone else can benefit from this issue.

Thanks for the help.

Can't grab frames from an ip camera (rtsp) with a C++ dll using OpenCv 3.4.5

Edit1:

What I have tried:

1 Answers