IP Camera Capture delay/lag

edit

Hello,

I am trying to so some processing on a IP Camera (Onvif) output image, and it works well, but I see a lag between the real world and the video capture in about 3~4 seconds.

I am using the rtsp:// protocol.

This camera have a web interface (IE / ActiveX) that shows the image with very low lag. (about 200~300 ms).

I have no idea why it's so slow on OpenCV. I wold like some tips to make the capture faster.

edit: It May have something to do with VideoCapture buffer. Is there a way to make it aways use the latest image?

edit2: I could get good lag results on VLC, after reducing cache/buffer to 300ms, I believe network and processing are not to blame. Now I got a stronger feeling that cache is to blame

Thank you!

You can see the code I am using bellow, i also included the output:

CODE

#include <stdio.h>
#include <opencv2/opencv.hpp>
#include <thread>
#include <unistd.h>

using namespace cv;
using namespace std;

int main(int argc, char *argv[])
{
    cout << getBuildInformation();
    VideoCapture cap;
    cout << "open stream: " << argv[1] << endl;
    if(!cap.open(argv[1]))
        exit(-1);
    cout << "stream open!\n";

    Mat test;
    do{
        cap >> test;

    if(test.empty()){
        cout << "Empty!\n";
    } else {
        imshow("imagem", test);
    }
} while(waitKey(1) < 0);

}

Output

leonardo@LeonardoB:~/Desktop/Ether_Test/build$ make ; ./EtherTest rtsp://admin:[email protected]:554/ucast/11
Scanning dependencies of target EtherTest
[ 50%] Building CXX object CMakeFiles/EtherTest.dir/main.cpp.o
[100%] Linking CXX executable EtherTest
[100%] Built target EtherTest

General configuration for OpenCV 3.1.0-dev =====================================
  Version control:               3.1.0-1362-gcde9d64

  Extra modules:
    Location (extra):            /home/leonardo/OpenCV/OpenCV3/opencv_contrib/modules
    Version control (extra):     3.1.0-297-g246ea8f

  Platform:
    Timestamp:                   2016-09-22T13:20:09Z
    Host:                        Linux 4.7.4-1-ARCH x86_64
    CMake:                       3.6.2
    CMake generator:             Unix Makefiles
    CMake build tool:            /usr/bin/make
    Configuration:               Release

  C/C++:
    Built as dynamic libs?:      NO
    C++ Compiler:                /usr/bin/c++  (ver 6.2.1)
    C++ flags (Release):         -fPIC   -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wno-narrowing -Wno-delete-non-virtual-dtor -Wno-comment -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -mno-avx -msse3 -mno-ssse3 -mno-sse4.1 -mno-sse4.2 -ffunction-sections -fvisibility=hidden -fvisibility-inlines-hidden -O3 -DNDEBUG  -DNDEBUG
    C++ flags (Debug):           -fPIC   -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wno-narrowing -Wno-delete-non-virtual-dtor -Wno-comment -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -mno-avx -msse3 -mno-ssse3 -mno-sse4.1 -mno-sse4.2 -ffunction-sections -fvisibility=hidden -fvisibility-inlines-hidden -g  -O0 -DDEBUG -D_DEBUG
    C Compiler:                  /usr/bin/cc
    C flags (Release):           -fPIC   -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wno-narrowing -Wno-comment -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -mno-avx -msse3 -mno-ssse3 -mno-sse4.1 -mno-sse4.2 -ffunction-sections -fvisibility=hidden -O3 -DNDEBUG  -DNDEBUG
    C flags (Debug):             -fPIC   -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations ...