cv::VideoWriter destroys an SSE register (Bug #3694)

The following test fails in Windows 7 pro, Visual Studio 2012 Express with x64/Release configuration using the pre-built OpenCV 2.4.9, 2.4.8 and 2.4.5 (x64/vc11).

#include "opencv2/opencv.hpp" 
void EXPECT_EQ(double a, double b) { if (a != b) { std::cout << "failed" << std::endl; } } 
int main()
{
    double current_time = 0.0;
    cv::Mat blank = cv::Mat::zeros(480, 640, CV_8UC3);
    cv::VideoWriter writer("output.avi", CV_FOURCC('M','J','P','G'),
                           50.0, blank.size(), true);
    current_time += 20.0;
    writer << blank;
    EXPECT_EQ(20.0, current_time);
    return 0;
}

The variable current_time is assigned to the xmm7 SEE register, which holds 00000000000000004034000000000000 before executing writer << blank;, then turns to have 00070007000700070007000700070007 after that. This (seemingly SSE-generated ) value is written by codes in opencv_ffmpeg24x_64.dll.

This behavior is fragile and a small change to the code can make it disappear (See my post at http://answers.opencv.org/question/31357/writing-mjpg-file-by-videowriter-in-visual-studio/).

Although this problem reproduces only when we write MJPG format files as far as I tried the above particular code, very similar behaviors happen for many other video formats with a more complicated code.