链接错误:对`cv :: VideoCapture :: open(std :: string const&)的未定义引用

我正在尝试使用.avi文件作为源. (相机捕获已经可以使用.)我的项目编译没有问题，但是在链接过程中出现错误:

I'm trying to use an .avi file as my source. (Camera capture already works.) My project compiles without problems, but during linking I get the error:

undefined reference to 'cv::VideoCapture::open(std::string const&)'

我该怎么办? VideoCapture::open()的std::string重载放在哪个库中?

What should I do? In which library is this std::string overload of VideoCapture::open() put?

VideoCapture(0)(摄像头捕获)可以编译，链接和运行，因此VideoCapture(std::string)必须位于我已经与之链接的libs中的其他位置...对吧?

VideoCapture(0) (camera capture) compiles, links and works, so VideoCapture(std::string) has to be somewhere else that in libs I'm already linking with... right?

OpenCV版本:2.4.9(昨天从git复制).

OpenCV version: 2.4.9 (cloned from git yesterday).