通过javacv对视频每隔1秒钟截取1张图片

之前每一秒钟截取一张图片，发现有些图片报了“[mpeg4 @ 05938aa0] warning: first frame is no keyframe”这个警告，而且截出的图片都是灰屏，根本没有图片。后来在网上找了很久，终于弄明白了，原来是ffmpeg它有“关键帧”这个说法，所以如果设置的帧的位置不是关键帧的位置的话，就可能截出的图片有问题。后来经过改进，终于搞定了。

public static void main(String[] args) {
System.out.println(System.getProperty("java.library.path"));
// System.out.println("Welcome to OpenCV " + Core.VERSION);
// System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
// Mat m = Mat.eye(3, 3, CvType.CV_8UC1);
// System.out.println("m = " + m.dump());

// 加载本地的OpenCV库，这样就可以用它来调用Java API
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
Test t = new Test();
// t.test();
// t.run();
// t.run2();
t.run3();
// System.out.println(t.CmpPic("d:/img/219.jpg"));
}

public void run3() {
CvCapture capture = opencv_highgui.cvCreateFileCapture("D:/085402.crf");

//帧率
int fps = (int) opencv_highgui.cvGetCaptureProperty(capture, opencv_highgui.CV_CAP_PROP_FPS);
System.out.println("帧率:"+fps);

IplImage frame = null;
double pos1 = 0;

int rootCount = 0;

while (true) {

//读取关键帧
frame = opencv_highgui.cvQueryFrame(capture);

rootCount = fps;
while(rootCount > 0 ){
//这一段的目的是跳过每一秒钟的帧数,也就是说fps是帧率(一秒钟有多少帧),在读取一帧后,跳过fps数量的帧就相当于跳过了1秒钟。
frame = opencv_highgui.cvQueryFrame(capture);
rootCount--;
}

//获取当前帧的位置
pos1 = opencv_highgui.cvGetCaptureProperty(capture,opencv_highgui.CV_CAP_PROP_POS_FRAMES);
System.out.println(pos1);

if (null == frame)
break;

opencv_highgui.cvSaveImage("d:/img/" + pos1 + ".jpg",frame);

}

opencv_highgui.cvReleaseCapture(capture);
}