一、OpenCV VideoCapture打开摄像头接口讲解和源码分析
VideoCapture
可以打开数据源（文件/摄像机/rtsp流）
以下两种方案打开：
- bool open ( int index )
- VideoCapture cap(index)
bool open ( int index )
VideoCapture cap(index)
二、OpenCV VideoCapture打开视频流接口讲解和源码分析
三、VideoCapture release关闭和空间释放源码分析
四、OpenCV read读取一帧视频接口讲解和源码分析
五、使用OpenCV VideoCapture播放视频示例
isOpen判断打开失败原因
1.opencv_ffmpeg.dll 没有放入bin
2. 尚未得知
注意:我使用的opencv-3.4.1/3.4.16 版本 无法打开MP4 我换avi格式 isOpen就成功了，怀疑是x264.dll 以及相关没有导致不支持mp4
读取Frame（解码+转rgb）
Read()
VideoCapture video; Mat frame; video.read(frame)
流形式
VideoCapture video; Mat frame; video >> frame;
解码+转化颜色
if (!video.grab()) { break; } //转换颜色格式 if (!video.retrieve(frame)) { break; }
解码和转化颜色分割开来，类似利于实现解码一个线程和渲染一个线程的道理
源码
int main(int argc, char *argv[]) { VideoCapture video; cv::String strPath = ".\\res\\test.avi"; video.open(strPath); if (!video.isOpened()) { cout << "open video failed!" << endl; getchar(); return -1; } cout << "open video success!" << endl; namedWindow("video"); Mat frame; for (;;) { //if (!video.read(frame)) //{ // break; //} //读帧，解码 if (!video.grab()) { break; } //转换颜色格式 if (!video.retrieve(frame)) { break; } if (frame.empty()) break; imshow("video", frame); waitKey(30); } getchar(); return 0; }
六、获取视频和相机的属性并分析获取视频属性的源码
获取视频、相机属性
- CAP_PROP_FPS帧率
- CAP_PROP_FRAME_COUNT总帧数
- CAP_PROP_POS_FRAMES 播放帧的位置
- CAP_PROP_FRAME_WIDTH
- CAP_PROP_FRAME_HEIGHT
源码
int main(int argc, char *argv[]) { VideoCapture video; video.open(".\\res\\test.avi"); if (!video.isOpened()) { cout << "open video failed!" << endl; getchar(); return -1; } cout << "open video success!" << endl; namedWindow("video"); Mat frame; int fps = video.get(CAP_PROP_FPS); int s = 30; if (fps != 0) s = 1000 / fps; cout << "fps is " << fps << endl; int fcount = video.get(CAP_PROP_FRAME_COUNT); cout << "total frame is " << fcount << endl; cout << "total sec is " << fcount / fps << endl; cout << "CAP_PROP_FRAME_WIDTH " << video.get(CAP_PROP_FRAME_WIDTH) << endl; cout << "CAP_PROP_FRAME_HEIGHT " << video.get(CAP_PROP_FRAME_HEIGHT) << endl; s = s / 2; int f = 0; for (;;) { video.read(frame); if (frame.empty()) break; imshow("video", frame); waitKey(s); } getchar(); return 0; }
七、使用opencv实现视频播放位置跳转
建议：使用帧数进行跳转；使用毫秒数跳转，需要先转为帧数，再进行帧数跳转
获得当前帧号
- CAP PROP POS FRAMES
video.get( CAP PROP POS FRAMES);
设置跳转帧
video.set( CAP PROP POS FRAMES，0);//跳到 第一帧
源码
int main(int argc, char *argv[]) { VideoCapture video; video.open(".\\res\\test.avi"); if (!video.isOpened()) { cout << "open video failed!" << endl; getchar(); return -1; } cout << "open video success!" << endl; namedWindow("video"); Mat frame; int fps = video.get(CAP_PROP_FPS); int s = 30; if (fps != 0) s = 1000 / fps; cout << "fps is " << fps << endl; int fcount = video.get(CAP_PROP_FRAME_COUNT); cout << "total frame is " << fcount << endl; cout << "total sec is " << fcount / fps << endl; cout << "CAP_PROP_FRAME_WIDTH " << video.get(CAP_PROP_FRAME_WIDTH) << endl; cout << "CAP_PROP_FRAME_HEIGHT " << video.get(CAP_PROP_FRAME_HEIGHT) << endl; s = s / 2; int f = 0; for (;;) { video.read(frame); if (frame.empty()) break; int cur = video.get(CAP_PROP_POS_FRAMES); if (cur > 90) { video.set(CAP_PROP_POS_FRAMES, 0); continue; } imshow("video", frame); waitKey(s); } getchar(); return 0; }
八、通过VideoWrite的open创建视频文件并分析源码
VideoWriter
open
CV_WRAP virtual bool open( const String& filename, int fourcc, double fps, Size frameSize, bool isColor = true );
create
static Ptr<IVideoWriter> create( const String& filename, int fourcc, double fps, Size frameSize, bool isColor = true );
九、通过VideoWrite的write创建视频文件并分析源码
VideoWriter
write
CV_WRAP virtual void write(const Mat& image)
writeFrame
十、以h264格式录制并预览摄像机视频代码演示
摄像头打开失败的几个原因
openH264dll少了
源码
#include <opencv2/core.hpp> #include <opencv2/imgcodecs.hpp> #include <opencv2/highgui.hpp> #include <opencv2/imgproc.hpp> #include <iostream> using namespace cv; using namespace std; int main(int argc, char *argv[]) { VideoCapture cam(0); if (!cam.isOpened()) { cout << "cam open failed!" << endl; getchar(); return -1; } cout << "cam open success!" << endl; namedWindow("cam"); Mat img; VideoWriter vw; int fps = cam.get(CAP_PROP_FPS); if (fps <= 0)fps = 25; vw.open("out.avi", VideoWriter::fourcc('X', '2', '6', '4'), fps, Size(cam.get(CAP_PROP_FRAME_WIDTH), cam.get(CAP_PROP_FRAME_HEIGHT)) ); if (!vw.isOpened()) { cout << "VideoWriter open failed!" << endl; getchar(); return -1; } cout << "VideoWriter open success!" << endl; for (;;) { cam.read(img); if (img.empty())break; imshow("cam", img); vw.write(img); if (waitKey(5) == 'q') break; } waitKey(0); return 0; }
十一、使用ffmpeg工具实现音频抽取、剪切和与视频
使用ffmpeg工具抽取音频
ffmpeg.exe -i 1.avi -vn 1.mp3
-i表示源
-vn表示不转换视频
使用ffmpeg剪切音频
ffmpeg -ss 0:0:30 -t 0:0:20 -i input.mp -c copy output.mp
使用ffmpeg工具音视频合并
ffmpeg.exe -i 1.mp3 -i 1.mp4 -c copyout.mp
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