描述

呼叫opencv庫來讀取寫入視訊

語言：C++
視訊格式：MP4

程式碼

1. 讀取視訊

#include <iostream>
#include <cstdlib>
#include <ctime>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc.hpp>
int main()
{
	cv::VideoCapture capture;
    cv::Mat frame;
    frame= capture.open("/Users/admin/Desktop/CodeBase/c++_try/1.mp4");// 視訊路徑
    
    if(!capture.isOpened())
    {
        printf("can not open ...\n");
        return -1;
    }
    while (capture.read(frame))
    {
        int width = frame.size().width;
        int height = frame.size().height;
        
        cv::imshow("origin", frame);
        cv::waitKey(100);
        
    }
    capture.release();
    return 0;
}

2. 寫入視訊

#include <iostream>
#include <cstdlib>
#include <ctime>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc.hpp>
int main()
{
	cv::VideoCapture capture;
    cv::Mat frame;
    frame= capture.open("/Users/admin/Desktop/CodeBase/c++_try/4.mp4");
    double fps = capture.get(cv::CAP_PROP_FPS);
    cv::VideoWriter writer("/Users/admin/Desktop/CodeBase/c++_try/out.mp4", cv::VideoWriter::fourcc('m','p','4','v'), fps, cv::Size(1280, 720));
       
    if(!capture.isOpened())
    {
        printf("can not open ...\n");
        return -1;
    }
    while (capture.read(frame))
    {
        int width = frame.size().width;
        int height = frame.size().height;
        
        writer << frame;
        cv::imshow("origin", frame);
        cv::waitKey(100);
        
    }
    capture.release();
    return 0;
}

關於視訊格式

程式碼中有一句話，定義了一個cv::VideoWriter負責寫入視訊

cv::VideoWriter writer("/Users/admin/Desktop/CodeBase/c++_try/out.mp4", cv::VideoWriter::fourcc('m','p','4','v'), fps, cv::Size(1280, 720));

參數也好理解：路徑、編碼格式、影格率、影象大小

• 我找了一些資料：

  cv::VideoWriter::fourcc(‘I’, ‘4’, ‘2’, ‘0’),該參數是YUV編碼型別，檔名後綴爲.avi
  cv::VideoWriter::fourcc(‘P’, ‘I’, ‘M’, ‘I’),該參數是MPEG-1編碼型別，檔名後綴爲.avi
  cv::VideoWriter::fourcc(‘X’, ‘V’, ‘I’, ‘D’),該參數是MPEG-4編碼型別，檔名後綴爲.avi
  cv::VideoWriter::fourcc(‘T’, ‘H’, ‘E’, ‘O’),該參數是Ogg Vorbis,檔名後綴爲.ogv
  cv::VideoWriter::fourcc(‘F’, ‘L’, ‘V’, ‘1’),該參數是Flash視訊，檔名後綴爲.flv

我還看到有人是這麼寫的
cv::VideoWriter::fourcc(‘M’, ‘J’, ‘P’, ‘G’)，檔名後綴是.avi

報錯

在執行程式碼時，提示過幾次錯誤

OpenCV: FFMPEG: tag 0x00000898/'???' is not found (format 'avi / AVI (Audio Video Interleaved)

和

OpenCV: FFMPEG: tag 0x47504a4d/'MJPG' is not supported with codec id 7 and format 'mp4 / MP4

最後排查，都是上面提到的視訊編碼格式的問題cv::VideoWriter::fourcc，寫程式碼時請注意你要的視訊後綴需要和編碼格式對應