Opencv读取写入视频_opencv: ffmpeg: tag 0x47504a4d/'mjpg' is not suppo

描述

调用opencv库来读取写入视频

语言：C++
视频格式：MP4

代码

1. 读取视频

#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");// 视频路径
    
    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;
}
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2. 写入视频

#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;
}
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关于视频格式

代码中有一句话，定义了一个cv::VideoWriter负责写入视频

cv::VideoWriter writer("/Users/admin/Desktop/CodeBase/c++_try/out.mp4", cv::VideoWriter::fourcc('m','p','4','v'), fps, cv::Size(1280, 720));
1

参数也好理解：路径、编码格式、帧率、图像大小

• 我找了一些资料：

  cv::VideoWriter::fourcc(‘I’, ‘4’, ‘2’, ‘0’),该参数是YUV编码类型，文件名后缀为.avi
  cv::VideoWriter::fourcc(‘P’, ‘I’, ‘M’, ‘I’),该参数是MPEG-1编码类型，文件名后缀为.avi
  cv::VideoWriter::fourcc(‘X’, ‘V’, ‘I’, ‘D’),该参数是MPEG-4编码类型，文件名后缀为.avi
  cv::VideoWriter::fourcc(‘T’, ‘H’, ‘E’, ‘O’),该参数是Ogg Vorbis,文件名后缀为.ogv
  cv::VideoWriter::fourcc(‘F’, ‘L’, ‘V’, ‘1’),该参数是Flash视频，文件名后缀为.flv

我还看到有人是这么写的
cv::VideoWriter::fourcc(‘M’, ‘J’, ‘P’, ‘G’)，文件名后缀是.avi

报错

在执行代码时，提示过几次错误

OpenCV: FFMPEG: tag 0x00000898/'???' is not found (format 'avi / AVI (Audio Video Interleaved)
1

和

OpenCV: FFMPEG: tag 0x47504a4d/'MJPG' is not supported with codec id 7 and format 'mp4 / MP4
1

最后排查，都是上面提到的视频编码格式的问题cv::VideoWriter::fourcc，写代码时请注意你要的视频后缀需要和编码格式对应