OpenCV保存视频的操作

一、opencv保存视频打不开

保存的视频打不开可能是因为文件编码格式不对，或者版本不兼容等原因。

检查文件编码格式，如果视频保存为AVI格式，在保存的时候应该指定编码器，并确保选择的编码器在本地系统上可用。如果视频格式为mp4，需要检查mp4格式的插件是否已经安装好，并且扩展名保存为.mp4才能兼容。

示例代码：

“`
#include
#include “opencv2/core.hpp”
#include “opencv2/highgui.hpp”
#include “opencv2/videoio.hpp”

using namespace std;
using namespace cv;

int main()
{
VideoCapture cap(0);
if (!cap.isOpened())
{
return 0;
}

int fourcc = VideoWriter::fourcc(‘X’, ‘V’, ‘I’, ‘D’);
int fps = 30;
Size size(int(cap.get(CAP_PROP_FRAME_WIDTH)), int(cap.get(CAP_PROP_FRAME_HEIGHT)));
VideoWriter writer(“output.avi”, fourcc, fps, size);
if (!writer.isOpened())
{
return 0;
}

Mat frame;
while (true)
{
cap >> frame;
if (frame.empty())
{
break;
}
writer.write(frame);
imshow(“frame”, frame);
if (waitKey(10) == 27)
{
break;
}
}

cap.release();
writer.release();
destroyAllWindows();
return 0;
}
“`

二、opencv保存视频mp4

mp4是一种常见的视频格式，OpenCV同样可以保存为mp4格式。mp4格式需要保证编码器可用，推荐使用H264编码器。

示例代码：

“`
#include
#include “opencv2/core.hpp”
#include “opencv2/highgui.hpp”
#include “opencv2/videoio.hpp”

using namespace std;
using namespace cv;

int main()
{
VideoCapture cap(0);
if (!cap.isOpened())
{
return 0;
}

int fourcc = VideoWriter::fourcc(‘a’, ‘v’, ‘c’, ‘1’);
int fps = 30;
Size size(int(cap.get(CAP_PROP_FRAME_WIDTH)), int(cap.get(CAP_PROP_FRAME_HEIGHT)));
VideoWriter writer(“output.mp4”, fourcc, fps, size, true);
if (!writer.isOpened())
{
return 0;
}

Mat frame;
while (true)
{
cap >> frame;
if (frame.empty())
{
break;
}
writer.write(frame);
imshow(“frame”, frame);
if (waitKey(10) == 27)
{
break;
}
}

cap.release();
writer.release();
destroyAllWindows();
return 0;
}
“`

三、opencv保存视频变快

保存视频变快可以通过控制帧率调整，适当提高帧率。

示例代码：

“`
#include
#include “opencv2/core.hpp”
#include “opencv2/highgui.hpp”
#include “opencv2/videoio.hpp”

using namespace std;
using namespace cv;

int main()
{
VideoCapture cap(0);
if (!cap.isOpened())
{
return 0;
}

int fourcc = VideoWriter::fourcc(‘X’, ‘V’, ‘I’, ‘D’);
int fps = 60;
Size size(int(cap.get(CAP_PROP_FRAME_WIDTH)), int(cap.get(CAP_PROP_FRAME_HEIGHT)));
VideoWriter writer(“output.avi”, fourcc, fps, size);
if (!writer.isOpened())
{
return 0;
}

Mat frame;
while (true)
{
cap >> frame;
if (frame.empty())
{
break;
}
writer.write(frame);
imshow(“frame”, frame);
if (waitKey(1) == 27)
{
break;
}
}

cap.release();
writer.release();
destroyAllWindows();
return 0;
}
“`

四、opencv保存视频每一帧

可以通过遍历每一帧，保存每一帧的方式将视频保存成一个序列帧。

示例代码：

“`
#include
#include
#include “opencv2/core.hpp”
#include “opencv2/highgui.hpp”
#include “opencv2/videoio.hpp”

using namespace std;
using namespace cv;

int main()
{
VideoCapture cap(0);
if (!cap.isOpened())
{
return 0;
}

int frameCount = 0;
Mat frame;
while (true)
{
cap >> frame;
if (frame.empty())
{
break;
}

stringstream ss;
ss << "frame_" << frameCount << ".png";
imwrite(ss.str(), frame);
frameCount++;
imshow("frame", frame);
if (waitKey(10) == 27)
{
break;
}
}

cap.release();
destroyAllWindows();
return 0;
}
“`

五、Opencv保存视频常见问题

问题一：保存视频过大

可以通过调整帧率和分辨率降低视频的大小。

示例代码：

“`
#include
#include “opencv2/core.hpp”
#include “opencv2/highgui.hpp”
#include “opencv2/videoio.hpp”

using namespace std;
using namespace cv;

int main()
{
VideoCapture cap(0);
if (!cap.isOpened())
{
return 0;
}

int fourcc = VideoWriter::fourcc(‘X’, ‘V’, ‘I’, ‘D’);
int fps = 15;
Size size(int(cap.get(CAP_PROP_FRAME_WIDTH)) / 2, int(cap.get(CAP_PROP_FRAME_HEIGHT)) / 2);
VideoWriter writer(“output.avi”, fourcc, fps, size);
if (!writer.isOpened())
{
return 0;
}

Mat frame;
while (true)
{
cap >> frame;
if (frame.empty())
{
break;
}

resize(frame, frame, size);
writer.write(frame);
imshow(“frame”, frame);
if (waitKey(10) == 27)
{
break;
}
}

cap.release();
writer.release();
destroyAllWindows();
return 0;
}
“`

问题二：保存的视频显示是蓝色的

保存的视频显示成蓝色的场景可能是因为视频的BGR三通道颜色顺序和某些视频播放器不一致导致的，建议使用其他播放器尝试。

六、opencv保存视频只有6kb

视频只有6kb可能是保存格式不正确导致的。

示例代码：

“`
#include
#include “opencv2/core.hpp”
#include “opencv2/highgui.hpp”
#include “opencv2/videoio.hpp”

using namespace std;
using namespace cv;

int main()
{
VideoCapture cap(0);
if (!cap.isOpened())
{
return 0;
}

int fourcc = VideoWriter::fourcc(‘X’, ‘V’, ‘I’, ‘D’);
int fps = 30;
Size size(int(cap.get(CAP_PROP_FRAME_WIDTH)), int(cap.get(CAP_PROP_FRAME_HEIGHT)));
VideoWriter writer(“output.avi”, fourcc, fps, size);
if (!writer.isOpened())
{
return 0;
}

Mat frame;
while (true)
{
cap >> frame;
if (frame.empty())
{
break;
}
writer.write(frame);
imshow(“frame”, frame);
if (waitKey(10) == 27)
{
break;
}
}

int frameCount = writer.get(CAP_PROP_FRAME_COUNT);
if (frameCount == 0)
{
return 0;
}
return 0;
}
“`

七、opencv保存视频python

OpenCV同样可以使用Python进行视频保存，类似的API接口，只是函数名不同。

示例代码：

“`Python
import cv2

cap = cv2.VideoCapture(0)
fourcc = cv2.VideoWriter_fourcc(*’XVID’)
fps = 30
size = (int(cap.get(cv2.CAP_PROP_FRAME_WIDTH)), int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT)))
out = cv2.VideoWriter(‘output.avi’, fourcc, fps, size)
while True:
ret, frame = cap.read()
if ret:
out.write(frame)
cv2.imshow(‘frame’, frame)
if cv2.waitKey(1) == 27:
break

cap.release()
out.release()
cv2.destroyAllWindows()
“`

八、Opencv保存视频 buffer

为了避免保存视频时出现buffer溢出，可以设置参数，提高缓冲区大小。

示例代码：

“`
#include
#include “opencv2/core.hpp”
#include “opencv2/highgui.hpp”
#include “opencv2/videoio.hpp”

using namespace std;
using namespace cv;

int main()
{
VideoCapture cap(0);
if (!cap.isOpened())
{
return 0;
}

int fourcc = VideoWriter::fourcc(‘X’, ‘V’, ‘I’, ‘D’);
int fps = 30;
Size size(int(cap.get(CAP_PROP_FRAME_WIDTH)), int(cap.get(CAP_PROP_FRAME_HEIGHT)));
VideoWriter writer(“output.avi”, fourcc, fps, size, true);

//需要增加的代码
int buffersize = 50;
int framesize = writer.get(CAP_PROP_FRAME_WIDTH) * writer.get(CAP_PROP_FRAME_HEIGHT);
int bufferlength = buffersize * framesize;
writer.set(CAP_PROP_BUFFERSIZE, bufferlength);
//增加代码结束

if (!writer.isOpened())
{
return 0;
}

Mat frame;
while (true)
{
cap >> frame;
if (frame.empty())
{
break;
}
writer.write(frame);
imshow(“frame”, frame);
if (waitKey(10) == 27)
{
break;
}
}

cap.release();
writer.release();
destroyAllWindows();
return 0;
}
“`

九、opencv保存视频后大小只有1kb

还是因为保存格式不正确导致的，可以尝试更换编码器。

示例代码：

“`
#include
#include “opencv2/core.hpp”
#include “opencv2/highgui.hpp”
#include “opencv2/videoio.hpp”

using namespace std;
using namespace cv;

int main()
{
VideoCapture cap(0);
if (!cap.isOpened())
{
return 0;
}

int fourcc = VideoWriter::fourcc(‘M’, ‘J’, ‘P’, ‘G’); //换成MJPEG编码器
int fps = 30;
Size size(int(cap.get(CAP_PROP_FRAME_WIDTH)), int(cap.get(CAP_PROP_FRAME_HEIGHT)));
VideoWriter writer(“output.avi”, fourcc, fps, size);
if (!writer.isOpened())
{
return 0;
}

Mat frame;
while (true)
{
cap >> frame;
if (frame.empty())
{
break;
}
writer.write(frame);
imshow(“frame”, frame);
if (waitKey(10) == 27)
{
break;
}
}

cap.release();
writer.release();
destroyAllWindows();
return 0;
}
“`