OpenCV保存視頻的操作

一、opencv保存視頻打不開

保存的視頻打不開可能是因為文件編碼格式不對，或者版本不兼容等原因。

檢查文件編碼格式，如果視頻保存為AVI格式，在保存的時候應該指定編碼器，並確保選擇的編碼器在本地系統上可用。如果視頻格式為mp4，需要檢查mp4格式的插件是否已經安裝好，並且擴展名保存為.mp4才能兼容。

示例代碼：

“`
#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保存視頻mp4

mp4是一種常見的視頻格式，OpenCV同樣可以保存為mp4格式。mp4格式需要保證編碼器可用，推薦使用H264編碼器。

示例代碼：

“`
#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保存視頻變快

保存視頻變快可以通過控制幀率調整，適當提高幀率。

示例代碼：

“`
#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保存視頻每一幀

可以通過遍歷每一幀，保存每一幀的方式將視頻保存成一個序列幀。

示例代碼：

“`
#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保存視頻常見問題

問題一：保存視頻過大

可以通過調整幀率和分辨率降低視頻的大小。

示例代碼：

“`
#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;
}
“`

問題二：保存的視頻顯示是藍色的

保存的視頻顯示成藍色的場景可能是因為視頻的BGR三通道顏色順序和某些視頻播放器不一致導致的，建議使用其他播放器嘗試。

六、opencv保存視頻只有6kb

視頻只有6kb可能是保存格式不正確導致的。

示例代碼：

“`
#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保存視頻python

OpenCV同樣可以使用Python進行視頻保存，類似的API接口，只是函數名不同。

示例代碼：

“`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保存視頻 buffer

為了避免保存視頻時出現buffer溢出，可以設置參數，提高緩衝區大小。

示例代碼：

“`
#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);

//需要增加的代碼
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);
//增加代碼結束

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保存視頻後大小只有1kb

還是因為保存格式不正確導致的，可以嘗試更換編碼器。

示例代碼：

“`
#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’); //換成MJPEG編碼器
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;
}
“`