Android：如何使用OpenCV C ++打开文件？

Question

I have a video file saved on my Android device.

Using a getPath() function I got "sdcard/video_app/sample_video.mp4".

I'm now trying to use this video file in my OpenCV C++ code (I'm using NDK and JNI) with this :

String filename = "sdcard/video_app/sample_video.mp4";

VideoCapture capture(filename);

Mat img;

capture >> img;

imwrite("sdcard/video_app/test.jpg", img);

I added :

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

Nothing is happening. What am I doing wrong ?

Answer 1

You can try,

VideoCapture capture=new VideoCapture();
capture.open("sdcard/video_app/sample_video.mp4");
Mat frames = new Mat();

 // to read each frame and to save in Mat class           
for(;;)
{
   capture.read(frames); 
   imwrite("sdcard/video_app/test.jpg",frame);
}