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我正在尝试编写一个应用程序来获取视频的所有帧并对其进行操作，我发现在 Android 上提取帧的最佳方法是使用 OpenCv lib。

我在示例代码中看到使用 VideoCapture 对象接收视频路径并可以从中抓取帧，因此我编写了以下代码，但 capture.open() 并没有真正打开视频文件 capture.isOpen( ) 总是错误的。

源代码：

#include <jni.h>
//opencv

#include <opencv2/highgui/highgui.hpp>
#include <opencv2/video/background_segm.hpp>
#include <opencv2/core/mat.hpp>
//C
#include <stdio.h>
#include <string.h>
//C++
#include <iostream>
#include <sstream>
//Android
#include <android/log.h>

//#define  LOGI(TAG,INFO)  __android_log_print(ANDROID_LOG_INFO,INFO,__VA_ARGS__)

using namespace cv;

extern "C" {

JNIEXPORT void JNICALL Java_com_example_nativeopencvcheck_MainActivity_processVideo(JNIEnv* env,
    jobject thsObj,jstring fileName) {

const char * fileNameNative;
jboolean isCopy;
fileNameNative = env->GetStringUTFChars(fileName, &isCopy);

//create the capture object
__android_log_print(ANDROID_LOG_ERROR, "From_Native",
            "trying to open file: %s", fileNameNative);
VideoCapture capture(fileNameNative);
capture.open(fileNameNative);

if (!capture.isOpened()) {  //!!!!!! ALWAYS CLOSED !!!!!
    __android_log_write(ANDROID_LOG_ERROR, "From_Native",
            "capture isn't open. closing..");
    exit( EXIT_FAILURE);
}

Mat iplimage;
capture.retrieve(iplimage,0); 
if (iplimage.size > 0) {
    jclass cls = env->FindClass( "com/example/opencvframesext/MainActivity");
    if (cls == 0) {
        return;
    }

    jmethodID javamethod = env->GetMethodID(cls, "getCurrentFrameFromNative", "()V");
    if (javamethod == 0) {
    //  LOGI("From_Native","GetMethodID error");
        return;
    }

    jobject obj; // TODO
    env->CallVoidMethod(obj, javamethod);

   return;
}


/*bool gotFrame = capture.read(mat);
 while (gotFrame) {
 mats.addref(mat);
 capture.read(mat);
 }*/

//delete capture object
capture.release();
}
}
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1 回答 1

3

yea, that wont work, unfortunately.

there's no ffmpeg backend for VideoCapture on android.

于 2013-11-07T16:45:07.823 回答