从视频文件中使用的OpenCV与本土code C阅读框++ [英] Reading frames from video file using openCV and Native code C++

问题描述

我想编写一个应用程序，获取视频的所有帧和操纵他们，我发现oout，要提取物对Android的框架最好的办法是使用OpenCV的库。

我在使用接收的视频路径，并可以抓住框架出来的VideoCapture对象样本code看见，所以我写了下面code，但capture.open（）doen't真正开放视频文件，在capture.isOpen（）始终是假的。

来源$ C ​​$ C：

 的#include＆LT; jni.h＆GT;
// OpenCV的

＃包括＆LT; opencv2 /一下HighGUI / highgui.hpp＆GT;
＃包括＆LT; opencv2 /视频/ background_segm.hpp＆GT;
＃包括＆LT; opencv2 /核心/ mat.hpp＆GT;
//C
＃包括＆LT; stdio.h中＆GT;
＃包括＆LT; string.h中＆GT;
// C ++
＃包括＆LT;的iostream＆GT;
＃包括＆LT; sstream＆GT;
//机器人
＃包括＆LT;安卓/ log.h＆GT;

//＃定义LOGI（TAG，INFO）__android_log_print（ANDROID_LOG_INFO，信息，__ VA_ARGS__）

使用命名空间的简历;

为externC{

JNIEXPORT无效JNICALL Java_com_example_nativeopencvcheck_MainActivity_processVideo（JNIEnv的* ENV，
    jobject thsObj，的jstring文件名）{

为const char * fileNameNative;
jboolean isCopy;
fileNameNative = ENV-＆GT; GetStringUTFChars（文件名，和放大器; isCopy）;

//创建捕获对象
__android_log_print（ANDROID_LOG_ERROR，From_Native
            试图打开文件：％s，fileNameNative）;
VideoCapture捕获（fileNameNative）;
capture.open（fileNameNative）;

如果（！capture.isOpened（））{// !!!!!!总是关!!!!!
    __android_log_write（ANDROID_LOG_ERROR，From_Native
            捕捉不开闭..）;
    出口（EXIT_FAILURE）;
}

太IplImage的;
capture.retrieve（IplImage结构，0）;
如果（iplimage.size大于0）{
    JCLASS CLS = ENV-＆GT;的findClass（COM /例子/ opencvframesext / MainActivity）;
    如果（CLS == 0）{
        返回;
    }

    jmethodID javamethod = ENV-＆GT;的GetMethodID（CLS，getCurrentFrameFromNative，（）V）;
    如果（javamethod == 0）{
    // LOGI（From_Native，的GetMethodID错误）;
        返回;
    }

    jobject OBJ; // 去做
    ENV-＆GT; CallVoidMethod（OBJ，javamethod）;

   返回;
}


/ *布尔gotFrame = capture.read（垫）;
 而（gotFrame）{
 mats.addref（垫）;
 capture.read（垫）;
 } * /

//删除捕获对象
capture.release（）;
}
}
 

解决方案

是啊，这不会工作，很遗憾。

有没有ffmpeg的后端VideoCapture在Android上。

I'm trying to write an app that gets all the frames of a video and manipulating them, I found oout that the best way to extract frames on Android is using OpenCv lib.

I saw in the sample code that uses VideoCapture object that receives the video path and can grab frames out of it, so I wrote the following code but the capture.open() doen't really open the video file, the capture.isOpen() is always false.

Source code:

#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();
}
}

解决方案

yea, that wont work, unfortunately.

there's no ffmpeg backend for VideoCapture on android.

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