opencv依赖了ffmpeg,所以可以轻松对avi视频文件进行操作。
打开视频文件或摄像头视频需要使用Opencv中的VideoCapture类,保存视频或摄像头视频到本地磁盘,需要使用Opencv中的VideoWriter类。
先上代码:
bool isInit= false;
VideoCapture *inputVideo=NULL;
VideoWriter *outputVideo=NULL;
JNIEXPORT void JNICALL
Java_org_opencv_samples_tutorial2_Tutorial2Activity_FindFeatures(JNIEnv *, jobject, jlong addrGray,
jlong addrRgba) {
Mat &mGr = *(Mat *) addrGray;
Mat &mRgb = *(Mat *) addrRgba;
vector<KeyPoint> v;
looperAddNum++;
if (looperAddNum > 15) {
looperAddNum = 0;
if (looperIndexNum < 100)
looperIndexNum += 1;
}
// code start-----------------------------------------------------------------------------
if (!isInit){
LOGI("index start");
const string source = "/data/data/org.opencv.samples.tutorial2/cache/Megamind.avi"; // the source file name
inputVideo=new VideoCapture(source.c_str());
if (!inputVideo->isOpened()){
LOGI("open video error");
return;
}
Mat lsFrame;
*inputVideo>> lsFrame;
if (lsFrame.empty())
return;
string::size_type pAt = source.find_last_of('.'); // Find extension point
const string NAME = source.substr(0, pAt) + "R" + ".avi"; // Form the new name with container
LOGI("index looper %d %d", lsFrame.cols, lsFrame.rows);
outputVideo=new VideoWriter();
outputVideo->open(NAME, VideoWriter::fourcc('M', 'J', 'P', 'G'), 25, Size(lsFrame.cols, lsFrame.rows), true);
if (!outputVideo->isOpened())
{
LOGI("index open video error %s", NAME.c_str());
return;
}
isInit= true;
}
if (isInit){
Mat videoFrame;
*inputVideo >> videoFrame;
if (videoFrame.empty())
return;
// show video
Mat dstW = mRgb(Rect(0,0, videoFrame.cols, videoFrame.rows));
cvtColor(videoFrame, dstW, COLOR_RGB2BGRA);
int channel = 2; // Select the channel to save
Mat res;
vector<Mat> spl;
split(videoFrame, spl); // process - extract only the correct channel
for (int i =0; i < 3; ++i)
if (i != channel)
spl[i] = Mat::zeros(Size(videoFrame.cols, videoFrame.rows), spl[0].type());
merge(spl, res);
*outputVideo << res;
}
// code end-----------------------------------------------------------------------------
}
代码说明:
1、使用VideoCapture读内容文件获取视频信息。
2、初始化输出视频VideoWriter。
3、开始读取mat 写入 VideoWriter。
4、同时将其中两个通道数据设置为0(黑色)。
编解码器标识说明:
CV_FOURCC(‘P’, ‘I’, ‘M’, ‘1’) = MPEG-1 codec
CV_FOURCC(‘M’, ‘J’, ‘P’, ‘G’) = motion-jpeg codec
CV_FOURCC(‘M’, ‘P’, ‘4’, ‘2’) = MPEG-4.2 codec
CV_FOURCC(‘D’, ‘I’, ‘V’, ‘3’) = MPEG-4.3 codec
CV_FOURCC(‘D’, ‘I’, ‘V’, ‘X’) = MPEG-4 codec
CV_FOURCC(‘U’, ‘2’, ‘6’, ‘3’) = H263 codec
CV_FOURCC(‘I’, ‘2’, ‘6’, ‘3’) = H263I codec
CV_FOURCC(‘F’, ‘L’, ‘V’, ‘1’) = FLV1 codec
效果: