no idea if this task actually needs opencv ( might be a bit of overkill ) but if you opt for that, its fairly easy.
see all we do here is record frames continuously, and toggle between realtime/playback mode on some event (onTouch for simplicity here):
package com.berak.echo; import java.util.ArrayList; import java.util.List; import android.os.Bundle; import android.view.Menu; import android.view.MotionEvent; import android.view.View; import android.view.View.OnTouchListener; import android.app.Activity; import org.opencv.android.BaseLoaderCallback; import org.opencv.android.CameraBridgeViewBase; import org.opencv.android.LoaderCallbackInterface; import org.opencv.android.OpenCVLoader; import org.opencv.android.CameraBridgeViewBase.CvCameraViewFrame; import org.opencv.android.CameraBridgeViewBase.CvCameraViewListener2; import org.opencv.core.Core; import org.opencv.core.Mat; import org.opencv.core.Point; import org.opencv.core.Scalar; import com.berak.echo.R; public class EchoActivity extends Activity implements CvCameraViewListener2, OnTouchListener { CameraBridgeViewBase mOpenCvCameraView; List<Mat> ring = new ArrayList<Mat>(); // recording buffer int delay = 100; // delay == length of buffer boolean delayed = false; // state @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_echo); mOpenCvCameraView = (CameraBridgeViewBase) findViewById(R.id.cam3_surface_view); mOpenCvCameraView.setCvCameraViewListener(this); mOpenCvCameraView.setOnTouchListener(this); // setup as touchlistener } // lots of boilerplate, ugly, but needed. private BaseLoaderCallback mLoaderCallback = new BaseLoaderCallback(this) { @Override public void onManagerConnected(int status) { switch (status) { case LoaderCallbackInterface.SUCCESS: mOpenCvCameraView.enableView(); break; default: super.onManagerConnected(status); break; } } }; @Override public void onResume() {; super.onResume(); OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION_2_4_5,this, mLoaderCallback); } @Override public void onPause() { super.onPause(); if (mOpenCvCameraView != null) mOpenCvCameraView.disableView(); } @Override public void onDestroy() { super.onDestroy(); } @Override public void onCameraViewStarted(int width, int height) { } @Override public void onCameraViewStopped() { } // here's the bread & butter stuff: @Override public Mat onCameraFrame(CvCameraViewFrame inputFrame) { Mat mRgba = inputFrame.rgba(); ring.add(mRgba.clone()); // add one at the end if ( ring.size() >= delay ) { // pop one from the front ring.get(0).release(); ring.remove(0); } Mat ret; String txt; if ( delayed && ring.size()>0 ) { // depending on 'delayed' return either playback ret = ring.get(0); // return the 'oldest' txt = "playback"; } else { ret = mRgba; // or realtime frame txt = "realtime"; } Core.putText(ret, txt, new Point(20,20), Core.FONT_HERSHEY_PLAIN, 1.2, new Scalar(200,0,0)); return ret; } @Override public boolean onTouch(View v, MotionEvent event) { // just toggle between delayed an realtime view: delayed = ! delayed; return false; } }
