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Hi all,

Really hope that someone can assist with the following problem. I'm currently trying to video stabilization on iOS, but I'm getting an out of memory exception.

I have the following code that attempts to stabilize the video:

+ (int)videoStabFileAtURL:(NSURL *)inputURL writeToURL:(NSURL *)outputURL {
  Ptr<IFrameSource> stabilizedFrames;

  try {
    // 1 - Prepare input video and check it
    String inputPath = *new String(inputURL.path.UTF8String);
    String outputPath = *new String(outputURL.path.UTF8String);

    Ptr<VideoFileSource> source = makePtr<VideoFileSource>(inputPath);
    cout << "Frame count (rough): " << source->count() << endl;

    // 2 - Prepare the motion estimator
    double min_inlier_ratio = 0.1;

    Ptr<MotionEstimatorRansacL2> est = makePtr<MotionEstimatorRansacL2>(MM_TRANSLATION_AND_SCALE);
    RansacParams ransac = est->ransacParams();
    ransac.thresh = 5;
    ransac.eps = 0.5;

    est->setRansacParams(ransac);
    est->setMinInlierRatio(min_inlier_ratio);

    // 3 - Create a feature detector
    int nkps = 20;

    Ptr<GFTTDetector> feature_detector = GFTTDetector::create(nkps);

    // 4 - Create motion estimator
    Ptr<KeypointBasedMotionEstimator> motionEstBuilder = makePtr<KeypointBasedMotionEstimator>(est);
    motionEstBuilder->setDetector(feature_detector);

    Ptr<IOutlierRejector> outlierRejector = makePtr<NullOutlierRejector>();
    motionEstBuilder->setOutlierRejector(outlierRejector);

    // 5 - Prepare stabilizer
    StabilizerBase *stabilizer = 0;

    int radius_pass = 15;
    bool est_trim = true;

//    TwoPassStabilizer *twoPassStabilizer = new TwoPassStabilizer();
//    twoPassStabilizer->setEstimateTrimRatio(est_trim);
//    twoPassStabilizer->setMotionStabilizer(makePtr<GaussianMotionFilter>(radius_pass));

    OnePassStabilizer *onePassStabilizer = new OnePassStabilizer();
    onePassStabilizer->setMotionFilter(makePtr<GaussianMotionFilter>(radius_pass));

    stabilizer = onePassStabilizer;

    // Setup parameters
    int radius = 15;
    double trim_ratio = 0.1;
    bool incl_constr = false;

    stabilizer->setFrameSource(source);
    stabilizer->setMotionEstimator(motionEstBuilder);
    stabilizer->setRadius(radius);
    stabilizer->setTrimRatio(trim_ratio);
    stabilizer->setCorrectionForInclusion(incl_constr);
    stabilizer->setBorderMode(BORDER_REPLICATE);

    // Cast stabilizer to simple frame source interface to read stabilized frames
    stabilizedFrames.reset(dynamic_cast<IFrameSource*>(stabilizer));

    // 6 - Processing the stabilized frames. The results are saved
    processing(stabilizedFrames, outputPath);
  } catch (const exception &e) {
    cout << "Error: " << e.what() << endl;
    stabilizedFrames.release();
    return -1;
  }

  stabilizedFrames.release();
  return 0;
}

void processing(Ptr<IFrameSource> stabilizedFrames, String outputPath) {
  dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
    @autoreleasepool {
      VideoWriter videoWriter;
      Mat stabilizedFrame;
      int nframes = 0;
      double outputFps = 30;

      // For each stabilized frame
      while (!(stabilizedFrame = stabilizedFrames->nextFrame()).empty()) {
        nframes++;

        // Init writer (once) and save stabilized frame
        if (!outputPath.empty()) {
          if (!videoWriter.isOpened()) {
            videoWriter.open(outputPath, VideoWriter::fourcc('H', '2', '6', '4'), outputFps, stabilizedFrame.size());
            videoWriter << stabilizedFrame;
          }
        }
      }
    }
  });
}

I can see it processing the frames, but it's using a lot of memory on an iPhone 6, which eventually leads to the app crashing. Does anyone know what I can do to reduce memory usage?