--- a/c/Parameters.cpp	Fri Dec 14 01:01:26 2012 -0500
+++ b/c/Parameters.cpp	Fri Dec 14 01:01:55 2012 -0500
@@ -34,7 +34,7 @@
     ("display", po::value<bool>(&display), "display trajectories on the video")
     ("video-fps", po::value<float>(&videoFPS), "original video frame rate")
     ("frame1", po::value<unsigned int>(&frame1), "first frame to process")
-    ("nframes", po::value<unsigned int>(&nFrames), "number of frame to process")
+    ("nframes", po::value<int>(&nFrames), "number of frame to process")
     // feature tracking
     ("max-nfeatures", po::value<int>(&maxNFeatures), "maximum number of features added at each frame")
     ("feature-quality", po::value<float>(&featureQuality), "quality level of the good features to track")