Fixes iSight camera capture issue for OpenCV 2.4.6.1 https://trac.macports.org/browser/trunk/dports/graphics/opencv/files/patch-issue-3156.diff

cap_qtkit.mm.diff

diff --git a/modules/highgui/src/cap_qtkit.mm b/modules/highgui/src/cap_qtkit.mm
index 207f01b..4f7b188 100644
--- a/modules/highgui/src/cap_qtkit.mm
+++ b/modules/highgui/src/cap_qtkit.mm
@@ -277,8 +277,11 @@ bool CvCaptureCAM::grabFrame(double timeOut) {
     double sleepTime = 0.005;
     double total = 0;
 
-    while (![capture updateImage] && (total += sleepTime)<=timeOut)
-        usleep((int)(sleepTime*1000));
+    NSDate *loopUntil = [NSDate dateWithTimeIntervalSinceNow:sleepTime]; 
+            while (![capture updateImage] && (total += sleepTime)<=timeOut && 
+                   [[NSRunLoop currentRunLoop] runMode: NSDefaultRunLoopMode 
+                                            beforeDate:loopUntil]) 
+                loopUntil = [NSDate dateWithTimeIntervalSinceNow:sleepTime];
 
     [localpool drain];