Switch to hardware zoom

Author: jrahaim

videocore/api/iOS/VCSimpleSession.mm

@@ -289,13 +289,12 @@ - (void) setVideoZoomFactor:(float)videoZoomFactor
 {
     _videoZoomFactor = videoZoomFactor;
     if(m_positionTransform) {
-        // We could use AVCaptureConnection's zoom factor, but in reality it's
-        // doing the exact same thing as this (in terms of the algorithm used),
-        // but it is not clear how CoreVideo accomplishes it.
-        // In this case this is just modifying the matrix
-        // multiplication that is already happening once per frame.
-        m_positionTransform->setSize(self.videoSize.width * videoZoomFactor,
-                                     self.videoSize.height * videoZoomFactor);
+        // Switched to Hardware zoom to better support iPhone 7 Plus
+        m_cameraSource->setVideoZoomFactor(MAX(1.0, MIN(videoZoomFactor, 6.4)));
+        
+        // Original VideoCore code:
+        //m_positionTransform->setSize(self.videoSize.width * videoZoomFactor,
+        //                             self.videoSize.height * videoZoomFactor);
     }
 }
 - (void) setAudioChannelCount:(int)channelCount

videocore/sources/iOS/CameraSource.h

@@ -114,6 +114,7 @@ namespace videocore { namespace iOS {
 
         bool setContinuousExposure(bool wantsContinuous);
 
+        bool setVideoZoomFactor(float zoomFactor);
 
     public:
         /*! Used by Objective-C Capture Session */

videocore/sources/iOS/CameraSource.mm

@@ -503,5 +503,17 @@ - (void) orientationChanged: (NSNotification*) notification
         return ret;
     }
 
+    bool
+    CameraSource::setVideoZoomFactor(float zoomFactor) {
+        AVCaptureDevice* device = (AVCaptureDevice*)m_captureDevice;
+        NSError* err = nil;
+        if([device lockForConfiguration:&err]) {
+            device.videoZoomFactor = zoomFactor;
+            return YES;
+        } else {
+            return NO;
+        }
+    }
+    
 }
 }