I have been implementing Custom Camera using AVCaptureDevice, which require AutoFocus & Exposure to work nicely. I am using the following code to do the camera initialisation
- (void) initializeCamera {
AVAuthorizationStatus status = [AVCaptureDevice authorizationStatusForMediaType:AVMediaTypeVideo];
if(status == AVAuthorizationStatusAuthorized) { // authorized
[self.captureVideoPreviewLayer removeFromSuperlayer];
self.captureSession = [[AVCaptureSession alloc] init];
self.captureSession.sessionPreset = AVCaptureSessionPresetPhoto;
[self removeDeviceObserverForFocus];
self.captureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
[self addDeviceObserverForFocus];
NSError *error = nil;
[self.captureDevice lockForConfiguration:nil]; //you must lock before setting torch mode
[self.captureDevice setSubjectAreaChangeMonitoringEnabled:YES];
[self.captureDevice unlockForConfiguration];
//Capture layer
self.captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:self.captureSession];
self.captureVideoPreviewLayer.bounds = CGRectMake(0, 0, CGRectGetWidth([UIScreen mainScreen].bounds), CGRectGetHeight([UIScreen mainScreen].bounds));
self.captureVideoPreviewLayer.position = CGPointMake(CGRectGetMidX(self.captureVideoPreviewLayer.bounds), CGRectGetMidY(self.captureVideoPreviewLayer.bounds));
[self.captureVideoPreviewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
self.captureVideoPreviewLayer.connection.enabled = YES;
[self.viewCamera.layer insertSublayer:self.captureVideoPreviewLayer atIndex:0];
//Capture input
self.captureInput = [AVCaptureDeviceInput deviceInputWithDevice:self.captureDevice error:&error];
if (!self.captureInput) {
[self capturePhoto];
}
else {
if ([self.captureSession canAddInput:self.captureInput]) {
[self.captureSession addInput:self.captureInput];
}
}
self.captureOutput = [[AVCaptureStillImageOutput alloc] init];
[self.captureOutput setOutputSettings:@{AVVideoCodecKey : AVVideoCodecJPEG}];
[self.captureSession addOutput:self.captureOutput];
//THIS LINE
[self.captureSession setSessionPreset:AVCaptureSessionPresetPhoto];
// setup metadata capture
AVCaptureMetadataOutput *metadataOutput = [[AVCaptureMetadataOutput alloc] init];
CGRect visibleMetadataOutputRect = [self.captureVideoPreviewLayer metadataOutputRectOfInterestForRect:self.vwCamera.bounds];
metadataOutput.rectOfInterest = visibleMetadataOutputRect;
[self.captureSession addOutput:metadataOutput];
dispatch_async(dispatch_get_main_queue(), ^{
[self.captureSession startRunning];
});
}
else if(status == AVAuthorizationStatusNotDetermined){ // not determined
//Try for getting permission
[AVCaptureDevice requestAccessForMediaType:AVMediaTypeVideo completionHandler:^(BOOL granted) {
[self performSelectorOnMainThread:@selector(initializeCamera) withObject:nil waitUntilDone:NO];
}];
}
}
- (void)removeDeviceObserverForFocus {
@try {
while ([self.captureDevice observationInfo] != nil) {
[self.captureDevice removeObserver:self forKeyPath:@"adjustingFocus"];
}
}
@catch (NSException *exception) {
NSLog(@"Exception");
}
@finally {
}
}
- (void)addDeviceObserverForFocus {
[self.captureDevice addObserver:self forKeyPath:@"adjustingFocus" options:NSKeyValueObservingOptionNew context:nil];
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
if( [keyPath isEqualToString:@"adjustingFocus"] ){
BOOL adjustingFocus = [ [change objectForKey:NSKeyValueChangeNewKey] isEqualToNumber:[NSNumber numberWithInt:1] ];
if (adjustingFocus) {
[self showFocusSquareAtPoint:self.viewCamera.center];
}
}
}
To monitor focus by movement of camera I am doing the following..
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(avCaptureDeviceSubjectAreaDidChangeNotification:) name:AVCaptureDeviceSubjectAreaDidChangeNotification object:nil];
#pragma mark - AVCaptureDeviceSubjectAreaDidChangeNotification
-(void)avCaptureDeviceSubjectAreaDidChangeNotification:(NSNotification *)notification{
CGPoint devicePoint = CGPointMake( 0.5, 0.5 );
[self focusWithMode:AVCaptureFocusModeContinuousAutoFocus exposeWithMode:AVCaptureExposureModeContinuousAutoExposure atDevicePoint:devicePoint monitorSubjectAreaChange:NO];
[self showFocusSquareAtPoint:self.vwCamera.center];
}
- (void)focusWithMode:(AVCaptureFocusMode)focusMode exposeWithMode:(AVCaptureExposureMode)exposureMode atDevicePoint:(CGPoint)point monitorSubjectAreaChange:(BOOL)monitorSubjectAreaChange
{
dispatch_async( dispatch_get_main_queue(), ^{
AVCaptureDevice *device = self.captureDevice;
NSError *error = nil;
if ( [device lockForConfiguration:&error] ) {
// Setting (focus/exposure)PointOfInterest alone does not initiate a (focus/exposure) operation.
// Call -set(Focus/Exposure)Mode: to apply the new point of interest.
if ( device.isFocusPointOfInterestSupported && [device isFocusModeSupported:focusMode] ) {
device.focusPointOfInterest = point;
device.focusMode = focusMode;
}
if ( device.isExposurePointOfInterestSupported && [device isExposureModeSupported:exposureMode] ) {
device.exposurePointOfInterest = point;
device.exposureMode = exposureMode;
}
device.subjectAreaChangeMonitoringEnabled = monitorSubjectAreaChange;
[device unlockForConfiguration];
}
else {
NSLog( @"Could not lock device for configuration: %@", error );
}
} );
}
Everything works as expected when I use this [self.captureSession setSessionPreset:AVCaptureSessionPresetPhoto];
If I change the camera preset to something else like AVCaptureSessionPresetHigh AutoFocus and Exposure doesn't work well as expected..
Anyone who has come across such situation?
Thank you for help.
Are you trying to take a picture or record video? Cause the High preset is for video and the exposure and focus work differently(I believe). Here is info on the different presets in the docs - AVCaptureSessionPresets