fix CvVideoCamera defaultfps

modules/videoio/src/cap_ios_video_camera.mm

@@ -295,13 +295,27 @@ static CGFloat DegreesToRadians(CGFloat degrees) {return degrees * M_PI / 180;}
 
 
     // set default FPS
-    if ([self.videoDataOutput connectionWithMediaType:AVMediaTypeVideo].supportsVideoMinFrameDuration) {
-        [self.videoDataOutput connectionWithMediaType:AVMediaTypeVideo].videoMinFrameDuration = CMTimeMake(1, self.defaultFPS);
+    AVCaptureDeviceInput *currentInput = [self.captureSession.inputs objectAtIndex:0];
+    AVCaptureDevice *device = currentInput.device;
+
+    NSError *error = nil;
+    [device lockForConfiguration:&error];
+
+    float maxRate = ((AVFrameRateRange*) [device.activeFormat.videoSupportedFrameRateRanges objectAtIndex:0]).maxFrameRate;
+    if (maxRate > self.defaultFPS - 1 && error == nil) {
+        [device setActiveVideoMinFrameDuration:CMTimeMake(1, self.defaultFPS)];
+        [device setActiveVideoMaxFrameDuration:CMTimeMake(1, self.defaultFPS)];
+        NSLog(@"[Camera] FPS set to %d", self.defaultFPS);
+    } else {
+        NSLog(@"[Camera] unable to set defaultFPS at %d FPS, max is %f FPS", self.defaultFPS, maxRate);
     }
-    if ([self.videoDataOutput connectionWithMediaType:AVMediaTypeVideo].supportsVideoMaxFrameDuration) {
-        [self.videoDataOutput connectionWithMediaType:AVMediaTypeVideo].videoMaxFrameDuration = CMTimeMake(1, self.defaultFPS);
+
+    if (error != nil) {
+        NSLog(@"[Camera] unable to set defaultFPS: %@", error);
     }
 
+    [device unlockForConfiguration];
+
     // set video mirroring for front camera (more intuitive)
     if ([self.videoDataOutput connectionWithMediaType:AVMediaTypeVideo].supportsVideoMirroring) {
         if (self.defaultAVCaptureDevicePosition == AVCaptureDevicePositionFront) {
@@ -329,7 +343,7 @@ static CGFloat DegreesToRadians(CGFloat degrees) {return degrees * M_PI / 180;}
     [self.videoDataOutput setSampleBufferDelegate:self queue:videoDataOutputQueue];
 
 
-    NSLog(@"[Camera] created AVCaptureVideoDataOutput at %d FPS", self.defaultFPS);
+    NSLog(@"[Camera] created AVCaptureVideoDataOutput");
 }