AVCameraInput - crash when switching camera from front to back - ios

Question

I'm using AV to record video via my app, and I have a button that swaps between the camera view being front and back camera, with back being the default. Switching from back to front works just fine. However, switching then from front to back causes the app to crash.
- (IBAction)btnSwapCamerasClicked:(id)sender {
//Change camera source
if(session)
{
//Indicate that some changes will be made to the session
[session beginConfiguration];
//Remove existing input
AVCaptureInput* currentCameraInput = [session.inputs objectAtIndex:0];
[session removeInput:currentCameraInput];
//Get new input
AVCaptureDevice *newCamera = nil;
if(((AVCaptureDeviceInput*)currentCameraInput).device.position == AVCaptureDevicePositionBack)
{
newCamera = [self cameraWithPosition:AVCaptureDevicePositionFront];
}
else
{
newCamera = [self cameraWithPosition:AVCaptureDevicePositionBack];
}
//Add input to session
NSError *err = nil;
AVCaptureDeviceInput *newVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:newCamera error:&err];
if(!newVideoInput || err)
{
NSLog(#"Error creating capture device input: %#", err.localizedDescription);
}
else
{
//THIS IS THE SPOT THAT CRASHES.
[session addInput:newVideoInput];
}
//Commit all the configuration changes at once
[session commitConfiguration];
}
}
The crash occurs under [session addInput:newVideoInput]; and I am returned the following error text:
2015-03-03 11:25:59.566 The SWAT App Beta[1769:365194] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* Multiple audio/video AVCaptureInputs are not currently supported.'
*** First throw call stack:
(0x185c002d4 0x1975c80e4 0x1843ad39c 0x1843accd4 0x10004ac14 0x18a818fb4 0x18a80201c 0x18a818950 0x18a8185dc 0x18a811a74 0x18a7e57f0 0x18aa85274 0x18a7e3d04 0x185bb8250 0x185bb74f4 0x185bb55a4 0x185ae1404 0x18f4eb6fc 0x18a84a2b4 0x10004bb70 0x197c6ea08)
libc++abi.dylib: terminating with uncaught exception of type NSException
I'm not entirely sure why there seems to be multiple inputs, since in the code I listed I removed the old input, and it works just fine for back to front. Not sure why front to back is making the app kill itself.
Any ideas?

Answer 1

I solved my issue by rewriting the code for switching cameras to something I wrote proprietarily. I created an NSString named currentCam that I change the text to between "Back" and "Front" depending on the current situation. Code below:
- (IBAction)btnSwapCamerasClicked:(id)sender {
[session beginConfiguration];
if ([currentCam isEqualToString:#"Back"])
{
NSArray *inputs = [session inputs];
for (AVCaptureInput *input in inputs)
{
[session removeInput:input];
}
//Video input
AVCaptureDevice *newCamera = nil;
newCamera = [self cameraWithPosition:AVCaptureDevicePositionFront];
//Audio input
AVCaptureDevice *audioDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
AVCaptureDeviceInput * audioInput = [AVCaptureDeviceInput deviceInputWithDevice:audioDevice error:nil];
NSError *err = nil;
AVCaptureDeviceInput *newVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:newCamera error:&err];
if(!newVideoInput || err)
{
NSLog(#"Error creating capture device input: %#", err.localizedDescription);
}
else
{
[session addInput:newVideoInput];
[session addInput:audioInput];
newVideoInput = nil;
audioInput = nil;
audioDevice = nil;
newCamera = nil;
inputs = nil;
}
currentCam = #"Front";
}
else if ([currentCam isEqualToString:#"Front"])
{
NSArray *inputs = [session inputs];
for (AVCaptureInput *input in inputs)
{
[session removeInput:input];
}
//Video input
AVCaptureDevice *newCamera = nil;
newCamera = [self cameraWithPosition:AVCaptureDevicePositionBack];
//Audio input
AVCaptureDevice *audioDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
AVCaptureDeviceInput * audioInput = [AVCaptureDeviceInput deviceInputWithDevice:audioDevice error:nil];
NSError *err = nil;
AVCaptureDeviceInput *newVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:newCamera error:&err];
if(!newVideoInput || err)
{
NSLog(#"Error creating capture device input: %#", err.localizedDescription);
}
else
{
[session addInput:newVideoInput];
[session addInput:audioInput];
newVideoInput = nil;
audioInput = nil;
audioDevice = nil;
newCamera = nil;
inputs = nil;
}
currentCam = #"Back";
}
else
{
//Camera is some weird third camera that doesn't exist yet! :O
NSLog(#"wat");
}
[session commitConfiguration];
}

Answer 2

only this much code can work
- (IBAction)switchCamera:(id)sender {
[captureSession beginConfiguration];
NSArray *inputs = [captureSession inputs];
//Remove all inputs
for (AVCaptureInput *input in inputs)
{
[captureSession removeInput:input];
}
//Video input
AVCaptureDevice *newCamera = nil;
if ([currentCam isEqualToString:#"Back"]){
newCamera = [self cameraWithPosition:AVCaptureDevicePositionFront];
currentCam = #"Front";
}else{
newCamera = [self cameraWithPosition:AVCaptureDevicePositionBack];
currentCam = #"Back";
}
//Audio input
AVCaptureDevice *audioDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
AVCaptureDeviceInput * audioInput = [AVCaptureDeviceInput deviceInputWithDevice:audioDevice error:nil];
NSError *err = nil;
AVCaptureDeviceInput *newVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:newCamera error:&err];
if(!newVideoInput || err)
{
NSLog(#"Error creating capture device input: %#", err.localizedDescription);
}
else
{
[captureSession addInput:newVideoInput];
[captureSession addInput:audioInput];
}
[captureSession commitConfiguration];
}