The iOS documentation says you can add and remove inputs while a session is running, for example to switch between front and back cameras.
However when I try this, my session stops. I'm locking the session with beginConfiguration and commitConfiguration calls as follows:
- (void)switchCamera:(UIButton *)sender {
dispatch_async([self sessionQueue], ^{
AVCaptureSession *session = self.captureSession;
[session beginConfiguration];
AVCaptureInput *currentInput = self.currentCameraIsBack ? self.videoDeviceInputBack : self.videoDeviceInputFront;
AVCaptureInput *newInput = self.currentCameraIsBack ? self.videoDeviceInputFront : self.videoDeviceInputBack;
[session removeInput:currentInput];
[session addInput:newInput];
self.currentCameraIsBack = !self.currentCameraIsBack;
[session setSessionPreset:AVCaptureSessionPresetMedium];
[self setCameraOutputProperties];
[session commitConfiguration];
});
}
I am outputting to an AVCaptureMovieFileOutput. Is there anything I need to do to configure this session so it is switchable?
(Note that the OP in this question is trying to add a new input without removing the old one, which isn't the problem here)
Turns out that to do this you need to use an AVAssetWriter and call appendSampleBuffer: yourself with the resulting CMSampleBuffer like so:
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
if (self.recording && self.videoWriterInput.isReadyForMoreMediaData) {
[self.videoWriterInput appendSampleBuffer:sampleBuffer];
}
}