How can I tell if the camera is in use by another process? - macos

Question

In OS X, how can I tell if the camera or microphone is in use by another application or process? The following doesn't seem to work unless the other application has locked the device.
NSArray *devices = [AVCaptureDevice devices];
for (AVCaptureDevice *device in devices) {
NSLog(#"In use by other application %hhd", [device isInUseByAnotherApplication]);
}

Answer 1

You can use CoreAudio to check if microphone is in use or not.
AudioObjectPropertyAddress propertyAddress = {
kAudioHardwarePropertyDevices,
kAudioObjectPropertyScopeGlobal,
kAudioObjectPropertyElementMaster
};
UInt32 dataSize = 0;
OSStatus status = AudioObjectGetPropertyDataSize(kAudioObjectSystemObject, &propertyAddress, 0, NULL, &dataSize);
if(kAudioHardwareNoError != status) {
fprintf(stderr, "AudioObjectGetPropertyDataSize (kAudioHardwarePropertyDevices) failed: %i\n", status);
//return NULL;
return;
}
UInt32 deviceCount = (UInt32)(dataSize / sizeof(AudioDeviceID));
AudioDeviceID *audioDevices = (AudioDeviceID*)(malloc(dataSize));
if(NULL == audioDevices) {
fputs("Unable to allocate memory", stderr);
return;
}
status = AudioObjectGetPropertyData(kAudioObjectSystemObject, &propertyAddress, 0, NULL, &dataSize, audioDevices);
if(kAudioHardwareNoError != status) {
fprintf(stderr, "AudioObjectGetPropertyData (kAudioHardwarePropertyDevices) failed: %i\n", status);
free(audioDevices), audioDevices = NULL;
return ;
}
CFMutableArrayRef inputDeviceArray = CFArrayCreateMutable(kCFAllocatorDefault, deviceCount, &kCFTypeArrayCallBacks);
if(NULL == inputDeviceArray) {
fputs("CFArrayCreateMutable failed", stderr);
free(audioDevices), audioDevices = NULL;
return ;
}`
Now Iterate through all the devices and fetch property data kAudioDevicePropertyDeviceIsRunningSomewhere
CFBooleanRef deviceIsRunning = NULL;
dataSize = sizeof(deviceIsRunning);
propertyAddress.mSelector = kAudioDevicePropertyDeviceIsRunningSomewhere;
status = AudioObjectGetPropertyData(audioDevices[i], &propertyAddress, 0, NULL, &dataSize, &deviceIsRunning);
Check deviceIsRunning variable.
I don't have idea about video device. But i will update my answer if i find some solution.
Hope this help.

Answer 2

I'm working on go module that detects camera/microphone state (using cgo) and here is my Objective-C implementations:
IsCameraOn(): https://github.com/antonfisher/go-media-devices-state/blob/main/pkg/camera/camera_darwin.mm
IsMicrophoneOn(): https://github.com/antonfisher/go-media-devices-state/blob/main/pkg/microphone/microphone_darwin.mm
Thanks #Rohan for the accepted answer!