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

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.