如何判断相机是否正在被另一个进程使用？

Question

在 OS X 中，如何判断摄像头或麦克风是否正在被其他应用程序或进程使用？除非其他应用程序已锁定设备，否则以下内容似乎不起作用。

NSArray *devices = [AVCaptureDevice devices];

for (AVCaptureDevice *device in devices) {
    NSLog(@"In use by other application %hhd", [device isInUseByAnotherApplication]);
}

Answer 1

您可以使用 CoreAudio 来检查麦克风是否在使用中。

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 ;
}`

现在遍历所有设备并获取属性数据 kAudioDevicePropertyDeviceIsRunningSomewhere

CFBooleanRef deviceIsRunning = NULL; dataSize = sizeof(deviceIsRunning); propertyAddress.mSelector = kAudioDevicePropertyDeviceIsRunningSomewhere; status = AudioObjectGetPropertyData(audioDevices[i], &propertyAddress, 0, NULL, &dataSize, &deviceIsRunning);

检查 deviceIsRunning 变量。

我不知道视频设备。但如果我找到一些解决方案，我会更新我的答案。

希望这有帮助。