I'm writing a program to control a PTZ camera connected via USB. I can get access to target camera's unique_id, and also other infos provided by AVFoundation. But I don't know how to locate my target USB device to send a UVC ControlRequest. There's many Cameras with same VendorID and ProductID connected at a time, so I need a more exact way to find out which device is my target. It looks that the unique_id provided is (locationID<<32|VendorID<<16|ProductID) as hex string, but I'm not sure if I can always assume this behavior won't change. Is there's a document declares how AVFoundation generate the unique_id for USB camera, so I can assume this convert will always work? Or is there's a way to send a PTZ control request to AVCaptureDevice? https://stackoverflow.com/questions/40006908/usb-interface-of-an-avcapturedevice I have seen this similar question. But I'm worrying that Exacting LocationID+VendorID+ProductID from unique_id seems like programming to implementation instead of interface. So, if there's any other better way to control my camera? here's my example code for getting unique_id: // // camera_unique_id_test.mm // // 测试代码：使用C++获取当前系统摄像头的AVCaptureDevice unique_id // // 编译命令: // clang++ -framework AVFoundation -framework CoreMedia -framework Foundation // camera_unique_id_test.mm -o camera_unique_id_test // #include <iostream> #include <string> #include <vector> #import <AVFoundation/AVFoundation.h> #import <Foundation/Foundation.h> struct CameraInfo { std::string uniqueId; }; std::vector<CameraInfo> getAllCameraDevices() { std::vector<CameraInfo> cameras; @autoreleasepool { NSArray<AVCaptureDevice*>* devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo]; AVCaptureDevice* defaultDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo]; // 遍历所有设备 for (AVCaptureDevice* device in devices) { CameraInfo info; // 获取unique_id info.uniqueId = std::string([device.uniqueID UTF8String]); cameras.push_back(info); } } return cameras; } int main(int argc, char* argv[]) { std::vector<CameraInfo> cameras = getAllCameraDevices(); for (size_t i = 0; i < cameras.size(); i++) { const CameraInfo& camera = cameras[i]; std::cout << " 设备 " << (i + 1) << ":" << std::endl; std::cout << " unique_id: " << camera.uniqueId << std::endl; } return 0; } and here's my code for UVC control: // clang++ -framework Foundation -framework IOKit uvc_test.cpp -o uvc_test #include <iostream> #include <CoreFoundation/CoreFoundation.h> #include <IOKit/IOCFPlugIn.h> #include <IOKit/IOKitLib.h> #include <IOKit/IOMessage.h> #include <IOKit/usb/IOUSBLib.h> #include <IOKit/usb/USB.h> CFStringRef CreateCFStringFromIORegistryKey(io_service_t ioService, const char* key) { CFStringRef keyString = CFStringCreateWithCString(kCFAllocatorDefault, key, kCFStringEncodingUTF8); if (!keyString) return nullptr; CFStringRef result = static_cast<CFStringRef>( IORegistryEntryCreateCFProperty(ioService, keyString, kCFAllocatorDefault, kIORegistryIterateRecursively)); CFRelease(keyString); return result; } std::string GetStringFromIORegistry(io_service_t ioService, const char* key) { CFStringRef cfString = CreateCFStringFromIORegistryKey(ioService, key); if (!cfString) return ""; char buffer[256]; Boolean success = CFStringGetCString(cfString, buffer, sizeof(buffer), kCFStringEncodingUTF8); CFRelease(cfString); return success ? std::string(buffer) : std::string(""); } uint32_t GetUInt32FromIORegistry(io_service_t ioService, const char* key) { CFStringRef keyString = CFStringCreateWithCString(kCFAllocatorDefault, key, kCFStringEncodingUTF8); if (!keyString) return 0; CFNumberRef number = static_cast<CFNumberRef>( IORegistryEntryCreateCFProperty(ioService, keyString, kCFAllocatorDefault, kIORegistryIterateRecursively)); CFRelease(keyString); if (!number) return 0; uint32_t value = 0; CFNumberGetValue(number, kCFNumberSInt32Type, &value); CFRelease(number); return value; } int main() { // Get matching dictionary for USB devices CFMutableDictionaryRef matchingDict = IOServiceMatching(kIOUSBDeviceClassName); // Get iterator for matching services io_iterator_t serviceIterator; IOServiceGetMatchingServices(kIOMasterPortDefault, matchingDict, &serviceIterator); // Iterate through matching devices io_service_t usbService; while ((usbService = IOIteratorNext(serviceIterator))) { uint32_t locationId = GetUInt32FromIORegistry(usbService, "locationID"); uint32_t vendorId = GetUInt32FromIORegistry(usbService, "idVendor"); uint32_t productId = GetUInt32FromIORegistry(usbService, "idProduct"); IOCFPlugInInterface** plugInInterface = nullptr; IOUSBDeviceInterface** deviceInterface = nullptr; SInt32 score; // Get device plugin interface IOCreatePlugInInterfaceForService(usbService, kIOUSBDeviceUserClientTypeID, kIOCFPlugInInterfaceID, &plugInInterface, &score); // Get device interface (*plugInInterface) ->QueryInterface(plugInInterface, CFUUIDGetUUIDBytes(kIOUSBDeviceInterfaceID), (LPVOID*)&deviceInterface); (*plugInInterface)->Release(plugInInterface); // Try to find UVC control interface using CreateInterfaceIterator io_iterator_t interfaceIterator; IOUSBFindInterfaceRequest interfaceRequest; interfaceRequest.bInterfaceClass = kUSBVideoInterfaceClass; // 14 interfaceRequest.bInterfaceSubClass = kUSBVideoControlSubClass; // 1 interfaceRequest.bInterfaceProtocol = kIOUSBFindInterfaceDontCare; interfaceRequest.bAlternateSetting = kIOUSBFindInterfaceDontCare; (*deviceInterface) ->CreateInterfaceIterator(deviceInterface, &interfaceRequest, &interfaceIterator); (*deviceInterface)->Release(deviceInterface); io_service_t usbInterface = IOIteratorNext(interfaceIterator); IOObjectRelease(interfaceIterator); if (usbInterface) { std::cout << "Get UVC device with:" << std::endl; std::cout << "locationId: " << std::hex << locationId << std::endl; std::cout << "vendorId: " << std::hex << vendorId << std::endl; std::cout << "productId: " << std::hex << productId << std::endl << std::endl; IOObjectRelease(usbInterface); } IOObjectRelease(usbService); } IOObjectRelease(serviceIterator); }