If I have an AVCaptureDevice, how can I get the related USB interface so I can access the underlying hardware via IOKit?
I've tried finding it via vid & pid, but this won't work if I plug in two devices with the same vid, pid. Here's the code I use to extract vid and pid from AVCaptureDevice:
AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithDeviceType:AVMediaTypeVideo];
NSString *modelID = [device modelID];
NSRange vidRange = [modelID rangeOfString:@"VendorID_"];
int vid = [[modelID substringWithRange:NSMakeRange(vidRange.location + 9, 5)] intValue];
NSRange pidRange = [modelID rangeOfString:@"ProductID_"];
int vid = [[modelID substringWithRange:NSMakeRange(pidRange.location + 10, 5)] intValue];
And then I search for a matching IOService:
CFMutableDictionaryRef matchingDict = IOServiceMatching(kIOUSBDeviceClassName);
CFNumberRef numberRef;
numberRef = CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt32Type, &vid);
CFDictionarySetValue(matchingDict, CFSTR(kUSBVendorID), numberRef);
CFRelease(numberRef);
numberRef = CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt32Type, &pid);
CFDictionarySetValue(matchingDict, CFSTR(kUSBProductID), numberRef);
CFRelease(numberRef);
io_service_t camera = IOServiceGetMatchingService(kIOMasterPortDefault, matchingDict);
Maybe a combination of AVCaptureDevice
modelID
and uniqueID
could help you find the matching IOService
. The formatting of the two IDs looks to be both undocumented and dependent on transport and media-type, but you should be able to figure something out. Here is a tentative mapping for USB audio (because I don't have any USB cameras), based on two devices:
modelID: USB Headphone Set:0C76:1607
uniqueID: AppleUSBAudioEngine:Unknown Manufacturer:USB Headphone Set:14200000:2,1,
USB Headphone Set:
Product ID: 0x1607
Vendor ID: 0x0c76 (Solid State System Co., Ltd.)
Version: 1.00
Speed: Up to 12 Mb/sec
Location ID: 0x14200000 / 9
Current Available (mA): 1000
Current Required (mA): 100
Extra Operating Current (mA): 0
uniqueID: AppleUSBAudioEngine:Burr-Brown from TI :USB Audio CODEC :14200000:2,
modelID: USB Audio CODEC :08BB:2902
USB Audio CODEC :
Product ID: 0x2902
Vendor ID: 0x08bb (Texas Instruments Japan)
Version: 1.00
Speed: Up to 12 Mb/sec
Manufacturer: Burr-Brown from TI
Location ID: 0x14200000 / 10
Current Available (mA): 1000
Current Required (mA): 100
Extra Operating Current (mA): 0
The (usb audio) format is something like
modelID: name:vendorID:productID
uniqueID: AppleUSBAudioEngine:Manufacturer or Unknown Manufacturer:location ID:???
If USB video's uniqueID
is similar, then the combination of productID
, vendorID
and locationID
(which USB port) should be enough to uniquely identify the underlying device's hardware, albeit in a fragile and undocumented way.