We are developing a project based on Chrome (old USB API now migrating to WEBUSB) and a webcam. The USB Webcam has a button used for taking picture. In MAC and Linux I can show the live video of the webcam using getUserMedia () and on the same time I can use Web USB API to communicate with the device for detecting button press. The problem is windows. On Windows Chorme can see the USB device as a Webcam accessible from getUserMedia (if I install the usb device original driver) or as USB device accessible form WebUSB (if I replace the original driver with WINUSB) but we are unable to use the two API toghether. This is a problem only on WINDOWS, in Mac or Linux all is working. How can we solve this?
N.B. To make the javascript USB commands work on linux and OSX I had to replace "interface" with "endpoint" in transfer commands.
Linux lsusb dump:
Bus 001 Device 008: ID a168:0872 AnMo Electronics Corporation
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 239 Miscellaneous Device
bDeviceSubClass 2
bDeviceProtocol 1 Interface Association
bMaxPacketSize0 64
idVendor 0xa168 AnMo Electronics Corporation
idProduct 0x0872
bcdDevice 20.01
iManufacturer 1 ANMO Electronics Corporation
iProduct 2 Dino-Lite Premier
iSerial 3
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 509
bNumInterfaces 2
bConfigurationValue 1
iConfiguration 0
bmAttributes 0x80
(Bus Powered)
MaxPower 500mA
Interface Association:
bLength 8
bDescriptorType 11
bFirstInterface 0
bInterfaceCount 2
bFunctionClass 14 Video
bFunctionSubClass 3 Video Interface Collection
bFunctionProtocol 0
iFunction 2 Dino-Lite Premier
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 1
bInterfaceClass 14 Video
bInterfaceSubClass 1 Video Control
bInterfaceProtocol 0
iInterface 2 Dino-Lite Premier
VideoControl Interface Descriptor:
bLength 13
bDescriptorType 36
bDescriptorSubtype 1 (HEADER)
bcdUVC 1.00
wTotalLength 80
dwClockFrequency 6.000000MHz
bInCollection 1
baInterfaceNr( 0) 1
VideoControl Interface Descriptor:
bLength 18
bDescriptorType 36
bDescriptorSubtype 2 (INPUT_TERMINAL)
bTerminalID 1
wTerminalType 0x0201 Camera Sensor
bAssocTerminal 0
iTerminal 0
wObjectiveFocalLengthMin 0
wObjectiveFocalLengthMax 0
wOcularFocalLength 0
bControlSize 3
bmControls 0x000200a2
Auto-Exposure Mode
Focus (Absolute)
Iris (Absolute)
Focus, Auto
VideoControl Interface Descriptor:
bLength 11
bDescriptorType 36
bDescriptorSubtype 5 (PROCESSING_UNIT)
Warning: Descriptor too short
bUnitID 3
bSourceID 1
wMaxMultiplier 0
bControlSize 2
bmControls 0x0000147f
Brightness
Contrast
Hue
Saturation
Sharpness
Gamma
White Balance Temperature
Power Line Frequency
White Balance Temperature, Auto
iProcessing 0
bmVideoStandards 0x1d
None
PAL - 625/50
SECAM - 625/50
NTSC - 625/50
VideoControl Interface Descriptor:
bLength 29
bDescriptorType 36
bDescriptorSubtype 6 (EXTENSION_UNIT)
bUnitID 4
guidExtensionCode {2652215a-8932-5641-894a-5c557cdf9664}
bNumControl 16
bNrPins 1
baSourceID( 0) 3
bControlSize 4
bmControls( 0) 0xff
bmControls( 1) 0xff
bmControls( 2) 0xff
bmControls( 3) 0xff
iExtension 0
VideoControl Interface Descriptor:
bLength 9
bDescriptorType 36
bDescriptorSubtype 3 (OUTPUT_TERMINAL)
bTerminalID 2
wTerminalType 0x0101 USB Streaming
bAssocTerminal 0
bSourceID 4
iTerminal 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x0008 1x 8 bytes
bInterval 9
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 0
bNumEndpoints 1
bInterfaceClass 14 Video
bInterfaceSubClass 2 Video Streaming
bInterfaceProtocol 0
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x82 EP 2 IN
bmAttributes 5
Transfer Type Isochronous
Synch Type Asynchronous
Usage Type Data
wMaxPacketSize 0x0000 1x 0 bytes
bInterval 1
INTERFACE CLASS: 0f 24 01 02 67 01 82 00 02 01 01 00 01 00 00
INTERFACE CLASS: 0b 24 06 01 05 00 01 00 00 00 00
INTERFACE CLASS: 1e 24 07 01 00 80 02 e0 01 00 00 08 ca 00 00 08 ca 00 60 09 00 15 16 05 00 01 15 16 05 00
INTERFACE CLASS: 1e 24 07 02 00 40 01 f0 00 80 00 02 32 80 00 02 32 00 58 02 00 15 16 05 00 01 15 16 05 00
INTERFACE CLASS: 1e 24 07 03 00 a0 00 78 00 a0 00 00 8c a0 00 00 8c 00 96 00 00 15 16 05 00 01 15 16 05 00
INTERFACE CLASS: 1e 24 07 04 00 00 05 00 04 00 00 19 00 00 00 19 00 00 00 28 00 20 a1 07 00 01 20 a1 07 00
INTERFACE CLASS: 1e 24 07 01 00 80 02 e0 01 00 00 08 ca 00 00 08 ca 00 60 09 00 15 16 05 00 01 15 16 05 00
INTERFACE CLASS: 1b 24 04 02 05 59 55 59 32 00 00 10 00 80 00 00 aa 00 38 9b 71 10 01 00 00 00 00
INTERFACE CLASS: 1e 24 05 01 00 80 02 e0 01 00 00 08 ca 00 00 08 ca 00 60 09 00 15 16 05 00 01 15 16 05 00
INTERFACE CLASS: 1e 24 05 02 00 40 01 f0 00 80 00 02 32 80 00 02 32 00 58 02 00 15 16 05 00 01 15 16 05 00
INTERFACE CLASS: 1e 24 05 03 00 a0 00 78 00 a0 00 00 8c a0 00 00 8c 00 96 00 00 15 16 05 00 01 15 16 05 00
INTERFACE CLASS: 1e 24 05 04 00 00 05 00 04 00 00 19 00 00 00 19 00 00 00 28 00 20 a1 07 00 01 20 a1 07 00
INTERFACE CLASS: 1e 24 05 01 00 80 02 e0 01 00 00 08 ca 00 00 08 ca 00 60 09 00 15 16 05 00 01 15 16 05 00
INTERFACE CLASS: 06 24 0d 00 00 00
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 1
bNumEndpoints 1
bInterfaceClass 14 Video
bInterfaceSubClass 2 Video Streaming
bInterfaceProtocol 0
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x82 EP 2 IN
bmAttributes 5
Transfer Type Isochronous
Synch Type Asynchronous
Usage Type Data
wMaxPacketSize 0x13fc 3x 1020 bytes
bInterval 1
Device Qualifier (for other device speed):
bLength 10
bDescriptorType 6
bcdUSB 2.00
bDeviceClass 239 Miscellaneous Device
bDeviceSubClass 2
bDeviceProtocol 1 Interface Association
bMaxPacketSize0 64
bNumConfigurations 1
can't get debug descriptor: Resource temporarily unavailable
Device Status: 0x0000
(Bus Powered)
Based on the output from lsusb -v above I can see that this device has a single function comprised of two USB interfaces. The Interface Association Descriptor (IAD) signals to the host operating system that these two interfaces are related and operating systems like Windows will treat them as a single interface for the purposes of driver binding.
My guess is that on Linux and macOS you are able to communicate with the EP 1 IN endpoint because only interface 1 is claimed by the USB video class (UVC) driver. On Windows, since it considers both interfaces a single entity "function 0", you are unable to claim interface 0 because interface 1 is already claimed as part of function 0.