背景 如果只是想实现简单的摄像头功能，其实没必要虚拟USB，可以考虑DirectShow 、AVstream等方案 项目要求将网络NDI摄像头传输的音视频数据传给zoom(zoom.us)来使用，同时要求通过zoom来控制摄像头（PTZ），据了解zoom只能控制UVC（USB video camera）摄像头，所以只能选择虚拟USB摄像头 开工之前也在网上找了许多参考，比较靠谱的 1.https://blog.csdn.net/fanxiushu/article/details/52761644 这位大神还有其它实现摄像头的文章供参考 2.https://github.com/cezanne/usbip-win
UDE 及 USB基础知识 这里介绍的是基于微软UDE框架的实现 如果你也想实现类似的功能，建议先熟悉下下面的内容，避免走弯路 https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/writing-a-ude-client-driver
https://www.spinelelectronics.com/pdf/UVC%201.5%20Class%20specification.pdf
https://github.com/microsoft/UDE/tree/master/UDEMbimClientSample
下面介绍下实现虚拟UVC摄像头需要关注的几个技术点
1. 设备描述符
具体可以参考UVC文档的3.1节 基本上我们只需要关心device descriptor和configuration descriptor 下面是Logitech Webcam C170 的描述符信息供参考 `
Bus 001 Device 006: ID 046d:082b Logitech, Inc. Webcam C170
Couldn't open device, some information will be missing
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 239 Miscellaneous Device
bDeviceSubClass 2
bDeviceProtocol 1 Interface Association
bMaxPacketSize0 64
idVendor 0x046d Logitech, Inc.
idProduct 0x082b Webcam C170
bcdDevice 28.26
iManufacturer 1
iProduct 2
iSerial 0
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 0x046c
bNumInterfaces 4
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 4
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 1
bInterfaceClass 14 Video
bInterfaceSubClass 1 Video Control
bInterfaceProtocol 0
iInterface 4
VideoControl Interface Descriptor:
bLength 13
bDescriptorType 36
bDescriptorSubtype 1 (HEADER)
bcdUVC 1.00
wTotalLength 0x004f
dwClockFrequency 30.000000MHz
bInCollection 1
baInterfaceNr( 0) 1
VideoControl Interface Descriptor:
bLength 28
bDescriptorType 36
bDescriptorSubtype 6 (EXTENSION_UNIT)
bUnitID 6
guidExtensionCode {68bbd0b0-61a4-4b83-90b7-a6215f3c4f70}
bNumControl 24
bNrPins 1
baSourceID( 0) 2
bControlSize 3
bmControls( 0) 0xff
bmControls( 1) 0xff
bmControls( 2) 0xff
iExtension 0
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 0x00000a0e
Auto-Exposure Mode
Auto-Exposure Priority
Exposure Time (Absolute)
Zoom (Absolute)
PanTilt (Absolute)
VideoControl Interface Descriptor:
bLength 11
bDescriptorType 36
bDescriptorSubtype 5 (PROCESSING_UNIT)
Warning: Descriptor too short
bUnitID 2
bSourceID 1
wMaxMultiplier 0
bControlSize 2
bmControls 0x0000157f
Brightness
Contrast
Hue
Saturation
Sharpness
Gamma
White Balance Temperature
Backlight Compensation
Power Line Frequency
White Balance Temperature, Auto
iProcessing 0
bmVideoStandards 0x09
None
SECAM - 625/50
VideoControl Interface Descriptor:
bLength 9
bDescriptorType 36
bDescriptorSubtype 3 (OUTPUT_TERMINAL)
bTerminalID 3
wTerminalType 0x0101 USB Streaming
bAssocTerminal 0
bSourceID 2
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 0x0010 1x 16 bytes
bInterval 7
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 0
bNumEndpoints 0
bInterfaceClass 14 Video
bInterfaceSubClass 2 Video Streaming
bInterfaceProtocol 0
iInterface 4
VideoStreaming Interface Descriptor:
bLength 15
bDescriptorType 36
bDescriptorSubtype 1 (INPUT_HEADER)
bNumFormats 2
wTotalLength 0x02e9
bEndPointAddress 130
bmInfo 0
bTerminalLink 3
bStillCaptureMethod 1
bTriggerSupport 1
bTriggerUsage 0
bControlSize 1
bmaControls( 0) 0
bmaControls( 1) 0
VideoStreaming Interface Descriptor:
bLength 27
bDescriptorType 36
bDescriptorSubtype 4 (FORMAT_UNCOMPRESSED)
bFormatIndex 1
bNumFrameDescriptors 9
guidFormat {32595559-0000-0010-8000-00aa00389b71}
bBitsPerPixel 16
bDefaultFrameIndex 1
bAspectRatioX 0
bAspectRatioY 0
bmInterlaceFlags 0x00
Interlaced stream or variable: No
Fields per frame: 2 fields
Field 1 first: No
Field pattern: Field 1 only
bCopyProtect 0
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 5 (FRAME_UNCOMPRESSED)
bFrameIndex 1
bmCapabilities 0x01
Still image supported
wWidth 640
wHeight 480
dwMinBitRate 73728000
dwMaxBitRate 147456000
dwMaxVideoFrameBufferSize 614400
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 5 (FRAME_UNCOMPRESSED)
bFrameIndex 2
bmCapabilities 0x01
Still image supported
wWidth 352
wHeight 288
dwMinBitRate 24330240
dwMaxBitRate 48660480
dwMaxVideoFrameBufferSize 202752
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 5 (FRAME_UNCOMPRESSED)
bFrameIndex 3
bmCapabilities 0x01
Still image supported
wWidth 320
wHeight 240
dwMinBitRate 18432000
dwMaxBitRate 36864000
dwMaxVideoFrameBufferSize 153600
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 5 (FRAME_UNCOMPRESSED)
bFrameIndex 4
bmCapabilities 0x01
Still image supported
wWidth 176
wHeight 144
dwMinBitRate 6082560
dwMaxBitRate 12165120
dwMaxVideoFrameBufferSize 50688
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 5 (FRAME_UNCOMPRESSED)
bFrameIndex 5
bmCapabilities 0x01
Still image supported
wWidth 160
wHeight 120
dwMinBitRate 4608000
dwMaxBitRate 9216000
dwMaxVideoFrameBufferSize 38400
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 5 (FRAME_UNCOMPRESSED)
bFrameIndex 6
bmCapabilities 0x01
Still image supported
wWidth 544
wHeight 288
dwMinBitRate 37601280
dwMaxBitRate 75202560
dwMaxVideoFrameBufferSize 313344
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 5 (FRAME_UNCOMPRESSED)
bFrameIndex 7
bmCapabilities 0x01
Still image supported
wWidth 432
wHeight 240
dwMinBitRate 24883200
dwMaxBitRate 49766400
dwMaxVideoFrameBufferSize 207360
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 5 (FRAME_UNCOMPRESSED)
bFrameIndex 8
bmCapabilities 0x01
Still image supported
wWidth 320
wHeight 176
dwMinBitRate 13516800
dwMaxBitRate 27033600
dwMaxVideoFrameBufferSize 112640
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 5 (FRAME_UNCOMPRESSED)
bFrameIndex 9
bmCapabilities 0x01
Still image supported
wWidth 640
wHeight 360
dwMinBitRate 55296000
dwMaxBitRate 110592000
dwMaxVideoFrameBufferSize 460800
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 6
bDescriptorType 36
bDescriptorSubtype 13 (COLORFORMAT)
bColorPrimaries 1 (BT.709,sRGB)
bTransferCharacteristics 1 (BT.709)
bMatrixCoefficients 4 (SMPTE 170M (BT.601))
VideoStreaming Interface Descriptor:
bLength 11
bDescriptorType 36
bDescriptorSubtype 6 (FORMAT_MJPEG)
bFormatIndex 2
bNumFrameDescriptors 11
bFlags 1
Fixed-size samples: Yes
bDefaultFrameIndex 1
bAspectRatioX 0
bAspectRatioY 0
bmInterlaceFlags 0x00
Interlaced stream or variable: No
Fields per frame: 1 fields
Field 1 first: No
Field pattern: Field 1 only
bCopyProtect 0
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 7 (FRAME_MJPEG)
bFrameIndex 1
bmCapabilities 0x01
Still image supported
wWidth 640
wHeight 480
dwMinBitRate 110592000
dwMaxBitRate 221184000
dwMaxVideoFrameBufferSize 921600
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 7 (FRAME_MJPEG)
bFrameIndex 2
bmCapabilities 0x01
Still image supported
wWidth 352
wHeight 288
dwMinBitRate 36495360
dwMaxBitRate 72990720
dwMaxVideoFrameBufferSize 304128
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 7 (FRAME_MJPEG)
bFrameIndex 3
bmCapabilities 0x01
Still image supported
wWidth 320
wHeight 240
dwMinBitRate 27648000
dwMaxBitRate 55296000
dwMaxVideoFrameBufferSize 230400
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 7 (FRAME_MJPEG)
bFrameIndex 4
bmCapabilities 0x01
Still image supported
wWidth 176
wHeight 144
dwMinBitRate 9123840
dwMaxBitRate 18247680
dwMaxVideoFrameBufferSize 76032
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 7 (FRAME_MJPEG)
bFrameIndex 5
bmCapabilities 0x01
Still image supported
wWidth 160
wHeight 120
dwMinBitRate 6912000
dwMaxBitRate 13824000
dwMaxVideoFrameBufferSize 57600
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 7 (FRAME_MJPEG)
bFrameIndex 6
bmCapabilities 0x01
Still image supported
wWidth 544
wHeight 288
dwMinBitRate 56401920
dwMaxBitRate 112803840
dwMaxVideoFrameBufferSize 470016
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 7 (FRAME_MJPEG)
bFrameIndex 7
bmCapabilities 0x01
Still image supported
wWidth 432
wHeight 240
dwMinBitRate 37324800
dwMaxBitRate 74649600
dwMaxVideoFrameBufferSize 311040
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 7 (FRAME_MJPEG)
bFrameIndex 8
bmCapabilities 0x01
Still image supported
wWidth 320
wHeight 176
dwMinBitRate 20275200
dwMaxBitRate 40550400
dwMaxVideoFrameBufferSize 168960
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 7 (FRAME_MJPEG)
bFrameIndex 9
bmCapabilities 0x01
Still image supported
wWidth 640
wHeight 360
dwMinBitRate 82944000
dwMaxBitRate 165888000
dwMaxVideoFrameBufferSize 691200
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 7 (FRAME_MJPEG)
bFrameIndex 10
bmCapabilities 0x01
Still image supported
wWidth 800
wHeight 480
dwMinBitRate 138240000
dwMaxBitRate 276480000
dwMaxVideoFrameBufferSize 1152000
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 34
bDescriptorType 36
bDescriptorSubtype 7 (FRAME_MJPEG)
bFrameIndex 11
bmCapabilities 0x01
Still image supported
wWidth 1024
wHeight 768
dwMinBitRate 283115520
dwMaxBitRate 566231040
dwMaxVideoFrameBufferSize 2359296
dwDefaultFrameInterval 333333
bFrameIntervalType 2
dwFrameInterval( 0) 333333
dwFrameInterval( 1) 666666
VideoStreaming Interface Descriptor:
bLength 6
bDescriptorType 36
bDescriptorSubtype 13 (COLORFORMAT)
bColorPrimaries 1 (BT.709,sRGB)
bTransferCharacteristics 1 (BT.709)
bMatrixCoefficients 4 (SMPTE 170M (BT.601))
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 1
bNumEndpoints 1
bInterfaceClass 14 Video
bInterfaceSubClass 2 Video Streaming
bInterfaceProtocol 0
iInterface 4
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x82 EP 2 IN
bmAttributes 5
Transfer Type Isochronous
Synch Type Asynchronous
Usage Type Data
wMaxPacketSize 0x1400 3x 1024 bytes
bInterval 1
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 2
bNumEndpoints 1
bInterfaceClass 14 Video
bInterfaceSubClass 2 Video Streaming
bInterfaceProtocol 0
iInterface 4
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x82 EP 2 IN
bmAttributes 5
Transfer Type Isochronous
Synch Type Asynchronous
Usage Type Data
wMaxPacketSize 0x0c00 2x 1024 bytes
bInterval 1
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 3
bNumEndpoints 1
bInterfaceClass 14 Video
bInterfaceSubClass 2 Video Streaming
bInterfaceProtocol 0
iInterface 4
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x82 EP 2 IN
bmAttributes 5
Transfer Type Isochronous
Synch Type Asynchronous
Usage Type Data
wMaxPacketSize 0x0400 1x 1024 bytes
bInterval 1
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 4
bNumEndpoints 1
bInterfaceClass 14 Video
bInterfaceSubClass 2 Video Streaming
bInterfaceProtocol 0
iInterface 4
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x82 EP 2 IN
bmAttributes 5
Transfer Type Isochronous
Synch Type Asynchronous
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 1
Interface Association:
bLength 8
bDescriptorType 11
bFirstInterface 2
bInterfaceCount 2
bFunctionClass 1 Audio
bFunctionSubClass 0
bFunctionProtocol 0
iFunction 5
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 2
bAlternateSetting 0
bNumEndpoints 0
bInterfaceClass 1 Audio
bInterfaceSubClass 1 Control Device
bInterfaceProtocol 0
iInterface 5
AudioControl Interface Descriptor:
bLength 9
bDescriptorType 36
bDescriptorSubtype 1 (HEADER)
bcdADC 1.00
wTotalLength 0x002b
bInCollection 1
baInterfaceNr(0) 3
AudioControl Interface Descriptor:
bLength 12
bDescriptorType 36
bDescriptorSubtype 2 (INPUT_TERMINAL)
bTerminalID 1
wTerminalType 0x0201 Microphone
bAssocTerminal 0
bNrChannels 1
wChannelConfig 0x0000
iChannelNames 0
iTerminal 0
AudioControl Interface Descriptor:
bLength 13
bDescriptorType 36
bDescriptorSubtype 6 (FEATURE_UNIT)
bUnitID 5
bSourceID 1
bControlSize 6
bmaControls(0) 0x000000000003
Mute Control
Volume Control
iFeature 0
AudioControl Interface Descriptor:
bLength 9
bDescriptorType 36
bDescriptorSubtype 3 (OUTPUT_TERMINAL)
bTerminalID 3
wTerminalType 0x0101 USB Streaming
bAssocTerminal 0
bSourceID 5
iTerminal 0
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 3
bAlternateSetting 0
bNumEndpoints 0
bInterfaceClass 1 Audio
bInterfaceSubClass 2 Streaming
bInterfaceProtocol 0
iInterface 5
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 3
bAlternateSetting 1
bNumEndpoints 1
bInterfaceClass 1 Audio
bInterfaceSubClass 2 Streaming
bInterfaceProtocol 0
iInterface 5
AudioStreaming Interface Descriptor:
bLength 7
bDescriptorType 36
bDescriptorSubtype 1 (AS_GENERAL)
bTerminalLink 3
bDelay 1 frames
wFormatTag 0x0001 PCM
AudioStreaming Interface Descriptor:
bLength 32
bDescriptorType 36
bDescriptorSubtype 2 (FORMAT_TYPE)
bFormatType 1 (FORMAT_TYPE_I)
bNrChannels 1
bSubframeSize 2
bBitResolution 16
bSamFreqType 8 Discrete
tSamFreq[ 0] 48000
tSamFreq[ 1] 44100
tSamFreq[ 2] 24000
tSamFreq[ 3] 22050
tSamFreq[ 4] 16000
tSamFreq[ 5] 12000
tSamFreq[ 6] 11025
tSamFreq[ 7] 8000
Endpoint Descriptor:
bLength 9
bDescriptorType 5
bEndpointAddress 0x83 EP 3 IN
bmAttributes 13
Transfer Type Isochronous
Synch Type Synchronous
Usage Type Data
wMaxPacketSize 0x0064 1x 100 bytes
bInterval 4
bRefresh 0
bSynchAddress 0
AudioStreaming Endpoint Descriptor:
bLength 7
bDescriptorType 37
bDescriptorSubtype 1 (EP_GENERAL)
bmAttributes 0x01
Sampling Frequency
bLockDelayUnits 1 Milliseconds
wLockDelay 0x0000
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 3
bAlternateSetting 2
bNumEndpoints 1
bInterfaceClass 1 Audio
bInterfaceSubClass 2 Streaming
bInterfaceProtocol 0
iInterface 5
AudioStreaming Interface Descriptor:
bLength 7
bDescriptorType 36
bDescriptorSubtype 1 (AS_GENERAL)
bTerminalLink 3
bDelay 1 frames
wFormatTag 0x0001 PCM
AudioStreaming Interface Descriptor:
bLength 32
bDescriptorType 36
bDescriptorSubtype 2 (FORMAT_TYPE)
bFormatType 1 (FORMAT_TYPE_I)
bNrChannels 1
bSubframeSize 1
bBitResolution 8
bSamFreqType 8 Discrete
tSamFreq[ 0] 48000
tSamFreq[ 1] 44100
tSamFreq[ 2] 24000
tSamFreq[ 3] 22050
tSamFreq[ 4] 16000
tSamFreq[ 5] 12000
tSamFreq[ 6] 11025
tSamFreq[ 7] 8000
Endpoint Descriptor:
bLength 9
bDescriptorType 5
bEndpointAddress 0x83 EP 3 IN
bmAttributes 13
Transfer Type Isochronous
Synch Type Synchronous
Usage Type Data
wMaxPacketSize 0x0032 1x 50 bytes
bInterval 4
bRefresh 0
bSynchAddress 0
AudioStreaming Endpoint Descriptor:
bLength 7
bDescriptorType 37
bDescriptorSubtype 1 (EP_GENERAL)
bmAttributes 0x01
Sampling Frequency
bLockDelayUnits 1 Milliseconds
wLockDelay 0x0000
`
注意下 A. 每次传输都需要填充头部信息 B. 虚拟设备需要驱动提供定时机制控制传输频率，不然会导致系统锁死
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