USB microphone with 24bit/sample - Descriptor seems to be wrong

Question

Hi, I'm currently developing a USB microphone-like device that is supposed to support:

fs = 48kHz

Up to 6 channels

24bit/sample

The USB framework that comes with the hardware supports USB Audio Class 1.0 at full-speed profile. I was able to make it work with 2 channels @ 16 bits/sample. However, it fails to operate for anything above that since the Windows USB driver doesn't seem to recognize the settings specified in the USB descriptor.

I've pasted the full USB description of my device below where I set bSubframeSize = 0x03 and bBitResolution = 0x18 to work on 24bit/sample. The USB device isn't working with these changes as my recording software fails to record with it. When I set those to 16 bit/sample (bSubframeSize = 0x02 and bBitResolution = 0x10) it works without issues.

I hope anybody can advise me on that.

Information for device Bose Mathers (VID=0x05A7 PID=0xBC61):

------------------------------
Connection Information:
------------------------------
Device current bus speed: FullSpeed
Device supports USB 1.1 specification
Device address: 0x0015
Current configuration value: 0x01
Number of open pipes: 3


------------------------------
Device Descriptor:
------------------------------
0x12	bLength
0x01	bDescriptorType
0x0200	bcdUSB
0x00	bDeviceClass      
0x00	bDeviceSubClass   
0x00	bDeviceProtocol   
0x40	bMaxPacketSize0   (64 bytes)
0x05A7	idVendor
0xBC61	idProduct
0x3050	bcdDevice
0x01	iManufacturer   "Bose Corporation"
0x02	iProduct        "Bose Mathers"
0x03	iSerialNumber   "P329980000388741007B010"
0x01	bNumConfigurations


-------------------------
Configuration Descriptor:
-------------------------
0x09	bLength
0x02	bDescriptorType
0x00A7	wTotalLength   (167 bytes)
0x04	bNumInterfaces
0x01	bConfigurationValue
0x00	iConfiguration
0xC0	bmAttributes   (Self-powered Device)
0x00	bMaxPower      (0 mA)

Interface Descriptor:
------------------------------
0x09	bLength
0x04	bDescriptorType
0x00	bInterfaceNumber
0x00	bAlternateSetting
0x00	bNumEndPoints
0x01	bInterfaceClass      (Audio Device Class)
0x01	bInterfaceSubClass   (Audio Control Interface)
0x00	bInterfaceProtocol   (Audio Protocol undefined)
0x00	iInterface

AC Interface Header Descriptor:
------------------------------
0x09	bLength
0x24	bDescriptorType
0x01	bDescriptorSubtype
0x0100	bcdADC
0x0028	wTotalLength   (40 bytes)
0x01	bInCollection
0x01	baInterfaceNr(1)

AC Input Terminal Descriptor:
------------------------------
0x0C	bLength
0x24	bDescriptorType
0x02	bDescriptorSubtype
0x07	bTerminalID
0x0201	wTerminalType   (Microphone)
0x00	bAssocTerminal
0x02	bNrChannels   (2 channels)
0x0003	wChannelConfig
0x00	iChannelNames
0x00	iTerminal

AC Feature Unit Descriptor:
------------------------------
0x0A	bLength
0x24	bDescriptorType
0x06	bDescriptorSubtype
0x08	bUnitID
0x07	bSourceID
0x01	bControlSize
bmaControls: 
 0x02	Channel(0) - Volume
 0x00	Channel(1)
 0x00	Channel(2)
0x00	iFeature


AC Output Terminal Descriptor:
------------------------------
0x09	bLength
0x24	bDescriptorType
0x03	bDescriptorSubtype
0x09	bTerminalID
0x0101	wTerminalType   (USB Streaming)
0x00	bAssocTerminal
0x08	bSourceID
0x00	iTerminal

Interface Descriptor:
------------------------------
0x09	bLength
0x04	bDescriptorType
0x01	bInterfaceNumber
0x00	bAlternateSetting
0x00	bNumEndPoints
0x01	bInterfaceClass      (Audio Device Class)
0x02	bInterfaceSubClass   (Audio Streaming Interface)
0x00	bInterfaceProtocol   (Audio Protocol undefined)
0x00	iInterface

Interface Descriptor:
------------------------------
0x09	bLength
0x04	bDescriptorType
0x01	bInterfaceNumber
0x01	bAlternateSetting
0x01	bNumEndPoints
0x01	bInterfaceClass      (Audio Device Class)
0x02	bInterfaceSubClass   (Audio Streaming Interface)
0x00	bInterfaceProtocol   (Audio Protocol undefined)
0x00	iInterface

AS Interface Descriptor:
------------------------------
0x07	bLength
0x24	bDescriptorType
0x01	bDescriptorSubtype
0x09	bTerminalLink
0x00	bDelay
0x0001	wFormatTag   (PCM)

AS Format Type 1 Descriptor:
------------------------------
0x0B	bLength
0x24	bDescriptorType
0x02	bDescriptorSubtype
0x01	bFormatType   (FORMAT_TYPE_1)
0x02	bNrChannels   (2 channels)
0x03	bSubframeSize
0x18	bBitResolution   (24 bits per sample)
0x01	bSamFreqType   (Discrete sampling frequencies)
0x00BB80 	tSamFreq(1)   (48000 Hz)

Endpoint Descriptor (Audio/MIDI 1.0):
------------------------------
0x09	bLength
0x05	bDescriptorType
0x81	bEndpointAddress  (IN endpoint 1)
0x01	bmAttributes      (Transfer: Isochronous / Synch: None / Usage: Data)
0x0120	wMaxPacketSize    (1 x 288 bytes)
0x01	bInterval         (1 frames)
0x00	bRefresh
0x00	bSynchAddress

AS Isochronous Data Endpoint Descriptor:
------------------------------
0x07	bLength
0x25	bDescriptorType
0x01	bDescriptorSubtype
0x00	bmAttributes
0x02	bLockDelayUnits   (decoded PCM samples)
0x0000	wLockDelay

Interface Descriptor:
------------------------------
0x09	bLength
0x04	bDescriptorType
0x02	bInterfaceNumber
0x00	bAlternateSetting
0x02	bNumEndPoints
0x03	bInterfaceClass      (Human Interface Device Class)
0x00	bInterfaceSubClass   
0x00	bInterfaceProtocol   
0x00	iInterface

HID Descriptor:
------------------------------
0x09	bLength
0x21	bDescriptorType
0x0111	bcdHID
0x99	bCountryCode
0x01	bNumDescriptors
0x22	bDescriptorType   (Report descriptor)
0x007E	bDescriptorLength

Endpoint Descriptor:
------------------------------
0x07	bLength
0x05	bDescriptorType
0x01	bEndpointAddress  (OUT endpoint 1)
0x03	bmAttributes      (Transfer: Interrupt / Synch: None / Usage: Data)
0x0040	wMaxPacketSize    (1 x 64 bytes)
0x01	bInterval         (1 frames)

Endpoint Descriptor:
------------------------------
0x07	bLength
0x05	bDescriptorType
0x82	bEndpointAddress  (IN endpoint 2)
0x03	bmAttributes      (Transfer: Interrupt / Synch: None / Usage: Data)
0x0040	wMaxPacketSize    (1 x 64 bytes)
0x01	bInterval         (1 frames)

Interface Descriptor:
------------------------------
0x09	bLength
0x04	bDescriptorType
0x03	bInterfaceNumber
0x00	bAlternateSetting
0x01	bNumEndPoints
0x03	bInterfaceClass      (Human Interface Device Class)
0x00	bInterfaceSubClass   
0x00	bInterfaceProtocol   
0x00	iInterface

HID Descriptor:
------------------------------
0x09	bLength
0x21	bDescriptorType
0x0111	bcdHID
0x00	bCountryCode
0x01	bNumDescriptors
0x22	bDescriptorType   (Report descriptor)
0x00B0	bDescriptorLength

Endpoint Descriptor:
------------------------------
0x07	bLength
0x05	bDescriptorType
0x83	bEndpointAddress  (IN endpoint 3)
0x03	bmAttributes      (Transfer: Interrupt / Synch: None / Usage: Data)
0x0040	wMaxPacketSize    (1 x 64 bytes)
0x01	bInterval         (1 frames)

Microsoft OS Descriptor is not available. Error code: 0x0000001F


--------------------------------
String Descriptor Table
--------------------------------
Index  LANGID  String
0x00   0x0000  0x0409 
0x01   0x0409  "Bose Corporation"
0x02   0x0409  "Bose Mathers"
0x03   0x0409  "P329980000388741007B010"

------------------------------

Connection path for device: 
USB xHCI Compliant Host Controller
Root Hub
Qualcomm USB Hub
Bose Mathers (VID=0x05A7 PID=0xBC61) Port: 1

Running on: Windows 10 or greater (Build Version 19045)

Brought to you by TDD v2.17.0, Feb 23 2021, 14:04:02