from usbd_audio.h:190
typedef struct
{
uint8_t bLength;
uint8_t bDescriptorType;
uint8_t bDescriptorSubtype;
uint8_t bTerminalID;
uint16_t wTerminalType;
uint8_t bAssocTerminal;
uint8_t bNrChannels;
uint16_t wChannelConfig;
uint8_t iChannelNames;
uint8_t iTerminal;
} __PACKED USBD_SpeakerInDescTypeDef;