华为UAC耳机 音频流接口

音频流接口分为麦克风和耳机(headphone)。

由于音频流传输只能是同步/等时传输方式进行，故在音频流接口描述符中，接口bAlternateSetting=0时为默认的无音频输出接口即无端点描述符，从bAlternateSetting=1开始有数据传输，即应该有等时传输端点描述符。

麦克风

在麦克风下只有一个音频转换接口，音频接口的采样率为48000HZ,格式为PCM.包的最大数据长度为192字节，即1ms,数据支持的是2通道（左右），每个通道16字节。

在UAC中，固定采用时间间隔是1ms.

所以48000/1000ms=48*2(通道)*2(字节) = 192字节/ms

        ---------------- Interface Descriptor -----------------          麦克风关闭   1
bLength                  : 0x09 (9 bytes)
bDescriptorType          : 0x04 (Interface Descriptor)
bInterfaceNumber         : 0x01
bAlternateSetting        : 0x00
bNumEndpoints            : 0x00 (Default Control Pipe only)
bInterfaceClass          : 0x01 (Audio)
bInterfaceSubClass       : 0x02 (Audio Streaming)
bInterfaceProtocol       : 0x00
iInterface               : 0x00 (No String Descriptor)
Data (HexDump)           : 09 04 01 00 00 01 02 00 00                        .........

        ---------------- Interface Descriptor -----------------       打开
bLength                  : 0x09 (9 bytes)
bDescriptorType          : 0x04 (Interface Descriptor)
bInterfaceNumber         : 0x01
bAlternateSetting        : 0x01
bNumEndpoints            : 0x01 (1 Endpoint)
bInterfaceClass          : 0x01 (Audio)
bInterfaceSubClass       : 0x02 (Audio Streaming)
bInterfaceProtocol       : 0x00
iInterface               : 0x00 (No String Descriptor)
Data (HexDump)           : 09 04 01 01 01 01 02 00 00                        .........

        -------- Audio Streaming Interface Descriptor ---------
bLength                  : 0x07 (7 bytes)
bDescriptorType          : 0x24 (Audio Interface Descriptor)
bDescriptorSubtype       : 0x01
bTerminalLink            : 0x05
bDelay                   : 0x00
wFormatTag               : 0x0001 (PCM)
Data (HexDump)           : 07 24 01 05 00 01 00                              .$.....

        ------- Audio Streaming Format Type Descriptor --------      麦克风
bLength                  : 0x0B (11 bytes)
bDescriptorType          : 0x24 (Audio Interface Descriptor)
bDescriptorSubtype       : 0x02 (Format Type)
bFormatType              : 0x01 (FORMAT_TYPE_I)
bNrChannels              : 0x02 (2 channels)
bSubframeSize            : 0x02 (2 bytes per subframe)
bBitResolution           : 0x10 (16 bits per sample)
bSamFreqType             : 0x01 (supports 1 sample frequence)
tSamFreq[1]              : 0x0BB80 (48000 Hz)
Data (HexDump)           : 0B 24 02 01 02 02 10 01 80 BB 00                  .$.........

        ----------------- Endpoint Descriptor -----------------         麦克风 输入数据
bLength                  : 0x09 (9 bytes)
bDescriptorType          : 0x05 (Endpoint Descriptor)
bEndpointAddress         : 0x83 (Direction=IN EndpointID=3)
bmAttributes             : 0x0D (TransferType=Isochronous  SyncType=Synchronous  EndpointType=Data)
wMaxPacketSize           : 0x00C0 (192 bytes)   //192/48=4
bInterval                : 0x01 (1 ms)
bRefresh                 : 0x00
bSynchAddress            : 0x00
Data (HexDump)           : 09 05 83 0D C0 00 01 00 00                        .........

        ----------- Audio Data Endpoint Descriptor ------------
bLength                  : 0x07 (7 bytes)
bDescriptorType          : 0x25 (Audio Endpoint Descriptor)
bDescriptorSubtype       : 0x01 (General)
bmAttributes             : 0x01
 D0   : Sampling Freq    : 0x01 (supported)
 D1   : Pitch            : 0x00 (not supported)
 D6..2: Reserved         : 0x00
 D7   : MaxPacketsOnly   : 0x00 (no)
bLockDelayUnits          : 0x00 (Undefined)
wLockDelay               : 0x0000
Data (HexDump)           : 07 25 01 01 00 00 00                              .%.....

耳机

耳机支持2个转换接口，按每通道的字节数分为2字节和3字节，分别对应的是转换接口2和3。

        ---------------- Interface Descriptor -----------------            耳机关闭 2
bLength                  : 0x09 (9 bytes)
bDescriptorType          : 0x04 (Interface Descriptor)
bInterfaceNumber         : 0x02
bAlternateSetting        : 0x00
bNumEndpoints            : 0x00 (Default Control Pipe only)
bInterfaceClass          : 0x01 (Audio)
bInterfaceSubClass       : 0x02 (Audio Streaming)
bInterfaceProtocol       : 0x00
iInterface               : 0x00 (No String Descriptor)
Data (HexDump)           : 09 04 02 00 00 01 02 00 00                        .........

        ---------------- Interface Descriptor -----------------           耳机打开  2
bLength                  : 0x09 (9 bytes)
bDescriptorType          : 0x04 (Interface Descriptor)
bInterfaceNumber         : 0x02
bAlternateSetting        : 0x01
bNumEndpoints            : 0x01 (1 Endpoint)
bInterfaceClass          : 0x01 (Audio)
bInterfaceSubClass       : 0x02 (Audio Streaming)
bInterfaceProtocol       : 0x00
iInterface               : 0x00 (No String Descriptor)
Data (HexDump)           : 09 04 02 01 01 01 02 00 00                        .........

        -------- Audio Streaming Interface Descriptor ---------
bLength                  : 0x07 (7 bytes)
bDescriptorType          : 0x24 (Audio Interface Descriptor)
bDescriptorSubtype       : 0x01
bTerminalLink            : 0x01
bDelay                   : 0x00
wFormatTag               : 0x0001 (PCM)
Data (HexDump)           : 07 24 01 01 00 01 00                              .$.....

        ------- Audio Streaming Format Type Descriptor --------
bLength                  : 0x11 (17 bytes)
bDescriptorType          : 0x24 (Audio Interface Descriptor)
bDescriptorSubtype       : 0x02 (Format Type)
bFormatType              : 0x01 (FORMAT_TYPE_I)
bNrChannels              : 0x02 (2 channels)
bSubframeSize            : 0x02 (2 bytes per subframe)
bBitResolution           : 0x10 (16 bits per sample)
bSamFreqType             : 0x03 (supports 3 sample frequencies)
tSamFreq[1]              : 0x0AC44 (44100 Hz)
tSamFreq[2]              : 0x0BB80 (48000 Hz)
tSamFreq[3]              : 0x17700 (96000 Hz)
Data (HexDump)           : 11 24 02 01 02 02 10 03 44 AC 00 80 BB 00 00 77   .$......D......w
                           01                                                .

        ----------------- Endpoint Descriptor -----------------             耳机输出数据=====1
bLength                  : 0x09 (9 bytes)
bDescriptorType          : 0x05 (Endpoint Descriptor)
bEndpointAddress         : 0x03 (Direction=OUT EndpointID=3)
bmAttributes             : 0x0D (TransferType=Isochronous  SyncType=Synchronous  EndpointType=Data)
wMaxPacketSize           : 0x0180 (384 bytes)        384/96=4  
bInterval                : 0x01 (1 ms)
bRefresh                 : 0x00
bSynchAddress            : 0x00
Data (HexDump)           : 09 05 03 0D 80 01 01 00 00                        .........

        ----------- Audio Data Endpoint Descriptor ------------
bLength                  : 0x07 (7 bytes)
bDescriptorType          : 0x25 (Audio Endpoint Descriptor)
bDescriptorSubtype       : 0x01 (General)
bmAttributes             : 0x01
 D0   : Sampling Freq    : 0x01 (supported)
 D1   : Pitch            : 0x00 (not supported)
 D6..2: Reserved         : 0x00
 D7   : MaxPacketsOnly   : 0x00 (no)
bLockDelayUnits          : 0x00 (Undefined)
wLockDelay               : 0x0000
Data (HexDump)           : 07 25 01 01 00 00 00                              .%.....

        ---------------- Interface Descriptor -----------------
bLength                  : 0x09 (9 bytes)
bDescriptorType          : 0x04 (Interface Descriptor)
bInterfaceNumber         : 0x02
bAlternateSetting        : 0x02
bNumEndpoints            : 0x01 (1 Endpoint)
bInterfaceClass          : 0x01 (Audio)
bInterfaceSubClass       : 0x02 (Audio Streaming)
bInterfaceProtocol       : 0x00
iInterface               : 0x00 (No String Descriptor)
Data (HexDump)           : 09 04 02 02 01 01 02 00 00                        .........

        -------- Audio Streaming Interface Descriptor ---------
bLength                  : 0x07 (7 bytes)
bDescriptorType          : 0x24 (Audio Interface Descriptor)
bDescriptorSubtype       : 0x01
bTerminalLink            : 0x01
bDelay                   : 0x00
wFormatTag               : 0x0001 (PCM)
Data (HexDump)           : 07 24 01 01 00 01 00                              .$.....

        ------- Audio Streaming Format Type Descriptor --------
bLength                  : 0x11 (17 bytes)
bDescriptorType          : 0x24 (Audio Interface Descriptor)
bDescriptorSubtype       : 0x02 (Format Type)
bFormatType              : 0x01 (FORMAT_TYPE_I)
bNrChannels              : 0x02 (2 channels)
bSubframeSize            : 0x03 (3 bytes per subframe)
bBitResolution           : 0x18 (24 bits per sample)
bSamFreqType             : 0x03 (supports 3 sample frequencies)
tSamFreq[1]              : 0x0AC44 (44100 Hz)
tSamFreq[2]              : 0x0BB80 (48000 Hz)
tSamFreq[3]              : 0x17700 (96000 Hz)
Data (HexDump)           : 11 24 02 01 02 03 18 03 44 AC 00 80 BB 00 00 77   .$......D......w
                           01                                                .

        ----------------- Endpoint Descriptor -----------------            =====2
bLength                  : 0x09 (9 bytes)
bDescriptorType          : 0x05 (Endpoint Descriptor)
bEndpointAddress         : 0x03 (Direction=OUT EndpointID=3)
bmAttributes             : 0x0D (TransferType=Isochronous  SyncType=Synchronous  EndpointType=Data)
wMaxPacketSize           : 0x0240 (576 bytes)                            576/96=6
bInterval                : 0x01 (1 ms)
bRefresh                 : 0x00
bSynchAddress            : 0x00
Data (HexDump)           : 09 05 03 0D 40 02 01 00 00                        ....@....

        ----------- Audio Data Endpoint Descriptor ------------
bLength                  : 0x07 (7 bytes)
bDescriptorType          : 0x25 (Audio Endpoint Descriptor)
bDescriptorSubtype       : 0x01 (General)
bmAttributes             : 0x01
 D0   : Sampling Freq    : 0x01 (supported)
 D1   : Pitch            : 0x00 (not supported)
 D6..2: Reserved         : 0x00
 D7   : MaxPacketsOnly   : 0x00 (no)
bLockDelayUnits          : 0x00 (Undefined)
wLockDelay               : 0x0000
Data (HexDump)           : 07 25 01 01 00 00 00                              .%.....