Support for Microphone Array Geometry Property

[xross]

Described here: https://learn.microsoft.com/en-us/windows-hardware/drivers/audio/microphone-array-geometry-property

A quick proof of concept has been authored by changing the UAC1 device descriptors to “microphone array” and adding the GET_MEM request as documented. These changes are described below. When done so the Windows host correctly does the GET_MEM request as documented.

Some thought would be required to enable a user to describe their own mic array geometries in the (variable size) descriptor – if they are capable of just authoring the raw bytes then this is relatively simple. Or, do we want to somewhat generate based on channel count? I think traditionally customers would be expected to program a byte array into an external memory.

The example app tested was the MC audio board using the line inputs as “mics”. Running a 2 in/2 out UAC1 device @16kHz.

In conclusion this is a relatively simple extension to the UA code base and we could support it with not too much effort, and a demo could be provided imminently.

Description of how to modify lib_xua for the quick proof of concept demo:

Set input wTerminalType to 0x205 - microphone array, host processing (currently UAC1 descriptors set to 0x201 - microphone). This will cause windows to do the GET_MEM request as documented (so far only tried with UAC1) i.e.

-    0x01, 0x02,                           /* Type - streaming in, mic */
+    0x05, 0x02,                           /* Type - streaming in, mic */

Add an example 2 mic array descriptor as an array:

unsigned char micArrayInfo[] =
{
    0x07, 0xFE, 0x86, 0xC1,
    0x89, 0x48,
    0x4d, 0xb5,
    0xB1, 0x84,
    0xC5, 0x16, 0x2D, 0x4A, 0xD3, 0x14,

    0x00, 0x3C, // wDescriptorLength
    0x10, 0x00, //wVersion
    0x00, 0x00, //bmMicArrayType
    0x00, 0x00,
    0x00, 0x00,
    0xDD, 0xE9,
    0x22, 0x17,
    0x00, 0x50,
    0x1d, 0x4c,
    0x00, 0x02,
    0x00, 0x00,
    0x00, 0x00,
    0xff, 0xce,
    0x00, 0x00,
    0x00, 0x00,
    0x00, 0x00,
    0x00, 0x00,
    0x00, 0x00,
    0x00, 0x32,
    0x00, 0x00,
    0x00, 0x00,
    0x00, 0x00,
};

Add response to GET_MEM request into xua_ep0_uacreqs.xc

XUD_Result_t AudioClassRequests_1(...

...

     switch(sp.bRequest)
    {
        case UAC_B_REQ_GET_MEM:
            int entity = sp.wIndex >> 8;
            int inter = sp.wIndex & 0xff;
            int control = sp.wValue >> 8;
            int channel = sp.wValue & 0xff;

            if((entity == 2) && (!inter) && (!control) && (!channel))
            {
                return XUD_DoGetRequest(ep0_out, ep0_in, buffer, sizeof(micArrayInfo), sp.wLength);
            }
            break;

Questions:

• Does windows support this for UAC2 or just UAC1?

Things left to do:

• try it with channel count > stereo
• try the ms mic array verif tool
• try uac2 (maybe not a requirement?)
• tidy up implementation such that customers can add their own microphone geo - maybe add some sort of auto-gen
• run it on a board with mics