Walking the IDeviceTopology tree to see audio driver settings

I've blogged
before about using the IDeviceTopology API to poke around the internal structure exposed by audio drivers.
In particular, given an audio endpoint, you can map out all the knobs and widgets of all the signal paths that feed into that endpoint (for playback) or out of it (for recording.)
A
version of this has been floating around the forums for some years, but I thought I would spiffy it up a little and make a blog post out of it.
Pseudocode:
for each endpoint exposed by IMMDeviceEnumerator:

figure out whether it's a playback endpoint or a recording endpoint

find the IPart which is

the very end of the signal path for a playback endpoint, or

the very beginning for a recording endpoint:

if the IPart advertises jack information, query it

if the IPart is a volume control, query the range and the current setting

if the IPart is a mute control, query the current setting

(we could continue here for various other kinds of controls, but I'm lazy)

for all parts which

feed in to the IPart for a playback endpoint, or

are fed by the IPart for a recording endpoint:

recursively process that IPart

if the IPart is a connector:

find the IPart on the other side of the connection

process it recursively

take care not to immediately hop back to this graph!
Output:
>devicetopology.exe

eRender endpoint

Name: Speakers (High Definition Audio Device)

Endpoint ID: {0.0.0.00000000}.{351933db-e9b5-41df-8fa5-69c3d84531df}

0x10000:

{2}.\\?\hdaudio#func_01&ven_10ec&dev_0262&subsys_103c1309&rev_1002#4&12f2dd06&0&0001#{6994ad04-93ef-11d0-a3cc-00a0c9223196}\elineouttopo

0x10001: Speakers

Jacks: 1

-- Jack 1 --

ChannelMapping: 0x3

Color: 0x00ff00 (red = 0, green = 255, blue = 0)

Connection Type: 1 (eConnType3Point5mm)

Geometric Location: 1 (eGeoLocRear)

General Location: 0 (eGenLocPrimaryBox)

Port Connection: 0 (ePortConnJack)

IsConnected: No

0x20001: Master Mute

0x20000: Speakers

0x10000:

{0.0.1.00000000}.{6dd94b4a-90d7-4ddc-926d-69312eb53841}

0x10000:
eRender endpoint

Name: Speakers (High Definition Audio Device)

Endpoint ID: {0.0.0.00000000}.{6ce8bdf4-d22f-4ec7-a007-2228540b6705}

0x10000:

{2}.\\?\hdaudio#func_01&ven_10ec&dev_0262&subsys_103c1309&rev_1002#4&12f2dd06&0&0001#{6994ad04-93ef-11d0-a3cc-00a0c9223196}\elineout2topo

0x10001: Speakers

Jacks: 1

-- Jack 1 --

ChannelMapping: 0x3

Color: 0x000000 (red = 0, green = 0, blue = 0)

Connection Type: 3 (eConnTypeAtapiInternal)

Geometric Location: 13 (eGeoLocATAPI)

General Location: 0 (eGenLocPrimaryBox)

Port Connection: 1 (ePortConnIntegratedDevice)

IsConnected: Yes

0x20001: Master Mute

Mute node: MUTED

0x20000: Speakers

Channel 0 volume, -46.5 dB to 0 dB in steps of 1.5 dB: -6 dB

0x10000:

{2}.\\?\hdaudio#func_01&ven_10ec&dev_0262&subsys_103c1309&rev_1002#4&12f2dd06&0&0001#{6994ad04-93ef-11d0-a3cc-00a0c9223196}\elineout2wave

0x10001:

0x20000: HD Audio line out

0x10000: PC Speaker
eRender endpoint

Name: Speakerphone (USB Audio Device)

Endpoint ID: {0.0.0.00000000}.{916afdff-2ba3-4a7f-bca9-0bf75c47c946}

0x10000:

{2}.\\?\usb#vid_095d&pid_0005&mi_00#7&335bfb1&0&0000#{6994ad04-93ef-11d0-a3cc-00a0c9223196}\global

0x10003: Speakerphone

0x20009: DAC

0x20008: Volume

Channel 0 volume, -30.0039 dB to 0 dB in steps of 0.5 dB: -17.747 dB

0x20007: Mute

Mute node: NOT MUTED

0x20006: Sample Rate Converter

0x10000:
eCapture endpoint

Name: Microphone (High Definition Audio Device)

Endpoint ID: {0.0.1.00000000}.{38178e43-ed21-4731-b8f0-1330c3b1cd0a}

0x10000:

{2}.\\?\hdaudio#func_01&ven_10ec&dev_0262&subsys_103c1309&rev_1002#4&12f2dd06&0&0001#{6994ad04-93ef-11d0-a3cc-00a0c9223196}\emixedcapturetopo

0x10001: Microphone

Jacks: 1

-- Jack 1 --

ChannelMapping: 0x0

Color: 0xff80c0 (red = 255, green = 128, blue = 192)

Connection Type: 1 (eConnType3Point5mm)

Geometric Location: 1 (eGeoLocRear)

General Location: 0 (eGenLocPrimaryBox)

Port Connection: 0 (ePortConnJack)

IsConnected: No

0x20001: Microphone

0x20002: Microphone

0x20003: Microphone Boost

0x20000: Sum

0x10000:

{0.0.0.00000000}.{f7bf26d7-89a3-4049-8cd3-8148a6615565}

0x10000:
eCapture endpoint

Name: Speakerphone (USB Audio Device)

Endpoint ID: {0.0.1.00000000}.{a21f51bc-5d0b-47af-93b6-ef9a968bb8ff}

0x10000:

{2}.\\?\usb#vid_095d&pid_0005&mi_00#7&335bfb1&0&0000#{6994ad04-93ef-11d0-a3cc-00a0c9223196}\global

0x10002: Speakerphone

0x20000: ADC

0x20001: Mute

Mute node: NOT MUTED

0x20002: Volume

Channel 0 volume, 0 dB to 32 dB in steps of 0.5 dB: 29 dB

0x20003: SuperMix

0x20004:

0x20005: Sample Rate Converter

0x10001:
eCapture endpoint

Name: Microphone (High Definition Audio Device)

Endpoint ID: {0.0.1.00000000}.{a9d04431-a99f-4ebe-b995-33f0d027559c}

0x10000:

{2}.\\?\hdaudio#func_01&ven_10ec&dev_0262&subsys_103c1309&rev_1002#4&12f2dd06&0&0001#{6994ad04-93ef-11d0-a3cc-00a0c9223196}\emixedcapturetopo

0x10002: Microphone

Jacks: 1

-- Jack 1 --

ChannelMapping: 0x0

Color: 0x000000 (red = 0, green = 0, blue = 0)

Connection Type: 1 (eConnType3Point5mm)

Geometric Location: 2 (eGeoLocFront)

General Location: 0 (eGenLocPrimaryBox)

Port Connection: 0 (ePortConnJack)

IsConnected: No

0x20004: Microphone

0x20005: Microphone

0x20006: Microphone Boost

0x20000: Sum

0x10000:

{0.0.0.00000000}.{f7bf26d7-89a3-4049-8cd3-8148a6615565}

0x10000:
eCapture endpoint

Name: Line In (High Definition Audio Device)

Endpoint ID: {0.0.1.00000000}.{bbf7eb42-7674-4a35-ad02-b723ea047dac}

0x10000:

{2}.\\?\hdaudio#func_01&ven_10ec&dev_0262&subsys_103c1309&rev_1002#4&12f2dd06&0&0001#{6994ad04-93ef-11d0-a3cc-00a0c9223196}\emixedcapturetopo

0x10003: Line In

Jacks: 1

-- Jack 1 --

ChannelMapping: 0x0

Color: 0x0000ff (red = 0, green = 0, blue = 255)

Connection Type: 1 (eConnType3Point5mm)

Geometric Location: 1 (eGeoLocRear)

General Location: 0 (eGenLocPrimaryBox)

Port Connection: 0 (ePortConnJack)

IsConnected: No

0x20007: Line In

0x20008: Line In

0x20000: Sum

0x10000:

{0.0.0.00000000}.{f7bf26d7-89a3-4049-8cd3-8148a6615565}

0x10000:
And here's a screenshot of the Windows Driver
Kit's Kernel Streaming Studio showing the topology exposed
by the audio drivers on my machine:



Source and x86/amd64 binaries attached.
EDIT September 22 2015: moved source to github https://github.com/mvaneerde/blog/tree/master/devicetopology



devicetopology.zip



Audio, Win32
http://blogs.msdn.com/b/matthew_van_eerde/archive/2014/11/20/walking-the-idevicetopology-tree-to-see-audio-driver-settings.aspx