audio-wasapi

name	audio-wasapi
description	Manipulate Windows audio via WASAPI (learn.microsoft.com/coreaudio): SoundVolumeView + svcl.exe (NirSoft — set default device, per-app volumes, save/load profiles), AudioDeviceCmdlets PowerShell module (Get-AudioDevice, Set-AudioDevice, Get-AudioDevicePlaybackMute), nircmd setdefaultsounddevice. Shared mode (Windows engine resamples all streams to endpoint fixed format) vs Exclusive mode (bit-perfect, audiophile, ~sub-3ms latency with IAudioClient3 + event-driven callbacks). WASAPI then MMDevice then Audio Engine (audiodg.exe) then WDM/KS. ASIO is Steinberg's parallel stack bypassing Windows audio. Virtual audio devices: VB-Audio Virtual Cable, VoiceMeeter/Banana/Potato. Use when the user asks to change Windows default audio device, route app audio, use VoiceMeeter, install VB-Cable, set a specific device from PowerShell, or enable exclusive-mode low-latency output.
argument-hint	[action]

Audio WASAPI

Context: $ARGUMENTS

Quick start

• List all audio endpoints: → Step 1 (winaudio.py list-devices)
• Check current default: → Step 2 (winaudio.py get-default)
• Change default output/input/communications: → Step 3 (winaudio.py set-default)
• Mute / unmute / change volume: → Step 4 (winaudio.py mute/unmute/volume)
• Check if exclusive mode is allowed on a device: → Step 5 (winaudio.py exclusive-test)
• Install VB-Cable virtual cable: → Step 6 (winaudio.py vbcable-install)
• Set up VoiceMeeter virtual mixer: → Step 7 (winaudio.py voicemeeter-config)

When to use

• User is on Windows and needs terminal / PowerShell-driven audio control.
• User wants to change the default playback/recording/communications device without clicking through Sound settings.
• User wants bit-perfect exclusive-mode output for audiophile playback, or to diagnose why an app can't grab the device in exclusive mode.
• User wants to install a virtual audio cable (VB-Cable, VoiceMeeter) to route system audio into OBS / streaming tools.
• User is debugging a shared-mode vs exclusive-mode mismatch (pops, silence, format negotiation errors).

Not for: macOS (use audio-coreaudio), Linux (use audio-pipewire).

The script exits 2 with a helpful message if run on non-Windows.

Read references/exclusive-vs-shared.md when the user asks about latency, bit-perfect playback, or IAudioClient::Initialize errors. Read references/virtual-cable.md when the user asks about OBS system-audio capture or VoiceMeeter routing.

---

Step 1 — List devices

uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py list-devices
uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py list-devices --kind playback
uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py list-devices --kind recording

Calls Get-AudioDevice -List (from the AudioDeviceCmdlets PowerShell module). If the module isn't installed the PowerShell errors out — install with:

Install-Module -Name AudioDeviceCmdlets -Scope CurrentUser

Output columns: Index, Default, Type, Name, ID.

---

Step 2 — Get current default

uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py get-default
uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py get-default --kind recording
uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py get-default --kind communications

Windows has three separate default roles:

Role	Used by
playback (eMultimedia)	Music/movie apps that request "default" device
recording (eMultimedia for capture)	Your default mic
communications (eCommunications)	Zoom / Teams / Discord for voice

---

Step 3 — Change the default

Pass the device name exactly as list-devices printed it (quote for spaces):

uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py set-default "Speakers (Realtek High Definition Audio)"
uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py set-default "Focusrite USB Audio" --kind recording
uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py set-default "Shure MV7+" --kind communications

Alternatives not wrapped here (also valid):

• nircmd setdefaultsounddevice "<Name>" — older NirCmd, smaller.
• svcl.exe /SetDefault "<Name>" Playback — NirSoft command-line version of SoundVolumeView. See references/virtual-cable.md for full svcl flags.

---

Step 4 — Mute / unmute / volume

uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py mute   "Speakers (Realtek High Definition Audio)"
uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py unmute "Speakers (Realtek High Definition Audio)"
uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py volume "Speakers (Realtek High Definition Audio)" --level 50

For per-app (not per-device) volume, use NirSoft's SoundVolumeView GUI or svcl.exe /SetAppDefault <process>.exe Playback. Per-app volume is not wrapped here because the app-vs-device distinction deserves explicit CLI args.

---

Step 5 — Probe exclusive-mode permission

Exclusive mode gives an app sole ownership of the device at a negotiated format. Bit-perfect, lowest latency, but blocks every other app.

Each endpoint has a registry flag "Allow applications to take exclusive control of this device". The wrapper reads it:

uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py exclusive-test "Speakers (Realtek High Definition Audio)"

Output:

Speakers (Realtek High Definition Audio) -> exclusive mode: allowed|blocked|unknown

allowed = apps can request exclusive mode. blocked = Windows will always return AUDCLNT_E_EXCLUSIVE_MODE_NOT_ALLOWED. The toggle lives in Sound Control Panel → Properties → Advanced.

To set that flag from script you need elevation + registry write — not wrapped here deliberately. See references/exclusive-vs-shared.md for the manual path and the audio-engine implications.

---

Step 6 — VB-Audio Virtual Cable

The go-to free virtual audio cable on Windows. Creates two endpoints (CABLE Input = a virtual speaker, CABLE Output = a virtual mic) that are internally wired. Anything played to CABLE Input is captured from CABLE Output.

uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py vbcable-install

Prints the download URL and install steps (does not auto-download). The script refuses to fetch the installer itself — VB-Audio is donationware + has paid tiers; auto-install risks violating their T&Cs.

Typical OBS system-audio pattern:

1. Install VB-Cable.
2. Set Windows default playback = VB-Cable Input. Now all system audio is routed into the cable instead of your speakers.
3. Configure OBS Audio Input Capture = VB-Cable Output.
4. To still hear system audio, also route VB-Cable Input out to your speakers via VoiceMeeter, or use "Listen to this device" on the CABLE Output properties.

---

Step 7 — VoiceMeeter

VoiceMeeter is a virtual mixer that ships its own set of virtual WDM devices (VAIO1/2/3) and acts as an ASIO host. Free for the 2-bus version, donationware for Banana (3 physical + 2 virtual) and Potato (5+3).

uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py voicemeeter-config

Prints the install URL and basic setup. Configuration is primarily GUI; the config XML lives under %APPDATA%\VB\Voicemeeter. Scriptable via the C API (VoicemeeterRemote.dll) or the unofficial Python binding pip install voicemeeter-api. See references/virtual-cable.md for a worked routing example.

---

Gotchas

• Windows has no first-party CLI to change audio devices. Everything here is third-party (AudioDeviceCmdlets, NirSoft SoundVolumeView/svcl, VB-Audio). Expect install steps.
• AudioDeviceCmdlets isn't signed by Microsoft — Install-Module from PSGallery is trust-by-repository. Users with strict execution policy may need Set-ExecutionPolicy -Scope CurrentUser RemoteSigned.
• Device names are not stable across Windows updates. A Windows update that reinstalls a Realtek driver renames endpoints from "Speakers (2- Realtek Audio)" to "Speakers (Realtek Audio)". Script around Name at your peril — prefer the immutable endpoint Id GUID from Get-AudioDevice -List.
• set-default via AudioDeviceCmdlets changes the Multimedia default; communications is a separate flag. Zoom/Discord pull from the communications endpoint by default, not the multimedia one. To change both, call set-default --kind playback then set-default --kind communications.
• Exclusive mode is gated per-endpoint, not per-app. The endpoint toggle blanket-allows or blanket-blocks. An app still has to successfully negotiate a format (bit depth + rate + channel layout) that the hardware supports in exclusive mode, or IAudioClient::Initialize returns AUDCLNT_E_UNSUPPORTED_FORMAT.
• The Windows audio engine (audiodg.exe) always resamples shared-mode streams to the endpoint's fixed "mix format". If the mix format is 48 kHz 24-bit, a 44.1 kHz 16-bit track gets resampled before it even hits the device. This is why bit-perfect listeners use exclusive mode.
• WASAPI's IAudioClient3::InitializeSharedAudioStream gives sub-3 ms latency without exclusive mode, but requires Windows 10+ and an endpoint whose audio engine period is small enough (GetSharedModeEnginePeriod). Not every driver / hardware combo supports it.
• VB-Cable is donationware + has paid A+B / C+D variants. Installing multiple variants gives you multiple cables — they don't conflict, but keep track of which one you're pointing apps at.
• VoiceMeeter + physical ASIO app conflict. Only one process can hold the ASIO driver. If your DAW has claimed the interface's ASIO driver, VoiceMeeter can't bridge to it simultaneously.
• ASIO4ALL and FlexASIO are different. ASIO4ALL wraps WDM/KS; FlexASIO wraps WASAPI. Both offer an ASIO layer to apps that only speak ASIO, but FlexASIO plays better with modern WASAPI-aware hardware.

---

Examples

Example 1 — "Swap default output to my headphones for Spotify"

uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py list-devices --kind playback
uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py set-default "Headphones (Sony WH-1000XM5 Stereo)"

Example 2 — "Make Zoom use my USB mic without affecting music apps"

uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py set-default "Microphone (USB PnP Sound Device)" --kind communications
# Multimedia default stays on your studio interface for music/games.

Example 3 — "Capture system audio into OBS"

uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py vbcable-install
# (run the printed installer; reboot)
uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py set-default "CABLE Input (VB-Audio Virtual Cable)"
# Point OBS Audio Input Capture at "CABLE Output (VB-Audio Virtual Cable)"

Example 4 — "Why does Foobar2000 say exclusive mode failed?"

uv run ${CLAUDE_SKILL_DIR}/scripts/winaudio.py exclusive-test "Speakers (Realtek High Definition Audio)"
# If output says "blocked", open Sound Control Panel -> the device -> Properties
# -> Advanced tab -> check "Allow applications to take exclusive control".
# If "allowed", the app's requested format is not supported at the hardware
# level — try 44100 Hz 16-bit to match CD, or inspect the endpoint's supported
# formats in that same Advanced tab.

Example 5 — "Script this across many machines"

# Skip the Python wrapper; call AudioDeviceCmdlets directly:
Import-Module AudioDeviceCmdlets
$d = Get-AudioDevice -List | Where-Object { $_.Name -like '*Focusrite*' -and $_.Type -eq 'Playback' }
Set-AudioDevice -Index $d.Index

The wrapper is a convenience layer; any PowerShell script targeting the same cmdlet works fine.

---

Troubleshooting

Import-Module: The specified module 'AudioDeviceCmdlets' was not loaded

Cause: Module not installed. Fix:

Install-Module -Name AudioDeviceCmdlets -Scope CurrentUser -Force

Get-AudioDevice : Running scripts is disabled on this system

Cause: Execution policy Restricted (default on Windows Server). Fix:

Set-ExecutionPolicy -Scope CurrentUser RemoteSigned

set-default succeeded but the app still plays through old device

Cause: Many apps cache the endpoint at startup and don't listen for MMDevice default-change notifications. Restart the app. Fix: Restart the app, or for Chromium-based apps use their internal "Audio output" setting in site permissions.

Exclusive-mode app gets AUDCLNT_E_UNSUPPORTED_FORMAT

Cause: Requested format isn't natively supported by the driver in exclusive mode. No resampler runs in exclusive mode. Fix: Match exactly what the Properties → Advanced tab lists as a supported format, or switch to shared mode (accepts the engine mix format via resampling).

VB-Cable installed but doesn't appear

Cause: Installer ran but driver signing was blocked; reboot skipped. Fix: Reboot. If still missing, reinstall as Administrator and approve the UAC / driver-signing prompt when it appears.

VoiceMeeter shows "Audio Engine" stopped

Cause: Sample-rate mismatch between physical A1 output and VoiceMeeter's internal engine rate. Fix: Menu → System Settings/Options → set engine rate to match the physical interface's configured sample rate.

---

Reference docs

• Shared-mode vs exclusive-mode deep dive, latency tradeoffs, IAudioClient3 → references/exclusive-vs-shared.md.
• VB-Cable tiers, svcl.exe flag reference, VoiceMeeter routing examples → references/virtual-cable.md.