fix(windows): capture the configured audio sink instead of the default device

[tonyctalope]

Description

On Windows, the audio_sink setting never selected the device that gets captured. WASAPI capture was always initialized against the default render endpoint.

Changes

• audio_control_t::microphone() now resolves the assigned (or configured) sink to its endpoint via a new get_sink_device() helper which handle virtual sink descriptors, device IDs, and friendly names, and checking DEVICE_STATE_ACTIVE then it opens the WASAPI loopback capture on that device directly. It falls back to the default render device when no sink is set.
• mic_wasapi_t now tracks whether capture follows the default device. When capture is pinned to an explicitly requested sink, default-device change notifications no longer trigger a capture reinit (the virtual-sink switch-back callback still runs).
• A sink that cannot be resolved now fails capture initialization with a clear error.
• set_sink() behavior (switching the Windows default to the sink at session start) is intentionally unchanged, to avoid breaking existing setups that rely on applications following the default device.

Validation

Built and tested on Windows 11 25H2 with the officially supported toolchain (MSYS2/ucrt64, -DBUILD_WERROR=ON -DCMAKE_BUILD_TYPE=RelWithDebInfo):

• Full build passes with -Werror (no new warnings).
• test_sunshine: 336 passed / 0 failed (5 skipped: mouse/HID and external-command tests, which cannot run in a non-interactive SSH session). All AudioTest.TestEncode variants (stereo, 5.1, 7.1, custom 5.1) pass against real audio hardware.
• Working properly in my sunshine environment

Note on unit tests: the changed code paths live in mic_wasapi_t / audio_control_t, which are internal to src/platform/windows/audio.cpp and require live WASAPI endpoints, so they are not reachable from the current test architecture. The existing AudioTest.TestEncode suite covers the unchanged default-device fallback path end to end.

Screenshot

Issues Fixed or Closed

• Fixes Audio Sink (explicit device ID) ignored and capture only works if the device is set as Windows default #4865

Roadmap Issues

Type of Change

• feat: New feature (non-breaking change which adds functionality)
• fix: Bug fix (non-breaking change which fixes an issue)
• docs: Documentation only changes
• style: Changes that do not affect the meaning of the code (white-space, formatting, missing semicolons, etc.)
• refactor: Code change that neither fixes a bug nor adds a feature
• perf: Code change that improves performance
• test: Adding missing tests or correcting existing tests
• build: Changes that affect the build system or external dependencies
• ci: Changes to CI configuration files and scripts
• chore: Other changes that don't modify src or test files
• revert: Reverts a previous commit
• BREAKING CHANGE: Introduces a breaking change (can be combined with any type above)

Checklist

• Code follows the style guidelines of this project
• Code has been self-reviewed
• Code has been commented, particularly in hard-to-understand areas
• Code docstring/documentation-blocks for new or existing methods/components have been added or updated
• Unit tests have been added or updated for any new or modified functionality

AI Usage

See our AI usage policy.

• None: No AI tools were used in creating this PR
• Light: AI provided minor assistance (formatting, simple suggestions)
• Moderate: AI helped with code generation or debugging specific parts
• Heavy: AI generated most or all of the code changes

🤖 Generated with Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud