fix: disable mic AGC by default to stop Windows audio crackle

[abdu11ahbaig]

Description

Default microphone recording on Windows to the no-agc browser voice-processing profile instead of processed, so Chromium's real-time Automatic Gain Control is off by default for the built-in mic fallback path.

Motivation

Users recording with the built-in mic on Windows reported audio breaking up repeatedly with a low-pitched, garbled/unclear voice (e.g. saying "hello" comes out warbled and stuttered). Investigation traced this to Chromium's real-time AGC, which the team had already identified in prior beta testing as causing short crackle/dropout bursts on some Realtek and headset mic paths (see the existing comment in electron/ipc/recording/audioFilters.ts). A no-agc mitigation already existed in the code, but it was only reachable via a hidden environment variable (RECORDLY_BROWSER_MIC_PROFILE) that a normal downloaded build never sets — so every real user still hit the buggy processed default. Echo cancellation and noise suppression remain enabled; volume is restored after the fact via the existing offline speechnorm/alimiter filter chain instead of AGC's real-time loop.

Type of Change

• New Feature
• Bug Fix
• Refactor / Code Cleanup
• Documentation Update
• Other (please specify)

Related Issue(s)

#931

Screenshots / Video

N/A — audio-only backend behavior change, no UI change.

Testing Guide

1. On Windows, enable the built-in/onboard mic and record a screen capture while speaking.
2. Confirm the recorded mic audio no longer breaks up, warbles, or drops in pitch.
3. Run unit tests:

   npx vitest run src/hooks/useScreenRecorder.test.ts electron/ipc/recording/audioFilters.test.ts

4. Confirm echo cancellation and noise suppression still audibly work (background hum/echo still suppressed), only AGC's real-time pumping is gone.

Checklist

• I have performed a self-review of my code.

Summary by CodeRabbit

• Improvements
  • Updated the default browser microphone profile to disable automatic gain control (AGC).
  • Microphone recording now consistently uses the no-AGC profile when no valid profile is selected.

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ℹ️ Recent review info

⚙️ Run configuration

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Review profile: CHILL

Plan: Advanced

Run ID: bb74c963-c3a7-4571-83cf-ee58baf4d4aa

📥 Commits

Reviewing files that changed from the base of the PR and between 7512ef1 and fa9ddaa.

📒 Files selected for processing (3)

• electron/ipc/register/settings.ts
• src/hooks/useScreenRecorder.test.ts
• src/hooks/useScreenRecorder.ts

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📝 Walkthrough

Walkthrough

The default browser microphone profile changes from "processed" to "no-agc". Fallback normalization and microphone constraint tests now expect automatic gain control to be disabled.

Changes

Browser microphone profile

Layer / File(s)	Summary
Default profile and microphone constraints electron/ipc/register/settings.ts, src/hooks/useScreenRecorder.ts, src/hooks/useScreenRecorder.test.ts	The default and fallback profile now use "no-agc". Tests verify autoGainControl: false for default and selected microphones, plus "no-agc" normalization for unknown and null profiles.

Priority: ➖ Normal

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Bug fix

Suggested reviewers: webadderall

Merge Risk: ⚪ Minimal · up to fa9dd

The updated default and tests consistently implement the intended no-AGC behavior, with no concrete merge-blocking issue identified.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the main change: disabling microphone AGC by default to address Windows audio crackle.
Description check	✅ Passed	The description covers the change, motivation, bug-fix classification, related issue, testing guidance, and the absence of UI media. It is mostly complete; the checklist does not explicitly address ch…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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