fix(windows): preserve WGC duration through static frames

[meiiie]

Summary

• Repeat the previous WGC frame across static-frame gaps before writing the next frame.
• Reuse the same padding path at stop so tail-static recordings keep a continuous MP4 timeline.
• Refresh the Windows wgc-capture.exe helper manifest and staged helper binary from a temp CMake build.

Why

Refs #375. Users are reporting recordings that are shorter in the editor/export, with one signal pointing at static screen sections. WGC can stop delivering frames while the captured scene is unchanged; if the MP4 only receives sparse samples, the editor can see a shorter effective timeline. This keeps the encoded video timeline continuous without touching the broader export/NVIDIA path.

Validation

• cmake -S electron/native/wgc-capture -B %TEMP%/recordly-wgc-build-* -G "Visual Studio 17 2022" -A x64
• cmake --build %TEMP%/recordly-wgc-build-* --config Release
• npx tsc --noEmit
• npm test -- src/hooks/useScreenRecorder.test.ts src/lib/mediaTiming.test.ts
• git diff --check

Known unrelated baseline: npm test -- electron/ipc/recording/diagnostics.test.ts src/hooks/useScreenRecorder.test.ts currently has one diagnostics expectation mismatch on getCompanionAudioFallbackPaths where code returns the .system.wav sidecar but the test expects only video + mic.

Summary by CodeRabbit

• Bug Fixes

  • Improved MP4 timeline continuity during video capture by more reliably filling short frame gaps before writing new samples.
  • Prevented invalid capture settings by rejecting non-positive frame-rate values.

• Refactor

  • Encoder frame-extension logic reorganized for clearer locked handling and more robust timing.

• Chores

  • Updated Windows helper manifest metadata (checksum/timestamp) for the native capture tooling.

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between ed11c26 and 58e413f.

⛔ Files ignored due to path filters (1)

• electron/native/bin/win32-x64/wgc-capture.exe is excluded by !**/*.exe

📒 Files selected for processing (2)

• electron/native/bin/win32-x64/helpers-manifest.json
• electron/native/wgc-capture/src/mf_encoder.cpp

✅ Files skipped from review due to trivial changes (1)

• electron/native/bin/win32-x64/helpers-manifest.json

---

📝 Walkthrough

Walkthrough

Adds MFEncoder::extendLastFrameToLocked to repeat the last buffered NV12 frame across intermediate timestamps (with readiness checks and fps-based durations); writeFrame now calls this helper and returns false if extension fails. Also updates wgc-capture helper binary metadata in the Windows manifest.

Changes

Frame Extension Refactoring

Layer / File(s)	Summary
Declaration and writeFrame integration electron/native/wgc-capture/src/mf_encoder.h, electron/native/wgc-capture/src/mf_encoder.cpp	Adds private extendLastFrameToLocked(int64_t) declaration, validates positive fps in initialize, updates writeFrame to call the locked extender when a prior buffered frame exists (aborting on extension failure), and uses computed frameDurationHns when setting sample duration.
extendLastFrameToLocked implementation electron/native/wgc-capture/src/mf_encoder.cpp	Implements locked helper with encoder/writer readiness checks, computes frame duration from fps_, early-returns when target timestamp is within one frame, and writes repeated buffered NV12 frames at successive timestamps until just before the requested timestamp.
Helper binary manifest update electron/native/bin/win32-x64/helpers-manifest.json	Updates helpers.wgc-capture binarySha256, sourceFingerprint, and updatedAt fields.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• webadderallorg/Recordly#100: Modifies mf_encoder.cpp write path (adds locking around writeFrame), overlapping the same function's core logic.

Suggested labels

Checked, Slop

Poem

🐰 I nudge the timeline, frame by frame,
Filling gaps so playback's tame,
NV12 echoes soft and bright,
Timestamps march through silent night,
Hopping frames until they're right.

🚥 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%.	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 accurately describes the main change: fixing Windows WGC recording duration preservation through handling static frames. It is concise and clearly conveys the primary purpose of the changeset.
Description check	✅ Passed	The PR description includes a clear Summary section explaining the changes, a Why section providing motivation (referencing issue #375), and a Validation section with detailed testing steps. However, it does not follow the required template structure with sections like Type of Change, Related Issue(s) link, Screenshots/Video, Testing Guide, or Checklist.
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

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• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/windows-recording-duration-triage

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Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@electron/native/wgc-capture/src/mf_encoder.cpp`:
- Around line 255-256: The code computes frameDurationHns using fps_ before
validating fps_, which will divide by zero if fps_ == 0; update the logic around
the computation that sets frameDurationHns so you first check/guard fps_ (e.g.,
if (fps_ <= 0) return false;) then compute const int64_t frameDurationHns =
10000000LL / fps_; and keep the existing check for frameDurationHns <= 0 if
still needed; reference fps_ and frameDurationHns when making this change.

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Fix all unresolved CodeRabbit comments on this PR:

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Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

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Run ID: 085d32e8-5967-4c53-9ce5-4b3e427b01bc

📥 Commits

Reviewing files that changed from the base of the PR and between 5924f92 and 6227eb8.

⛔ Files ignored due to path filters (1)

• electron/native/bin/win32-x64/wgc-capture.exe is excluded by !**/*.exe

📒 Files selected for processing (3)

• electron/native/bin/win32-x64/helpers-manifest.json
• electron/native/wgc-capture/src/mf_encoder.cpp
• electron/native/wgc-capture/src/mf_encoder.h

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Review triggered.

Note: CodeRabbit is an incremental review system and does not re-review already reviewed commits. This command is applicable only when automatic reviews are paused.

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Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@electron/native/wgc-capture/src/mf_encoder.cpp`:
- Around line 255-257: The code only checks fps_ when padding frames, but
writeNv12SampleLocked() also computes frameDurationHns = 10000000LL / fps_
(risking divide-by-zero) and initialize() currently doesn't validate fps_; add
validation of fps_ in initialize() to ensure fps_ > 0 (or set a safe default)
and/or add a guard at the start of writeNv12SampleLocked() to return an error if
fps_ <= 0; update any callers (e.g., extendLastFrameToLocked()) to rely on this
invariant so frameDurationHns computation is always safe.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: c27185c9-d5ba-4904-ae6a-32f4abf5a36c

📥 Commits

Reviewing files that changed from the base of the PR and between 6227eb8 and ed11c26.

⛔ Files ignored due to path filters (1)

• electron/native/bin/win32-x64/wgc-capture.exe is excluded by !**/*.exe

📒 Files selected for processing (2)

• electron/native/bin/win32-x64/helpers-manifest.json
• electron/native/wgc-capture/src/mf_encoder.cpp

✅ Files skipped from review due to trivial changes (1)

• electron/native/bin/win32-x64/helpers-manifest.json

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