[EtienneLescot]

Summary

Two holes in the native Windows webcam setup added by d93a2b1af (shipped in v2.0.0):

• Mode choice ranked pixels before frame rate. A Logitech C920 exposes YUY2 2304x1536 at 2 fps and 1920x1080 at 5 fps, so the default 2160p preset drove it at 2 fps (1080p: 5 fps). chooseWebcamFormat now takes the highest rate up to the target first, then the most pixels. The C920 lands on 800x448@30. Cameras that already reach 30 fps at their best size (BRIO, StreamCam) pick the same mode as before.
• NV12 output had no fallback. MF_SOURCE_READER_ENABLE_VIDEO_PROCESSING only documents "Conversion from YUV to RGB-32", so a reader turning NV12 down for a YUY2/MJPEG source is within contract, and that ended in webcam-unavailable. NV12 is still tried first; RGB32 is the fallback (the webcam encoder takes BGRA too), and deliversNv12() reports what the reader accepted.

Related issue

Refs #1112 (the reporter has not confirmed their camera model yet)

Type of change

• Bug fix

Release impact

• Patch

Desktop impact

• Windows

Testing

• webcam_format_test gains a C920 case. Against the old chooseWebcamFormat it fails: expected 800x448@30, got 2304x1536@2 (2160p) and got 1920x1080@5 (1080p). With the fix, all assertions pass.
• Full helper built locally with MSVC (CMake + Ninja), all targets link.
• Probe on a real Logitech StreamCam, configuration only (no frames read): same mode chosen before and after. On Windows 11 26200 the reader accepted NV12 from YUY2 and from MJPEG even with simple processing, so the fallback could not be triggered here.
• Not run: a real take with a C920 or with a reader that refuses NV12.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Improved webcam mode selection to prioritize frame rates that meet the target, helping avoid larger but slower modes.
  • Improved capture setup to try alternate output formats and relax resolution constraints when the requested mode isn’t supported.

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ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: defaults
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📥 Commits

Reviewing files that changed from the base of the PR and between 8c063c7 and bf4101b.

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📒 Files selected for processing (1)

• electron/native/wgc-capture/src/webcam_capture.cpp

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📝 Walkthrough

Walkthrough

Webcam mode selection now ranks eligible modes by useful frame rate before pixel count. Output configuration tries media subtypes at the selected dimensions and rate, retries without size or rate constraints, and falls back from NV12 to RGB32. New C920 tests cover 2160p and 1080p targets.

Changes

Webcam Capture

Layer / File(s)	Summary
Mode ranking and regression coverage electron/native/wgc-capture/src/webcam_format.cpp, electron/native/wgc-capture/src/webcam_format.h, electron/native/wgc-capture/src/webcam_format_test.cpp	Mode selection compares useful frame rates before pixel counts. The comments describe the ranking and fallback. C920 tests expect 800×448 at 30 fps for 2160p and 1080p targets.
Output media-type requests electron/native/wgc-capture/src/webcam_capture.cpp	Output configuration tries each applicable subtype at the selected dimensions and rate, or the requested rate when the selected mode has no rate. If that request fails, it retries without size or rate constraints. When NV12 is preferred, it tries RGB32 if NV12 fails. Configuration returns false if RGB32 also fails.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

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Merge Risk: ⚪ Minimal · up to bf410

The webcam mode and output-format paths are consistent in the inspected source. The NV12-rejection fallback was not runtime-tested, but no concrete merge-blocking issue is established.

Pre-merge checks | 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check		The title clearly and concisely describes the primary webcam mode-selection change: prioritizing frame rate before size.
Description check		The description is complete and relevant. It covers both bug fixes, related issue, change type, release impact, platform impact, and detailed testing. The screenshots section is not needed because thi…
Docstring Coverage		Docstring coverage is 83.33% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 6 functions across 4 files.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at @electron/native/wgc-capture/src/webcam_capture.cpp:
- Line 442: Update the sized output request’s frame-rate attribute in the nearby
`MFSetAttributeRatio` call to use `chosen.fps` when it is positive, falling back
to `requestedFps` otherwise.

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• Configuration used: defaults
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• Run ID: a0fea683-cd09-42d3-ad8c-2c46be6d8598

📥 Commits

Reviewing files that changed from the base of the PR and between 7e25586 and 8c063c7.

📒 Files selected for processing (4)

• electron/native/wgc-capture/src/webcam_capture.cpp
• electron/native/wgc-capture/src/webcam_format.cpp
• electron/native/wgc-capture/src/webcam_format.h
• electron/native/wgc-capture/src/webcam_format_test.cpp

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