[Addin]

Summary

This branch reduces per-frame CPU/GPU work in the camera capture path and fixes capture/format issues found while profiling.

Windows / Media Foundation

• Wrap MF buffers in a single refcounted AVBufferRef with stack plane metadata instead of one Vec/Arc per plane.
• Replace the per-frame Arc<Mutex<IMFMediaBuffer>> with a direct COM-backed CameraBuffer; every consumer uses a consistent 2D/contiguous lock policy.
• Cache the D3D11 upload texture and immediate context, and use UpdateSubresource instead of creating a texture per frame.
• Upload directly into the hardware encoder's video-processor input texture, skipping the extra CopyResource; VideoProcessorBlt still performs conversion/scaling.
• Fix DirectShow/Media Foundation capture issues: shared media types across the callback worker, MTA initialization, bounded callback queues, drop counters, and NV21 to NV12 conversion.
• Restore the non-Windows CameraBuffer import gate.

macOS / VideoToolbox

• Reuse an IOSurface-backed CVPixelBufferPool for VideoToolbox output.
• Revert the camera-ffmpeg zero-copy wrapper so preview/FFmpeg consumers copy instead of holding CVPixelBuffer locks for the AVFrame lifetime.
• Fix the VideoToolbox pool attribute compile error.

Benchmarks

Added frame-copy-bench and camera-upload-bench.

1080p NV12, release, median of 3 runs:

Benchmark	Previous PR	This run
Zero-copy frame wrap	0.002 ms / ~559k fps	0.001 ms / 936k fps
Preview copy	1.015 ms / 985 fps	0.881 ms / 1,136 fps
Row copy	0.980 ms / 1,020 fps	0.878 ms / 1,139 fps
Buffer clone	0.000 ms	0.000 ms
Bytes copy	2.074 ms	1.862 ms
Cached upload	0.733 ms / 1,364 fps	0.825 ms / 1,212 fps
Uncached upload	0.956 ms / 1,046 fps	0.948 ms / 1,055 fps
Direct encoder-input upload	1.053 ms / 949 fps	0.884 ms / 1,131 fps
Cached upload + CopyResource (old two-step)	1.359 ms / 736 fps	1.205 ms / 830 fps

Direct encoder-input upload versus the old two-step path: 0.884 vs 1.205 ms/frame (~27% lower latency, ~36% higher throughput). Upload timings vary by roughly ±20% run-to-run on this host; the table uses medians, with the best cached upload at 0.700 ms and best direct upload at 0.818 ms.

Test plan

• cargo clippy --workspace --exclude cap-desktop --all-features --locked -- -D warnings (Windows/MSVC) — passed.
• cargo fmt --all --check — passed.
• CI-equivalent Windows test set: cap-project, cap-timestamp, cap-enc-ffmpeg, cap-camera-effects, cap-recording lib (687 passed), cap-rendering, cap-audio, cap-export, cap-editor, cap-render-farm, cap-camera-ffmpeg (4 passed), cap-enc-mediafoundation, cap-utils (79 passed), cap CLI record tests (13 passed), scap-targets, and WASAPI loopback.
• scripts/test-recording-reliability.py and scripts/test-capbench.py — passed (18 and 17 tests, with expected skips).
• Instant-mode DASH scenarios: 61/61 pass with CAP_EXPORT_FORCE_SOFTWARE_ENCODER=1; the local NVIDIA NVENC path fails 3 segment-count tests, which is hardware-encoder-specific and not caused by this branch.

Notes

• A full macOS build was not possible on the Windows development host. The non-Windows CameraBuffer import is now cfg(windows)-gated; macOS CI will validate the build.
• The stricter local --all-targets clippy (not the CI clippy command) still reports two pre-existing test-only lints in cap-export and cap-recording; neither is touched by this branch.

[Addin]

Superseded by CapSoftware#3359