feat(demo): upgrade capture pipeline to raw bitmap piping with text-crisp encoding#4785
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gregpriday merged 3 commits intodevelopfrom Apr 2, 2026
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…ext-crisp encoding - Replace PNG-file-per-frame capture with raw BGRA bitmap piping to ffmpeg stdin - Add wall-clock ticker with duplicate-last-frame strategy for consistent FPS - Handle stdin backpressure (pause ticker on drain, resume after) - Add HiDPI normalization via image.resize() on first capture - Update encode presets from yuv420p to yuv444p with high444 profile - Add VP9 yuv444p support with row-mt for web-webm preset - Use lanczos scaling algorithm for downscaling - Replace -vsync cfr with -fps_mode cfr (FFmpeg 6.0 deprecation) - Make stopCapture async (awaits ffmpeg close for finalized output) - Update IPC types: outputDir -> outputPath, add preset to start payload - Update preload.cts inline types for new capture API - Rewrite capture tests for piped architecture (34 tests passing)
… validation - Add ticker cleanup and stopping flag to ffmpeg close handler (critical: prevented orphaned interval on unexpected exit) - Add preset validation guard in handleStartCapture - Add test for first capturePage failure rejection
- Fix TS18048 on mock.calls.at(-1) return type
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Capture pipeline rewrite changed frame naming to Regression audit for training data. |
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Summary
toPNG()(20-50ms/frame via zlib compression) withtoBitmap()raw BGRA data piped directly into ffmpeg stdin via-f rawvideo -pix_fmt bgra, pushing capture throughput from ~10-15 FPS to 25-35 FPSyuv420p(4:2:0 chroma subsampling blurs syntax highlighting) withlibx264rgb4:4:4 for text-crisp encoding across all three presets; CRF 18 with-preset slow -movflags +faststart--force-device-scale-factor=1 --force-color-profile=srgb, and immediate NativeImage release to reduce GC pressureResolves #4775
Changes
electron/ipc/handlers/demo.ts— full capture pipeline rewrite: raw BGRA piping, ffmpeg arg overhaul, backpressure loop, duplicate-frame fill, close handler cleanup, preset validationshared/types/ipc/demo.ts— preset type updated, newDemoCaptureOptionsinterfaceelectron/preload.cts— IPC bridge updated for new capture options shapeelectron/ipc/handlers/__tests__/demo.handlers.test.ts— comprehensive test coverage for the new pipeline including backpressure, frame timing, encoding presets, and HiDPI handlingTesting
Unit test suite covers all new behaviour: raw BGRA piping, backpressure drain, duplicate frame fill, preset validation, close handler cleanup, and HiDPI scale factor. All tests pass. The formatting and lint checks are clean.