feat: FFmpeg hardware-accelerated export pipeline (NVENC/AMF/QuickSync)

[lsj5031]

Summary

This PR adds a new FFmpeg-based export path that can use hardware video encoders when available, while still falling back safely to CPU encoding.

It does not replace the existing WebCodecs/WebMuxer export flow. Instead, it introduces an additional pipeline that can be used for MP4 export in environments where FFmpeg-backed encoding is preferable.

What’s included

FFmpeg export pipeline

• Adds a new FFmpegExporter
• Streams raw RGBA frames to FFmpeg over IPC instead of writing large temporary raw video files
• Supports hardware encoder probing in this order:
  1. NVENC (NVIDIA)
  2. AMF (AMD)
  3. Quick Sync (Intel)
  4. CPU fallback (libx265 / libx264)

Encoder selection and safety

• Checks whether each encoder is actually available before using it
• Runs a lightweight startup probe before beginning the real export
• Falls through automatically if a hardware encoder is missing or unusable
• Remains safe for non-NVIDIA Windows users because CPU fallback is always available

Export metadata

• Returns encoding details back to the renderer so the UI can show which encoder/path was used
• Adds ExportEncodingInfo to describe:
  • encoder name
  • codec family
  • acceleration type
  • whether the export was hardware-accelerated

Supporting changes

• Adds
  eadCompositeRgbaFrame() to FrameRenderer so the composite canvas can be streamed into FFmpeg
• Exposes new FFmpeg IPC methods through preload.ts and �lectron-env.d.ts
• Cleans up WGC helper shutdown by replacing detached stdin thread handling + ExitProcess(0) with normal thread join + return

Why this helps

The current export pipeline already works well, but FFmpeg gives us another option that can be useful for:

• leveraging vendor-specific hardware encoders
• reducing memory/disk pressure by streaming frames directly
• giving clearer visibility into which encoding path was used
• broadening compatibility when WebCodecs support is limited or inconsistent

Notes on compatibility

This change is designed to degrade gracefully:

• If NVENC is unavailable, it tries AMF
• If AMF is unavailable, it tries Quick Sync
• If no hardware encoder works, it falls back to CPU encoding

So this should still be safe on systems without NVIDIA GPUs.

Files changed

• src/lib/exporter/ffmpegExporter.ts
• src/lib/exporter/frameRenderer.ts
• src/lib/exporter/types.ts
• src/lib/exporter/index.ts
• �lectron/ipc/handlers.ts
• �lectron/preload.ts
• �lectron/electron-env.d.ts
• �lectron/native/wgc-capture/src/main.cpp

Validation

Tested locally on Windows:

• native helper build succeeded
• TypeScript build succeeded
• Vite build succeeded
• Electron packaging succeeded

Follow-up ideas

If this direction looks good, a follow-up could wire this exporter more explicitly into the editor UI so users can choose or inspect the export path more directly.

[webadderall]

will take a look at this soon