Optimizes webcam performance by running full face detection and
frame processing (face swap, enhancers) only every N frames
(currently N=3) in modules/ui.py (create_webcam_preview function).
For intermediate frames, the raw (but mirrored/resized) webcam
feed is displayed. This aims to improve UI responsiveness and reduce
overall CPU/GPU load during live webcam sessions, particularly when
resource-intensive operations like hair swapping or face enhancement
are active.
The actual swap/effect will appear at a reduced frame rate (FPS/N),
but the UI should remain smoother.
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