broll-composite

Applies the cutaways chosen by broll-pick. For each pick [t0,t1] the whole 1080×1920 frame is replaced by the B-roll (hard cut, no transition). The 16:9 source is scaled to COVER and SUBJECT-cropped to 1080×1920 — full-bleed, never letterboxed (same philosophy as fill-vertical). The crop offset on the slack axis follows the cutaway's subject (a face if present, else a person, else the thresholded multi-frame saliency mass), so the subject reads centered instead of sliced off to one side. The podcast audio stays continuous for the whole clip; B-roll audio is dropped. No transition SFX by default — audio stays pure stream-copy. BROLL_SFX=1 re-enables a 0.3s synthesized whoosh (make_whoosh.py, ~-15dBFS under speech) that sweeps up into each cutaway and down out of it. Runs BEFORE burn-subtitles so karaoke captions render on top of the cutaways.

Invoke

.claude/skills/broll-composite/broll-composite.sh <in_clip.mp4> <broll_plan.json> <out.mp4>

• in_clip: the vertical 1080×1920 clip (from fill-vertical)
• broll_plan.json: from broll-pick
• out: composited clip

Behavior

• Zero picks, or every clip_path missing → copy-passthrough, exit 0.
• A pick whose clip_path no longer exists is skipped; remaining picks apply.
• ffmpeg failure → falls back to passthrough (never blocks the pipeline).

Idempotency

Caches on in_clip+plan mtimes + BROLL_SFX via <out>.compmeta.

Notes

• Subject-cover crop reuses fill-vertical's framing engine (build_filter.py imports fill_vertical for face/pose detection): per cutaway it samples 5 frames and picks the slack-axis offset face -> person -> thresholded multi-frame saliency. Still COVER (no extra punch-in) — only WHERE the crop sits changes. Degrades to a centered crop when MediaPipe/cv2 are unavailable.
• Whole video is re-encoded (overlay can't partial stream-copy); audio is amix'd with the whoosh bed to AAC 192k (or -c:a copy when BROLL_SFX=0 / no picks). Uses _lib/encode.sh (VideoToolbox/x264) + thread caps.