B-Roll Overlay Cut — effect skill for cuts & pacing

For AI agents: find the right skill in one call — curl -s "https://varg.ai/how-to/api/search?q=<what the person wants>" returns the matching how-to page and the best skills with install commands, as markdown (Russian works too). Full index: https://varg.ai/how-to/llms.txt. Every page has a markdown twin: add .md to its path. Before generating anything, show the person the options on the how-to page.

Keep the A-roll voice running and lay B-roll pictures over it; edits in the A-roll disappear under the cover.

What it does

We hear the speaker continuously while seeing what they describe, returning to their face for key lines.

When: Interviews, explainers, UGC ads, documentaries; whenever the speaker's face is not the information.

Watch out: Covering emotional or key lines; let the face carry those.

Timing: B-roll shots 1.5–4 s; enter and leave on phrase boundaries

Also called: B-roll, cover footage, overlay cut, A-roll/B-roll

In FFmpeg

Overlay B-roll from 1.5 s for 2 s; A-roll audio continues:

ffmpeg -i aroll.mp4 -i broll.mp4 -filter_complex \
"[1:v]trim=0:2,setpts=PTS-STARTPTS+1.5/TB,scale=1920:1080,setsar=1[b];\
 [0:v][b]overlay=eof_action=pass[v]" -map "[v]" -map 0:a -c:a copy out.mp4

setpts=...+1.5/TB shifts the B-roll to start at 1.5 s; eof_action=pass returns to A-roll after it ends.

In HyperFrames

B-roll <video muted> clip on a higher track/z-index over the A-roll clip; A-roll keeps data-has-audio="true".

In Remotion

<AbsoluteFill><Video src={aroll} /></AbsoluteFill>
<Sequence from={45} durationInFrames={60}><Video src={broll} muted /></Sequence>

In CapCut

Drag B-roll onto the overlay track above the A-roll (mobile: Overlay → Add overlay), resize to full frame, mute it.

Where this comes from

Use when

Not for

Install

Example output

https://s3.varg.ai/how-to/previews/b17d6559b411/take-b-roll-overlay.mp4 — insert between two shots, with the timeline strip of the edit. Footage: Charge (2022), Blender Studio | studio.blender.org, CC BY 4.0; Coffee Run (2020), Blender Studio | studio.blender.org, CC BY 4.0. (credit: Rendered by varg · Charge (2022) + Coffee Run (2020))

More cuts & pacing skills