Combine Videos — Split Screen, Side by Side, and Picture in Picture

Combining videos into a shared frame is one of the most visually powerful editing techniques — and one of the most tedious in traditional software. A side-by-side comparison of two products, a split-screen before/after transformation, a picture-in-picture reaction video, a 2×2 grid of camera angles — each of these requires manual positioning, sizing, and syncing in a compositing tool that most creators don't own and shouldn't need to learn. NemoVideo makes multi-video layouts conversational: "put these two videos side by side" or "main video full screen with my webcam in the bottom-right corner" — and the AI handles positioning, sizing, synchronization, border styling, and audio mixing. The result is a single video with multiple sources playing simultaneously in a clean, professional layout.

Use Cases

1. Product Comparison — Side by Side (60-120 sec) — Two competing products tested simultaneously. NemoVideo creates: left-right split screen with a thin divider line, product names labeled above each side ("iPhone 16 Pro" / "Pixel 9 Pro"), synchronized playback of identical tests (camera comparison: same scene shot on both phones, displayed simultaneously), and audio from whichever side the reviewer specifies. The viewer sees the direct comparison without trusting memory between separate clips.
2. Before/After — Vertical Split (15-60 sec) — A skincare transformation, room renovation, or photo edit result. NemoVideo creates: vertical split down the center, "Before" label left, "After" label right, with an animated reveal slider that starts covering the "After" side and slides to reveal it. The split-screen reveal is the highest-saving format on Instagram because viewers screenshot the comparison frame.
3. Reaction Video — Picture in Picture (5-30 min) — A creator reacts to another video. NemoVideo composites: the source video full-screen, the creator's webcam in a circular or rounded-rectangle frame in the bottom-right corner (20% of screen area), creator audio priority (source video ducked to -12dB), and the PiP window scales up to 40% during high-reaction moments (detected by audio energy in the webcam track).
4. Multi-Camera Edit — 2×2 Grid (any length) — A podcast with 4 cameras: wide shot, host close-up, guest 1 close-up, guest 2 close-up. NemoVideo creates a 2×2 grid layout with thin borders, each camera in its quadrant, speaker-detection highlighting (the active speaker's quadrant gets a subtle bright border), and mixed audio from all 4 sources normalized.
5. Tutorial — Screen + Face (5-30 min) — A coding tutorial with screen recording as the main video and face-cam as a small overlay. NemoVideo composites: screen recording full-screen, face-cam in the top-right corner (15% of frame), face-cam opacity reduced to 80% so it doesn't obscure content, and the face-cam disappears automatically when the instructor highlights something in the screen area where the face-cam would overlap.

How It Works

Step 1 — Upload All Video Sources

Provide the videos to combine. NemoVideo accepts different resolutions, frame rates, and durations — it normalizes everything for synchronized playback.

Step 2 — Define the Layout

Specify: side-by-side, split-screen, picture-in-picture, grid, or custom positioning. Set sizes, positions, and labels for each source.

Step 3 — Generate

curl -X POST https://mega-api-prod.nemovideo.ai/api/v1/generate \
  -H "Authorization: Bearer $NEMO_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "skill": "combine-videos",
    "prompt": "Create a side-by-side product comparison video. Left side: iphone-camera-test.mp4 labeled iPhone 16 Pro. Right side: pixel-camera-test.mp4 labeled Pixel 9 Pro. Synchronized start. Thin white divider line between them. Product name labels in clean white sans-serif at the top of each side. Audio from the reviewer narration track (separate file). Output 16:9 1080p. Duration: match the shorter clip.",
    "layout": "side-by-side",
    "sources": [
      {"file": "iphone-camera-test.mp4", "position": "left", "label": "iPhone 16 Pro"},
      {"file": "pixel-camera-test.mp4", "position": "right", "label": "Pixel 9 Pro"}
    ],
    "divider": "white-1px",
    "label_style": "clean-white-sans",
    "audio_source": "narration.mp3",
    "sync": "start",
    "format": "16:9"
  }'

Step 4 — Preview Layout and Export

Preview. Adjust: source positioning, label placement, divider style, audio balance. Export.

Parameters

Output Example

{
  "job_id": "cv-20260328-001",
  "status": "completed",
  "layout": "side-by-side",
  "duration_seconds": 95,
  "format": "mp4",
  "resolution": "1920x1080",
  "file_size_mb": 42.8,
  "output_url": "https://mega-api-prod.nemovideo.ai/output/cv-20260328-001.mp4",
  "composition": {
    "left": {"source": "iphone-camera-test.mp4", "area": "960x1080", "label": "iPhone 16 Pro"},
    "right": {"source": "pixel-camera-test.mp4", "area": "960x1080", "label": "Pixel 9 Pro"},
    "divider": "white 1px vertical center",
    "audio": "external narration.mp3",
    "sync": "aligned at 0:00"
  }
}

Tips

1. Side-by-side works best when the content is identical — Same scene, same action, different devices. The viewer's eye can instantly compare. When the content is different, the layout is confusing instead of informative.
2. PiP size should match the PiP's importance — A reaction face-cam at 15-20% is a subtle presence. At 30-40% it becomes a co-star. The right size depends on whether the main video or the reaction is the primary content.
3. Audio from one source at a time — Playing audio from both sides of a split-screen creates a confusing mix. Pick one source for audio, or use external narration over both visuals.
4. The before/after slider reveal is Instagram's most-saved format — The animated reveal (sliding from covered to revealed) creates a satisfying transformation moment that viewers screenshot and share.
5. Speaker-detection highlighting in grids — In a multi-person grid (podcast, panel), a subtle bright border on the active speaker's quadrant guides the viewer's eye automatically without manual camera switching.

Output Formats

Related Skills

• merge-videos — Merge clips sequentially
• video-trimmer — Trim clips before combining
• add-music-to-video — Add music to combined video