video-spec-sheet

Overview

Each social platform has its own combination of aspect ratio, max duration, codec, bitrate, frame rate, and caption / UI safe zones. Getting any of these wrong on the export means the platform will either reject, re-encode (quality drop), or crop your creative. This skill encodes the 2026 specs as a single table the agent extracts from per brief. Caps and safe zones move several times a year: treat every number marked 2026 as a starting point and confirm it against the platform's live spec page before a paid launch.

Instructions

Core Rules

• Always pick the platform spec before generating frames — generation must match the export aspect ratio (don't generate 16:9 then crop to 9:16 unless intentional).
• Burn captions on top of the base render, not as a sidecar. Meta feeds are watched largely muted and TikTok mostly with sound, so captions carry the message for the muted viewer and accessibility while the audio carries it for everyone else.
• Respect the safe zone — keep all critical text and faces away from where the platform's UI sits (top, bottom, right side for TikTok).
• Final encode in H.264 / yuv420p, even if the source is HEVC / 10-bit. Universal compatibility beats marginal quality.
• Audio: AAC-LC stereo, 48 kHz, 128 kbps minimum (YouTube recommends 384 kbps stereo for uploads). Mono audio reads as low-quality on most feeds.
• Loudness: master to about -14 LUFS integrated, true peak ≤ -1 dBTP. YouTube normalizes to roughly that level; TikTok and Meta don't publish a target, so -14 is a safe common master.
• AI-generated clips usually come out at 720p (Runway Gen-4 Turbo renders 1280×720 / 720×1280). Upscale picked shots before the final 1080p encode; never let the platform upscale.
• Re-encoding with ffmpeg drops any C2PA Content Credentials the generator embedded, so platform auto-labelling of AI content will not fire. Disclose manually at upload (see Disclosure and Rights).

Platform Spec Table (2026 — verify live)

Safe Zones (keep critical text, faces and logos out of these UI bands)

(Pixels at 1080×1920 or 1920×1080; scale with output resolution. Ads that carry a legal disclaimer on Meta need the bottom 40% clear.) Instagram's profile grid crops covers to 3:4, so keep the cover's subject and title inside the centre 1080×1440.

Captions / On-Screen Text Rules

• Center caption block, never bottom-aligned (bottom is platform UI).
• For 9:16: caption block sits roughly in the upper-center third (between Y=600 and Y=1200 of 1080×1920) — avoids both header and CTA bar.
• Font: bold sans (Inter Bold, Helvetica Black, SF Pro Display Bold, Montserrat Black). 80–110 pt for headline hooks at 1080×1920.
• Stroke + drop shadow: 2 px stroke, 1 px shadow, opacity 0.6 — preserves readability over any background.
• One sentence per card max. Two-sentence cards get skipped.
• Word-by-word reveal in time with VO outperforms full-sentence flat captions on TikTok / Reels.

Output Presets (ffmpeg) — copy-paste ready

# 9:16 — TikTok / Reels / Shorts / Stories
-vf "scale=1080:1920:force_original_aspect_ratio=decrease,pad=1080:1920:(ow-iw)/2:(oh-ih)/2:color=black,fps=30" \
  -c:v libx264 -profile:v high -level 4.0 -crf 21 -preset slow -pix_fmt yuv420p \
  -c:a aac -b:a 128k -ar 48000 -ac 2 \
  -movflags +faststart

# 1:1 — IG / FB feed
-vf "scale=1080:1080:force_original_aspect_ratio=decrease,pad=1080:1080:(ow-iw)/2:(oh-ih)/2:color=black,fps=30" \
  -c:v libx264 -profile:v high -crf 21 -preset slow -pix_fmt yuv420p \
  -c:a aac -b:a 128k -ar 48000 -ac 2 -movflags +faststart

# 16:9 — YouTube long-form / LinkedIn
-vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2:color=black,fps=30" \
  -c:v libx264 -profile:v high -level 4.2 -crf 19 -preset slow -pix_fmt yuv420p \
  -c:a aac -b:a 192k -ar 48000 -ac 2 -movflags +faststart

Workflow

1. Identify primary platform for the brief (TikTok / Reels / Shorts / etc.).
2. Pick aspect, length cap, fps from the table.
3. Mark safe zones when storyboarding — keep face, hook text, CTA inside the center region.
4. At export, use the matching ffmpeg preset above.
5. If publishing to multiple platforms, render the master in the largest aspect (e.g. 9:16 1080×1920 30fps) and downconvert to others — never upscale.

Decision Guide

Disclosure and Rights (2026 — verify live)

Examples

Example 1: TikTok ad export

Source: 4K 16:9 24fps generated at Veo. Target: TikTok ad.

ffmpeg -i source.mp4 \
  -vf "scale=1080:1920:force_original_aspect_ratio=decrease,pad=1080:1920:(ow-iw)/2:(oh-ih)/2:color=black,fps=30" \
  -c:v libx264 -profile:v high -level 4.0 -crf 21 -preset slow -pix_fmt yuv420p \
  -c:a aac -b:a 128k -ar 48000 -ac 2 \
  -movflags +faststart \
  tiktok-ad-9x16.mp4

Example 2: Cross-platform render plan

Brief: One ad, ship to TikTok + IG Reels + IG feed + YT Shorts + YT long-form trailer.

Checklist

• Aspect and resolution match the platform row; no platform-side upscaling.
• Length is under the 2026 cap and the cap was checked live for paid launches.
• Captions, faces and CTA sit outside every UI band of every placement the cut will run in.
• H.264 yuv420p, AAC 48 kHz stereo, +faststart, about -14 LUFS / -1 dBTP.
• AI-disclosure and music-rights rows resolved for each platform.

References

• TikTok in-feed ad specs
• TikTok ad disclaimers (AI-generated content)
• Instagram Reels ad specs and safe zones
• YouTube Shorts up to 3 minutes
• YouTube recommended upload encoding settings
• YouTube altered or synthetic content disclosure
• Meta Ads Guide