Homepage Video Assets

Documents

homepage-video-assets

Homepage Video Assets is an Agent Skill for documents published in the remotion-dev/remotion repository on GitHub: a SKILL.md instruction file an AI agent can load to do this task.

Use when rendering or replacing Remotion homepage creator strip videos, especially transparent Chrome WebM and Safari MP4 assets copied into both promo-pages and docs.

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How to use this skill

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Prompt to paste

Inspect the Agent Skill at https://github.com/remotion-dev/remotion/blob/HEAD/.agents/skills/homepage-video-assets/SKILL.md and all supporting files. Report provenance, permissions, scripts, dependencies, and security risks. Propose an exact installation into .agents/skills/homepage-video-assets, but wait for my approval before writing files or running scripts.

Copying this prompt does not install or run the skill. Review third-party files before use.

Homepage Video Assets

Use this workflow for homepage creator strip assets such as:

homepage-assets-master
editing-vp9-chrome / editing-safari
what-is-remotion

Workflow

Render a fresh transparent ProRes 4444 master from packages/brand.

cd packages/brand
bunx remotion render <composition-id> /tmp/<asset>-master.mov \
  --codec=prores \
  --prores-profile=4444 \
  --pixel-format=yuva444p10le \
  --image-format=png \
  --timeout=120000 \
  --overwrite

Convert from the ProRes master, not from a previous WebM/MOV.

Chrome WebM:

ffmpeg -y -i /tmp/<asset>-master.mov \
  -vf scale=540:540 \
  -c:v libvpx \
  -pix_fmt yuva420p \
  -auto-alt-ref 0 \
  -an /tmp/<chrome-name>.webm

Safari MP4:

ffmpeg -y -i /tmp/<asset>-master.mov \
  -vf scale=540:540 \
  -c:v prores_ks \
  -profile:v 4 \
  -pix_fmt yuva444p10le \
  -an /tmp/<asset>-540-prores.mov

avconvert \
  --source /tmp/<asset>-540-prores.mov \
  --preset PresetHEVCHighestQualityWithAlpha \
  --output /tmp/<safari-name>.mp4 \
  --replace

Copy both outputs into both app folders:

cp /tmp/<chrome-name>.webm ../promo-pages/public/img/<chrome-name>.webm
cp /tmp/<safari-name>.mp4 ../promo-pages/public/img/<safari-name>.mp4
cp /tmp/<chrome-name>.webm ../docs/static/img/<chrome-name>.webm
cp /tmp/<safari-name>.mp4 ../docs/static/img/<safari-name>.mp4

Verification

Verify the ProRes master has real alpha before converting, and verify the Safari MP4 exists in both folders:

ffmpeg -i /tmp/<asset>-master.mov
ffmpeg -i ../promo-pages/public/img/<safari-name>.mp4
ffmpeg -y -i /tmp/<asset>-master.mov \
  -vf alphaextract -frames:v 1 /tmp/<asset>-alpha.png

The master should report prores (4444) and a yuva... pixel format. alphaextract should succeed, and the alpha image should not be fully opaque. A common failure mode is alphaextract succeeding but every sampled pixel is opaque; in that case, the master was rendered with a black/opaque background or a stale opaque master was reused.

Verify every copied Chrome WebM and Safari MP4 is exactly 540x540:

for f in \
  ../promo-pages/public/img/<chrome-name>.webm \
  ../promo-pages/public/img/<safari-name>.mp4 \
  ../docs/static/img/<chrome-name>.webm \
  ../docs/static/img/<safari-name>.mp4; do
  ffmpeg -i "$f"
done

The Safari MP4 should look like the known-good file shape: major_brand: mp42, compatible_brands: isommp41mp42, Video: hevc (Main) (hvc1), 540x540, and handler_name: Core Media Video. If it reports h264 (avc1) or dimensions such as 960x540, it is the wrong file and will render differently in Safari.

Do not add ProRes .mov files to the homepage PR; they are too large. Safari should use the small .mp4 fallback. Chrome should use the transparent .webm.