Knowledge science card

The "3 minutes to learn X" portrait knowledge video. Three principles: legible captions, steady pacing, visuals that don't compete.

Full code: examples/20-knowledge-science-card.

Structure

Time	Content
0-2s	Title "3 minutes to learn: X"
2-12s	Point 1: one sentence + image + Ken Burns
12-30s	Point 2
30-50s	Point 3
50-60s	Recap + CTA

The signature visual: caption background card

The defining look for educational portrait video is the semi-transparent black rounded caption card. cutcli does it in one CLI flag set:

cutcli captions add "$DRAFT_ID" --captions @captions.json \
  --font-size 9 --bold --text-color "#FFFFFF" \
  --bg-color "#000000" --bg-alpha 0.55 --bg-style 1 --bg-round 8 \
  --transform-y -0.6

Flag	Meaning
--bg-style 1	Enable background fill (0 = none)
--bg-color "#000000"	Background color
--bg-alpha 0.55	Alpha (0-1)
--bg-round 8	Corner radius

Auto Ken Burns on every image

Each image gets its own zoom. Build the keyframes JSON dynamically in bash:

SEGMENTS=$(cutcli images list "$DRAFT_ID" | jq -r '.[].segmentId')
KFS="["
i=0
for SEG in $SEGMENTS; do
  if [ $i -gt 0 ]; then KFS="${KFS},"; fi
  KFS="${KFS}{\"segmentId\":\"$SEG\",\"property\":\"scale_x\",\"offset\":0,\"value\":1.0},"
  KFS="${KFS}{\"segmentId\":\"$SEG\",\"property\":\"scale_x\",\"offset\":10000000,\"value\":1.15},"
  KFS="${KFS}{\"segmentId\":\"$SEG\",\"property\":\"scale_y\",\"offset\":0,\"value\":1.0},"
  KFS="${KFS}{\"segmentId\":\"$SEG\",\"property\":\"scale_y\",\"offset\":10000000,\"value\":1.15}"
  i=$((i + 1))
done
KFS="${KFS}]"
cutcli keyframes add "$DRAFT_ID" --keyframes "$KFS"

Adding voice-over

Knowledge videos almost always have a real voice-over or AI TTS:

cutcli audios add "$DRAFT_ID" --audio-infos '[
  {"audioUrl":"https://your-cdn/bgm.mp3","duration":60000000,"start":0,"end":60000000,"volume":0.25},
  {"audioUrl":"https://your-cdn/narration.mp3","duration":60000000,"start":0,"end":60000000,"volume":1.0}
]'

BGM down to 0.25 so the narration owns the mix.

Full code

examples/20-knowledge-science-card