YouTube channel trailer: trim three clips, add music, 30 seconds

A 30-second channel trailer from existing uploads takes three trims, one music track and one Timeline render: 3 x $0.02 + $0.125 + $0.10 = $0.285. Trim your three best moments with POST /v1/video-trim, generate an instrumental bed with POST /v1/music-router/generate, and join the clips in POST /v1/timeline-1.0/render with fades between them.

Cost table

Do it

Trim with start and duration, using precision: "keyframe" for speed or exact when a cut must land on a frame. Music Router has no duration field, so ask for thirty seconds in the prompt, then set soundtrack.fade_out_seconds in the render. Put the channel name in caption cues rather than in the video. Keep the hook first: viewers decide in the first three seconds.

{
  "audio": { "mode": "silence", "duration_seconds": 30 },
  "video": [
    { "source_url": "https://media.sume.com/artifacts/a1/clip1.mp4", "start": 0, "duration": 10 },
    { "source_url": "https://media.sume.com/artifacts/a2/clip2.mp4", "start": 10, "duration": 10, "transition": { "type": "dissolve", "duration": 0.5 } },
    { "source_url": "https://media.sume.com/artifacts/a3/clip3.mp4", "start": 20, "duration": 10, "transition": { "type": "dissolve", "duration": 0.5 } }
  ],
  "soundtrack": { "url": "https://media.sume.com/artifacts/a4/bed.mp3", "gain_db": -6, "fade_out_seconds": 3 }
}

Limits

A trailer should show what the channel is; Sume cannot judge which moments are best. Generated music is a bed, not a branded jingle, and a soundtrack cannot duck under silence because ducking needs a real spine. Check the music licence terms in the docs before commercial use.