Weekly video series on Sume: Format run, captions, trim, timeline cost

A weekly series is one Format run plus three finishing steps with published flat prices: a trim at $0.02, standalone captions at $0.20 for a clip up to 60 seconds, and a timeline render at $0.10 per started minute. Only the generation inside the Format run varies, so that is the only step that needs a spend cap.

The chain

Each step takes the previous step's media.sume.com URL. The Format run returns primary_output_url and artifacts[]. Trim cuts a range out of one clip and returns a new MP4. Captions burn text onto a public video URL. Timeline joins clips on an audio spine and returns one MP4.

None of these three finishing steps calls a generation model. Trim and timeline run ffmpeg on the worker media runtime, so their price is fixed in advance and does not move with the clip.

The arithmetic for one 30-second episode

Take one trim, one caption job and one timeline render. The timeline reserve is ceil(audio.duration_seconds / 60) minutes, so a 30-second episode reserves one minute. That is $0.02 + $0.20 + $0.10 = $0.32 of finishing, before the Format run itself.

The Format run is billed against the cap you set. Read usage.billable_amount_usd_micros on the terminal receipt to see what it spent. Add that to the $0.32 to get the cost of the episode.

Keep the chain repeatable

Every write in the chain needs an Idempotency-Key. Derive each one from the episode and the step, for example ep-14-trim and ep-14-captions. A retry of a step replays the original job and does not charge again.

The finishing steps read only this workspace's media.sume.com URLs (captions is the exception and takes a public HTTPS video URL). That is why the Format's output URL feeds them directly.

• Check a timeline before you pay with POST /v1/timeline-1.0/plan. It is unbilled and returns billable_minutes and estimated_cost_usd_micros.
• Check a dim or crop with POST /v1/video-filter/check. It is free.
• Poll each job at GET /v1/jobs/:id/status, then read GET /v1/jobs/:id/result.

When a new model launches mid-series

Only the first step changes. Fork the Format, point its recipe at the new model, and run one episode with a low cap. The trim, captions and timeline calls stay as they are, because they work on any MP4 that lives on the Sume media host.

That is the reason to put the finishing steps outside the Format: the part that changes with every model launch stays small, and the part that must stay stable does.