Mux 12-hour asset limit vs Sume's 1,800-second Timeline render cap

Short answer

Mux's page says the maximum duration for any single asset is 12 hours. Sume Timeline 1.0 accepts audio.duration_seconds from 1 to 1,800, so one render tops out at 30 minutes, billed at $0.10 per rounded-up output minute ($3.00 at the cap). For a two-hour webinar you cannot render the whole thing in one Timeline job; you render parts and play or stitch them downstream.

This comparison matters for hosting, not for rendering: the hosting limit is generous, and the render limit is what shapes your workflow.

Numbers side by side

The table gives the cap each tool documents and the number of Sume renders a given length needs.

Where the 30-minute cap shows up

Besides Timeline, Sume's Video Inspect also takes a source up to 1,800 seconds, with 24 stills per call. If you want to review a long recording, you inspect it in windows; for a 2-hour file you would need to cut it to 30-minute pieces first.

Timeline's other limits are separate: up to 200 video slots, up to 20 audio.parts slices, and a render.strategy that chunks automatically past 12 segments. A long program will usually hit the 30-minute cap before it hits the 200-slot cap, unless the slots are very short (the minimum slot is 0.2 seconds).

• Plan each part with POST /v1/timeline-1.0/plan; it is unbilled and returns billable_minutes and estimated_cost_usd_micros.
• Name parts in order and join them as chapters or an ordered playlist in your player.
• Keep each part's idempotency key distinct so a retry does not double-bill.

What to do about chapters

A 30-minute part is a natural chapter length. Rather than fighting the cap, design the program as a series of 20 to 30 minute chapters with a clear title card, and let the host or player present them as one list. That also keeps each render cheap to redo if one chapter changes: re-rendering one 30-minute chapter costs $3.00, not the cost of the whole program.

Total cost is straightforward arithmetic. Two hours is 120 output minutes, $12.00 at the public rate, and each chapter bills independently.

Related reading

See the 30-minute render cost for the budget view, and the TikTok length post for a platform that is far stricter than Mux.

Designing around the cap

Treat the 30-minute cap as a chapter size. Write the script or run of show in chapters from the start, give each chapter its own title and its own timeline, and keep a manifest listing chapter order, source clips and the idempotency key used for each render. When one chapter changes, only that chapter re-renders.

On the hosting side, you can upload each chapter as its own asset or join them into one long asset before upload; Mux's page lists 12 hours as the single-asset limit, so a joined two-hour program is within range. Joining is a separate step that Timeline does not do across renders, so plan the tool for it. The point of this post is to keep the two limits straight: hosting allows far more than a single render does.