4K 3840x2160 for YouTube: Sume Timeline output stops at 2160 per edge

No: Sume Timeline cannot render 3840x2160. Its docs limit output.width and output.height to even integers from 256 to 2160, so 3840 wide is out of range, and 1920x1080 is the practical 16:9 choice (a 2160 wide 16:9 frame would be 1215 tall, which is odd, and edges must be even). YouTube's encoding page (read 2026-10-08) lists 35 to 45 Mbps for 4K SDR, so a 4K upload is a normal thing to ask about. This post says what Sume does instead.

The two sets of numbers

YouTube's page lists bitrates by resolution. Sume's docs list the output range. Where the two meet, the table shows what is possible.

What to do for a 4K delivery

If the video must be 4K, Timeline is the wrong step for the final file. A 4K clip you already have can go to YouTube as it is. Sume's video trim, with precision keyframe, stream-copies without re-encoding, so it can cut a 4K source without changing its size; the docs allow a source of up to 1800 seconds. Its output block, which re-sizes, needs exact precision and is limited to 256 to 2160 per edge, so do not send one. Keep in mind that the video filter, trim and inspect routes read a media.sume.com copy, so import the file first.

If a 1080p result is enough, render 1920x1080 on Timeline at $0.10 per ceil minute. The Shorts page caps resolution at 1080p anyway, so a Short never needs more.

A related crop recipe

The 4K case where a vertical strip is cut from a landscape frame, with the 2160 edge in play, is worked in this post. For the default Short size, see the 1080x1920 post.

A short checklist

Before you decide, check which step actually needs the pixels. If you only trim, caption or crop for a platform that caps at 1080p, there is no need for 4K. If you must deliver a 4K master, plan the Sume steps around it.

The Timeline docs also say a request outside the range is refused, and plan runs a free compile check, so you can confirm the refusal without a charge.

• Shorts: 1080p is the cap on YouTube's page, so render at 1080x1920.
• Long-form 1080p: 1920x1080 at $0.10 per ceil minute.
• True 4K delivery: keep the original file and use keyframe trim only if a cut is needed.
• Always run POST /v1/timeline-1.0/plan before a paid render.

What the refusal looks like

The Timeline docs list the 256 to 2160 range for output.width and output.height and the other stable refusal codes, and the plan route runs the compile checks without a charge. A request with output.width 3840 should be caught there before any render is paid for, so test the body with plan if you are unsure.