Why Media Encoder Will Not Use All of the CPU

A four-minute 1080 timeline that takes hours, while the CPU and the memory sit half idle, is not a setting you flip to “use 100 percent.” Media Encoder is waiting on an effect that cannot be split across every core. Forcing the machine to look busy does not make that effect faster.

The slow part is the effect

Remove Grain is the effect to suspect first. It looks at each frame in a way that does not spread cleanly across a many-core CPU, and people routinely see it turn a short render into an overnight one. Take it off and export again. If the time collapses, you have the answer. Unsharp Mask, curves, and a color correction are cheap next to it. The encoder itself, writing the YouTube file, is the fast part at the end.

Memory stays low because frames move through and out. Encoding is a stream. It does not build a giant picture of the whole movie in RAM. A tool that filled 64 GB on this job would not finish sooner.

Do the slow effect once

Render the grain reduction on its own, to a ProRes or other intermediate file, and build the rest of the grade on that file. You pay for Remove Grain one time. Every export after that is a normal encode, and the CPU can stay busy because the work left is work that parallelizes. A GPU helps only the effects that are built for it. Remove Grain is not one you should expect to saturate a card.

A finished film is not rendered as one After Effects comp of the whole feature with grain reduction on every shot. Shots are rendered, then conformed. The long encode you are looking at is that workflow skipped.