Think of the workload as several multipliers stacked together rather than one “HEVC penalty.”

First, 4K already contains four times as many pixels as 1080p. Second, higher frame rates increase the number of frames that must be decoded each second. Third, 10-bit processing moves more precision through parts of the pipeline and may require a different hardware decode profile. Fourth, HEVC long-GOP prediction means random access can require reference-frame reconstruction. Then the editor may also be doing color conversion, scaling, scopes and effects.

The most important check is hardware support for the exact stream. A GPU can accelerate 8-bit HEVC Main profile but have limited or no acceleration for a different 10-bit/chroma combination. In that case the application falls back to CPU decoding and the performance difference can be dramatic.

Use a media-inspection tool to identify codec, profile, bit depth, chroma subsampling, resolution and frame rate, then compare those values with the GPU's decode capabilities.

The color pipeline can add a second layer of cost that is easy to blame on the codec.

If the 10-bit file is Log or HDR, the editor may need to apply a transfer-function conversion, tone mapping, LUT, color-space transform or higher-precision processing before you see the preview. Add scopes and several corrections and the GPU can become the bottleneck even if decode itself is fine.

A clean diagnostic is to test in stages: first play the untouched clip with effects disabled; then enable color management or LUTs; then add the rest of the grade. If raw playback is smooth but the graded timeline is not, changing the capture codec will not solve the real issue.

The opposite is also useful: if a low-resolution proxy is perfectly smooth with the same effects, source decode/resolution is probably a major part of the bottleneck.

Storage can be the hidden bottleneck too, especially with several streams.

One HEVC file may have a lower bitrate than H.264, but multicam editing means reading and decoding multiple streams at once. If the media is on a slow external drive, SD card, network share or cloud-synced folder, the editor is solving both I/O and decode problems while you scrub.

For diagnosis I would copy one problematic clip to a local SSD, create a simple empty project at the correct frame rate, turn off background sync, and test it with no effects. If it is still slow, inspect decode acceleration. If it becomes smooth, reintroduce the real project components one at a time.

That method is much more informative than immediately buying a faster CPU.

From the VSDC side, this is exactly the kind of source where the hardware decoder and proxy workflow should be tested before changing the masters. A proxy reduces the cost of repeatedly decoding and scaling the full-resolution source during editing, while the final render can still use the original 10-bit/HEVC footage.

Also avoid the simplistic claim that HEVC decoding is universally “twice as hard.” Codec complexity studies are more nuanced than that, and real editing load includes resolution, profile, bit depth, effects and hardware support.

For a quick conceptual overview, the comparison article H.264 vs H.265/HEVC separates compression efficiency from editing workload. That distinction helps because a smaller HEVC file can still produce a heavier timeline.