Reviewed answer
Why do video encoders often prefer even pixel dimensions?
Many video pipelines use chroma-subsampled pixel formats that group colour information across more than one pixel. Even width and height values avoid partial chroma blocks and compatibility errors in common encoding workflows.
Claims reviewed 2026-10-16.
The exact restriction depends on the pixel format, codec, encoder, and filter chain. Even dimensions are a safe default, not a universal rule for every format.
If proportional scaling produces an odd height, rounding to the nearest even value changes the ratio only slightly and is usually preferable to an encoder failure.