Even Dimensions Only: width not divisible by 2
When the error reads width not divisible by 2, the first instinct is a broken file. The file is fine — the size you asked for is odd, and odd sizes do not exist in the video-encoding world.
Why encoders demand even numbers
Mainstream codecs (H.264/HEVC) work in YUV 4:2:0: chroma is stored at half the luma resolution, and the encoder processes the picture in 2×2 macroblocks — a 2×2 luma block maps to a 1×1 chroma block, and both sides must be whole. An odd width or height leaves a final row or column of chroma without a complete block, and the encoder refuses outright.
So this is not tool pedantry but a hard constraint of the format. Sizes like 853×480 or 1081×607 fail in every strict encoder.
How odd sizes get created
The classic is hand-calculated ratios: scale 16:9 down to 853×480 and 853 is odd — the ratio is right, the size is illegal. Second, 90-degree rotation: 1920×1080 becomes 1080×1920 safely, but a size with one odd side swaps its oddness to the other axis and fails there. Third, pixel-based cropping: trimming 27 pixels off each edge turns an even width odd.
Odd sources exist too — some capture tools and older devices produce 1367×768 natively, and such files sit on the line the moment they are re-encoded.
The fix: scale or crop to even
The fix is never complicated. If the size should change, use a resize tool with an even target height (480/720/1080) — width is computed proportionally and rounded to even automatically, the recommended path. If the resolution must stay, crop off the extra pixel (1921 to 1920): one column lost, invisible to the eye.
Odd on both axes means one pixel off each. Never try to tweak the error away — an odd size fails every re-encode, and the error will come back verbatim.
Prevention: let tools round
Prevention is one habit: when a size must be exact, confirm it is even before encoding; when in doubt, use a tool that auto-rounds and let it handle parity. Batches especially — one odd-sized source in forty files stalls the whole job, and rounding up front is cheaper than firefighting mid-run.
A side benefit: some platform transcoders handle odd sizes by silently stretching the picture — a subtle distortion nobody notices at first glance. Even dimensions are also distortion insurance.