Video banding: where the banding in gradient skies comes from
After a compress, the sky shows stair-step bands and smoke turns into concentric rings — that is banding. It is not corruption but the physical result of quantized color, amplified further when bitrate runs short.
The cause: quantization steps
Consumer video carries 8 bits per channel — 256 levels: a sky gradient from deep to pale blue has only a couple hundred usable brightness steps. Gradients are exactly where brightness changes slowly and continuously, so the steps become visible as layers. 10-bit offers 1,024 levels, four times finer — one of the core reasons professional pipelines use it.
Encoding compounds it: compression works in blocks, and smooth gradients are precisely where the encoder "saves" — at low bitrates neighboring blocks quantize at different coarseness, amplifying the steps. Large-area gradients (skies, smoke, underwater scenes, night light halos) expose it first.
Prevention during transcode
The first lever is bitrate: content rich in large gradients (aerial skies, stage smoke, sunrise timelapses) should get a bitrate bump — detail-heavy footage is actually less sensitive (noise masks quantization), while flat gradients are the banding hotspot. The second lever is honest resolution: upscaling a low-res source to 1080p invites blocking and banding together.
The post-transcode check is specific: find the largest gradient in frame (usually the sky) and scan for steps. Aerials, timelapses, and stage footage must get the sky check — banding appears there first and viewers notice it first.
Can existing banding be saved?
Honestly: hardly. Banding is information discarded at quantization time and already encoded into the data; browser tools ship no dedicated debanding filter, and re-dithering requires deep pipeline work. The practical mitigation is one re-encode at higher bitrate: more gradient detail survives and steps soften slightly, but broken steps do not rejoin.
Prevention at the source beats every repair: shoot and export in 10-bit when the device supports it, give transcodes enough bitrate, and never re-compress generations — every extra generation adds steps to the gradient. Make gradient areas a fixed item in your quality checklist.