Prevents soft gradients, like sky, walls, or glowing light, from breaking into steps.
Sunsets, night skies, dark interiors, scenes with a vignette or light leaks, and after heavy compression.
The Seedance 1080p original is 10-bit (yuv420p10le), so its gradients are smooth, but bands can appear when you drop it to 8-bit (yuv420p). Do color grading and brightness ramps before dropping to 8-bit, and if you see bands, apply deband and then dither with a very light grain (noise=alls=2:allf=t). If you raise crf to save file size, the bands come back. gradfun is a playback filter, so if you apply it before encoding, compression erases the dither and the bands return.
Remove banding stripes from skies and walls, then dither with very light noise before the 8-bit export: ffmpeg -i in.mp4 -vf "deband,noise=alls=2:allf=t" -c:v libx264 -crf 17 -pix_fmt yuv420p -c:a copy out.mp4. Do color changes before this step, since raising crf makes banding return.
Not verified