subsampling.md

{
degradation {
  type = "subsampling"
  down = ["box", "nearest", "linear",  "lagrange", "cubic_catrom", "cubic_mitchell", "cubic_bspline",
    "lanczos", "gauss"]
  up = ["box",  "linear", "nearest", "lagrange", "cubic_catrom", "cubic_mitchell", "cubic_bspline",
    "lanczos", "gauss"]
  sampling = ["4:4:4", "4:2:2", "4:2:1", "4:1:1", "4:2:0", "4:1:0", "3:1:1"]
  yuv = ["601","709","2020"]
  blur = [0.0,4]
  probability = 0.5
}

Basic Parameters

• down* - Downscaling algorithms for color channels

  • Default: ["nearest"]
  • Options:
    • "nearest": Fast but blocky
    • "bilinear": Smooth but can blur
    • "bicubic": Best quality but slower
  • One algorithm randomly selected per image

• up* - Upscaling algorithms for color channels

  • Default: ["nearest"]
  • Same options as down
  • Different up/down combinations create unique artifacts

Color Settings

• sampling* - Chroma subsampling formats

  • Default: ["4:4:4"]
  • Options:
    • "4:4:4": No subsampling (full quality)
    • "4:2:2": Half horizontal chroma resolution
    • "4:2:0": Quarter chroma resolution
    • "4:1:1": Quarter horizontal chroma resolution
  • Lower ratios = more color artifacts

• yuv* - YUV color space standard

  • Default: ["601"]
  • Options:
    • "601": Standard for SD content (BT.601)
    • "709": Standard for HD content (BT.709)
    • "2020": Standard for UHD content (BT.2020)
  • Affects color conversion accuracy

Enhancement

• blur* - Optional blur kernel size

  • Format: [min, max]
  • Default: None (no blur)
  • Must be odd numbers
  • Larger values create more blur
  • Helps reduce subsampling artifacts

• probability* - Chance of applying effect

  • Default: 1.0
  • Range: 0.0 to 1.0