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swscaler methods
Guest on 9th February 2023 02:14:27 PM


  1.  
  2. artifact types:
  3. ---------------------------------------------------------------------
  4. ringing
  5.         wave or noise like patterns around sharp edges
  6.         bad: sinc, lanczos (with high filter length)
  7.         acceptable: lanczos (with low filter length), cubic, spline
  8.         ok: area, (fast)blinear, gauss, point
  9.  
  10. blur
  11.         loss of detail / high frequency
  12.         bad: gauss with high variance
  13.         acceptable: (fast)bilinear, area
  14.         ok: others
  15.  
  16. aliasing (only downscale)
  17.         straight lines look like staircases
  18.         areas of high detail look worse
  19.         regular patterns turn into a funny looking mess (moire patterns)
  20.         bad: fast bilinear, point, gauss with low variance
  21.         acceptable: area
  22.         ok: others
  23.  
  24. blocky (upscale only)
  25.         looks like the image is made of rectangular blocks like a mosaic
  26.         bad: point
  27.         ok: others
  28.  
  29. recommendations: (based upon my personal opinion many ppl might disagree ...)
  30. ---------------------------------------------------------------------
  31.  
  32. the recommended scalers for upscaling:
  33. fast_bilinear, point if speed is important
  34. cubic, spline, lanczos if quality is important
  35.  
  36. the recommended scalers for downscaling:
  37. fast_bilinear, point if speed is important
  38. gauss, bilinear if quality is important
  39. cubic, spline, lanczos if a sharper picture is important
  40.  
  41. note: when encoding at a limited amount of bits (not constant quantizer)
  42. then a slightly blurred input might look better after decoding than a slightly
  43. sharpened one, especially for lower bitrates
  44.  
  45. sws numbers / names / artifact types
  46. -------------------------------------------------------------------------
  47. r ringing
  48. b blurry
  49. a aliasing (downscale only)
  50. m mosaic (blocky) (upscale only)
  51.  
  52. -sws 0  fast bilinear                   bA
  53. -sws 1  bilinear                        b
  54. -sws 2  bicubic high sharpness          r
  55.                 low sharpness           b
  56. -sws 3  experimental                    ????
  57. -sws 4  nearest neighbour               AM
  58. -sws 5  area                            ba
  59. -sws 6  luma bicubic / chroma bilinear  r
  60. -sws 7  gauss   low sharpness           B
  61.                 high sharpness          AM
  62. -sws 8  sinc                            R
  63. -sws 9  lanczos long filter             R
  64.                 short filter            b
  65. -sws 10 bicubic spline                  r
  66.  
  67. Notes:
  68.         area upscale is identical to bilinear
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