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mpv/DOCS/OUTDATED-tech/swscaler_methods.txt
wm4 5368c46453 Rename DOCS/tech/ to DOCS/OUTATED-tech/
While DOCS/tech/ contains lots of documentation about mplayer's
internals, most of it seems outdated, and hasn't been touched in many
years. On the other hand, there still might be useful things in there,
but it's hard to tell which parts.

Instead of deleting all it, rename the directory to "warn" potential
developers that the documentation is completely outdated.
2012-07-28 20:44:59 +02:00

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artifact types:
---------------------------------------------------------------------
ringing
wave or noise like patterns around sharp edges
bad: sinc, lanczos (with high filter length)
acceptable: lanczos (with low filter length), cubic, spline
ok: area, (fast)blinear, gauss, point
blur
loss of detail / high frequency
bad: gauss with high variance
acceptable: (fast)bilinear, area
ok: others
aliasing (only downscale)
straight lines look like staircases
areas of high detail look worse
regular patterns turn into a funny looking mess (moire patterns)
bad: fast bilinear, point, gauss with low variance
acceptable: area
ok: others
blocky (upscale only)
looks like the image is made of rectangular blocks like a mosaic
bad: point
ok: others
recommendations: (based upon my personal opinion many ppl might disagree ...)
---------------------------------------------------------------------
the recommended scalers for upscaling:
fast_bilinear, point if speed is important
cubic, spline, lanczos if quality is important
the recommended scalers for downscaling:
fast_bilinear, point if speed is important
gauss, bilinear if quality is important
cubic, spline, lanczos if a sharper picture is important
note: when encoding at a limited amount of bits (not constant quantizer)
then a slightly blurred input might look better after decoding than a slightly
sharpened one, especially for lower bitrates
sws numbers / names / artifact types
-------------------------------------------------------------------------
r ringing
b blurry
a aliasing (downscale only)
m mosaic (blocky) (upscale only)
-sws 0 fast bilinear bA
-sws 1 bilinear b
-sws 2 bicubic high sharpness r
low sharpness b
-sws 3 experimental ????
-sws 4 nearest neighbour AM
-sws 5 area ba
-sws 6 luma bicubic / chroma bilinear r
-sws 7 gauss low sharpness B
high sharpness AM
-sws 8 sinc R
-sws 9 lanczos long filter R
short filter b
-sws 10 bicubic spline r
Notes:
area upscale is identical to bilinear