swscaler_methods.txt

uclinux下mplayer的源码

artifact types:
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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 ...)
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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
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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