[SCM] libav/experimental: cubic filter instead of truncated sinc looks much better for upscaling & scaling where src and dst size are quite similar
siretart at users.alioth.debian.org
siretart at users.alioth.debian.org
Sun Jun 30 15:40:36 UTC 2013
The following commit has been merged in the experimental branch:
commit fdce4f3132f52f5ea550637694f70e037e8a8c3d
Author: Michael Niedermayer <michaelni at gmx.at>
Date: Sun Jun 6 13:46:50 2004 +0000
cubic filter instead of truncated sinc
looks much better for upscaling & scaling where src and dst size are quite similar
Originally committed as revision 3201 to svn://svn.ffmpeg.org/ffmpeg/trunk
diff --git a/libavcodec/imgresample.c b/libavcodec/imgresample.c
index 14fdb10..dc5ccf9 100644
--- a/libavcodec/imgresample.c
+++ b/libavcodec/imgresample.c
@@ -554,12 +554,18 @@ static void build_filter(int16_t *filter, float factor)
for(ph=0;ph<NB_PHASES;ph++) {
norm = 0;
for(i=0;i<NB_TAPS;i++) {
-
+#if 1
+ const float d= -0.5; //first order derivative = -0.5
+ x = fabs(((float)(i - FCENTER) - (float)ph / NB_PHASES) * factor);
+ if(x<1.0) y= 1 - 3*x*x + 2*x*x*x + d*( -x*x + x*x*x);
+ else y= d*(-4 + 8*x - 5*x*x + x*x*x);
+#else
x = M_PI * ((float)(i - FCENTER) - (float)ph / NB_PHASES) * factor;
if (x == 0)
y = 1.0;
else
y = sin(x) / x;
+#endif
tab[i] = y;
norm += y;
}
--
Libav/FFmpeg packaging
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