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cubic filter instead of truncated sinc

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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
This commit is contained in:
Michael Niedermayer 2004-06-06 13:46:50 +00:00
parent 305fa26445
commit fdce4f3132
1 changed files with 7 additions and 1 deletions
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8
libavcodec/imgresample.c
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@ -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;
}