Hi,
I've patched the transcode source to support 2 more zoom filters.
Especially the Cubic4 filter produced very good results for me. Attached
is the patch file, use "patch -p1 < ../transcode-1.0.2-filters.patch" to
apply it. It's for a slightly older version of transcode but worked also
with later versions. It has been some months since I've wrote this but I
just thought it could be useful for others, too.
Regards
Johannes
diff -Naur transcode-1.0.2-orig/src/transcode.c transcode-1.0.2/src/transcode.c
--- transcode-1.0.2-orig/src/transcode.c 2005-10-02 03:38:22.000000000
+0200
+++ transcode-1.0.2/src/transcode.c 2006-06-30 23:10:54.000000000 +0200
@@ -1848,8 +1848,24 @@
vob->zoom_support=Triangle_support;
zoom_filter="Triangle";
break;
+ }
+
+ if(strncasecmp(optarg,"cubicK4",1)==0) {
+ vob->zoom_filter=CubicKeys4_filter;
+ vob->zoom_support=CubicKeys4_support;
+ zoom_filter="CubicKeys4";
+ break;
+
+ }
+
+ if(strncasecmp(optarg,"sinc8",1)==0) {
+ vob->zoom_filter=Sinc8_filter;
+ vob->zoom_support=Sinc8_support;
+ zoom_filter="sinc:8";
+ break;
+
}
- tc_error("invalid argument for --zoom_filter option\nmethod:
L[anczos] M[itchell] T[riangle] H[ermite] B[_spline] bell box");
+ tc_error("invalid argument for --zoom_filter option\nmethod:
L[anczos] M[itchell] T[riangle] H[ermite] B[_spline] bell box cubicK4 sinc8");
tc_error("invalid filter selection for --zoom_filter");
} else tc_error("invalid parameter for option --zoom_filter");
diff -Naur transcode-1.0.2-orig/src/zoom.c transcode-1.0.2/src/zoom.c
--- transcode-1.0.2-orig/src/zoom.c 2005-07-04 09:09:35.000000000 +0200
+++ transcode-1.0.2/src/zoom.c 2006-06-30 23:11:46.000000000 +0200
@@ -279,6 +279,32 @@
return(0.0);
}
+double CubicKeys4_filter(double t) // Keys 4th-order Cubic
+{
+ if (t < 0.0) t = -t;
+ if (t < 1.0)
+ return (3.0 + (t * t * (-7.0 + (t * 4.0)))) / 3.0;
+ if (t < 2.0)
+ return (30.0 + (t * (-59.0 + (t * (36.0 + (t * -7.0)))))) / 12.0;
+ if (t < 3.0)
+ return (-18.0 + (t * (21.0 + (t * (-8.0 + t))))) / 12.0;
+ return 0.0;
+}
+
+#define PI 3.1415926535897932384626433832795029L
+double Sinc8_filter(double t) // Sinc with Lanczos window, 8 cycles
+{
+ if (t < 0.0) t = -t;
+ if (t == 0.0) {
+ return 1.0;
+ } else if (t < 8.0) {
+ double w = sin(PI*t / 8.0) / (PI*t / 8.0);
+ return w * sin(t*PI) / (t*PI);
+ } else {
+ return 0.0;
+ }
+}
+
/*
* image rescaling routine
*/
diff -Naur transcode-1.0.2-orig/src/zoom.h transcode-1.0.2/src/zoom.h
--- transcode-1.0.2-orig/src/zoom.h 2005-07-04 09:15:59.000000000 +0200
+++ transcode-1.0.2/src/zoom.h 2006-06-30 23:10:06.000000000 +0200
@@ -105,5 +105,8 @@
extern double Mitchell_filter(double t);
#define Lanczos3_support (3.0)
extern double Lanczos3_filter(double t);
-
+#define CubicKeys4_support (3.0)
+extern double CubicKeys4_filter(double t);
+#define Sinc8_support (8.0)
+extern double Sinc8_filter(double t);
#endif
