video-resampler: Fix lanczos parameters for variable taps

when using variable taps and when we are limiting the number of taps,
recalculate the lanczos parameters to match the clamped value.
Set the max number of taps to 128

diff --git a/gst-libs/gst/video/video-resampler.c b/gst-libs/gst/video/video-resampler.c
index 3696b35..64c4734 100644 (file)
--- a/gst-libs/gst/video/video-resampler.c
+++ b/gst-libs/gst/video/video-resampler.c
@@ -35,7 +35,7 @@
 #define DEFAULT_OPT_SHARPNESS 1.0
 #define DEFAULT_OPT_SHARPEN 0.0
 
-#define DEFAULT_OPT_MAX_TAPS 16
+#define DEFAULT_OPT_MAX_TAPS 128
 
 typedef struct _ResamplerParams ResamplerParams;
 
@@ -354,6 +354,7 @@ gst_video_resampler_init (GstVideoResampler * resampler,
   GST_DEBUG ("%d %u  %u->%u", method, n_taps, in_size, out_size);
 
   max_taps = GET_OPT_MAX_TAPS (options);
+  n_taps = CLAMP (n_taps, 0, max_taps);
 
   switch (method) {
     case GST_VIDEO_RESAMPLER_METHOD_NEAREST:
@@ -379,22 +380,27 @@ gst_video_resampler_init (GstVideoResampler * resampler,
       break;
     case GST_VIDEO_RESAMPLER_METHOD_LANCZOS:
     {
-      gdouble resample_inc = in_size / (gdouble) out_size;
 
       params.envelope = GET_OPT_ENVELOPE (options);
       params.sharpness = GET_OPT_SHARPNESS (options);
       params.sharpen = GET_OPT_SHARPEN (options);
 
-      if (resample_inc > 1.0) {
-        params.fx = (1.0 / resample_inc) * params.sharpness;
-      } else {
-        params.fx = (1.0) * params.sharpness;
+      if (n_taps == 0) {
+        gdouble resample_inc = in_size / (gdouble) out_size;
+
+        if (resample_inc > 1.0) {
+          params.fx = (1.0 / resample_inc) * params.sharpness;
+        } else {
+          params.fx = (1.0) * params.sharpness;
+        }
+        params.ex = params.fx / params.envelope;
+        params.dx = ceil (params.envelope / params.fx);
+
+        n_taps = CLAMP (2 * params.dx, 0, max_taps);
       }
-      params.ex = params.fx / params.envelope;
-      params.dx = ceil (params.envelope / params.fx);
+      params.fx = 2.0 * params.envelope / n_taps;
+      params.ex = 2.0 / n_taps;
 
-      if (n_taps == 0)
-        n_taps = 2 * params.dx;
       params.get_tap = get_lanczos_tap;
       break;
     }
@@ -402,8 +408,6 @@ gst_video_resampler_init (GstVideoResampler * resampler,
       break;
   }
 
-  n_taps = CLAMP (n_taps, 0, max_taps);
-
   if (n_taps > in_size)
     n_taps = in_size;