From 7b7270ecff2aca89fff74e4a639fe6ef36554ed3 Mon Sep 17 00:00:00 2001
From: Wim Taymans <wtaymans@redhat.com>
Date: Fri, 21 Nov 2014 11:12:50 +0100
Subject: [PATCH] video-resampler: add option to limits taps

Add an option to limit the number of taps to use in automatic mode. The
problem is that for lanczos, we might use more taps than what we can
handle with the current precision.
Rework the other options a little to make it nicer to set defaults.
---
 gst-libs/gst/video/video-resampler.c | 71 ++++++++++++++++++++--------
 gst-libs/gst/video/video-resampler.h |  7 +++
 2 files changed, 58 insertions(+), 20 deletions(-)

diff --git a/gst-libs/gst/video/video-resampler.c b/gst-libs/gst/video/video-resampler.c
index aa5f96b4fc..3696b3500f 100644
--- a/gst-libs/gst/video/video-resampler.c
+++ b/gst-libs/gst/video/video-resampler.c
@@ -27,6 +27,16 @@
 
 #include "video-resampler.h"
 
+
+#define DEFAULT_OPT_CUBIC_B (1.0 / 3.0)
+#define DEFAULT_OPT_CUBIC_C (1.0 / 3.0)
+
+#define DEFAULT_OPT_ENVELOPE 2.0
+#define DEFAULT_OPT_SHARPNESS 1.0
+#define DEFAULT_OPT_SHARPEN 0.0
+
+#define DEFAULT_OPT_MAX_TAPS 16
+
 typedef struct _ResamplerParams ResamplerParams;
 
 struct _ResamplerParams
@@ -50,6 +60,37 @@ struct _ResamplerParams
   GstVideoResampler *resampler;
 };
 
+static gdouble
+get_opt_double (GstStructure * options, const gchar * name, gdouble def)
+{
+  gdouble res;
+  if (!options || !gst_structure_get_double (options, name, &res))
+    res = def;
+  return res;
+}
+
+static gint
+get_opt_int (GstStructure * options, const gchar * name, gint def)
+{
+  gint res;
+  if (!options || !gst_structure_get_int (options, name, &res))
+    res = def;
+  return res;
+}
+
+#define GET_OPT_CUBIC_B(options) get_opt_double(options, \
+    GST_VIDEO_RESAMPLER_OPT_CUBIC_B, DEFAULT_OPT_CUBIC_B)
+#define GET_OPT_CUBIC_C(options) get_opt_double(options, \
+    GST_VIDEO_RESAMPLER_OPT_CUBIC_C, DEFAULT_OPT_CUBIC_C)
+#define GET_OPT_ENVELOPE(options) get_opt_double(options, \
+    GST_VIDEO_RESAMPLER_OPT_ENVELOPE, DEFAULT_OPT_ENVELOPE)
+#define GET_OPT_SHARPNESS(options) get_opt_double(options, \
+    GST_VIDEO_RESAMPLER_OPT_SHARPNESS, DEFAULT_OPT_SHARPNESS)
+#define GET_OPT_SHARPEN(options) get_opt_double(options, \
+    GST_VIDEO_RESAMPLER_OPT_SHARPEN, DEFAULT_OPT_SHARPEN)
+#define GET_OPT_MAX_TAPS(options) get_opt_int(options, \
+    GST_VIDEO_RESAMPLER_OPT_MAX_TAPS, DEFAULT_OPT_MAX_TAPS)
+
 static double
 sinc (double x)
 {
@@ -295,6 +336,7 @@ gst_video_resampler_init (GstVideoResampler * resampler,
     GstStructure * options)
 {
   ResamplerParams params;
+  gint max_taps;
 
   g_return_val_if_fail (in_size != 0, FALSE);
   g_return_val_if_fail (out_size != 0, FALSE);
@@ -311,6 +353,8 @@ 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);
+
   switch (method) {
     case GST_VIDEO_RESAMPLER_METHOD_NEAREST:
       params.get_tap = get_nearest_tap;
@@ -323,14 +367,8 @@ gst_video_resampler_init (GstVideoResampler * resampler,
         n_taps = 2;
       break;
     case GST_VIDEO_RESAMPLER_METHOD_CUBIC:
-      if (!options
-          || !gst_structure_get_double (options,
-              GST_VIDEO_RESAMPLER_OPT_CUBIC_B, &params.b))
-        params.b = 1.0 / 3.0;
-      if (!options
-          || !gst_structure_get_double (options,
-              GST_VIDEO_RESAMPLER_OPT_CUBIC_C, &params.c))
-        params.c = 1.0 / 3.0;
+      params.b = GET_OPT_CUBIC_B (options);
+      params.c = GET_OPT_CUBIC_C (options);
       n_taps = 4;
       params.get_tap = get_cubic_tap;
       break;
@@ -343,18 +381,9 @@ gst_video_resampler_init (GstVideoResampler * resampler,
     {
       gdouble resample_inc = in_size / (gdouble) out_size;
 
-      if (!options
-          || !gst_structure_get_double (options,
-              GST_VIDEO_RESAMPLER_OPT_ENVELOPE, &params.envelope))
-        params.envelope = 2.0;
-      if (!options
-          || !gst_structure_get_double (options,
-              GST_VIDEO_RESAMPLER_OPT_SHARPNESS, &params.sharpness))
-        params.sharpness = 1.0;
-      if (!options
-          || !gst_structure_get_double (options,
-              GST_VIDEO_RESAMPLER_OPT_SHARPEN, &params.sharpen))
-        params.sharpen = 0.0;
+      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;
@@ -373,6 +402,8 @@ gst_video_resampler_init (GstVideoResampler * resampler,
       break;
   }
 
+  n_taps = CLAMP (n_taps, 0, max_taps);
+
   if (n_taps > in_size)
     n_taps = in_size;
 
diff --git a/gst-libs/gst/video/video-resampler.h b/gst-libs/gst/video/video-resampler.h
index 9ebe4df607..13331b10bb 100644
--- a/gst-libs/gst/video/video-resampler.h
+++ b/gst-libs/gst/video/video-resampler.h
@@ -105,6 +105,13 @@ typedef enum {
  * 0.0 and 1.0. 0.0 is the default.
  */
 #define GST_VIDEO_RESAMPLER_OPT_SHARPEN      "GstVideoResampler.sharpen"
+/**
+ * GST_VIDEO_RESAMPLER_OPT_MAX_TAPS:
+ *
+ * G_TYPE_INT, limits the maximum number of taps to use.
+ * 16 is the default.
+ */
+#define GST_VIDEO_RESAMPLER_OPT_MAX_TAPS     "GstVideoResampler.max-taps"
 
 /**
  * GstVideoResamplerFlags: