Add Echo DSP filter.

audio/dsp_filter.c

@@ -222,9 +222,13 @@ static bool create_filter_graph(rarch_dsp_filter_t *dsp, float sample_rate)
 
 #if defined(HAVE_FILTERS_BUILTIN)
 extern const struct dspfilter_implementation *panning_dspfilter_get_implementation(dspfilter_simd_mask_t mask);
+extern const struct dspfilter_implementation *iir_dspfilter_get_implementation(dspfilter_simd_mask_t mask);
+extern const struct dspfilter_implementation *echo_dspfilter_get_implementation(dspfilter_simd_mask_t mask);
 
 static const dspfilter_get_implementation_t dsp_plugs_builtin[] = {
    panning_dspfilter_get_implementation,
+   iir_dspfilter_get_implementation,
+   echo_dspfilter_get_implementation,
 };
 
 static bool append_plugs(rarch_dsp_filter_t *dsp)

audio/filters/Echo.dsp

@@ -0,0 +1,10 @@
+filters = 1
+filter0 = echo
+
+# Somewhat fancy Echo filter. Can take any number of echo channels with varying delays (ms) and feedback factors.
+# Echo output from all channels can be fed back into each other to create a somewhat reverb-like effect if desired.
+echo_delay    = " 60  80 120 172 200 320 380"
+echo_feedback = "0.5 0.5 0.4 0.3 0.5 0.3 0.2"
+
+# Overall echo amplification. If too high, the echo becomes unstable due to feedback.
+echo_amp = "0.12"

audio/filters/echo.c

@@ -0,0 +1,167 @@
+/*  RetroArch - A frontend for libretro.
+ *  Copyright (C) 2010-2014 - Hans-Kristian Arntzen
+ *
+ *  RetroArch is free software: you can redistribute it and/or modify it under the terms
+ *  of the GNU General Public License as published by the Free Software Found-
+ *  ation, either version 3 of the License, or (at your option) any later version.
+ *
+ *  RetroArch is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+ *  without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+ *  PURPOSE.  See the GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along with RetroArch.
+ *  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "dspfilter.h"
+#include <math.h>
+#include <stdlib.h>
+
+#ifndef min
+#define min(a, b) ((a) < (b) ? (a) : (b))
+#endif
+
+struct echo_channel
+{
+   float *buffer;
+   unsigned ptr;
+   unsigned frames;
+   float feedback;
+};
+
+struct echo_data
+{
+   struct echo_channel *channels;
+   unsigned num_channels;
+   float amp;
+};
+
+static void echo_free(void *data)
+{
+   unsigned i;
+   struct echo_data *echo = (struct echo_data*)data;
+
+   for (i = 0; i < echo->num_channels; i++)
+      free(echo->channels[i].buffer);
+   free(echo->channels);
+   free(echo);
+}
+
+static void echo_process(void *data, struct dspfilter_output *output,
+      const struct dspfilter_input *input)
+{
+   unsigned i, c;
+   struct echo_data *echo = (struct echo_data*)data;
+
+   output->samples = input->samples;
+   output->frames  = input->frames;
+
+   float *out = output->samples;
+
+   for (i = 0; i < input->frames; i++, out += 2)
+   {
+      float echo_left  = 0.0f;
+      float echo_right = 0.0f;
+
+      for (c = 0; c < echo->num_channels; c++)
+      {
+         echo_left  += echo->channels[c].buffer[(echo->channels[c].ptr << 1) + 0];
+         echo_right += echo->channels[c].buffer[(echo->channels[c].ptr << 1) + 1];
+      }
+
+      echo_left  *= echo->amp;
+      echo_right *= echo->amp;
+
+      float left  = out[0] + echo_left;
+      float right = out[1] + echo_right;
+
+      for (c = 0; c < echo->num_channels; c++)
+      {
+         float feedback_left  = out[0] + echo->channels[c].feedback * echo_left;
+         float feedback_right = out[1] + echo->channels[c].feedback * echo_right;
+
+         echo->channels[c].buffer[(echo->channels[c].ptr << 1) + 0] = feedback_left;
+         echo->channels[c].buffer[(echo->channels[c].ptr << 1) + 1] = feedback_right;
+
+         echo->channels[c].ptr = (echo->channels[c].ptr + 1) % echo->channels[c].frames;
+      }
+
+      out[0] = left;
+      out[1] = right;
+   }
+}
+
+static void *echo_init(const struct dspfilter_info *info,
+      const struct dspfilter_config *config, void *userdata)
+{
+   unsigned i;
+   struct echo_data *echo = (struct echo_data*)calloc(1, sizeof(*echo));
+   if (!echo)
+      return NULL;
+
+   float *delay = NULL, *feedback = NULL;
+   unsigned num_delay = 0, num_feedback = 0;
+
+   static const float default_delay[] = { 200.0f };
+   static const float default_feedback[] = { 0.5f };
+
+   config->get_float_array(userdata, "delay", &delay, &num_delay, default_delay, 1);
+   config->get_float_array(userdata, "feedback", &feedback, &num_feedback, default_feedback, 1);
+   config->get_float(userdata, "amp", &echo->amp, 0.2f);
+
+   unsigned channels = num_feedback = num_delay = min(num_delay, num_feedback);
+
+   echo->channels = (struct echo_channel*)calloc(channels, sizeof(*echo->channels));
+   if (!echo->channels)
+      goto error;
+
+   echo->num_channels = channels;
+
+   for (i = 0; i < channels; i++)
+   {
+      unsigned frames = (unsigned)(delay[i] * info->input_rate / 1000.0f + 0.5f);
+      if (!frames)
+         goto error;
+
+      echo->channels[i].buffer = (float*)calloc(frames, 2 * sizeof(float));
+      if (!echo->channels[i].buffer)
+         goto error;
+
+      echo->channels[i].frames = frames;
+      echo->channels[i].feedback = feedback[i];
+   }
+
+   config->free(delay);
+   config->free(feedback);
+   return echo;
+
+error:
+   config->free(delay);
+   config->free(feedback);
+   echo_free(echo);
+   return NULL;
+}
+
+
+static const struct dspfilter_implementation echo_plug = {
+   echo_init,
+   echo_process,
+   echo_free,
+
+   DSPFILTER_API_VERSION,
+   "Multi-Echo",
+   "echo",
+};
+
+#ifdef HAVE_FILTERS_BUILTIN
+#define dspfilter_get_implementation echo_dspfilter_get_implementation
+#endif
+
+const struct dspfilter_implementation *dspfilter_get_implementation(dspfilter_simd_mask_t mask)
+{
+   (void)mask;
+   return &echo_plug;
+}
+
+#undef dspfilter_get_implementation
+

griffin/griffin.c

@@ -486,6 +486,8 @@ FILTERS
 #include "../gfx/filters/phosphor2x.c"
 
 #include "../audio/filters/panning.c"
+#include "../audio/filters/iir.c"
+#include "../audio/filters/echo.c"
 #endif
 /*============================================================
 DYNAMIC