RetroArch/libretro-common/audio/dsp_filters/phaser.c

/* Copyright  (C) 2010-2020 The RetroArch team
 *
 * ---------------------------------------------------------------------------------------
 * The following license statement only applies to this file (phaser.c).
 * ---------------------------------------------------------------------------------------
 *
 * Permission is hereby granted, free of charge,
 * to any person obtaining a copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#include <math.h>
#include <stdlib.h>
#include <string.h>

#include <retro_miscellaneous.h>
#include <libretro_dspfilter.h>

#define PHASER_LFO_SHAPE 4.0
#define PHASER_LFO_SKIP_SAMPLES 20

struct phaser_data
{
   float freq;
   float startphase;
   float fb;
   float depth;
   float drywet;
   float old[2][24];
   float gain;
   float fbout[2];
   float lfoskip;
   float phase;

   int stages;
   unsigned long skipcount;
};

static void phaser_free(void *data)
{
   free(data);
}

static void phaser_process(void *data, struct dspfilter_output *output,
      const struct dspfilter_input *input)
{
   unsigned i, c;
   int s;
   float m[2], tmp[2];
   struct phaser_data *ph = (struct phaser_data*)data;
   float *out             = output->samples;

   output->samples        = input->samples;
   output->frames         = input->frames;

   for (i = 0; i < input->frames; i++, out += 2)
   {
      float in[2] = { out[0], out[1] };

      for (c = 0; c < 2; c++)
         m[c] = in[c] + ph->fbout[c] * ph->fb * 0.01f;

      if ((ph->skipcount++ % PHASER_LFO_SKIP_SAMPLES) == 0)
      {
         ph->gain = 0.5 * (1.0 + cos(ph->skipcount * ph->lfoskip + ph->phase));
         ph->gain = (exp(ph->gain * PHASER_LFO_SHAPE) - 1.0) / (exp(PHASER_LFO_SHAPE) - 1);
         ph->gain = 1.0 - ph->gain * ph->depth;
      }

      for (s = 0; s < ph->stages; s++)
      {
         for (c = 0; c < 2; c++)
         {
            tmp[c] = ph->old[c][s];
            ph->old[c][s] = ph->gain * tmp[c] + m[c];
            m[c] = tmp[c] - ph->gain * ph->old[c][s];
         }
      }

      for (c = 0; c < 2; c++)
      {
         ph->fbout[c] = m[c];
         out[c] = m[c] * ph->drywet + in[c] * (1.0f - ph->drywet);
      }
   }
}

static void *phaser_init(const struct dspfilter_info *info,
      const struct dspfilter_config *config, void *userdata)
{
   float lfo_freq, lfo_start_phase;
   struct phaser_data *ph = (struct phaser_data*)calloc(1, sizeof(*ph));
   if (!ph)
      return NULL;

   config->get_float(userdata, "lfo_freq", &lfo_freq, 0.4f);
   config->get_float(userdata, "lfo_start_phase", &lfo_start_phase, 0.0f);
   config->get_float(userdata, "feedback", &ph->fb, 0.0f);
   config->get_float(userdata, "depth", &ph->depth, 0.4f);
   config->get_float(userdata, "dry_wet", &ph->drywet, 0.5f);
   config->get_int(userdata, "stages", &ph->stages, 2);

   if (ph->stages < 1)
      ph->stages = 1;
   else if (ph->stages > 24)
      ph->stages = 24;

   ph->lfoskip = lfo_freq * 2.0 * M_PI / info->input_rate;
   ph->phase   = lfo_start_phase * M_PI / 180.0;

   return ph;
}

static const struct dspfilter_implementation phaser_plug = {
   phaser_init,
   phaser_process,
   phaser_free,

   DSPFILTER_API_VERSION,
   "Phaser",
   "phaser",
};

#ifdef HAVE_FILTERS_BUILTIN
#define dspfilter_get_implementation phaser_dspfilter_get_implementation
#endif

const struct dspfilter_implementation *dspfilter_get_implementation(dspfilter_simd_mask_t mask)
{
   return &phaser_plug;
}

#undef dspfilter_get_implementation