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

/* Copyright  (C) 2010-2020 The RetroArch team
 *
 * ---------------------------------------------------------------------------------------
 * The following license statement only applies to this file (vibrato.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>
#include <string/stdstring.h>

#define sqr(a) ((a) * (a))

static const float BASE_DELAY_SEC = 0.002; /* 2 ms */
static const float VIBRATO_FREQUENCY_DEFAULT_HZ  = 2;
static const float VIBRATO_FREQUENCY_MAX_HZ      = 14;
static const float VIBRATO_DEPTH_DEFAULT_PERCENT = 50;
static const int add_delay                       = 3;

static float hermite_interp(float x, float *y)
{
   float c0 = y[1];
   float c1 = (1.0f / 2.0f) * (y[2] - y[0]);
   float c2 = (y[0] - (5.0f / 2.0f) * y[1]) + (2.0f * y[2] - (1.0f / 2.0f) * y[3]);
   float c3 = (1.0f / 2.0f) * (y[3] - y[0]) + (3.0f / 2.0f) * (y[1] - y[2]);
   return ((c3 * x + c2) * x + c1) * x + c0;
}

struct vibrato_core
{
   float* buffer;
   float freq;
   float samplerate;
   float depth;
   int phase;
   int writeindex;
   int size;
};

struct vibrato
{
   struct vibrato_core left, right;
};

static void vibrato_free(void *data)
{
   struct vibrato *vib = (struct vibrato*)data;
   free(vib->left.buffer);
   free(vib->right.buffer);
   free(data);
}

static void vibratocore_init(struct vibrato_core *core,float depth,int samplerate,float freq)
{
	core->size       = BASE_DELAY_SEC * samplerate * 2;
	core->buffer     = malloc((core->size + add_delay) * sizeof(float));
	memset(core->buffer, 0, (core->size + add_delay)   * sizeof(float));
	core->samplerate = samplerate;
	core->freq       = freq;
	core->depth      = depth;
	core->phase      = 0;
	core->writeindex = 0;
}

float vibratocore_core(struct vibrato_core *core,float in)
{
   int ipart;
   float delay, readindex, fpart, value;
   float M                        = core->freq / core->samplerate;
   int maxphase                   = core->samplerate / core->freq;
   float lfo                      = sin(M * 2. * M_PI * core->phase++);
   int maxdelay                   = BASE_DELAY_SEC * core->samplerate;
   core->phase                    = core->phase % maxphase;
   lfo                            = (lfo + 1) * 1.; // transform from [-1; 1] to [0; 1]
   delay                          =  lfo * core->depth * maxdelay;
   delay                         += add_delay;
   readindex                      = core->writeindex - 1 - delay;
   while (readindex < 0)
      readindex                  += core->size;
   while (readindex >= core->size)
      readindex                  -= core->size;
   ipart                          = (int)readindex;    /* Integer part of the delay */
   fpart                          = readindex - ipart; /* fractional part of the delay */
   value                          = hermite_interp(fpart, &(core->buffer[ipart]));
   core->buffer[core->writeindex] = in;
   if (core->writeindex < add_delay)
      core->buffer[core->size + core->writeindex] = in;
   core->writeindex++;
   if (core->writeindex == core->size)
      core->writeindex = 0;
   return value;
}

static void vibrato_process(void *data,
      struct dspfilter_output *output,
      const struct dspfilter_input *input)
{
   unsigned i;
   float *out;
   struct vibrato *vib = (struct vibrato*)data;

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

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

static void *vibrato_init(const struct dspfilter_info *info,
      const struct dspfilter_config *config, void *userdata)
{
   float freq, depth;
   struct vibrato *vib = (struct vibrato*)calloc(1, sizeof(*vib));
   if (!vib)
      return NULL;

   config->get_float(userdata, "freq", &freq,5.0f);
   config->get_float(userdata, "depth", &depth, 0.5f);
   vibratocore_init(&vib->left,depth,info->input_rate,freq);
   vibratocore_init(&vib->right,depth,info->input_rate,freq);
   return vib;
}

static const struct dspfilter_implementation vibrato_plug = {
   vibrato_init,
   vibrato_process,
   vibrato_free,

   DSPFILTER_API_VERSION,
   "Vibrato",
   "vibrato",
};

#ifdef HAVE_FILTERS_BUILTIN
#define dspfilter_get_implementation vibrato_dspfilter_get_implementation
#endif

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

#undef dspfilter_get_implementation