libfluidsynth  2.0.1
fluidsynth_fx.c

Example of using effects with fluidsynth

/* FluidSynth FX - An example of using effects with fluidsynth
*
* This code is in the public domain.
*
* To compile:
* gcc -g -O -o fluidsynth_fx fluidsynth_fx.c -lfluidsynth
*
* To run
* fluidsynth_fx soundfont gain
*
* [Peter Hanappe]
*/
#include <stdio.h>
#include <stdlib.h>
#include <fluidsynth.h>
/* The structure with the effects data. This example simply applies a
* linear gain the to synthesizer output. */
struct fx_data_t
{
fluid_synth_t *synth;
float gain;
} fx_data_t;
/* This function implements the callback function of the audio driver
* (see new_fluid_audio_driver2 below). The data argument is a pointer
* to your private data structure. 'len' is the number of audio frames
* in the buffers. 'nfx' and 'nout' are the number of input and output
* audio buffers. 'fx' and 'out' are arrays of float buffers containing
* the audio. The audio driver fills zero-initializes those buffers.
* You are responsible for filling up those buffers, as the result will
* be sent to the sound card. This is usually done by asking the synth
* to fill those buffers appropriately using fluid_synth_process()
*
* NOTE: The API was designed to be generic. Audio driver may fill the
* buffers with audio input from the soundcard, rather than zeros.
*/
int fx_function(void *data, int len,
int nfx, float **fx,
int nout, float **out)
{
struct fx_data_t *fx_data = (struct fx_data_t *) data;
int i, k;
float *out_i;
/* Call the synthesizer to fill the output buffers with its
* audio output. */
if(fluid_synth_process(fx_data->synth, len, nfx, fx, nout, out) != FLUID_OK)
{
/* Some error occured. Very unlikely to happen, though. */
return FLUID_FAILED;
}
/* Apply your effects here. In this example, the gain is
* applied to all the output buffers. */
for(i = 0; i < nout; i++)
{
out_i = out[i];
for(k = 0; k < len; k++)
{
out_i[k] *= fx_data->gain;
}
}
return FLUID_OK;
}
int main(int argc, char **argv)
{
fluid_settings_t *settings;
fluid_synth_t *synth = NULL;
fluid_audio_driver_t *adriver = NULL;
int err = 0;
struct fx_data_t fx_data;
if(argc != 3)
{
fprintf(stderr, "Usage: fluidsynth_simple [soundfont] [gain]\n");
return 1;
}
/* Create the settings object. This example uses the default
* values for the settings. */
settings = new_fluid_settings();
if(settings == NULL)
{
fprintf(stderr, "Failed to create the settings\n");
err = 2;
goto cleanup;
}
/* Create the synthesizer */
synth = new_fluid_synth(settings);
if(synth == NULL)
{
fprintf(stderr, "Failed to create the synthesizer\n");
err = 3;
goto cleanup;
}
/* Load the soundfont */
if(fluid_synth_sfload(synth, argv[1], 1) == -1)
{
fprintf(stderr, "Failed to load the SoundFont\n");
err = 4;
goto cleanup;
}
/* Fill in the data of the effects unit */
fx_data.synth = synth;
fx_data.gain = atof(argv[2]);
/* Create the audio driver. As soon as the audio driver is
* created, the synthesizer can be played. */
adriver = new_fluid_audio_driver2(settings, fx_function, (void *) &fx_data);
if(adriver == NULL)
{
fprintf(stderr, "Failed to create the audio driver\n");
err = 5;
goto cleanup;
}
/* Play a note */
fluid_synth_noteon(synth, 0, 60, 100);
printf("Press \"Enter\" to stop: ");
fgetc(stdin);
printf("done\n");
cleanup:
if(adriver)
{
}
if(synth)
{
}
if(settings)
{
}
return err;
}