fluidsynth/doc/fluidsynth_fx.c

/* 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 samples in
 * the buffers. 'nin' and 'nout' are the number of input and output
 * audio buffers. 'in' and 'out' are an array of float buffers with
 * the samples. The audio driver fills the 'in' buffers the incoming
 * audio. The 'out' buffers should be filled by your function. The
 * 'out' buffers will be sent to the audio output of the sound card.
 *
 * IMPORTANT NOTE: The API was designed to be generic but none of the
 * audio drivers currently handles audio input. Either 'nin' will be
 * zero, or the buffers will be filled with zero samples.
 */
int fx_function(void* data, int len, 
		int nin, float** in, 
		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, nin, in, nout, out) != 0) {
		/* Some error occured. Very unlikely to happen, though. */
		return -1;
	}

	/* 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 0;
}


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) {
		delete_fluid_audio_driver(adriver);
	}
	if (synth) {
		delete_fluid_synth(synth);
	}
	if (settings) {
		delete_fluid_settings(settings);
	}
	
	return err;
}