/**

 * $Id: audio.h,v 1.3 2006-01-12 12:38:59 nkeynes Exp $

 * 

 * Audio engine, ie the part that does the actual work.

 *

 * Copyright (c) 2005 Nathan Keynes.

 *

 * This program 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 Foundation; either version 2 of the License, or

 * (at your option) any later version.

 *

 * This program 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.

 */

#ifndef dream_audio_H

#define dream_audio_H 1

#include <stdint.h>

#include <glib/gtypes.h>

#ifdef __cplusplus

extern "C" {

#endif

#define AUDIO_FMT_8BIT 0

#define AUDIO_FMT_16BIT 1

#define AUDIO_FMT_ADPCM 2

#define AUDIO_FMT_MONO 0

#define AUDIO_FMT_STEREO 4

#define AUDIO_FMT_SIGNED 0

#define AUDIO_FMT_UNSIGNED 8

typedef struct audio_channel {

    gboolean active;

    uint32_t posn;

    uint32_t posn_left;

    uint32_t start;

    uint32_t end;

    gboolean loop;

    uint32_t loop_start;

    int vol_left; /* 0..255 */

    int vol_right; /* 0..255 */

    uint32_t sample_rate;

    int sample_format; 

    /* Envelope etc stuff */

    /* ADPCM */

    int adpcm_nibble; /* 0 = low nibble, 1 = high nibble */

    int adpcm_step;

    int adpcm_predict;

} *audio_channel_t;

typedef struct audio_buffer {

    uint32_t length; /* Bytes */

    uint32_t posn; /* Bytes */

    int status;

    char data[0];

} *audio_buffer_t;

struct audio_driver {

    char *name;

    gboolean (*set_output_format)( uint32_t sample_rate, uint32_t format );

    gboolean (*process_buffer)( audio_buffer_t buffer );

};

typedef struct audio_driver *audio_driver_t;

extern struct audio_driver null_audio_driver;

extern struct audio_driver esd_audio_driver;

/**

 * Set the output driver, sample rate and format. Also initializes the 

 * output buffers, flushing any current data and reallocating as 

 * necessary. Must be called before attempting to generate any audio.

 */

void audio_set_output( audio_driver_t driver, uint32_t samplerate,

		       int format );

/**

 * Mark the current write buffer as full and prepare the next buffer for

 * writing. Returns the next buffer to write to.

 * If all buffers are full, returns NULL.

 */

audio_buffer_t audio_next_write_buffer();

/**

 * Mark the current read buffer as empty and return the next buffer for

 * reading. If there is no next buffer yet, returns NULL.

 */

audio_buffer_t audio_next_read_buffer();

/**

 * Mix a single output sample and append it to the output buffers

 */

void audio_mix_samples( int num_samples );

/**

 * Retrieve the channel information for the channel, numbered 0..63. 

 */

audio_channel_t audio_get_channel( int channel );

void audio_start_channel( int channel );

void audio_stop_channel( int channel );

#ifdef __cplusplus

}

#endif

#endif