/**

  * $Id: audio.h,v 1.7 2006-03-16 12:41:59 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

 #define AUDIO_FMT_16ST (AUDIO_FMT_16BIT|AUDIO_FMT_STEREO)

 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; /* 0..255 */

     int pan; /* 0 (left) .. 31 (right) */

     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;

 typedef struct audio_driver {

     char *name;

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

     gboolean (*process_buffer)( audio_buffer_t buffer );

 } *audio_driver_t;

 extern struct audio_driver audio_null_driver;

 extern struct audio_driver audio_esd_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.

  */

 gboolean audio_set_driver( 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