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mixer.c
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/*
MIXERLIB: An audio mixer library based on the SDL library
Copyright (C) 1997-1999 Sam Lantinga
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.
This library 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with this library; if not, write to the Free
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
Sam Lantinga
5635-34 Springhouse Dr.
Pleasanton, CA 94588 (USA)
slouken@devolution.com
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <SDL/SDL_mutex.h>
#include <SDL/SDL_endian.h>
#include "mixer.h"
static int audio_opened = 0;
static SDL_AudioSpec mixer;
static SDL_mutex *mixer_lock;
static struct _Mix_Channel {
Mix_Chunk *chunk;
int playing;
int paused;
Uint8 *samples;
int volume;
int looping;
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Mix_Fading fading;
int fade_volume;
int fade_length;
Uint32 ticks_fade;
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} channel[MIX_CHANNELS];
#define MUSIC_VOL 64 /* Music volume 0-64 */
/* Support for user defined music functions, plus the default one */
extern int music_active;
extern void music_mixer(void *udata, Uint8 *stream, int len);
static void (*mix_music)(void *udata, Uint8 *stream, int len) = music_mixer;
static int num_channels; /* Holds the number of channels actually mixed, for debugging */
static int reserved_channels = 0;
void *music_data = NULL;
/* Mixing function */
static void mix_channels(void *udata, Uint8 *stream, int len)
{
int i, mixable, volume;
/* Grab the channels we need to mix */
SDL_mutexP(mixer_lock);
num_channels = 0;
for ( i=0; i<MIX_CHANNELS; ++i ) {
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if ( channel[i].fading != MIX_NO_FADING ) {
Uint32 ticks = SDL_GetTicks() - channel[i].ticks_fade;
if( ticks > channel[i].fade_length ) {
if( channel[i].fading == MIX_FADING_OUT ) {
channel[i].playing = 0;
Mix_Volume(i, channel[i].fading); /* Restore the volume */
}
channel[i].fading = MIX_NO_FADING;
} else {
if( channel[i].fading == MIX_FADING_OUT ) {
Mix_Volume(i, (channel[i].fade_volume * (channel[i].fade_length-ticks))
/ channel[i].fade_length );
} else {
Mix_Volume(i, (channel[i].fade_volume * ticks) / channel[i].fade_length );
}
}
}
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if ( channel[i].playing && !channel[i].paused ) {
++ num_channels;
mixable = channel[i].playing;
if ( mixable > len ) {
mixable = len;
}
volume = (channel[i].volume*channel[i].chunk->volume) /
MIX_MAX_VOLUME;
SDL_MixAudio(stream,channel[i].samples,mixable,volume);
channel[i].samples += mixable;
channel[i].playing -= mixable;
if ( ! channel[i].playing && channel[i].looping ) {
if ( --channel[i].looping ) {
channel[i].samples = channel[i].chunk->abuf;
channel[i].playing = channel[i].chunk->alen;
}
}
}
}
SDL_mutexV(mixer_lock);
/* Mix the music */
if ( music_active ) {
mix_music(music_data, stream, len);
}
}
static void PrintFormat(char *title, SDL_AudioSpec *fmt)
{
printf("%s: %d bit %s audio (%s) at %u Hz\n", title, (fmt->format&0xFF),
(fmt->format&0x8000) ? "signed" : "unsigned",
(fmt->channels > 1) ? "stereo" : "mono", fmt->freq);
}
/* Open the mixer with a certain desired audio format */
int Mix_OpenAudio(int frequency, Uint16 format, int channels, int chunksize)
{
int i;
SDL_AudioSpec desired;
/* If the mixer is already opened, increment open count */
if ( audio_opened ) {
++audio_opened;
return(0);
}
/* Set the desired format and frequency */
desired.freq = frequency;
desired.format = format;
desired.channels = channels;
desired.samples = chunksize;
desired.callback = mix_channels;
desired.userdata = NULL;
/* Accept nearly any audio format */
if ( SDL_OpenAudio(&desired, &mixer) < 0 ) {
return(-1);
}
#if 0
PrintFormat("Audio device", &mixer);
#endif
/* Create the channel lock mutex */
mixer_lock = SDL_CreateMutex();
if ( mixer_lock == NULL ) {
SDL_CloseAudio();
SDL_SetError("Unable to create mixer lock");
return(-1);
}
/* Initialize the music players */
if ( open_music(&mixer) < 0 ) {
SDL_CloseAudio();
SDL_DestroyMutex(mixer_lock);
return(-1);
}
/* Clear out the audio channels */
for ( i=0; i<MIX_CHANNELS; ++i ) {
channel[i].chunk = NULL;
channel[i].playing = 0;
channel[i].looping = 0;
channel[i].volume = SDL_MIX_MAXVOLUME;
}
Mix_VolumeMusic(SDL_MIX_MAXVOLUME);
audio_opened = 1;
SDL_PauseAudio(0);
return(0);
}
/* Return the actual mixer parameters */
int Mix_QuerySpec(int *frequency, Uint16 *format, int *channels)
{
if ( audio_opened ) {
if ( frequency ) {
*frequency = mixer.freq;
}
if ( format ) {
*format = mixer.format;
}
if ( channels ) {
*channels = mixer.channels;
}
}
return(audio_opened);
}
/* Load a wave file */
Mix_Chunk *Mix_LoadWAV_RW(SDL_RWops *src, int freesrc)
{
Mix_Chunk *chunk;
SDL_AudioSpec wavespec;
SDL_AudioCVT wavecvt;
/* Make sure audio has been opened */
if ( ! audio_opened ) {
SDL_SetError("Audio device hasn't been opened");
if ( freesrc ) {
SDL_RWclose(src);
}
return(NULL);
}
/* Allocate the chunk memory */
chunk = (Mix_Chunk *)malloc(sizeof(Mix_Chunk));
if ( chunk == NULL ) {
SDL_SetError("Out of memory");
if ( freesrc ) {
SDL_RWclose(src);
}
return(NULL);
}
/* Load the WAV file into the chunk */
if ( SDL_LoadWAV_RW(src, freesrc,
&wavespec, (Uint8 **)&chunk->abuf, &chunk->alen) == NULL ) {
free(chunk);
return(NULL);
}
#if 0
PrintFormat("Audio device", &mixer);
PrintFormat("-- Wave file", &wavespec);
#endif
/* Build the audio converter and create conversion buffers */
if ( SDL_BuildAudioCVT(&wavecvt,
wavespec.format, wavespec.channels, wavespec.freq,
mixer.format, mixer.channels, mixer.freq) < 0 ) {
SDL_FreeWAV(chunk->abuf);
free(chunk);
return(NULL);
}
wavecvt.len = chunk->alen;
wavecvt.buf = (Uint8 *)malloc(wavecvt.len*wavecvt.len_mult);
if ( wavecvt.buf == NULL ) {
SDL_SetError("Out of memory");
SDL_FreeWAV(chunk->abuf);
free(chunk);
return(NULL);
}
memcpy(wavecvt.buf, chunk->abuf, chunk->alen);
SDL_FreeWAV(chunk->abuf);
/* Run the audio converter */
if ( SDL_ConvertAudio(&wavecvt) < 0 ) {
free(wavecvt.buf);
free(chunk);
return(NULL);
}
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chunk->allocated = 1;
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chunk->abuf = wavecvt.buf;
chunk->alen = wavecvt.len_cvt;
chunk->volume = MIX_MAX_VOLUME;
return(chunk);
}
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/* Load a wave file of the mixer format from a memory buffer */
Mix_Chunk *Mix_QuickLoad_WAV(Uint8 *mem)
{
Mix_Chunk *chunk;
Uint8 magic[4];
/* Make sure audio has been opened */
if ( ! audio_opened ) {
SDL_SetError("Audio device hasn't been opened");
return(NULL);
}
/* Allocate the chunk memory */
chunk = (Mix_Chunk *)malloc(sizeof(Mix_Chunk));
if ( chunk == NULL ) {
SDL_SetError("Out of memory");
return(NULL);
}
/* Essentially just skip to the audio data (no error checking - fast) */
chunk->allocated = 0;
mem += 12; /* WAV header */
do {
memcpy(magic, mem, 4);
mem += 4;
chunk->alen = ((mem[3]<<24)|(mem[2]<<16)|(mem[1]<<8)|(mem[0]));
mem += 4;
chunk->abuf = mem;
mem += chunk->alen;
} while ( memcmp(magic, "data", 4) != 0 );
chunk->volume = MIX_MAX_VOLUME;
return(chunk);
}
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/* Free an audio chunk previously loaded */
void Mix_FreeChunk(Mix_Chunk *chunk)
{
int i;
/* Caution -- if the chunk is playing, the mixer will crash */
if ( chunk ) {
/* Guarantee that this chunk isn't playing */
SDL_mutexP(mixer_lock);
for ( i=0; i<MIX_CHANNELS; ++i ) {
if ( chunk == channel[i].chunk ) {
channel[i].playing = 0;
}
}
SDL_mutexV(mixer_lock);
/* Actually free the chunk */
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if ( chunk->allocated ) {
free(chunk->abuf);
}
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free(chunk);
}
}
/* Add your own music player or mixer function.
If 'mix_func' is NULL, the default music player is re-enabled.
*/
void Mix_HookMusic(void (*mix_func)(void *udata, Uint8 *stream, int len),
void *arg)
{
SDL_LockAudio();
if ( mix_func != NULL ) {
music_data = arg;
mix_music = mix_func;
} else {
music_data = NULL;
mix_music = music_mixer;
}
SDL_UnlockAudio();
}
void *Mix_GetMusicHookData(void)
{
return(music_data);
}
/* Reserve the first channels (0 -> n-1) for the application, i.e. don't allocate
them dynamically to the next sample if requested with a -1 value below.
Returns the number of reserved channels.
*/
int Mix_ReserveChannels(int num)
{
if (num > MIX_CHANNELS)
num = MIX_CHANNELS;
reserved_channels = num;
return num;
}
/* Play an audio chunk on a specific channel.
If the specified channel is -1, play on the first free channel.
Returns which channel was used to play the sound.
*/
int Mix_PlayChannel(int which, Mix_Chunk *chunk, int loops)
{
int i;
/* Don't play null pointers :-) */
if ( chunk == NULL ) {
return(-1);
}
/* Lock the mixer while modifying the playing channels */
SDL_mutexP(mixer_lock);
{
/* If which is -1, play on the first free channel */
if ( which == -1 ) {
for ( i=reserved_channels; i<MIX_CHANNELS; ++i ) {
if ( channel[i].playing <= 0 )
break;
}
if ( i == MIX_CHANNELS ) {
which = -1;
} else {
which = i;
}
}
/* Queue up the audio data for this channel */
if ( which >= 0 ) {
channel[which].samples = chunk->abuf;
channel[which].playing = chunk->alen;
channel[which].looping = loops;
channel[which].chunk = chunk;
channel[which].paused = 0;
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channel[which].fading = MIX_NO_FADING;
}
}
SDL_mutexV(mixer_lock);
/* Return the channel on which the sound is being played */
return(which);
}
/* Fade in a sound on a channel, over ms milliseconds */
int Mix_FadeInChannel(int which, Mix_Chunk *chunk, int loops, int ms)
{
int i;
/* Don't play null pointers :-) */
if ( chunk == NULL ) {
return(-1);
}
/* Lock the mixer while modifying the playing channels */
SDL_mutexP(mixer_lock);
{
/* If which is -1, play on the first free channel */
if ( which == -1 ) {
for ( i=reserved_channels; i<MIX_CHANNELS; ++i ) {
if ( channel[i].playing <= 0 )
break;
}
if ( i == MIX_CHANNELS ) {
which = -1;
} else {
which = i;
}
}
/* Queue up the audio data for this channel */
if ( which >= 0 ) {
channel[which].samples = chunk->abuf;
channel[which].playing = chunk->alen;
channel[which].looping = loops;
channel[which].chunk = chunk;
channel[which].paused = 0;
channel[which].fading = MIX_FADING_IN;
channel[which].fade_volume = channel[which].volume;
channel[which].volume = 0;
channel[which].fade_length = ms;
channel[which].ticks_fade = SDL_GetTicks();
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}
}
SDL_mutexV(mixer_lock);
/* Return the channel on which the sound is being played */
return(which);
}
/* Set volume of a particular channel */
int Mix_Volume(int which, int volume)
{
int i;
int prev_volume;
if ( which == -1 ) {
prev_volume = 0;
for ( i=0; i<MIX_CHANNELS; ++i ) {
prev_volume += Mix_Volume(i, volume);
}
prev_volume /= MIX_CHANNELS;
} else {
prev_volume = channel[which].volume;
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if ( volume < 0 ) {
volume = 0;
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}
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if ( volume > SDL_MIX_MAXVOLUME ) {
volume = SDL_MIX_MAXVOLUME;
}
channel[which].volume = volume;
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}
return(prev_volume);
}
/* Set volume of a particular chunk */
int Mix_VolumeChunk(Mix_Chunk *chunk, int volume)
{
int prev_volume;
prev_volume = chunk->volume;
if ( volume >= 0 ) {
if ( volume > MIX_MAX_VOLUME ) {
volume = MIX_MAX_VOLUME;
}
chunk->volume = volume;
}
return(prev_volume);
}
/* Halt playing of a particular channel */
int Mix_HaltChannel(int which)
{
int i;
if ( which == -1 ) {
for ( i=0; i<MIX_CHANNELS; ++i ) {
Mix_HaltChannel(i);
}
} else {
SDL_mutexP(mixer_lock);
channel[which].playing = 0;
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if(channel[which].fading != MIX_NO_FADING) /* Restore volume */
channel[which].volume = channel[which].fade_volume;
channel[which].fading = MIX_NO_FADING;
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SDL_mutexV(mixer_lock);
}
return(0);
}
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/* Fade out a channel and then stop it automatically */
int Mix_FadeOutChannel(int which, int ms)
{
int status;
status = 0;
if ( which == -1 ) {
int i;
for ( i=0; i<MIX_CHANNELS; ++i ) {
status += Mix_FadeOutChannel(i,ms);
}
} else {
SDL_mutexP(mixer_lock);
if ( channel[which].playing && channel[which].volume>0 &&
channel[which].fading==MIX_NO_FADING ) {
channel[which].fading = MIX_FADING_OUT;
channel[which].fade_volume = channel[which].volume;
channel[which].fade_length = ms;
channel[which].ticks_fade = SDL_GetTicks();
++ status;
}
SDL_mutexV(mixer_lock);
}
return(status);
}
Mix_Fading Mix_FadingChannel(int which)
{
return channel[which].fading;
}
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/* Check the status of a specific channel.
If the specified channel is -1, check all channels.
*/
int Mix_Playing(int which)
{
int status;
status = 0;
if ( which == -1 ) {
int i;
for ( i=0; i<MIX_CHANNELS; ++i ) {
if ( channel[i].playing > 0 ) {
++status;
}
}
} else {
if ( channel[which].playing > 0 ) {
++status;
}
}
return(status);
}
/* Close the mixer, halting all playing audio */
void Mix_CloseAudio(void)
{
if ( audio_opened ) {
if ( audio_opened == 1 ) {
close_music();
Mix_HaltChannel(-1);
SDL_CloseAudio();
SDL_DestroyMutex(mixer_lock);
}
--audio_opened;
}
}
/* Pause a particular channel (or all) */
void Mix_Pause(int which)
{
if ( which == -1 ) {
int i;
for ( i=0; i<MIX_CHANNELS; ++i ) {
if ( channel[i].playing > 0 ) {
channel[i].paused = 1;
}
}
} else {
if ( channel[which].playing > 0 ) {
channel[which].paused = 1;
}
}
}
/* Resume a paused channel */
void Mix_Resume(int which)
{
if ( which == -1 ) {
int i;
for ( i=0; i<MIX_CHANNELS; ++i ) {
if ( channel[i].playing > 0 ) {
channel[i].paused = 0;
}
}
} else {
if ( channel[which].playing > 0 ) {
channel[which].paused = 0;
}
}
}