SDL_mixer: An audio mixer library based on the SDL library

Copyright (C) 1997, 1998, 1999, 2000, 2001 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

*/

/* This file supports streaming WAV files, without volume adjustment */

#include <stdlib.h>

#include <string.h>

#include "SDL_audio.h"

#include "SDL_mutex.h"

#include "SDL_rwops.h"

#include "SDL_endian.h"

#include "wavestream.h"

/*

Taken with permission from SDL_wave.h, part of the SDL library,

available at: http://www.libsdl.org/

and placed under the same license as this mixer library.

*/

/* WAVE files are little-endian */

/*******************************************/

/* Define values for Microsoft WAVE format */

/*******************************************/

#define RIFF 0x46464952 /* "RIFF" */

#define WAVE 0x45564157 /* "WAVE" */

#define FACT 0x74636166 /* "fact" */

#define LIST 0x5453494c /* "LIST" */

#define FMT 0x20746D66 /* "fmt " */

#define DATA 0x61746164 /* "data" */

#define PCM_CODE 1

#define ADPCM_CODE 2

#define WAVE_MONO 1

#define WAVE_STEREO 2

/* Normally, these three chunks come consecutively in a WAVE file */

typedef struct WaveFMT {

/* Not saved in the chunk we read:

Uint32 FMTchunk;

Uint32 fmtlen;

*/

Uint16 encoding;

Uint16 channels; /* 1 = mono, 2 = stereo */

Uint32 frequency; /* One of 11025, 22050, or 44100 Hz */

Uint32 byterate; /* Average bytes per second */

Uint16 blockalign; /* Bytes per sample block */

Uint16 bitspersample; /* One of 8, 12, 16, or 4 for ADPCM */

} WaveFMT;

/* The general chunk found in the WAVE file */

typedef struct Chunk {

Uint32 magic;

Uint32 length;

Uint8 *data; /* Data includes magic and length */

} Chunk;

/*********************************************/

/* Define values for AIFF (IFF audio) format */

/*********************************************/

#define FORM 0x4d524f46 /* "FORM" */

#define AIFF 0x46464941 /* "AIFF" */

#define SSND 0x444e5353 /* "SSND" */

#define COMM 0x4d4d4f43 /* "COMM" */

/* Currently we only support a single stream at a time */

static WAVStream *theWave = NULL;

/* This is initialized by the music mixer */

static SDL_mutex *music_lock = NULL;

/* This is the format of the audio mixer data */

static SDL_AudioSpec mixer;

/* Function to load the WAV/AIFF stream */

static FILE *LoadWAVStream (const char *file, SDL_AudioSpec *spec,

long *start, long *stop);

static FILE *LoadAIFFStream (const char *file, SDL_AudioSpec *spec,

long *start, long *stop);

/* Initialize the WAVStream player, with the given mixer settings

This function returns 0, or -1 if there was an error.

*/

int WAVStream_Init(SDL_AudioSpec *mixerfmt)

{

/* FIXME: clean up the mutex, or move it into music.c */

music_lock = SDL_CreateMutex();

#ifndef macintosh /* Hmm.. */

if ( music_lock == NULL ) {

return(-1);

}

#endif

mixer = *mixerfmt;

return(0);

}

/* Unimplemented */

extern void WAVStream_SetVolume(int volume)

{

}

/* Load a WAV stream from the given file */

extern WAVStream *WAVStream_LoadSong(const char *file, const char *magic)

{

WAVStream *wave;

SDL_AudioSpec wavespec;

if ( ! mixer.format ) {

return(NULL);

}

wave = (WAVStream *)malloc(sizeof *wave);

if ( wave ) {

memset(wave, 0, (sizeof *wave));

if ( strcmp(magic, "RIFF") == 0 ) {

wave->wavefp = LoadWAVStream(file, &wavespec,

&wave->start, &wave->stop);

} else

if ( strcmp(magic, "FORM") == 0 ) {

wave->wavefp = LoadAIFFStream(file, &wavespec,

&wave->start, &wave->stop);

} else {

Mix_SetError("Unknown WAVE format");

}

if ( wave->wavefp == NULL ) {

free(wave);

return(NULL);

}

SDL_BuildAudioCVT(&wave->cvt,

wavespec.format, wavespec.channels, wavespec.freq,

mixer.format, mixer.channels, mixer.freq);

}

return(wave);

}

/* Start playback of a given WAV stream */

extern void WAVStream_Start(WAVStream *wave)

{

clearerr(wave->wavefp);

fseek(wave->wavefp, wave->start, SEEK_SET);

theWave = wave;

SDL_mutexV(music_lock);

}

/* Play some of a stream previously started with WAVStream_Start()

{

long pos;

SDL_mutexP(music_lock);

if ( theWave && ((pos=ftell(theWave->wavefp)) < theWave->stop) ) {

if ( theWave->cvt.needed ) {

int original_len;

original_len=(int)((double)len/theWave->cvt.len_ratio);

if ( theWave->cvt.len != original_len ) {

if ( theWave->cvt.buf != NULL ) {

free(theWave->cvt.buf);

worksize = original_len*theWave->cvt.len_mult;

theWave->cvt.buf=(Uint8 *)malloc(worksize);

if ( theWave->cvt.buf == NULL ) {

SDL_mutexV(music_lock);

return;

}

if ( (theWave->stop - pos) < original_len ) {

original_len = (theWave->stop - pos);

original_len = fread(theWave->cvt.buf,1,original_len,theWave->wavefp);

/* At least at the time of writing, SDL_ConvertAudio()

does byte-order swapping starting at the end of the

buffer. Thus, if we are reading 16-bit samples, we

had better make damn sure that we get an even

number of bytes, or we'll get garbage.

*/

if ( (theWave->cvt.src_format & 0x0010) && (original_len & 1) ) {

original_len--;

}

theWave->cvt.len = original_len;

SDL_ConvertAudio(&theWave->cvt);

memcpy(stream, theWave->cvt.buf, theWave->cvt.len_cvt);

if ( (theWave->stop - pos) < len ) {

len = (theWave->stop - pos);

}

}

}

/* Stop playback of a stream previously started with WAVStream_Start() */

extern void WAVStream_Stop(void)

{

SDL_mutexP(music_lock);

theWave = NULL;

SDL_mutexV(music_lock);

}

/* Close the given WAV stream */

extern void WAVStream_FreeSong(WAVStream *wave)

{

if ( wave ) {

/* Remove song from the currently playing list */

SDL_mutexP(music_lock);

if ( wave == theWave ) {

theWave = NULL;

}

SDL_mutexV(music_lock);

/* Clean up associated data */

if ( wave->wavefp ) {

fclose(wave->wavefp);

}

if ( wave->cvt.buf ) {

free(wave->cvt.buf);

}

free(wave);

}

}

/* Return non-zero if a stream is currently playing */

{

int active;

active = 1;

}

return(active);

}

static int ReadChunk(SDL_RWops *src, Chunk *chunk, int read_data)

{

chunk->magic = SDL_ReadLE32(src);

chunk->length = SDL_ReadLE32(src);

if ( read_data ) {

chunk->data = (Uint8 *)malloc(chunk->length);

if ( chunk->data == NULL ) {

return(-1);

}

if ( SDL_RWread(src, chunk->data, chunk->length, 1) != 1 ) {

free(chunk->data);

return(-1);

}

} else {

SDL_RWseek(src, chunk->length, SEEK_CUR);

}

return(chunk->length);

}

static FILE *LoadWAVStream (const char *file, SDL_AudioSpec *spec,

long *start, long *stop)

{

int was_error;

FILE *wavefp;

SDL_RWops *src;

Chunk chunk;

int lenread;

/* WAV magic header */

Uint32 RIFFchunk;

Uint32 wavelen;

Uint32 WAVEmagic;

/* FMT chunk */

WaveFMT *format = NULL;

/* Make sure we are passed a valid data source */

was_error = 0;

wavefp = fopen(file, "rb");

src = NULL;

if ( wavefp ) {

src = SDL_RWFromFP(wavefp, 0);

}

if ( src == NULL ) {

was_error = 1;

goto done;

}

/* Check the magic header */

RIFFchunk = SDL_ReadLE32(src);

wavelen = SDL_ReadLE32(src);

WAVEmagic = SDL_ReadLE32(src);

if ( (RIFFchunk != RIFF) || (WAVEmagic != WAVE) ) {

was_error = 1;

goto done;

}

/* Read the audio data format chunk */

chunk.data = NULL;

do {

/* FIXME! Add this logic to SDL_LoadWAV_RW() */

if ( chunk.data ) {

free(chunk.data);

}

lenread = ReadChunk(src, &chunk, 1);

if ( lenread < 0 ) {

was_error = 1;

goto done;

}

} while ( (chunk.magic == FACT) || (chunk.magic == LIST) );

/* Decode the audio data format */

format = (WaveFMT *)chunk.data;

if ( chunk.magic != FMT ) {

free(chunk.data);

was_error = 1;

goto done;

}

switch (SDL_SwapLE16(format->encoding)) {

case PCM_CODE:

/* We can understand this */

break;

default:

was_error = 1;

goto done;

}

memset(spec, 0, (sizeof *spec));

spec->freq = SDL_SwapLE32(format->frequency);

switch (SDL_SwapLE16(format->bitspersample)) {

case 8:

spec->format = AUDIO_U8;

break;

case 16:

spec->format = AUDIO_S16;

break;

default:

was_error = 1;

goto done;

}

spec->samples = 4096; /* Good default buffer size */

/* Set the file offset to the DATA chunk data */

chunk.data = NULL;

do {

*start = SDL_RWtell(src) + 2*sizeof(Uint32);

lenread = ReadChunk(src, &chunk, 0);

if ( lenread < 0 ) {

was_error = 1;

goto done;

}

} while ( chunk.magic != DATA );

*stop = SDL_RWtell(src);

done:

if ( format != NULL ) {

free(format);

}

if ( src ) {

SDL_RWclose(src);

}

if ( was_error ) {

if ( wavefp ) {

fclose(wavefp);

wavefp = NULL;

}

}

return(wavefp);

}

/* I couldn't get SANE_to_double() to work, so I stole this from libsndfile.

* I don't pretend to fully understand it.

*/

static Uint32 SANE_to_Uint32 (Uint8 *sanebuf)

/* Negative number? */

if (sanebuf[0] & 0x80)

return 0;

/* Less than 1? */

if (sanebuf[0] <= 0x3F)

return 1;

/* Way too big? */

if (sanebuf[0] > 0x40)

return 0x4000000;

/* Still too big? */

if (sanebuf[0] == 0x40 && sanebuf[1] > 0x1C)

return 800000000;

return ((sanebuf[2] << 23) | (sanebuf[3] << 15) | (sanebuf[4] << 7)

| (sanebuf[5] >> 1)) >> (29 - sanebuf[1]);

}

static FILE *LoadAIFFStream (const char *file, SDL_AudioSpec *spec,

long *start, long *stop)

{

int was_error;

int found_SSND;

int found_COMM;

FILE *wavefp;

SDL_RWops *src;

Uint32 chunk_type;

Uint32 chunk_length;

long next_chunk;

/* AIFF magic header */

Uint32 FORMchunk;

Uint32 AIFFmagic;

/* SSND chunk */

Uint32 offset;

Uint32 blocksize;

/* COMM format chunk */

Uint16 channels = 0;

Uint32 numsamples = 0;

Uint16 samplesize = 0;

/* Make sure we are passed a valid data source */

was_error = 0;

wavefp = fopen(file, "rb");

src = NULL;

if ( wavefp ) {

src = SDL_RWFromFP(wavefp, 0);

}

if ( src == NULL ) {

was_error = 1;

goto done;

}

/* Check the magic header */

FORMchunk = SDL_ReadLE32(src);

AIFFmagic = SDL_ReadLE32(src);

if ( (FORMchunk != FORM) || (AIFFmagic != AIFF) ) {

was_error = 1;

goto done;

}

/* From what I understand of the specification, chunks may appear in

* any order, and we should just ignore unknown ones.

*

* TODO: Better sanity-checking. E.g. what happens if the AIFF file

* contains compressed sound data?

found_SSND = 0;

found_COMM = 0;

do {

chunk_type = SDL_ReadLE32(src);

chunk_length = SDL_ReadBE32(src);

next_chunk = SDL_RWtell(src) + chunk_length;

/* Paranoia to avoid infinite loops */

if (chunk_length == 0)

break;

switch (chunk_type) {

case SSND:

found_SSND = 1;

offset = SDL_ReadBE32(src);

blocksize = SDL_ReadBE32(src);

*start = SDL_RWtell(src) + offset;

break;

case COMM:

found_COMM = 1;

/* Read the audio data format chunk */

channels = SDL_ReadBE16(src);

numsamples = SDL_ReadBE32(src);

samplesize = SDL_ReadBE16(src);

SDL_RWread(src, sane_freq, sizeof(sane_freq), 1);

frequency = SANE_to_Uint32(sane_freq);

break;

default:

break;

}

} while ((!found_SSND || !found_COMM)

&& SDL_RWseek(src, next_chunk, SEEK_SET) != -1);

if (!found_SSND) {

was_error = 1;

goto done;

}

if (!found_COMM) {

was_error = 1;

goto done;

/* Decode the audio data format */

memset(spec, 0, (sizeof *spec));

spec->freq = frequency;

switch (samplesize) {

case 8:

break;

case 16:

break;

default:

was_error = 1;

goto done;

}

spec->samples = 4096; /* Good default buffer size */

done:

if ( src ) {

SDL_RWclose(src);

}

if ( was_error ) {

if ( wavefp ) {

fclose(wavefp);

wavefp = NULL;

}

}

return(wavefp);

}