src/audio/SDL_audio.c
author Ryan C. Gordon <icculus@icculus.org>
Thu, 31 Aug 2006 20:59:42 +0000
changeset 1993 7a3889fc9e5d
parent 1982 3b4ce57c6215
child 2045 510892a215a2
permissions -rw-r--r--
Reordered the favored audio format list a little.

/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2006 Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 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
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    Sam Lantinga
    slouken@libsdl.org
*/
#include "SDL_config.h"

/* Allow access to a raw mixing buffer */

#include "SDL.h"
#include "SDL_audio_c.h"
#include "SDL_audiomem.h"
#include "SDL_sysaudio.h"

#ifdef __OS2__
/* We'll need the DosSetPriority() API! */
#define INCL_DOSPROCESS
#include <os2.h>
#endif

/* Available audio drivers */
static AudioBootStrap *bootstrap[] = {
#if SDL_AUDIO_DRIVER_BSD
    &BSD_AUDIO_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_OSS
    &DSP_bootstrap,
    &DMA_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_ALSA
    &ALSA_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_QNXNTO
    &QNXNTOAUDIO_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_SUNAUDIO
    &SUNAUDIO_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_DMEDIA
    &DMEDIA_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_ARTS
    &ARTS_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_ESD
    &ESD_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_NAS
    &NAS_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_DSOUND
    &DSOUND_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_WAVEOUT
    &WAVEOUT_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_PAUD
    &Paud_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_BAUDIO
    &BAUDIO_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_COREAUDIO
    &COREAUDIO_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_SNDMGR
    &SNDMGR_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_AHI
    &AHI_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_MINT
    &MINTAUDIO_GSXB_bootstrap,
    &MINTAUDIO_MCSN_bootstrap,
    &MINTAUDIO_STFA_bootstrap,
    &MINTAUDIO_XBIOS_bootstrap,
    &MINTAUDIO_DMA8_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_DISK
    &DISKAUD_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_DUMMY
    &DUMMYAUD_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_DC
    &DCAUD_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_MMEAUDIO
    &MMEAUDIO_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_DART
    &DART_bootstrap,
#endif
    NULL
};
SDL_AudioDevice *current_audio = NULL;

/* Various local functions */
int SDL_AudioInit(const char *driver_name);
void SDL_AudioQuit(void);

#if SDL_AUDIO_DRIVER_AHI
static int audio_configured = 0;
#endif

/* The general mixing thread function */
int SDLCALL
SDL_RunAudio(void *audiop)
{
    SDL_AudioDevice *audio = (SDL_AudioDevice *) audiop;
    Uint8 *stream;
    int stream_len;
    void *udata;
    void (SDLCALL * fill) (void *userdata, Uint8 * stream, int len);
    int silence;
#if SDL_AUDIO_DRIVER_AHI
    int started = 0;

/* AmigaOS NEEDS that the audio driver is opened in the thread that uses it! */

    D(bug("Task audio started audio struct:<%lx>...\n", audiop));

    D(bug("Before Openaudio..."));
    if (audio->OpenAudio(audio, &audio->spec) == -1) {
        D(bug("Open audio failed...\n"));
        return (-1);
    }
    D(bug("OpenAudio...OK\n"));
#endif

    /* Perform any thread setup */
    if (audio->ThreadInit) {
        audio->ThreadInit(audio);
    }
    audio->threadid = SDL_ThreadID();

    /* Set up the mixing function */
    fill = audio->spec.callback;
    udata = audio->spec.userdata;

#if SDL_AUDIO_DRIVER_AHI
    audio_configured = 1;

    D(bug("Audio configured... Checking for conversion\n"));
    SDL_mutexP(audio->mixer_lock);
    D(bug("Semaphore obtained...\n"));
#endif

    if (audio->convert.needed) {
        if (audio->convert.src_format == AUDIO_U8) {
            silence = 0x80;
        } else {
            silence = 0;
        }
        stream_len = audio->convert.len;
    } else {
        silence = audio->spec.silence;
        stream_len = audio->spec.size;
    }

#if SDL_AUDIO_DRIVER_AHI
    SDL_mutexV(audio->mixer_lock);
    D(bug("Entering audio loop...\n"));
#endif

#ifdef __OS2__
    /* Increase the priority of this thread to make sure that
       the audio will be continuous all the time! */
#ifdef USE_DOSSETPRIORITY
    if (SDL_getenv("SDL_USE_TIMECRITICAL_AUDIO")) {
#ifdef DEBUG_BUILD
        printf
            ("[SDL_RunAudio] : Setting priority to TimeCritical+0! (TID%d)\n",
             SDL_ThreadID());
#endif
        DosSetPriority(PRTYS_THREAD, PRTYC_TIMECRITICAL, 0, 0);
    } else {
#ifdef DEBUG_BUILD
        printf
            ("[SDL_RunAudio] : Setting priority to ForegroundServer+0! (TID%d)\n",
             SDL_ThreadID());
#endif
        DosSetPriority(PRTYS_THREAD, PRTYC_FOREGROUNDSERVER, 0, 0);
    }
#endif
#endif

    /* Loop, filling the audio buffers */
    while (audio->enabled) {

        /* Fill the current buffer with sound */
        if (audio->convert.needed) {
            if (audio->convert.buf) {
                stream = audio->convert.buf;
            } else {
                continue;
            }
        } else {
            stream = audio->GetAudioBuf(audio);
            if (stream == NULL) {
                stream = audio->fake_stream;
            }
        }
        SDL_memset(stream, silence, stream_len);

        if (!audio->paused) {
            SDL_mutexP(audio->mixer_lock);
            (*fill) (udata, stream, stream_len);
            SDL_mutexV(audio->mixer_lock);
        }

        /* Convert the audio if necessary */
        if (audio->convert.needed) {
            SDL_ConvertAudio(&audio->convert);
            stream = audio->GetAudioBuf(audio);
            if (stream == NULL) {
                stream = audio->fake_stream;
            }
            SDL_memcpy(stream, audio->convert.buf, audio->convert.len_cvt);
        }

        /* Ready current buffer for play and change current buffer */
        if (stream != audio->fake_stream) {
            audio->PlayAudio(audio);
        }

        /* Wait for an audio buffer to become available */
        if (stream == audio->fake_stream) {
            SDL_Delay((audio->spec.samples * 1000) / audio->spec.freq);
        } else {
            audio->WaitAudio(audio);
        }
    }

    /* Wait for the audio to drain.. */
    if (audio->WaitDone) {
        audio->WaitDone(audio);
    }
#if SDL_AUDIO_DRIVER_AHI
    D(bug("WaitAudio...Done\n"));

    audio->CloseAudio(audio);

    D(bug("CloseAudio..Done, subtask exiting...\n"));
    audio_configured = 0;
#endif
#ifdef __OS2__
#ifdef DEBUG_BUILD
    printf("[SDL_RunAudio] : Task exiting. (TID%d)\n", SDL_ThreadID());
#endif
#endif
    return (0);
}

static void
SDL_LockAudio_Default(SDL_AudioDevice * audio)
{
    if (audio->thread && (SDL_ThreadID() == audio->threadid)) {
        return;
    }
    SDL_mutexP(audio->mixer_lock);
}

static void
SDL_UnlockAudio_Default(SDL_AudioDevice * audio)
{
    if (audio->thread && (SDL_ThreadID() == audio->threadid)) {
        return;
    }
    SDL_mutexV(audio->mixer_lock);
}

static SDL_AudioFormat
SDL_ParseAudioFormat(const char *string)
{
    SDL_AudioFormat format = 0;

    switch (*string) {
    case 'U':
        ++string;
        format |= 0x0000;
        break;
    case 'S':
        ++string;
        format |= 0x8000;
        break;
    default:
        return 0;
    }
    switch (SDL_atoi(string)) {
    case 8:
        string += 1;
        format |= 8;
        break;
    case 16:
        string += 2;
        format |= 16;
        if (SDL_strcmp(string, "LSB") == 0
#if SDL_BYTEORDER == SDL_LIL_ENDIAN
            || SDL_strcmp(string, "SYS") == 0
#endif
            ) {
            format |= 0x0000;
        }
        if (SDL_strcmp(string, "MSB") == 0
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
            || SDL_strcmp(string, "SYS") == 0
#endif
            ) {
            format |= 0x1000;
        }
        break;
    default:
        return 0;
    }
    return format;
}

int
SDL_GetNumAudioDrivers(void)
{
    return (SDL_arraysize(bootstrap) - 1);
}

const char *
SDL_GetAudioDriver(int index)
{
    if (index >= 0 && index < SDL_GetNumAudioDrivers()) {
        return (bootstrap[index]->name);
    }
    return (NULL);
}

int
SDL_AudioInit(const char *driver_name)
{
    SDL_AudioDevice *audio;
    int i = 0, idx;

    /* Check to make sure we don't overwrite 'current_audio' */
    if (current_audio != NULL) {
        SDL_AudioQuit();
    }

    /* Select the proper audio driver */
    audio = NULL;
    idx = 0;
    if (driver_name == NULL) {
        driver_name = SDL_getenv("SDL_AUDIODRIVER");
    }
#if SDL_AUDIO_DRIVER_ESD
    if ((driver_name == NULL) && (SDL_getenv("ESPEAKER") != NULL)) {
        /* Ahem, we know that if ESPEAKER is set, user probably wants
           to use ESD, but don't start it if it's not already running.
           This probably isn't the place to do this, but... Shh! :)
         */
        for (i = 0; bootstrap[i]; ++i) {
            if (SDL_strcmp(bootstrap[i]->name, "esd") == 0) {
#ifdef HAVE_PUTENV
                const char *esd_no_spawn;

                /* Don't start ESD if it's not running */
                esd_no_spawn = getenv("ESD_NO_SPAWN");
                if (esd_no_spawn == NULL) {
                    putenv("ESD_NO_SPAWN=1");
                }
#endif
                if (bootstrap[i]->available()) {
                    audio = bootstrap[i]->create(0);
                    break;
                }
#ifdef HAVE_UNSETENV
                if (esd_no_spawn == NULL) {
                    unsetenv("ESD_NO_SPAWN");
                }
#endif
            }
        }
    }
#endif /* SDL_AUDIO_DRIVER_ESD */
    if (audio == NULL) {
        if (driver_name != NULL) {
            for (i = 0; bootstrap[i]; ++i) {
                if (SDL_strncmp(bootstrap[i]->name, driver_name,
                                SDL_strlen(bootstrap[i]->name)) == 0) {
                    if (bootstrap[i]->available()) {
                        audio = bootstrap[i]->create(idx);
                    }
                    break;
                }
            }
        } else {
            for (i = 0; bootstrap[i]; ++i) {
                if (bootstrap[i]->available()) {
                    audio = bootstrap[i]->create(idx);
                    if (audio != NULL) {
                        break;
                    }
                }
            }
        }
        if (audio == NULL) {
            if (driver_name) {
                SDL_SetError("%s not available", driver_name);
            } else {
                SDL_SetError("No available audio device");
            }
#if 0
            /* Don't fail SDL_Init() if audio isn't available.
               SDL_OpenAudio() will handle it at that point.  *sigh*
             */
            return (-1);
#endif
        }
    }
    current_audio = audio;
    if (current_audio) {
        current_audio->name = bootstrap[i]->name;
        if (!current_audio->LockAudio && !current_audio->UnlockAudio) {
            current_audio->LockAudio = SDL_LockAudio_Default;
            current_audio->UnlockAudio = SDL_UnlockAudio_Default;
        }
    }
    return (0);
}

/*
 * Get the current audio driver name
 */
const char *
SDL_GetCurrentAudioDriver()
{
    if (current_audio) {
        return current_audio->name;
    }
    return (NULL);
}

int
SDL_OpenAudio(SDL_AudioSpec * desired, SDL_AudioSpec * obtained)
{
    SDL_AudioDevice *audio;
    const char *env;

    /* Start up the audio driver, if necessary */
    if (!current_audio) {
        if ((SDL_InitSubSystem(SDL_INIT_AUDIO) < 0) ||
            (current_audio == NULL)) {
            return (-1);
        }
    }
    audio = current_audio;

    if (audio->opened) {
        SDL_SetError("Audio device is already opened");
        return (-1);
    }

    /* Verify some parameters */
    if (desired->freq == 0) {
        env = SDL_getenv("SDL_AUDIO_FREQUENCY");
        if (env) {
            desired->freq = SDL_atoi(env);
        }
    }
    if (desired->freq == 0) {
        /* Pick some default audio frequency */
        desired->freq = 22050;
    }
    if (desired->format == 0) {
        env = SDL_getenv("SDL_AUDIO_FORMAT");
        if (env) {
            desired->format = SDL_ParseAudioFormat(env);
        }
    }
    if (desired->format == 0) {
        /* Pick some default audio format */
        desired->format = AUDIO_S16;
    }
    if (desired->channels == 0) {
        env = SDL_getenv("SDL_AUDIO_CHANNELS");
        if (env) {
            desired->channels = (Uint8) SDL_atoi(env);
        }
    }
    if (desired->channels == 0) {
        /* Pick a default number of channels */
        desired->channels = 2;
    }
    switch (desired->channels) {
    case 1:                    /* Mono */
    case 2:                    /* Stereo */
    case 4:                    /* surround */
    case 6:                    /* surround with center and lfe */
        break;
    default:
        SDL_SetError("1 (mono) and 2 (stereo) channels supported");
        return (-1);
    }
    if (desired->samples == 0) {
        env = SDL_getenv("SDL_AUDIO_SAMPLES");
        if (env) {
            desired->samples = (Uint16) SDL_atoi(env);
        }
    }
    if (desired->samples == 0) {
        /* Pick a default of ~46 ms at desired frequency */
        int samples = (desired->freq / 1000) * 46;
        int power2 = 1;
        while (power2 < samples) {
            power2 *= 2;
        }
        desired->samples = power2;
    }
    if (desired->callback == NULL) {
        SDL_SetError("SDL_OpenAudio() passed a NULL callback");
        return (-1);
    }
#if defined(__MINT__) && SDL_THREADS_DISABLED
    /* Uses interrupt driven audio, without thread */
#else
    /* Create a semaphore for locking the sound buffers */
    audio->mixer_lock = SDL_CreateMutex();
    if (audio->mixer_lock == NULL) {
        SDL_SetError("Couldn't create mixer lock");
        SDL_CloseAudio();
        return (-1);
    }
#endif /* __MINT__ */

    /* Calculate the silence and size of the audio specification */
    SDL_CalculateAudioSpec(desired);

    /* Open the audio subsystem */
    SDL_memcpy(&audio->spec, desired, sizeof(audio->spec));
    audio->convert.needed = 0;
    audio->enabled = 1;
    audio->paused = 1;

#if !SDL_AUDIO_DRIVER_AHI

/* AmigaOS opens audio inside the main loop */
    audio->opened = audio->OpenAudio(audio, &audio->spec) + 1;

    if (!audio->opened) {
        SDL_CloseAudio();
        return (-1);
    }
#else
    D(bug("Locking semaphore..."));
    SDL_mutexP(audio->mixer_lock);


    audio->thread = SDL_CreateThread(SDL_RunAudio, audio);
    D(bug("Created thread...\n"));

    if (audio->thread == NULL) {
        SDL_mutexV(audio->mixer_lock);
        SDL_CloseAudio();
        SDL_SetError("Couldn't create audio thread");
        return (-1);
    }

    while (!audio_configured)
        SDL_Delay(100);
#endif

    /* If the audio driver changes the buffer size, accept it */
    if (audio->spec.samples != desired->samples) {
        desired->samples = audio->spec.samples;
        SDL_CalculateAudioSpec(desired);
    }

    /* Allocate a fake audio memory buffer */
    audio->fake_stream = SDL_AllocAudioMem(audio->spec.size);
    if (audio->fake_stream == NULL) {
        SDL_CloseAudio();
        SDL_OutOfMemory();
        return (-1);
    }

    /* See if we need to do any conversion */
    if (obtained != NULL) {
        SDL_memcpy(obtained, &audio->spec, sizeof(audio->spec));
    } else if (desired->freq != audio->spec.freq ||
               desired->format != audio->spec.format ||
               desired->channels != audio->spec.channels) {
        /* Build an audio conversion block */
        if (SDL_BuildAudioCVT(&audio->convert,
                              desired->format, desired->channels,
                              desired->freq,
                              audio->spec.format, audio->spec.channels,
                              audio->spec.freq) < 0) {
            SDL_CloseAudio();
            return (-1);
        }
        if (audio->convert.needed) {
            audio->convert.len = desired->size;
            audio->convert.buf =
                (Uint8 *) SDL_AllocAudioMem(audio->convert.len *
                                            audio->convert.len_mult);
            if (audio->convert.buf == NULL) {
                SDL_CloseAudio();
                SDL_OutOfMemory();
                return (-1);
            }
        }
    }
#if !SDL_AUDIO_DRIVER_AHI
    /* Start the audio thread if necessary */
    switch (audio->opened) {
    case 1:
        /* Start the audio thread */
#if (defined(__WIN32__) && !defined(_WIN32_WCE)) && !defined(HAVE_LIBC)
#undef SDL_CreateThread
        audio->thread = SDL_CreateThread(SDL_RunAudio, audio, NULL, NULL);
#else
        audio->thread = SDL_CreateThread(SDL_RunAudio, audio);
#endif
        if (audio->thread == NULL) {
            SDL_CloseAudio();
            SDL_SetError("Couldn't create audio thread");
            return (-1);
        }
        break;

    default:
        /* The audio is now playing */
        break;
    }
#else
    SDL_mutexV(audio->mixer_lock);
    D(bug("SDL_OpenAudio USCITA...\n"));

#endif

    return (0);
}

SDL_audiostatus
SDL_GetAudioStatus(void)
{
    SDL_AudioDevice *audio = current_audio;
    SDL_audiostatus status;

    status = SDL_AUDIO_STOPPED;
    if (audio && audio->enabled) {
        if (audio->paused) {
            status = SDL_AUDIO_PAUSED;
        } else {
            status = SDL_AUDIO_PLAYING;
        }
    }
    return (status);
}

void
SDL_PauseAudio(int pause_on)
{
    SDL_AudioDevice *audio = current_audio;

    if (audio) {
        audio->paused = pause_on;
    }
}

void
SDL_LockAudio(void)
{
    SDL_AudioDevice *audio = current_audio;

    /* Obtain a lock on the mixing buffers */
    if (audio && audio->LockAudio) {
        audio->LockAudio(audio);
    }
}

void
SDL_UnlockAudio(void)
{
    SDL_AudioDevice *audio = current_audio;

    /* Release lock on the mixing buffers */
    if (audio && audio->UnlockAudio) {
        audio->UnlockAudio(audio);
    }
}

void
SDL_CloseAudio(void)
{
    SDL_QuitSubSystem(SDL_INIT_AUDIO);
}

void
SDL_AudioQuit(void)
{
    SDL_AudioDevice *audio = current_audio;

    if (audio) {
        audio->enabled = 0;
        if (audio->thread != NULL) {
            SDL_WaitThread(audio->thread, NULL);
        }
        if (audio->mixer_lock != NULL) {
            SDL_DestroyMutex(audio->mixer_lock);
        }
        if (audio->fake_stream != NULL) {
            SDL_FreeAudioMem(audio->fake_stream);
        }
        if (audio->convert.needed) {
            SDL_FreeAudioMem(audio->convert.buf);

        }
#if !SDL_AUDIO_DRIVER_AHI
        if (audio->opened) {
            audio->CloseAudio(audio);
            audio->opened = 0;
        }
#endif
        /* Free the driver data */
        audio->free(audio);
        current_audio = NULL;
    }
}

#define NUM_FORMATS 10
static int format_idx;
static int format_idx_sub;
static SDL_AudioFormat format_list[NUM_FORMATS][NUM_FORMATS] = {
    {AUDIO_U8, AUDIO_S8, AUDIO_S16LSB, AUDIO_S16MSB, AUDIO_U16LSB,
     AUDIO_U16MSB, AUDIO_S32LSB, AUDIO_S32MSB, AUDIO_F32LSB, AUDIO_F32MSB},
    {AUDIO_S8, AUDIO_U8, AUDIO_S16LSB, AUDIO_S16MSB, AUDIO_U16LSB,
     AUDIO_U16MSB, AUDIO_S32LSB, AUDIO_S32MSB, AUDIO_F32LSB, AUDIO_F32MSB},
    {AUDIO_S16LSB, AUDIO_S16MSB, AUDIO_U16LSB, AUDIO_U16MSB, AUDIO_S32LSB,
     AUDIO_S32MSB, AUDIO_F32LSB, AUDIO_F32MSB, AUDIO_U8, AUDIO_S8},
    {AUDIO_S16MSB, AUDIO_S16LSB, AUDIO_U16MSB, AUDIO_U16LSB, AUDIO_S32MSB,
     AUDIO_S32LSB, AUDIO_F32MSB, AUDIO_F32LSB, AUDIO_U8, AUDIO_S8},
    {AUDIO_U16LSB, AUDIO_U16MSB, AUDIO_S16LSB, AUDIO_S16MSB, AUDIO_S32LSB,
     AUDIO_S32MSB, AUDIO_F32LSB, AUDIO_F32MSB, AUDIO_U8, AUDIO_S8},
    {AUDIO_U16MSB, AUDIO_U16LSB, AUDIO_S16MSB, AUDIO_S16LSB, AUDIO_S32MSB,
     AUDIO_S32LSB, AUDIO_F32MSB, AUDIO_F32LSB, AUDIO_U8, AUDIO_S8},
    {AUDIO_S32LSB, AUDIO_S32MSB, AUDIO_F32LSB, AUDIO_F32MSB, AUDIO_S16LSB,
     AUDIO_S16MSB, AUDIO_U16LSB, AUDIO_U16MSB, AUDIO_U8, AUDIO_S8},
    {AUDIO_S32MSB, AUDIO_S32LSB, AUDIO_F32MSB, AUDIO_F32LSB, AUDIO_S16MSB,
     AUDIO_S16LSB, AUDIO_U16MSB, AUDIO_U16LSB, AUDIO_U8, AUDIO_S8},
    {AUDIO_F32LSB, AUDIO_F32MSB, AUDIO_S32LSB, AUDIO_S32MSB, AUDIO_S16LSB,
     AUDIO_S16MSB, AUDIO_U16LSB, AUDIO_U16MSB, AUDIO_U8, AUDIO_S8},
    {AUDIO_F32MSB, AUDIO_F32LSB, AUDIO_S32MSB, AUDIO_S32LSB, AUDIO_S16MSB,
     AUDIO_S16LSB, AUDIO_U16MSB, AUDIO_U16LSB, AUDIO_U8, AUDIO_S8},
};

SDL_AudioFormat
SDL_FirstAudioFormat(SDL_AudioFormat format)
{
    for (format_idx = 0; format_idx < NUM_FORMATS; ++format_idx) {
        if (format_list[format_idx][0] == format) {
            break;
        }
    }
    format_idx_sub = 0;
    return (SDL_NextAudioFormat());
}

SDL_AudioFormat
SDL_NextAudioFormat(void)
{
    if ((format_idx == NUM_FORMATS) || (format_idx_sub == NUM_FORMATS)) {
        return (0);
    }
    return (format_list[format_idx][format_idx_sub++]);
}

void
SDL_CalculateAudioSpec(SDL_AudioSpec * spec)
{
    switch (spec->format) {
    case AUDIO_U8:
        spec->silence = 0x80;
        break;
    default:
        spec->silence = 0x00;
        break;
    }
    spec->size = (spec->format & 0xFF) / 8;
    spec->size *= spec->channels;
    spec->size *= spec->samples;
}

/* vi: set ts=4 sw=4 expandtab: */