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Fixed bug #137

If SDL_OpenAudio() is passed zero for the desired format
fields, the following environment variables will be used
to fill them in:
	SDL_AUDIO_FREQUENCY
	SDL_AUDIO_FORMAT
	SDL_AUDIO_CHANNELS
	SDL_AUDIO_SAMPLES
If an environment variable is not specified, it will be set
to a reasonable default value.
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slouken committed May 9, 2006
1 parent 37e5bd4 commit 6658761ea66819a2188b78020c6bc374073175a4
Showing with 104 additions and 3 deletions.
  1. +10 −0 WhatsNew
  2. +94 −3 src/audio/SDL_audio.c
@@ -4,6 +4,16 @@ This is a list of API changes in SDL's version history.
Version 1.0:

1.2.10:
If SDL_OpenAudio() is passed zero for the desired format
fields, the following environment variables will be used
to fill them in:
SDL_AUDIO_FREQUENCY
SDL_AUDIO_FORMAT
SDL_AUDIO_CHANNELS
SDL_AUDIO_SAMPLES
If an environment variable is not specified, it will be set
to a reasonable default value.

Added support for the SDL_VIDEO_FULLSCREEN_HEAD environment
variable, currently supported on X11 Xinerama configurations.

@@ -285,6 +285,51 @@ static void SDL_UnlockAudio_Default(SDL_AudioDevice *audio)
SDL_mutexV(audio->mixer_lock);
}

static Uint16 SDL_ParseAudioFormat(const char *string)
{
Uint16 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_AudioInit(const char *driver_name)
{
SDL_AudioDevice *audio;
@@ -386,6 +431,7 @@ char *SDL_AudioDriverName(char *namebuf, int maxlen)
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 ) {
@@ -402,9 +448,35 @@ int SDL_OpenAudio(SDL_AudioSpec *desired, SDL_AudioSpec *obtained)
}

/* Verify some parameters */
if ( desired->callback == NULL ) {
SDL_SetError("SDL_OpenAudio() passed a NULL callback");
return(-1);
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 = SDL_atoi(env);
}
}
if ( desired->channels == 0 ) {
/* Pick a default number of channels */
desired->channels = 2;
}
switch ( desired->channels ) {
case 1: /* Mono */
@@ -416,6 +488,25 @@ int SDL_OpenAudio(SDL_AudioSpec *desired, SDL_AudioSpec *obtained)
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 = 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(__MACOS__) || (defined(__RISCOS__) && SDL_THREADS_DISABLED)
/* FIXME: Need to implement PPC interrupt asm for SDL_LockAudio() */

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