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<HTML
><HEAD
><TITLE
>Audio Examples</TITLE
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>Audio Examples</H1
><P
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><A
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></A
>Opening the audio device</H2
><P
><PRE
CLASS="PROGRAMLISTING"
> SDL_AudioSpec wanted;
extern void fill_audio(void *udata, Uint8 *stream, int len);
/* Set the audio format */
wanted.freq = 22050;
wanted.format = AUDIO_S16;
wanted.channels = 2; /* 1 = mono, 2 = stereo */
wanted.samples = 1024; /* Good low-latency value for callback */
wanted.callback = fill_audio;
wanted.userdata = NULL;
/* Open the audio device, forcing the desired format */
if ( SDL_OpenAudio(&wanted, NULL) < 0 ) {
fprintf(stderr, "Couldn't open audio: %s\n", SDL_GetError());
return(-1);
}
return(0);</PRE
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><H2
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><A
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></A
>Playing audio</H2
><P
><PRE
CLASS="PROGRAMLISTING"
> static Uint8 *audio_chunk;
static Uint32 audio_len;
static Uint8 *audio_pos;
/* The audio function callback takes the following parameters:
stream: A pointer to the audio buffer to be filled
len: The length (in bytes) of the audio buffer
*/
void fill_audio(void *udata, Uint8 *stream, int len)
{
/* Only play if we have data left */
if ( audio_len == 0 )
return;
/* Mix as much data as possible */
len = ( len > audio_len ? audio_len : len );
SDL_MixAudio(stream, audio_pos, len, SDL_MIX_MAXVOLUME);
audio_pos += len;
audio_len -= len;
}
/* Load the audio data ... */
;;;;;
audio_pos = audio_chunk;
/* Let the callback function play the audio chunk */
SDL_PauseAudio(0);
/* Do some processing */
;;;;;
/* Wait for sound to complete */
while ( audio_len > 0 ) {
SDL_Delay(100); /* Sleep 1/10 second */
}
SDL_CloseAudio();</PRE
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