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     78 >Audio Examples</H1
     79 ><P
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     82 CLASS="SECT2"
     83 ><H2
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     85 ><A
     86 NAME="AEN382"
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     88 >Opening the audio device</H2
     89 ><P
     90 ><PRE
     91 CLASS="PROGRAMLISTING"
     92 >    SDL_AudioSpec wanted;
     93     extern void fill_audio(void *udata, Uint8 *stream, int len);
     94 
     95     /* Set the audio format */
     96     wanted.freq = 22050;
     97     wanted.format = AUDIO_S16;
     98     wanted.channels = 2;    /* 1 = mono, 2 = stereo */
     99     wanted.samples = 1024;  /* Good low-latency value for callback */
    100     wanted.callback = fill_audio;
    101     wanted.userdata = NULL;
    102 
    103     /* Open the audio device, forcing the desired format */
    104     if ( SDL_OpenAudio(&#38;wanted, NULL) &#60; 0 ) {
    105         fprintf(stderr, "Couldn't open audio: %s\n", SDL_GetError());
    106         return(-1);
    107     }
    108     return(0);</PRE
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    115 ><A
    116 NAME="AEN386"
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    118 >Playing audio</H2
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    121 CLASS="PROGRAMLISTING"
    122 >    static Uint8 *audio_chunk;
    123     static Uint32 audio_len;
    124     static Uint8 *audio_pos;
    125 
    126     /* The audio function callback takes the following parameters:
    127        stream:  A pointer to the audio buffer to be filled
    128        len:     The length (in bytes) of the audio buffer
    129     */
    130     void fill_audio(void *udata, Uint8 *stream, int len)
    131     {
    132         /* Only play if we have data left */
    133         if ( audio_len == 0 )
    134             return;
    135 
    136         /* Mix as much data as possible */
    137         len = ( len &#62; audio_len ? audio_len : len );
    138         SDL_MixAudio(stream, audio_pos, len, SDL_MIX_MAXVOLUME);
    139         audio_pos += len;
    140         audio_len -= len;
    141     }
    142 
    143     /* Load the audio data ... */
    144 
    145     ;;;;;
    146 
    147     audio_pos = audio_chunk;
    148 
    149     /* Let the callback function play the audio chunk */
    150     SDL_PauseAudio(0);
    151 
    152     /* Do some processing */
    153 
    154     ;;;;;
    155 
    156     /* Wait for sound to complete */
    157     while ( audio_len &#62; 0 ) {
    158         SDL_Delay(100);         /* Sleep 1/10 second */
    159     }
    160     SDL_CloseAudio();</PRE
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