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  78 >Audio Examples</H1
  79 ><P
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  82 CLASS="SECT2"
  83 ><H2
  84 CLASS="SECT2"
  85 ><A
  86 NAME="AEN382"
  87 ></A
  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"
 117 ></A
 118 >Playing audio</H2
 119 ><P
 120 ><PRE
 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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