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pixhawk's avatar
Fixed QMapControl, added SDL
6d91ce03
 
pixhawk committed
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<HTML
><HEAD
><TITLE
>Audio Examples</TITLE
><META
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"><LINK
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TITLE="SDL Library Documentation"
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>Chapter 4. Examples</TD
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><DIV
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><H1
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><A
NAME="GUIDEAUDIOEXAMPLES"
></A
>Audio Examples</H1
><P
></P
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN382"
></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(&#38;wanted, NULL) &#60; 0 ) {
        fprintf(stderr, "Couldn't open audio: %s\n", SDL_GetError());
        return(-1);
    }
    return(0);</PRE
></P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN386"
></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 &#62; 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 &#62; 0 ) {
        SDL_Delay(100);         /* Sleep 1/10 second */
    }
    SDL_CloseAudio();</PRE
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