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Date: Mon, 30 Aug 2004 18:20:25 +0200 From: Joost Baas Subject: why call arts artsc? I, and a few other people at the mplayer-docs-mailinglist were wondering why you decided to call arts artsc. I understand usually users have nothing to do with libsdl, just developers, but because you can choose the audio-driver being used by mplayer, one of which is sdl, and you can also choose the sdl subdriver, it is necessary to have a well-known or logical name. artsc is not the logical choice, and it's very hard to look up the right name if you don't know what you're looking for.
author Sam Lantinga <slouken@libsdl.org>
date Fri, 17 Sep 2004 13:25:06 +0000
parents 355632dca928
children
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<HTML
><HEAD
><TITLE
>Audio Examples</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
"><LINK
REL="HOME"
TITLE="SDL Library Documentation"
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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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