Mercurial > sdl-ios-xcode

view docs/html/sdlconvertaudio.html @ 2787:93764fe8601a

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
It turns out both the software and the OpenGL renderer had the same problem. According to the spec, when SDL_SRCALPHA is set, the colorkey is ignored, so we just need to convert the colorkey into the alpha channel.
author Sam Lantinga <slouken@libsdl.org>
date Tue, 25 Nov 2008 05:29:14 +0000
parents 355632dca928
children
line wrap: on
line source

<HTML
><HEAD
><TITLE
>SDL_ConvertAudio</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
"><LINK
REL="HOME"
TITLE="SDL Library Documentation"
HREF="index.html"><LINK
REL="UP"
TITLE="Audio"
HREF="audio.html"><LINK
REL="PREVIOUS"
TITLE="SDL_BuildAudioCVT"
HREF="sdlbuildaudiocvt.html"><LINK
REL="NEXT"
TITLE="SDL_MixAudio"
HREF="sdlmixaudio.html"></HEAD
><BODY
CLASS="REFENTRY"
BGCOLOR="#FFF8DC"
TEXT="#000000"
LINK="#0000ee"
VLINK="#551a8b"
ALINK="#ff0000"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>SDL Library Documentation</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="sdlbuildaudiocvt.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
></TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="sdlmixaudio.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><H1
><A
NAME="SDLCONVERTAUDIO"
></A
>SDL_ConvertAudio</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN7048"
></A
><H2
>Name</H2
>SDL_ConvertAudio&nbsp;--&nbsp;Convert audio data to a desired audio format.</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN7051"
></A
><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><A
NAME="AEN7052"
></A
><P
></P
><PRE
CLASS="FUNCSYNOPSISINFO"
>#include "SDL.h"</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>int <B
CLASS="FSFUNC"
>SDL_ConvertAudio</B
></CODE
>(SDL_AudioCVT *cvt);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN7058"
></A
><H2
>Description</H2
><P
><TT
CLASS="FUNCTION"
>SDL_ConvertAudio</TT
> takes one parameter, <TT
CLASS="PARAMETER"
><I
>cvt</I
></TT
>, which was previously initilized. Initilizing a <A
HREF="sdlaudiocvt.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_AudioCVT</SPAN
></A
> is a two step process. First of all, the structure must be passed to <A
HREF="sdlbuildaudiocvt.html"
><TT
CLASS="FUNCTION"
>SDL_BuildAudioCVT</TT
></A
> along with source and destination format parameters. Secondly, the <SPAN
CLASS="STRUCTNAME"
>cvt</SPAN
>-&#62;<TT
CLASS="STRUCTFIELD"
><I
>buf</I
></TT
> and <SPAN
CLASS="STRUCTNAME"
>cvt</SPAN
>-&#62;<TT
CLASS="STRUCTFIELD"
><I
>len</I
></TT
> fields must be setup. <SPAN
CLASS="STRUCTNAME"
>cvt</SPAN
>-&#62;<TT
CLASS="STRUCTFIELD"
><I
>buf</I
></TT
> should point to the audio data and <SPAN
CLASS="STRUCTNAME"
>cvt</SPAN
>-&#62;<TT
CLASS="STRUCTFIELD"
><I
>len</I
></TT
> should be set to the length of the audio data in bytes. Remember, the length of the buffer pointed to by <TT
CLASS="STRUCTFIELD"
><I
>buf</I
></TT
> show be <TT
CLASS="STRUCTFIELD"
><I
>len</I
></TT
>*<TT
CLASS="STRUCTFIELD"
><I
>len_mult</I
></TT
> bytes in length.</P
><P
>Once the <SPAN
CLASS="STRUCTNAME"
>SDL_AudioCVT</SPAN
>structure is initilized then we can pass it to <TT
CLASS="FUNCTION"
>SDL_ConvertAudio</TT
>, which will convert the audio data pointer to by <SPAN
CLASS="STRUCTNAME"
>cvt</SPAN
>-&#62;<TT
CLASS="STRUCTFIELD"
><I
>buf</I
></TT
>. If <TT
CLASS="FUNCTION"
>SDL_ConvertAudio</TT
> returned <SPAN
CLASS="RETURNVALUE"
>0</SPAN
> then the conversion was completed successfully, otherwise <SPAN
CLASS="RETURNVALUE"
>-1</SPAN
> is returned.</P
><P
>If the conversion completed successfully then the converted audio data can be read from <SPAN
CLASS="STRUCTNAME"
>cvt</SPAN
>-&#62;<TT
CLASS="STRUCTFIELD"
><I
>buf</I
></TT
>. The amount of valid, converted, audio data in the buffer is equal to <SPAN
CLASS="STRUCTNAME"
>cvt</SPAN
>-&#62;<TT
CLASS="STRUCTFIELD"
><I
>len</I
></TT
>*<TT
CLASS="STRUCTFIELD"
><I
>cvt</I
></TT
>-&#62;<SPAN
CLASS="STRUCTNAME"
>len_ratio</SPAN
>.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN7093"
></A
><H2
>Examples</H2
><PRE
CLASS="PROGRAMLISTING"
>/* Converting some WAV data to hardware format */
void my_audio_callback(void *userdata, Uint8 *stream, int len);

SDL_AudioSpec *desired, *obtained;
SDL_AudioSpec wav_spec;
SDL_AudioCVT  wav_cvt;
Uint32 wav_len;
Uint8 *wav_buf;
int ret;

/* Allocated audio specs */
desired = malloc(sizeof(SDL_AudioSpec));
obtained = malloc(sizeof(SDL_AudioSpec));

/* Set desired format */
desired-&#62;freq=22050;
desired-&#62;format=AUDIO_S16LSB;
desired-&#62;samples=8192;
desired-&#62;callback=my_audio_callback;
desired-&#62;userdata=NULL;

/* Open the audio device */
if ( SDL_OpenAudio(desired, obtained) &#60; 0 ){
  fprintf(stderr, "Couldn't open audio: %s\n", SDL_GetError());
  exit(-1);
}
        
free(desired);

/* Load the test.wav */
if( SDL_LoadWAV("test.wav", &#38;wav_spec, &#38;wav_buf, &#38;wav_len) == NULL ){
  fprintf(stderr, "Could not open test.wav: %s\n", SDL_GetError());
  SDL_CloseAudio();
  free(obtained);
  exit(-1);
}
                                            
/* Build AudioCVT */
ret = SDL_BuildAudioCVT(&#38;wav_cvt,
                        wav_spec.format, wav_spec.channels, wav_spec.freq,
                        obtained-&#62;format, obtained-&#62;channels, obtained-&#62;freq);

/* Check that the convert was built */
if(ret==-1){
  fprintf(stderr, "Couldn't build converter!\n");
  SDL_CloseAudio();
  free(obtained);
  SDL_FreeWAV(wav_buf);
}

/* Setup for conversion */
wav_cvt.buf = malloc(wav_len * wav_cvt.len_mult);
wav_cvt.len = wav_len;
memcpy(wav_cvt.buf, wav_buf, wav_len);

/* We can delete to original WAV data now */
SDL_FreeWAV(wav_buf);

/* And now we're ready to convert */
SDL_ConvertAudio(&#38;wav_cvt);

/* do whatever */
.
.
.
.
&#13;</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN7096"
></A
><H2
>See Also</H2
><P
><A
HREF="sdlbuildaudiocvt.html"
><TT
CLASS="FUNCTION"
>SDL_BuildAudioCVT</TT
></A
>,
<A
HREF="sdlaudiocvt.html"
><TT
CLASS="FUNCTION"
>SDL_AudioCVT</TT
></A
></P
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="sdlbuildaudiocvt.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="sdlmixaudio.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>SDL_BuildAudioCVT</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="audio.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>SDL_MixAudio</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>