Mercurial > sdl-ios-xcode
view docs/html/sdlconvertaudio.html @ 2434:12d3b55ebbfc gsoc2008_iphone
Added string for iPhone OS platform to the list
author | Holmes Futrell <hfutrell@umail.ucsb.edu> |
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date | Fri, 15 Aug 2008 00:59:44 +0000 |
parents | 355632dca928 |
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<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 -- 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 >-><TT CLASS="STRUCTFIELD" ><I >buf</I ></TT > and <SPAN CLASS="STRUCTNAME" >cvt</SPAN >-><TT CLASS="STRUCTFIELD" ><I >len</I ></TT > fields must be setup. <SPAN CLASS="STRUCTNAME" >cvt</SPAN >-><TT CLASS="STRUCTFIELD" ><I >buf</I ></TT > should point to the audio data and <SPAN CLASS="STRUCTNAME" >cvt</SPAN >-><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 >-><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 >-><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 >-><TT CLASS="STRUCTFIELD" ><I >len</I ></TT >*<TT CLASS="STRUCTFIELD" ><I >cvt</I ></TT >-><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->freq=22050; desired->format=AUDIO_S16LSB; desired->samples=8192; desired->callback=my_audio_callback; desired->userdata=NULL; /* Open the audio device */ if ( SDL_OpenAudio(desired, obtained) < 0 ){ fprintf(stderr, "Couldn't open audio: %s\n", SDL_GetError()); exit(-1); } free(desired); /* Load the test.wav */ if( SDL_LoadWAV("test.wav", &wav_spec, &wav_buf, &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(&wav_cvt, wav_spec.format, wav_spec.channels, wav_spec.freq, obtained->format, obtained->channels, obtained->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(&wav_cvt); /* do whatever */ . . . . </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 >