| <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 |
| > |
