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399 lines
6.2 KiB
HTML
399 lines
6.2 KiB
HTML
<HTML
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><HEAD
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><TITLE
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>SDL_ConvertAudio</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.64
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"><LINK
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REL="HOME"
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TITLE="SDL Library Documentation"
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TITLE="Audio"
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TITLE="SDL_BuildAudioCVT"
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HREF="sdlbuildaudiocvt.html"><LINK
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TITLE="SDL_MixAudio"
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HREF="sdlmixaudio.html"></HEAD
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><TR
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><TH
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COLSPAN="3"
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>SDL Library Documentation</TH
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><TD
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WIDTH="10%"
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ALIGN="left"
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><A
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HREF="sdlbuildaudiocvt.html"
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>Prev</A
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HREF="sdlmixaudio.html"
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>Next</A
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ALIGN="LEFT"
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WIDTH="100%"></DIV
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><H1
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><A
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NAME="SDLCONVERTAUDIO"
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>SDL_ConvertAudio</A
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></H1
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><DIV
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CLASS="REFNAMEDIV"
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><A
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NAME="AEN6501"
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></A
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><H2
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>Name</H2
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>SDL_ConvertAudio -- Convert audio data to a desired audio format.</DIV
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><DIV
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CLASS="REFSYNOPSISDIV"
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><A
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NAME="AEN6504"
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></A
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><H2
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>Synopsis</H2
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><DIV
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CLASS="FUNCSYNOPSIS"
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><A
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NAME="AEN6505"
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></A
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><P
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></P
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><PRE
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CLASS="FUNCSYNOPSISINFO"
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>#include "SDL.h"</PRE
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><P
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><CODE
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><CODE
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CLASS="FUNCDEF"
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>int <B
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CLASS="FSFUNC"
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>SDL_ConvertAudio</B
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></CODE
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>(SDL_AudioCVT *cvt);</CODE
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></P
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><P
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></P
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></DIV
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></DIV
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><DIV
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CLASS="REFSECT1"
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><A
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NAME="AEN6511"
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></A
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><H2
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>Description</H2
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><P
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><TT
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CLASS="FUNCTION"
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>SDL_ConvertAudio</TT
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> takes one parameter, <TT
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CLASS="PARAMETER"
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><I
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>cvt</I
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></TT
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>, which was previously initilized. Initilizing a <A
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HREF="sdlaudiocvt.html"
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><SPAN
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CLASS="STRUCTNAME"
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>SDL_AudioCVT</SPAN
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></A
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> is a two step process. First of all, the structure must be passed to <A
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HREF="sdlbuildaudiocvt.html"
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><TT
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CLASS="FUNCTION"
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>SDL_BuildAudioCVT</TT
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></A
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> along with source and destination format parameters. Secondly, the <SPAN
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CLASS="STRUCTNAME"
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>cvt</SPAN
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>-><TT
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CLASS="STRUCTFIELD"
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><I
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>buf</I
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></TT
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> and <SPAN
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CLASS="STRUCTNAME"
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>cvt</SPAN
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>-><TT
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CLASS="STRUCTFIELD"
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><I
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>len</I
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></TT
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> fields must be setup. <SPAN
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CLASS="STRUCTNAME"
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>cvt</SPAN
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>-><TT
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CLASS="STRUCTFIELD"
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><I
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>buf</I
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></TT
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> should point to the audio data and <SPAN
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CLASS="STRUCTNAME"
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>cvt</SPAN
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>-><TT
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CLASS="STRUCTFIELD"
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><I
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>len</I
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></TT
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> should be set to the length of the audio data in bytes. Remember, the length of the buffer pointed to by <TT
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CLASS="STRUCTFIELD"
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><I
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>buf</I
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></TT
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> show be <TT
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CLASS="STRUCTFIELD"
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><I
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>len</I
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></TT
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>*<TT
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CLASS="STRUCTFIELD"
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><I
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>len_mult</I
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></TT
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> bytes in length.</P
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><P
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>Once the <SPAN
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CLASS="STRUCTNAME"
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>SDL_AudioCVT</SPAN
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>structure is initilized then we can pass it to <TT
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CLASS="FUNCTION"
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>SDL_ConvertAudio</TT
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>, which will convert the audio data pointer to by <SPAN
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CLASS="STRUCTNAME"
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>cvt</SPAN
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>-><TT
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CLASS="STRUCTFIELD"
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><I
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>buf</I
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></TT
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>. If <TT
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CLASS="FUNCTION"
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>SDL_ConvertAudio</TT
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> returned <SPAN
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CLASS="RETURNVALUE"
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>0</SPAN
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> then the conversion was completed successfully, otherwise <SPAN
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CLASS="RETURNVALUE"
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>-1</SPAN
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> is returned.</P
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><P
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>If the conversion completed successfully then the converted audio data can be read from <SPAN
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CLASS="STRUCTNAME"
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>cvt</SPAN
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>-><TT
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CLASS="STRUCTFIELD"
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><I
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>buf</I
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></TT
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>. The amount of valid, converted, audio data in the buffer is equal to <SPAN
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CLASS="STRUCTNAME"
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>cvt</SPAN
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>-><TT
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CLASS="STRUCTFIELD"
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><I
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>len</I
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></TT
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>*<TT
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CLASS="STRUCTFIELD"
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><I
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>cvt</I
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></TT
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>-><SPAN
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CLASS="STRUCTNAME"
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>len_ratio</SPAN
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>.</P
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></DIV
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><DIV
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CLASS="REFSECT1"
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><A
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NAME="AEN6546"
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></A
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><H2
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>Examples</H2
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><PRE
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CLASS="PROGRAMLISTING"
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>/* Converting some WAV data to hardware format */
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void my_audio_callback(void *userdata, Uint8 *stream, int len);
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SDL_AudioSpec *desired, *obtained;
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SDL_AudioSpec wav_spec;
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SDL_AudioCVT wav_cvt;
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Uint32 wav_len;
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Uint8 *wav_buf;
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int ret;
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/* Allocated audio specs */
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desired=(SDL_AudioSpec *)malloc(sizeof(SDL_AudioSpec));
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obtained=(SDL_AudioSpec *)malloc(sizeof(SDL_AudioSpec));
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/* Set desired format */
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desired->freq=22050;
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desired->format=AUDIO_S16LSB;
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desired->samples=8192;
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desired->callback=my_audio_callback;
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desired->userdata=NULL;
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/* Open the audio device */
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if ( SDL_OpenAudio(desired, obtained) < 0 ){
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fprintf(stderr, "Couldn't open audio: %s\n", SDL_GetError());
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exit(-1);
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}
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free(desired);
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/* Load the test.wav */
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if( SDL_LoadWAV("test.wav", &wav_spec, &wav_buf, &wav_len) == NULL ){
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fprintf(stderr, "Could not open test.wav: %s\n", SDL_GetError());
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SDL_CloseAudio();
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free(obtained);
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exit(-1);
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}
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/* Build AudioCVT */
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ret = SDL_BuildAudioCVT(&wav_cvt,
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wav_spec.format, wav_spec.channels, wav_spec.freq,
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obtained->format, obtained->channels, obtained->freq);
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/* Check that the convert was built */
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if(ret==-1){
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fprintf(stderr, "Couldn't build converter!\n");
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SDL_CloseAudio();
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free(obtained);
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SDL_FreeWAV(wav_buf);
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}
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/* Setup for conversion */
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wav_cvt.buf=(Uint8 *)malloc(wav_len*wav_cvt.len_mult);
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wav_cvt.len=wav_len;
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memcpy(wav_cvt.buf, wav_buf, wav_len);
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/* We can delete to original WAV data now */
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SDL_FreeWAV(wav_buf);
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/* And now we're ready to convert */
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SDL_ConvertAudio(&wav_cvt);
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/* do whatever */
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.
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.
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.
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.
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</PRE
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></DIV
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><DIV
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CLASS="REFSECT1"
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><A
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NAME="AEN6549"
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></A
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><H2
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>See Also</H2
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><P
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><A
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HREF="sdlbuildaudiocvt.html"
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><TT
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CLASS="FUNCTION"
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>SDL_BuildAudioCVT</TT
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></A
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>,
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<A
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HREF="sdlaudiocvt.html"
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><TT
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CLASS="FUNCTION"
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>SDL_AudioCVT</TT
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></A
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></P
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>Prev</A
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