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Date: Sun, 4 Jan 2004 23:48:19 +0100
From: Max Horn
Subject: Re: Again Audio CD patch
Am 04.01.2004 um 22:38 schrieb Sam Lantinga:
>
> Okay, I fixed the buffering problems by simply using a 4 second buffer
> instead of a 1 second buffer. However, using your code I can't play an
> entire CD - the playback stops after the first song.
>
Found the problem: FSReadFork returns eofErr when the file is finished.
However, we check its return value for errors, and if anything but
noErr occurs, the reader thread aborts its current iteration. That is
bad, because it aborts before it can ever set the flag which tells that
the file is over (also, any remaining data which FSRead did return is
lost - so you'd not hear about to 4 seconds from the end of the file.
Furthermore, the computed data size was 8 bytes to high (I forgot to
account for the fact that the size of an (A)IFF chunk always contains
the chunk header & size fields, too). This is enough to make it work.
However, the end condition is rather fragile, so I tuned some other
things to be pessimistic (check for <= 0 instead of == 0, when eofErr
is encountered enforce mReadFilePosition == mFileLength). You never
know...
The attached patch fixes the issue for me.
author | Sam Lantinga <slouken@libsdl.org> |
---|---|
date | Mon, 05 Jan 2004 00:57:51 +0000 |
parents | e5bc29de3f0a |
children | 355632dca928 |
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<HTML ><HEAD ><TITLE >SDL_LoadWAV</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.64 "><LINK REL="HOME" TITLE="SDL Library Documentation" HREF="index.html"><LINK REL="UP" TITLE="Audio" HREF="audio.html"><LINK REL="PREVIOUS" TITLE="SDL_GetAudioStatus" HREF="sdlgetaudiostatus.html"><LINK REL="NEXT" TITLE="SDL_FreeWAV" HREF="sdlfreewav.html"></HEAD ><BODY CLASS="REFENTRY" BGCOLOR="#FFF8DC" TEXT="#000000" LINK="#0000ee" VLINK="#551a8b" ALINK="#ff0000" ><DIV CLASS="NAVHEADER" ><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="sdlgetaudiostatus.html" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="sdlfreewav.html" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="SDLLOADWAV" >SDL_LoadWAV</A ></H1 ><DIV CLASS="REFNAMEDIV" ><A NAME="AEN6428" ></A ><H2 >Name</H2 >SDL_LoadWAV -- Load a WAVE file</DIV ><DIV CLASS="REFSYNOPSISDIV" ><A NAME="AEN6431" ></A ><H2 >Synopsis</H2 ><DIV CLASS="FUNCSYNOPSIS" ><A NAME="AEN6432" ></A ><P ></P ><PRE CLASS="FUNCSYNOPSISINFO" >#include "SDL.h"</PRE ><P ><CODE ><CODE CLASS="FUNCDEF" >SDL_AudioSpec *<B CLASS="FSFUNC" >SDL_LoadWAV</B ></CODE >(const char *file, SDL_AudioSpec *spec, Uint8 **audio_buf, Uint32 *audio_len);</CODE ></P ><P ></P ></DIV ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN6438" ></A ><H2 >Description</H2 ><P ><TT CLASS="FUNCTION" >SDL_LoadWAV</TT > This function loads a WAVE <TT CLASS="PARAMETER" ><I >file</I ></TT > into memory.</P ><P >If this function succeeds, it returns the given <A HREF="sdlaudiospec.html" ><TT CLASS="FUNCTION" >SDL_AudioSpec</TT ></A >, filled with the audio data format of the wave data, and sets <TT CLASS="PARAMETER" ><I >audio_buf</I ></TT > to a <TT CLASS="FUNCTION" >malloc</TT >'d buffer containing the audio data, and sets <TT CLASS="PARAMETER" ><I >audio_len</I ></TT > to the length of that audio buffer, in bytes. You need to free the audio buffer with <A HREF="sdlfreewav.html" ><TT CLASS="FUNCTION" >SDL_FreeWAV</TT ></A > when you are done with it.</P ><P >This function returns <TT CLASS="LITERAL" >NULL</TT > and sets the SDL error message if the wave file cannot be opened, uses an unknown data format, or is corrupt. Currently raw, MS-ADPCM and IMA-ADPCM WAVE files are supported.</P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN6453" ></A ><H2 >Example</H2 ><PRE CLASS="PROGRAMLISTING" >SDL_AudioSpec wav_spec; Uint32 wav_length; Uint8 *wav_buffer; /* Load the WAV */ if( SDL_LoadWAV("test.wav", &wav_spec, &wav_buffer, &wav_length) == NULL ){ fprintf(stderr, "Could not open test.wav: %s\n", SDL_GetError()); exit(-1); } . . . /* Do stuff with the WAV */ . . /* Free It */ SDL_FreeWAV(wav_buffer);</PRE ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN6456" ></A ><H2 >See Also</H2 ><P ><A HREF="sdlaudiospec.html" ><SPAN CLASS="STRUCTNAME" >SDL_AudioSpec</SPAN ></A >, <A HREF="sdlopenaudio.html" ><TT CLASS="FUNCTION" >SDL_OpenAudio</TT ></A >, <A HREF="sdlfreewav.html" ><TT CLASS="FUNCTION" >SDL_FreeWAV</TT ></A ></P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="sdlgetaudiostatus.html" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="sdlfreewav.html" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >SDL_GetAudioStatus</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="audio.html" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >SDL_FreeWAV</TD ></TR ></TABLE ></DIV ></BODY ></HTML >