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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 55f1f1b3e27d
children 355632dca928
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<HTML
><HEAD
><TITLE
>Audio</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.64
"><LINK
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TITLE="SDL Library Documentation"
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TITLE="SDL_AudioSpec"
HREF="sdlaudiospec.html"><META
NAME="KEYWORD"
CONTENT="audio"><META
NAME="KEYWORD"
CONTENT="function"></HEAD
><BODY
CLASS="CHAPTER"
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VLINK="#551a8b"
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><DIV
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><HR
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WIDTH="100%"></DIV
><DIV
CLASS="CHAPTER"
><H1
><A
NAME="AUDIO"
>Chapter 10. Audio</A
></H1
><DIV
CLASS="TOC"
><DL
><DT
><B
>Table of Contents</B
></DT
><DT
><A
HREF="sdlaudiospec.html"
>SDL_AudioSpec</A
> &#8212; Audio Specification Structure</DT
><DT
><A
HREF="sdlopenaudio.html"
>SDL_OpenAudio</A
> &#8212; Opens the audio device with the desired parameters.</DT
><DT
><A
HREF="sdlpauseaudio.html"
>SDL_PauseAudio</A
> &#8212; Pauses and unpauses the audio callback processing</DT
><DT
><A
HREF="sdlgetaudiostatus.html"
>SDL_GetAudioStatus</A
> &#8212; Get the current audio state</DT
><DT
><A
HREF="sdlloadwav.html"
>SDL_LoadWAV</A
> &#8212; Load a WAVE file</DT
><DT
><A
HREF="sdlfreewav.html"
>SDL_FreeWAV</A
> &#8212; Frees previously opened WAV data</DT
><DT
><A
HREF="sdlaudiocvt.html"
>SDL_AudioCVT</A
> &#8212; Audio Conversion Structure</DT
><DT
><A
HREF="sdlbuildaudiocvt.html"
>SDL_BuildAudioCVT</A
> &#8212; Initializes a SDL_AudioCVT structure for conversion</DT
><DT
><A
HREF="sdlconvertaudio.html"
>SDL_ConvertAudio</A
> &#8212; Convert audio data to a desired audio format.</DT
><DT
><A
HREF="sdlmixaudio.html"
>SDL_MixAudio</A
> &#8212; Mix audio data</DT
><DT
><A
HREF="sdllockaudio.html"
>SDL_LockAudio</A
> &#8212; Lock out the callback function</DT
><DT
><A
HREF="sdlunlockaudio.html"
>SDL_UnlockAudio</A
> &#8212; Unlock the callback function</DT
><DT
><A
HREF="sdlcloseaudio.html"
>SDL_CloseAudio</A
> &#8212; Shuts down audio processing and closes the audio device.</DT
></DL
></DIV
><P
>Sound on the computer is translated from waves that you hear into a series of 
values, or samples, each representing the amplitude of the wave.  When these
samples are sent in a stream to a sound card, an approximation of the original
wave can be recreated.  The more bits used to represent the amplitude, and the
greater frequency these samples are gathered, the closer the approximated
sound is to the original, and the better the quality of sound.</P
><P
>This library supports both 8 and 16 bit signed and unsigned sound samples,
at frequencies ranging from 11025 Hz to 44100 Hz, depending on the 
underlying hardware.  If the hardware doesn't support the desired audio
format or frequency, it can be emulated if desired (See 
<A
HREF="sdlopenaudio.html"
><TT
CLASS="FUNCTION"
>SDL_OpenAudio()</TT
></A
>)</P
><P
>A commonly supported audio format is 16 bits per sample at 22050 Hz.</P
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