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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
>CD-ROM</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="SDL Reference"
HREF="reference.html"><LINK
REL="PREVIOUS"
TITLE="SDL_CloseAudio"
HREF="sdlcloseaudio.html"><LINK
REL="NEXT"
TITLE="SDL_CDNumDrives"
HREF="sdlcdnumdrives.html"><META
NAME="KEYWORD"
CONTENT="cdrom"><META
NAME="KEYWORD"
CONTENT="function"></HEAD
><BODY
CLASS="CHAPTER"
BGCOLOR="#FFF8DC"
TEXT="#000000"
LINK="#0000ee"
VLINK="#551a8b"
ALINK="#ff0000"
><DIV
CLASS="NAVHEADER"
><TABLE
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BORDER="0"
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><TR
><TH
COLSPAN="3"
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>SDL Library Documentation</TH
></TR
><TR
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><A
HREF="sdlcloseaudio.html"
>Prev</A
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VALIGN="bottom"
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HREF="sdlcdnumdrives.html"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="CHAPTER"
><H1
><A
NAME="CDROM"
>Chapter 11. CD-ROM</A
></H1
><DIV
CLASS="TOC"
><DL
><DT
><B
>Table of Contents</B
></DT
><DT
><A
HREF="sdlcdnumdrives.html"
>SDL_CDNumDrives</A
> &#8212; Returns the number of CD-ROM drives on the system.</DT
><DT
><A
HREF="sdlcdname.html"
>SDL_CDName</A
> &#8212; Returns a human-readable, system-dependent identifier for the CD-ROM.</DT
><DT
><A
HREF="sdlcdopen.html"
>SDL_CDOpen</A
> &#8212; Opens a CD-ROM drive for access.</DT
><DT
><A
HREF="sdlcdstatus.html"
>SDL_CDStatus</A
> &#8212; Returns the current status of the given drive.</DT
><DT
><A
HREF="sdlcdplay.html"
>SDL_CDPlay</A
> &#8212; Play a CD</DT
><DT
><A
HREF="sdlcdplaytracks.html"
>SDL_CDPlayTracks</A
> &#8212; Play the given CD track(s)</DT
><DT
><A
HREF="sdlcdpause.html"
>SDL_CDPause</A
> &#8212; Pauses a CDROM</DT
><DT
><A
HREF="sdlcdresume.html"
>SDL_CDResume</A
> &#8212; Resumes a CDROM</DT
><DT
><A
HREF="sdlcdstop.html"
>SDL_CDStop</A
> &#8212; Stops a CDROM</DT
><DT
><A
HREF="sdlcdeject.html"
>SDL_CDEject</A
> &#8212; Ejects a CDROM</DT
><DT
><A
HREF="sdlcdclose.html"
>SDL_CDClose</A
> &#8212; Closes a SDL_CD handle</DT
><DT
><A
HREF="sdlcd.html"
>SDL_CD</A
> &#8212; CDROM Drive Information</DT
><DT
><A
HREF="sdlcdtrack.html"
>SDL_CDtrack</A
> &#8212; CD Track Information Structure</DT
></DL
></DIV
><P
>SDL supports audio control of up to 32 local CD-ROM drives at once.</P
><P
>You use this API to perform all the basic functions of a CD player,
including listing the tracks, playing, stopping, and ejecting the CD-ROM.
(Currently, multi-changer CD drives are not supported.)</P
><P
>Before you call any of the SDL CD-ROM functions, you must first call
"<TT
CLASS="FUNCTION"
>SDL_Init(SDL_INIT_CDROM)</TT
>", which scans the system for
CD-ROM drives, and sets the program up for audio control.  Check the 
return code, which should be <SPAN
CLASS="RETURNVALUE"
>0</SPAN
>, to see if there 
were any errors in starting up.</P
><P
>After you have initialized the library, you can find out how many drives
are available using the <TT
CLASS="FUNCTION"
>SDL_CDNumDrives()</TT
> function.  
The first drive listed is the system default CD-ROM drive.  After you have 
chosen a drive, and have opened it with <TT
CLASS="FUNCTION"
>SDL_CDOpen()</TT
>, 
you can check the status and start playing if there's a CD in the drive.</P
><P
>A CD-ROM is organized into one or more tracks, each consisting of a certain
number of "frames".  Each frame is ~2K in size, and at normal playing speed,
a CD plays 75 frames per second.  SDL works with the number of frames on a
CD, but this can easily be converted to the more familiar minutes/seconds
format by using the <TT
CLASS="FUNCTION"
>FRAMES_TO_MSF()</TT
> macro.</P
></DIV
><DIV
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><HR
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></TD
><TD
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>SDL_CDNumDrives</TD
></TR
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></DIV
></BODY
></HTML
>