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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_CD</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="CD-ROM"
HREF="cdrom.html"><LINK
REL="PREVIOUS"
TITLE="SDL_CDClose"
HREF="sdlcdclose.html"><LINK
REL="NEXT"
TITLE="SDL_CDtrack"
HREF="sdlcdtrack.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="sdlcdclose.html"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
></TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="sdlcdtrack.html"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><H1
><A
NAME="SDLCD"
>SDL_CD</A
></H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN7178"
></A
><H2
>Name</H2
>SDL_CD&nbsp;--&nbsp;CDROM Drive Information</DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN7181"
></A
><H2
>Structure Definition</H2
><PRE
CLASS="PROGRAMLISTING"
>typedef struct{
  int id;
  CDstatus status;
  int numtracks;
  int cur_track;
  int cur_frame;
  SDL_CDtrack track[SDL_MAX_TRACKS+1];
} SDL_CD;</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN7184"
></A
><H2
>Structure Data</H2
><DIV
CLASS="INFORMALTABLE"
><A
NAME="AEN7186"
></A
><P
></P
><TABLE
BORDER="0"
CLASS="CALSTABLE"
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>id</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Private drive identifier</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>status</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Drive <A
HREF="sdlcdstatus.html"
>status</A
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>numtracks</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Number of tracks on the CD</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>cur_track</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Current track</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>cur_frame</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Current frame offset within the track</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>track</I
></TT
>[SDL_MAX_TRACKS+1]</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Array of track descriptions. (see <A
HREF="sdlcdtrack.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_CDtrack</SPAN
></A
>)</TD
></TR
></TBODY
></TABLE
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN7216"
></A
><H2
>Description</H2
><P
>An <SPAN
CLASS="STRUCTNAME"
>SDL_CD</SPAN
> structure is returned by <A
HREF="sdlcdopen.html"
><TT
CLASS="FUNCTION"
>SDL_CDOpen</TT
></A
>. It represents an opened CDROM device and stores information on the layout of the tracks on the disc.</P
><P
>A frame is the base data unit of a CD. <TT
CLASS="LITERAL"
>CD_FPS</TT
> frames is equal to 1 second of music. SDL provides two macros for converting between time and frames: <TT
CLASS="LITERAL"
>FRAMES_TO_MSF(f, M,S,F)</TT
> and <TT
CLASS="LITERAL"
>MSF_TO_FRAMES</TT
>.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN7226"
></A
><H2
>Examples</H2
><PRE
CLASS="PROGRAMLISTING"
>int min, sec, frame;
int frame_offset;

FRAMES_TO_MSF(cdrom-&#62;cur_frame, &#38;min, &#38;sec, &#38;frame);
printf("Current Position: %d minutes, %d seconds, %d frames\n", min, sec, frame);

frame_offset=MSF_TO_FRAMES(min, sec, frame);</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN7229"
></A
><H2
>See Also</H2
><P
><A
HREF="sdlcdopen.html"
><TT
CLASS="FUNCTION"
>SDL_CDOpen</TT
></A
>,
<A
HREF="sdlcdtrack.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_CDtrack</SPAN
></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="sdlcdclose.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="sdlcdtrack.html"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>SDL_CDClose</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="cdrom.html"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>SDL_CDtrack</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>