Mercurial > sdl-ios-xcode
annotate docs/html/sdlmixaudio.html @ 773:da0a2ad35bf4
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> |
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date | Mon, 05 Jan 2004 00:57:51 +0000 (2004-01-05) |
parents | e5bc29de3f0a |
children | 355632dca928 |
rev | line source |
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0 | 1 <HTML |
2 ><HEAD | |
3 ><TITLE | |
4 >SDL_MixAudio</TITLE | |
5 ><META | |
6 NAME="GENERATOR" | |
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7 CONTENT="Modular DocBook HTML Stylesheet Version 1.64 |
0 | 8 "><LINK |
9 REL="HOME" | |
10 TITLE="SDL Library Documentation" | |
11 HREF="index.html"><LINK | |
12 REL="UP" | |
13 TITLE="Audio" | |
14 HREF="audio.html"><LINK | |
15 REL="PREVIOUS" | |
16 TITLE="SDL_ConvertAudio" | |
17 HREF="sdlconvertaudio.html"><LINK | |
18 REL="NEXT" | |
19 TITLE="SDL_LockAudio" | |
20 HREF="sdllockaudio.html"></HEAD | |
21 ><BODY | |
22 CLASS="REFENTRY" | |
23 BGCOLOR="#FFF8DC" | |
24 TEXT="#000000" | |
25 LINK="#0000ee" | |
26 VLINK="#551a8b" | |
27 ALINK="#ff0000" | |
28 ><DIV | |
29 CLASS="NAVHEADER" | |
30 ><TABLE | |
31 WIDTH="100%" | |
32 BORDER="0" | |
33 CELLPADDING="0" | |
34 CELLSPACING="0" | |
35 ><TR | |
36 ><TH | |
37 COLSPAN="3" | |
38 ALIGN="center" | |
39 >SDL Library Documentation</TH | |
40 ></TR | |
41 ><TR | |
42 ><TD | |
43 WIDTH="10%" | |
44 ALIGN="left" | |
45 VALIGN="bottom" | |
46 ><A | |
47 HREF="sdlconvertaudio.html" | |
48 >Prev</A | |
49 ></TD | |
50 ><TD | |
51 WIDTH="80%" | |
52 ALIGN="center" | |
53 VALIGN="bottom" | |
54 ></TD | |
55 ><TD | |
56 WIDTH="10%" | |
57 ALIGN="right" | |
58 VALIGN="bottom" | |
59 ><A | |
60 HREF="sdllockaudio.html" | |
61 >Next</A | |
62 ></TD | |
63 ></TR | |
64 ></TABLE | |
65 ><HR | |
66 ALIGN="LEFT" | |
67 WIDTH="100%"></DIV | |
68 ><H1 | |
69 ><A | |
70 NAME="SDLMIXAUDIO" | |
71 >SDL_MixAudio</A | |
72 ></H1 | |
73 ><DIV | |
74 CLASS="REFNAMEDIV" | |
75 ><A | |
181
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76 NAME="AEN6719" |
0 | 77 ></A |
78 ><H2 | |
79 >Name</H2 | |
80 >SDL_MixAudio -- Mix audio data</DIV | |
81 ><DIV | |
82 CLASS="REFSYNOPSISDIV" | |
83 ><A | |
181
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84 NAME="AEN6722" |
0 | 85 ></A |
86 ><H2 | |
87 >Synopsis</H2 | |
88 ><DIV | |
89 CLASS="FUNCSYNOPSIS" | |
90 ><A | |
181
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91 NAME="AEN6723" |
0 | 92 ></A |
93 ><P | |
94 ></P | |
95 ><PRE | |
96 CLASS="FUNCSYNOPSISINFO" | |
97 >#include "SDL.h"</PRE | |
98 ><P | |
99 ><CODE | |
100 ><CODE | |
101 CLASS="FUNCDEF" | |
102 >void <B | |
103 CLASS="FSFUNC" | |
104 >SDL_MixAudio</B | |
105 ></CODE | |
106 >(Uint8 *dst, Uint8 *src, Uint32 len, int volume);</CODE | |
107 ></P | |
108 ><P | |
109 ></P | |
110 ></DIV | |
111 ></DIV | |
112 ><DIV | |
113 CLASS="REFSECT1" | |
114 ><A | |
181
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115 NAME="AEN6729" |
0 | 116 ></A |
117 ><H2 | |
118 >Description</H2 | |
119 ><P | |
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120 >This function takes two audio buffers of <TT |
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121 CLASS="PARAMETER" |
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122 ><I |
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123 >len</I |
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124 ></TT |
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125 > bytes each |
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126 of the playing audio format and mixes them, performing addition, volume |
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127 adjustment, and overflow clipping. The <TT |
0 | 128 CLASS="PARAMETER" |
129 ><I | |
130 >volume</I | |
131 ></TT | |
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132 > ranges |
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133 from 0 to <TT |
0 | 134 CLASS="LITERAL" |
135 >SDL_MIX_MAXVOLUME</TT | |
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136 > and should be set to the maximum |
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137 value for full audio volume. Note this does not change hardware volume. This is |
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138 provided for convenience -- you can mix your own audio data.</P |
181
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139 ><DIV |
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140 CLASS="NOTE" |
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141 ><BLOCKQUOTE |
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142 CLASS="NOTE" |
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143 ><P |
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144 ><B |
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145 >Note: </B |
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146 >Do not use this function for mixing together more than two streams of sample |
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147 data. The output from repeated application of this function may be distorted |
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148 by clipping, because there is no accumulator with greater range than the |
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149 input (not to mention this being an inefficient way of doing it). |
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150 Use mixing functions from SDL_mixer, OpenAL, or write your own mixer instead.</P |
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151 ></BLOCKQUOTE |
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152 ></DIV |
0 | 153 ></DIV |
154 ><DIV | |
155 CLASS="REFSECT1" | |
156 ><A | |
181
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157 NAME="AEN6737" |
0 | 158 ></A |
159 ><H2 | |
160 >See Also</H2 | |
161 ><P | |
162 ><A | |
163 HREF="sdlopenaudio.html" | |
164 ><TT | |
165 CLASS="FUNCTION" | |
166 >SDL_OpenAudio</TT | |
167 ></A | |
168 ></P | |
169 ></DIV | |
170 ><DIV | |
171 CLASS="NAVFOOTER" | |
172 ><HR | |
173 ALIGN="LEFT" | |
174 WIDTH="100%"><TABLE | |
175 WIDTH="100%" | |
176 BORDER="0" | |
177 CELLPADDING="0" | |
178 CELLSPACING="0" | |
179 ><TR | |
180 ><TD | |
181 WIDTH="33%" | |
182 ALIGN="left" | |
183 VALIGN="top" | |
184 ><A | |
185 HREF="sdlconvertaudio.html" | |
186 >Prev</A | |
187 ></TD | |
188 ><TD | |
189 WIDTH="34%" | |
190 ALIGN="center" | |
191 VALIGN="top" | |
192 ><A | |
193 HREF="index.html" | |
194 >Home</A | |
195 ></TD | |
196 ><TD | |
197 WIDTH="33%" | |
198 ALIGN="right" | |
199 VALIGN="top" | |
200 ><A | |
201 HREF="sdllockaudio.html" | |
202 >Next</A | |
203 ></TD | |
204 ></TR | |
205 ><TR | |
206 ><TD | |
207 WIDTH="33%" | |
208 ALIGN="left" | |
209 VALIGN="top" | |
210 >SDL_ConvertAudio</TD | |
211 ><TD | |
212 WIDTH="34%" | |
213 ALIGN="center" | |
214 VALIGN="top" | |
215 ><A | |
216 HREF="audio.html" | |
217 >Up</A | |
218 ></TD | |
219 ><TD | |
220 WIDTH="33%" | |
221 ALIGN="right" | |
222 VALIGN="top" | |
223 >SDL_LockAudio</TD | |
224 ></TR | |
225 ></TABLE | |
226 ></DIV | |
227 ></BODY | |
228 ></HTML | |
229 > |