Mercurial > sdl-ios-xcode
annotate docs/html/sdlmixaudio.html @ 968:4675910b0b7b
Date: Mon, 11 Oct 2004 15:17:27 +0300 (EEST)
From: Hannu Savolainen
Subject: Re: SDL uses obsolete OSS features
I did some work on getting OSS to work better with SDL. There have been
some problems with select which should be fixed now.
I'm having some problems in understanding what is the purpose of the
DSP_WaitAudio() routine. I added a return to the very beginning of this
routine and commendted out the define for USE_BLOCKING_WRITES. At least
lbreakout2 seems to work as well as earlier. The latencies are the same.
An ordinary blocking write does exactly the same thing than DSP_WaitAudio
does. So I would recommend using the USE_BLOCKING_WRITES approach and
removing everything from the DSP_WaitAudio routine. Also enabling
USE_BLOCKING_WRITES makes it possible to simplify DSP_PlayAudio() because
you don't need to handle the partial writes (the do-while loop).
Attached is a patch against SDL-1.2.7. After these changes SDL will use
OSS as it's designed to be used (make it as simple as possible). This code
should work with all OSS implementations because it uses only the very
fundamental features that have been there since the jurassic times.
author | Sam Lantinga <slouken@libsdl.org> |
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date | Fri, 12 Nov 2004 21:39:04 +0000 |
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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 1.76b+ |
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 | |
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31 SUMMARY="Header navigation table" |
0 | 32 WIDTH="100%" |
33 BORDER="0" | |
34 CELLPADDING="0" | |
35 CELLSPACING="0" | |
36 ><TR | |
37 ><TH | |
38 COLSPAN="3" | |
39 ALIGN="center" | |
40 >SDL Library Documentation</TH | |
41 ></TR | |
42 ><TR | |
43 ><TD | |
44 WIDTH="10%" | |
45 ALIGN="left" | |
46 VALIGN="bottom" | |
47 ><A | |
48 HREF="sdlconvertaudio.html" | |
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49 ACCESSKEY="P" |
0 | 50 >Prev</A |
51 ></TD | |
52 ><TD | |
53 WIDTH="80%" | |
54 ALIGN="center" | |
55 VALIGN="bottom" | |
56 ></TD | |
57 ><TD | |
58 WIDTH="10%" | |
59 ALIGN="right" | |
60 VALIGN="bottom" | |
61 ><A | |
62 HREF="sdllockaudio.html" | |
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63 ACCESSKEY="N" |
0 | 64 >Next</A |
65 ></TD | |
66 ></TR | |
67 ></TABLE | |
68 ><HR | |
69 ALIGN="LEFT" | |
70 WIDTH="100%"></DIV | |
71 ><H1 | |
72 ><A | |
73 NAME="SDLMIXAUDIO" | |
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74 ></A |
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75 >SDL_MixAudio</H1 |
0 | 76 ><DIV |
77 CLASS="REFNAMEDIV" | |
78 ><A | |
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79 NAME="AEN7107" |
0 | 80 ></A |
81 ><H2 | |
82 >Name</H2 | |
83 >SDL_MixAudio -- Mix audio data</DIV | |
84 ><DIV | |
85 CLASS="REFSYNOPSISDIV" | |
86 ><A | |
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87 NAME="AEN7110" |
0 | 88 ></A |
89 ><H2 | |
90 >Synopsis</H2 | |
91 ><DIV | |
92 CLASS="FUNCSYNOPSIS" | |
93 ><A | |
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94 NAME="AEN7111" |
0 | 95 ></A |
96 ><P | |
97 ></P | |
98 ><PRE | |
99 CLASS="FUNCSYNOPSISINFO" | |
100 >#include "SDL.h"</PRE | |
101 ><P | |
102 ><CODE | |
103 ><CODE | |
104 CLASS="FUNCDEF" | |
105 >void <B | |
106 CLASS="FSFUNC" | |
107 >SDL_MixAudio</B | |
108 ></CODE | |
109 >(Uint8 *dst, Uint8 *src, Uint32 len, int volume);</CODE | |
110 ></P | |
111 ><P | |
112 ></P | |
113 ></DIV | |
114 ></DIV | |
115 ><DIV | |
116 CLASS="REFSECT1" | |
117 ><A | |
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118 NAME="AEN7117" |
0 | 119 ></A |
120 ><H2 | |
121 >Description</H2 | |
122 ><P | |
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123 >This function takes two audio buffers of <TT |
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124 CLASS="PARAMETER" |
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125 ><I |
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126 >len</I |
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127 ></TT |
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128 > bytes each |
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129 of the playing audio format and mixes them, performing addition, volume |
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130 adjustment, and overflow clipping. The <TT |
0 | 131 CLASS="PARAMETER" |
132 ><I | |
133 >volume</I | |
134 ></TT | |
55
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135 > ranges |
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136 from 0 to <TT |
0 | 137 CLASS="LITERAL" |
138 >SDL_MIX_MAXVOLUME</TT | |
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139 > and should be set to the maximum |
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140 value for full audio volume. Note this does not change hardware volume. This is |
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141 provided for convenience -- you can mix your own audio data.</P |
181
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142 ><DIV |
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143 CLASS="NOTE" |
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144 ><BLOCKQUOTE |
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145 CLASS="NOTE" |
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146 ><P |
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147 ><B |
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148 >Note: </B |
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149 >Do not use this function for mixing together more than two streams of sample |
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150 data. The output from repeated application of this function may be distorted |
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151 by clipping, because there is no accumulator with greater range than the |
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152 input (not to mention this being an inefficient way of doing it). |
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153 Use mixing functions from SDL_mixer, OpenAL, or write your own mixer instead.</P |
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154 ></BLOCKQUOTE |
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155 ></DIV |
0 | 156 ></DIV |
157 ><DIV | |
158 CLASS="REFSECT1" | |
159 ><A | |
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160 NAME="AEN7125" |
0 | 161 ></A |
162 ><H2 | |
163 >See Also</H2 | |
164 ><P | |
165 ><A | |
166 HREF="sdlopenaudio.html" | |
167 ><TT | |
168 CLASS="FUNCTION" | |
169 >SDL_OpenAudio</TT | |
170 ></A | |
171 ></P | |
172 ></DIV | |
173 ><DIV | |
174 CLASS="NAVFOOTER" | |
175 ><HR | |
176 ALIGN="LEFT" | |
177 WIDTH="100%"><TABLE | |
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178 SUMMARY="Footer navigation table" |
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180 BORDER="0" | |
181 CELLPADDING="0" | |
182 CELLSPACING="0" | |
183 ><TR | |
184 ><TD | |
185 WIDTH="33%" | |
186 ALIGN="left" | |
187 VALIGN="top" | |
188 ><A | |
189 HREF="sdlconvertaudio.html" | |
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190 ACCESSKEY="P" |
0 | 191 >Prev</A |
192 ></TD | |
193 ><TD | |
194 WIDTH="34%" | |
195 ALIGN="center" | |
196 VALIGN="top" | |
197 ><A | |
198 HREF="index.html" | |
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199 ACCESSKEY="H" |
0 | 200 >Home</A |
201 ></TD | |
202 ><TD | |
203 WIDTH="33%" | |
204 ALIGN="right" | |
205 VALIGN="top" | |
206 ><A | |
207 HREF="sdllockaudio.html" | |
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208 ACCESSKEY="N" |
0 | 209 >Next</A |
210 ></TD | |
211 ></TR | |
212 ><TR | |
213 ><TD | |
214 WIDTH="33%" | |
215 ALIGN="left" | |
216 VALIGN="top" | |
217 >SDL_ConvertAudio</TD | |
218 ><TD | |
219 WIDTH="34%" | |
220 ALIGN="center" | |
221 VALIGN="top" | |
222 ><A | |
223 HREF="audio.html" | |
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224 ACCESSKEY="U" |
0 | 225 >Up</A |
226 ></TD | |
227 ><TD | |
228 WIDTH="33%" | |
229 ALIGN="right" | |
230 VALIGN="top" | |
231 >SDL_LockAudio</TD | |
232 ></TR | |
233 ></TABLE | |
234 ></DIV | |
235 ></BODY | |
236 ></HTML | |
237 > |