Mercurial > sdl-ios-xcode
annotate docs/html/sdlmixaudio.html @ 1157:baf35853ad54
Date: Mon, 10 Oct 2005 13:09:32 +0300
From: Tommi Kyntola <tommi.kyntola@ray.fi>
To: sdl@libsdl.org
Subject: [SDL] [RFC] get_ticks broken on linux
It uses gettimeofday to calculate the timedifference.
Gettimeofday returns current time which is seldom monotonous.
This breaks SDL timer subsystem. (time callbacks and all that
get borked when the time difference ms is suddenly ~ 2^32)
I posted a message about this earlier but got no response.
Some thoughts on this matter would be appreciated.
(Or even an explanation for the lack of interest.)
A patch below would use the posix timers that have been around
since posix 93 and do provide a good source of monotonous time
on linux boxes (and on few others too).
The following patch is also availabe at:
http://www.hut.fi/u/tkyntola/SDL-1.2.9-clockfix.patch
It's against 1.2.9, but I can easily rediffit against
the cvs branch is needed.
cheers,
Tommi Kyntola tommi.kyntola@ray.fi
| author | Ryan C. Gordon <icculus@icculus.org> |
|---|---|
| date | Tue, 11 Oct 2005 18:16:12 +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 | |
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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 |
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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" |
| 0 | 179 WIDTH="100%" |
| 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 > |