Mercurial > sdl-ios-xcode

annotate src/timer/mint/SDL_vbltimer.S @ 3880:74e828c64315 SDL-1.2

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Fixed bug #292 I might be on crack here. It looks like SDL_ConvertMono() in src/audio/SDL_audiocvt.c adds the left and right channels of a stereo stream together, and clamps the new mono channel if it would overflow. Shouldn't it be dividing by 2 to average the two sample points instead of clamping? Otherwise the mono sample point's volume doubles in the conversion. This would also make the conversion faster, as it replaces two branches per sample frame with a bitwise shift. --ryan.
author Sam Lantinga <slouken@libsdl.org>
date Sun, 24 Sep 2006 15:45:37 +0000
parents c9b51268668f
children eb5e61b72da3
rev   line source
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1 /*
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2 SDL - Simple DirectMedia Layer
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3 Copyright (C) 1997-2006 Sam Lantinga
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4
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5 This library is free software; you can redistribute it and/or
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6 modify it under the terms of the GNU Lesser General Public
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7 License as published by the Free Software Foundation; either
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8 version 2.1 of the License, or (at your option) any later version.
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9
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10 This library is distributed in the hope that it will be useful,
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11 but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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13 Lesser General Public License for more details.
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14
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15 You should have received a copy of the GNU Lesser General Public
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16 License along with this library; if not, write to the Free Software
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17 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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18
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19 Sam Lantinga
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20 slouken@libsdl.org
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21 */
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22
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23 /*
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24 * VBL queue routine
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25 *
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26 * Patrice Mandin
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27 */
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28
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29 #define _vbl_queue 0x456
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30
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31 .text
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32
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33 .globl _SDL_AtariVblInstall
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34 .globl _SDL_AtariVblUninstall
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35
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36 /*--- Vector installer ---*/
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37
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38 _SDL_AtariVblInstall:
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39 movel sp@(4),my_vector
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40 lea _my_vbl,a0
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41
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42 clrw vbl_mutex
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43
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44 /* Stop interrupts */
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45
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46 movew #0x2700,sr
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47
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48 /* Read vbl_queue pointer */
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49 movel _vbl_queue.w,a1
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50
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51 /* Search a free place */
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52 moveq #7,d0
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53 bcl_search_place:
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54 movel (a1),d1
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55 beqs place_found
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56 addql #4,a1
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57 dbra d0,bcl_search_place
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58
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59 /* Not found */
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60 moveq #1,d0
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61 bras exit_vbl_queue
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62
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63 /* Then install ourselves */
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64 place_found:
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65 movel a0,(a1)
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66 moveq #0,d0
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67
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68 exit_vbl_queue:
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69 /* Restart interrupts */
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70 movew #0x2300,sr
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71
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72 rts
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73
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74 /*--- Vector uninstaller ---*/
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75
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76 _SDL_AtariVblUninstall:
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77 movel sp@(4),d0
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78 cmpl my_vector,d0
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79 bnes badvector
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80
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81 movel #_my_vbl,d0
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82
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83 /* Stop interrupts */
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84
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85 movew #0x2700,sr
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86
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87 /* Read vbl_queue pointer */
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88 movel _vbl_queue.w,a1
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89
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90 /* Search where we are */
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91 moveq #7,d1
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92 bcl2_search_place:
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93 cmpl (a1),d0
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94 bnes next_place
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95 clrl (a1)
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96 moveq #0,d1
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97 next_place:
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98 addql #4,a1
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99 dbra d1,bcl2_search_place
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100
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101 /* Restart interrupts */
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102 movew #0x2300,sr
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103 badvector:
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104 rts
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105
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106 /*--- Our vbl ---*/
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107
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108 _my_vbl:
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109 /* Verify if this is not already running */
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110
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111 tstw vbl_mutex
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112 bnes vbl_end
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113 notw vbl_mutex
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114
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115 moveml d0-d7/a0-a6,sp@-
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116 movel my_vector,a0
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117 jsr a0@
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118 moveml sp@+,d0-d7/a0-a6
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119
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120 clrw vbl_mutex
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121 vbl_end:
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122 rts
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123
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124 .data
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125 .even
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126 .comm vbl_mutex,2*1
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127 .even
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128 .comm my_vector,4*1