annotate decoders/timidity/output.c @ 474:c66080364dff

Most decoders now report total sample play time, now. Technically, this breaks binary compatibility with the 1.0 branch, since it extends the Sound_Sample struct, but most (all?) programs are just passing pointers allocated by SDL_sound around, and might be okay. Source-level compatibility is not broken...yet! :) --ryan. -------- Original Message -------- Subject: SDL_sound patch: Finding total length of time of sound file. Date: Sun, 26 Jan 2003 09:31:17 -0800 (PST) Hi Ryan, I am working with Eric Wing and helping him modify SDL_sound. AS part of our efforts in improving and enhancing SDL_sound, we like to submit this patch. We modified the codecs to find the total time of a sound file. Below is the explanation of the patch. The patch is appended as an attachment to this email. * MOTIVATION: We needed the ability to get the total play time of a sample (And we noticed that we're not the only ones). Since SDL_sound blocks direct access to the specific decoders, there is no way for a user to know this information short of decoding the whole thing. Because of this, we believe this will be a useful addition, even though the accuracy may not be perfect (subject to each decoder) or the information may not always be available. * CONTRIBUTORS: Wesley Leong (modified the majority of the codecs and verified the results) Eric Wing (showed everyone how to do modify codec, modified mikmod) Wang Lam (modified a handful of codecs, researched into specs and int overflow) Ahilan Anantha (modified a few codecs and helped with integer math) * GENERAL ISSUES: We chose the value to be milliseconds as an Sint32. Milliseconds because that's what Sound_Seek takes as a parameter and -1 to allow for instances/codecs where the value could not be determined. We are not sure if this is the final convention you want, so we are willing to work with you on this. We also expect the total_time field to be set on open and never again modified by SDL_sound. Users may access it directly much like the sample buffer and buffer_size. We thought about recomputing the time on DecodeAll, but since users may seek or decode small chunks first, not all the data may be there. So this is better done by the user. This may be good information to document. Currently, all the main codecs are implemented except for QuickTime.
author Ryan C. Gordon <icculus@icculus.org>
date Sat, 08 May 2004 08:19:50 +0000
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199
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1 /*
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2
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3 TiMidity -- Experimental MIDI to WAVE converter
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4 Copyright (C) 1995 Tuukka Toivonen <toivonen@clinet.fi>
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5
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6 This program is free software; you can redistribute it and/or modify
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7 it under the terms of the GNU General Public License as published by
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8 the Free Software Foundation; either version 2 of the License, or
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Ryan C. Gordon <icculus@icculus.org>
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9 (at your option) any later version.
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10
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11 This program is distributed in the hope that it will be useful,
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12 but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 GNU General Public License for more details.
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15
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16 You should have received a copy of the GNU General Public License
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17 along with this program; if not, write to the Free Software
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18 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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19
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20 output.c
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21
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22 Audio output (to file / device) functions.
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23 */
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24
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25 #if HAVE_CONFIG_H
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26 # include <config.h>
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27 #endif
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28
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29 #include "SDL_sound.h"
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30
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31 #define __SDL_SOUND_INTERNAL__
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32 #include "SDL_sound_internal.h"
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33
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34 #include "options.h"
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35 #include "output.h"
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36
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37 /*****************************************************************/
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38 /* Some functions to convert signed 32-bit data to other formats */
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39
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40 void s32tos8(void *dp, Sint32 *lp, Sint32 c)
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41 {
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42 Sint8 *cp=(Sint8 *)(dp);
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43 Sint32 l;
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44 while (c--)
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45 {
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46 l=(*lp++)>>(32-8-GUARD_BITS);
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47 if (l>127) l=127;
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48 else if (l<-128) l=-128;
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49 *cp++ = (Sint8) (l);
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50 }
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51 }
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52
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53 void s32tou8(void *dp, Sint32 *lp, Sint32 c)
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54 {
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55 Uint8 *cp=(Uint8 *)(dp);
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56 Sint32 l;
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57 while (c--)
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58 {
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59 l=(*lp++)>>(32-8-GUARD_BITS);
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60 if (l>127) l=127;
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61 else if (l<-128) l=-128;
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62 *cp++ = 0x80 ^ ((Uint8) l);
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63 }
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64 }
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65
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66 void s32tos16(void *dp, Sint32 *lp, Sint32 c)
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67 {
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68 Sint16 *sp=(Sint16 *)(dp);
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69 Sint32 l;
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70 while (c--)
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71 {
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72 l=(*lp++)>>(32-16-GUARD_BITS);
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73 if (l > 32767) l=32767;
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74 else if (l<-32768) l=-32768;
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75 *sp++ = (Sint16)(l);
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76 }
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77 }
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78
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79 void s32tou16(void *dp, Sint32 *lp, Sint32 c)
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80 {
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81 Uint16 *sp=(Uint16 *)(dp);
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82 Sint32 l;
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83 while (c--)
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84 {
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85 l=(*lp++)>>(32-16-GUARD_BITS);
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86 if (l > 32767) l=32767;
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87 else if (l<-32768) l=-32768;
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88 *sp++ = 0x8000 ^ (Uint16)(l);
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89 }
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90 }
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91
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92 void s32tos16x(void *dp, Sint32 *lp, Sint32 c)
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93 {
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94 Sint16 *sp=(Sint16 *)(dp);
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95 Sint32 l;
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96 while (c--)
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97 {
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98 l=(*lp++)>>(32-16-GUARD_BITS);
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99 if (l > 32767) l=32767;
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100 else if (l<-32768) l=-32768;
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101 *sp++ = SDL_Swap16((Sint16)(l));
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102 }
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103 }
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104
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105 void s32tou16x(void *dp, Sint32 *lp, Sint32 c)
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106 {
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107 Uint16 *sp=(Uint16 *)(dp);
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108 Sint32 l;
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109 while (c--)
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110 {
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111 l=(*lp++)>>(32-16-GUARD_BITS);
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112 if (l > 32767) l=32767;
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113 else if (l<-32768) l=-32768;
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114 *sp++ = SDL_Swap16(0x8000 ^ (Uint16)(l));
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115 }
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116 }