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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 9561 | turbocat | 1 | /* |
| 2 | SDL - Simple DirectMedia Layer |
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| 3 | Copyright (C) 1997, 1998, 1999, 2000, 2001 Sam Lantinga |
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| 4 | |||
| 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 Library General Public |
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| 7 | License as published by the Free Software Foundation; either |
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| 8 | version 2 of the License, or (at your option) any later version. |
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| 9 | |||
| 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 | Library General Public License for more details. |
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| 14 | |||
| 15 | You should have received a copy of the GNU Library General Public |
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| 16 | License along with this library; if not, write to the Free |
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| 17 | Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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| 18 | |||
| 19 | Sam Lantinga |
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| 20 | slouken@devolution.com |
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| 21 | */ |
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| 22 | |||
| 23 | #ifdef SAVE_RCSID |
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| 24 | static char rcsid = |
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| 25 | "@(#) $Id: SDL_audiocvt.c,v 1.2 2001/04/26 16:50:17 hercules Exp $"; |
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| 26 | #endif |
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| 27 | |||
| 28 | /* Functions for audio drivers to perform runtime conversion of audio format */ |
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| 29 | |||
| 30 | #include |
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| 31 | |||
| 32 | #include "SDL_error.h" |
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| 33 | #include "SDL_audio.h" |
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| 34 | |||
| 35 | |||
| 36 | /* Effectively mix right and left channels into a single channel */ |
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| 37 | void SDL_ConvertMono(SDL_AudioCVT *cvt, Uint16 format) |
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| 38 | { |
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| 39 | int i; |
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| 40 | Sint32 sample; |
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| 41 | |||
| 42 | #ifdef DEBUG_CONVERT |
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| 43 | fprintf(stderr, "Converting to mono\n"); |
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| 44 | #endif |
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| 45 | switch (format&0x8018) { |
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| 46 | |||
| 47 | case AUDIO_U8: { |
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| 48 | Uint8 *src, *dst; |
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| 49 | |||
| 50 | src = cvt->buf; |
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| 51 | dst = cvt->buf; |
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| 52 | for ( i=cvt->len_cvt/2; i; --i ) { |
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| 53 | sample = src[0] + src[1]; |
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| 54 | if ( sample > 255 ) { |
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| 55 | *dst = 255; |
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| 56 | } else { |
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| 57 | *dst = sample; |
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| 58 | } |
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| 59 | src += 2; |
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| 60 | dst += 1; |
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| 61 | } |
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| 62 | } |
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| 63 | break; |
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| 64 | |||
| 65 | case AUDIO_S8: { |
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| 66 | Sint8 *src, *dst; |
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| 67 | |||
| 68 | src = (Sint8 *)cvt->buf; |
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| 69 | dst = (Sint8 *)cvt->buf; |
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| 70 | for ( i=cvt->len_cvt/2; i; --i ) { |
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| 71 | sample = src[0] + src[1]; |
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| 72 | if ( sample > 127 ) { |
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| 73 | *dst = 127; |
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| 74 | } else |
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| 75 | if ( sample < -128 ) { |
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| 76 | *dst = -128; |
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| 77 | } else { |
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| 78 | *dst = sample; |
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| 79 | } |
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| 80 | src += 2; |
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| 81 | dst += 1; |
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| 82 | } |
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| 83 | } |
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| 84 | break; |
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| 85 | |||
| 86 | case AUDIO_U16: { |
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| 87 | Uint8 *src, *dst; |
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| 88 | |||
| 89 | src = cvt->buf; |
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| 90 | dst = cvt->buf; |
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| 91 | if ( (format & 0x1000) == 0x1000 ) { |
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| 92 | for ( i=cvt->len_cvt/4; i; --i ) { |
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| 93 | sample = (Uint16)((src[0]<<8)|src[1])+ |
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| 94 | (Uint16)((src[2]<<8)|src[3]); |
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| 95 | if ( sample > 65535 ) { |
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| 96 | dst[0] = 0xFF; |
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| 97 | dst[1] = 0xFF; |
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| 98 | } else { |
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| 99 | dst[1] = (sample&0xFF); |
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| 100 | sample >>= 8; |
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| 101 | dst[0] = (sample&0xFF); |
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| 102 | } |
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| 103 | src += 4; |
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| 104 | dst += 2; |
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| 105 | } |
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| 106 | } else { |
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| 107 | for ( i=cvt->len_cvt/4; i; --i ) { |
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| 108 | sample = (Uint16)((src[1]<<8)|src[0])+ |
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| 109 | (Uint16)((src[3]<<8)|src[2]); |
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| 110 | if ( sample > 65535 ) { |
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| 111 | dst[0] = 0xFF; |
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| 112 | dst[1] = 0xFF; |
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| 113 | } else { |
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| 114 | dst[0] = (sample&0xFF); |
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| 115 | sample >>= 8; |
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| 116 | dst[1] = (sample&0xFF); |
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| 117 | } |
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| 118 | src += 4; |
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| 119 | dst += 2; |
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| 120 | } |
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| 121 | } |
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| 122 | } |
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| 123 | break; |
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| 124 | |||
| 125 | case AUDIO_S16: { |
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| 126 | Uint8 *src, *dst; |
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| 127 | |||
| 128 | src = cvt->buf; |
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| 129 | dst = cvt->buf; |
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| 130 | if ( (format & 0x1000) == 0x1000 ) { |
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| 131 | for ( i=cvt->len_cvt/4; i; --i ) { |
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| 132 | sample = (Sint16)((src[0]<<8)|src[1])+ |
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| 133 | (Sint16)((src[2]<<8)|src[3]); |
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| 134 | if ( sample > 32767 ) { |
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| 135 | dst[0] = 0x7F; |
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| 136 | dst[1] = 0xFF; |
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| 137 | } else |
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| 138 | if ( sample < -32768 ) { |
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| 139 | dst[0] = 0x80; |
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| 140 | dst[1] = 0x00; |
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| 141 | } else { |
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| 142 | dst[1] = (sample&0xFF); |
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| 143 | sample >>= 8; |
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| 144 | dst[0] = (sample&0xFF); |
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| 145 | } |
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| 146 | src += 4; |
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| 147 | dst += 2; |
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| 148 | } |
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| 149 | } else { |
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| 150 | for ( i=cvt->len_cvt/4; i; --i ) { |
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| 151 | sample = (Sint16)((src[1]<<8)|src[0])+ |
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| 152 | (Sint16)((src[3]<<8)|src[2]); |
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| 153 | if ( sample > 32767 ) { |
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| 154 | dst[1] = 0x7F; |
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| 155 | dst[0] = 0xFF; |
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| 156 | } else |
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| 157 | if ( sample < -32768 ) { |
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| 158 | dst[1] = 0x80; |
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| 159 | dst[0] = 0x00; |
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| 160 | } else { |
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| 161 | dst[0] = (sample&0xFF); |
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| 162 | sample >>= 8; |
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| 163 | dst[1] = (sample&0xFF); |
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| 164 | } |
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| 165 | src += 4; |
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| 166 | dst += 2; |
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| 167 | } |
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| 168 | } |
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| 169 | } |
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| 170 | break; |
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| 171 | } |
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| 172 | cvt->len_cvt /= 2; |
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| 173 | if ( cvt->filters[++cvt->filter_index] ) { |
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| 174 | cvt->filters[cvt->filter_index](cvt, format); |
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| 175 | } |
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| 176 | } |
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| 177 | |||
| 178 | |||
| 179 | /* Duplicate a mono channel to both stereo channels */ |
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| 180 | void SDL_ConvertStereo(SDL_AudioCVT *cvt, Uint16 format) |
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| 181 | { |
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| 182 | int i; |
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| 183 | |||
| 184 | #ifdef DEBUG_CONVERT |
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| 185 | fprintf(stderr, "Converting to stereo\n"); |
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| 186 | #endif |
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| 187 | if ( (format & 0xFF) == 16 ) { |
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| 188 | Uint16 *src, *dst; |
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| 189 | |||
| 190 | src = (Uint16 *)(cvt->buf+cvt->len_cvt); |
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| 191 | dst = (Uint16 *)(cvt->buf+cvt->len_cvt*2); |
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| 192 | for ( i=cvt->len_cvt/2; i; --i ) { |
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| 193 | dst -= 2; |
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| 194 | src -= 1; |
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| 195 | dst[0] = src[0]; |
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| 196 | dst[1] = src[0]; |
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| 197 | } |
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| 198 | } else { |
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| 199 | Uint8 *src, *dst; |
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| 200 | |||
| 201 | src = cvt->buf+cvt->len_cvt; |
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| 202 | dst = cvt->buf+cvt->len_cvt*2; |
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| 203 | for ( i=cvt->len_cvt; i; --i ) { |
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| 204 | dst -= 2; |
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| 205 | src -= 1; |
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| 206 | dst[0] = src[0]; |
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| 207 | dst[1] = src[0]; |
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| 208 | } |
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| 209 | } |
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| 210 | cvt->len_cvt *= 2; |
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| 211 | if ( cvt->filters[++cvt->filter_index] ) { |
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| 212 | cvt->filters[cvt->filter_index](cvt, format); |
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| 213 | } |
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| 214 | } |
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| 215 | |||
| 216 | /* Convert 8-bit to 16-bit - LSB */ |
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| 217 | void SDL_Convert16LSB(SDL_AudioCVT *cvt, Uint16 format) |
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| 218 | { |
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| 219 | int i; |
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| 220 | Uint8 *src, *dst; |
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| 221 | |||
| 222 | #ifdef DEBUG_CONVERT |
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| 223 | fprintf(stderr, "Converting to 16-bit LSB\n"); |
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| 224 | #endif |
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| 225 | src = cvt->buf+cvt->len_cvt; |
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| 226 | dst = cvt->buf+cvt->len_cvt*2; |
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| 227 | for ( i=cvt->len_cvt; i; --i ) { |
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| 228 | src -= 1; |
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| 229 | dst -= 2; |
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| 230 | dst[1] = *src; |
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| 231 | dst[0] = 0; |
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| 232 | } |
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| 233 | format = ((format & ~0x0008) | AUDIO_U16LSB); |
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| 234 | cvt->len_cvt *= 2; |
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| 235 | if ( cvt->filters[++cvt->filter_index] ) { |
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| 236 | cvt->filters[cvt->filter_index](cvt, format); |
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| 237 | } |
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| 238 | } |
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| 239 | /* Convert 8-bit to 16-bit - MSB */ |
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| 240 | void SDL_Convert16MSB(SDL_AudioCVT *cvt, Uint16 format) |
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| 241 | { |
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| 242 | int i; |
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| 243 | Uint8 *src, *dst; |
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| 244 | |||
| 245 | #ifdef DEBUG_CONVERT |
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| 246 | fprintf(stderr, "Converting to 16-bit MSB\n"); |
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| 247 | #endif |
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| 248 | src = cvt->buf+cvt->len_cvt; |
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| 249 | dst = cvt->buf+cvt->len_cvt*2; |
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| 250 | for ( i=cvt->len_cvt; i; --i ) { |
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| 251 | src -= 1; |
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| 252 | dst -= 2; |
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| 253 | dst[0] = *src; |
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| 254 | dst[1] = 0; |
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| 255 | } |
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| 256 | format = ((format & ~0x0008) | AUDIO_U16MSB); |
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| 257 | cvt->len_cvt *= 2; |
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| 258 | if ( cvt->filters[++cvt->filter_index] ) { |
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| 259 | cvt->filters[cvt->filter_index](cvt, format); |
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| 260 | } |
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| 261 | } |
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| 262 | |||
| 263 | /* Convert 16-bit to 8-bit */ |
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| 264 | void SDL_Convert8(SDL_AudioCVT *cvt, Uint16 format) |
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| 265 | { |
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| 266 | int i; |
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| 267 | Uint8 *src, *dst; |
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| 268 | |||
| 269 | #ifdef DEBUG_CONVERT |
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| 270 | fprintf(stderr, "Converting to 8-bit\n"); |
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| 271 | #endif |
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| 272 | src = cvt->buf; |
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| 273 | dst = cvt->buf; |
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| 274 | if ( (format & 0x1000) != 0x1000 ) { /* Little endian */ |
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| 275 | ++src; |
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| 276 | } |
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| 277 | for ( i=cvt->len_cvt/2; i; --i ) { |
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| 278 | *dst = *src; |
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| 279 | src += 2; |
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| 280 | dst += 1; |
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| 281 | } |
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| 282 | format = ((format & ~0x9010) | AUDIO_U8); |
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| 283 | cvt->len_cvt /= 2; |
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| 284 | if ( cvt->filters[++cvt->filter_index] ) { |
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| 285 | cvt->filters[cvt->filter_index](cvt, format); |
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| 286 | } |
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| 287 | } |
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| 288 | |||
| 289 | /* Toggle signed/unsigned */ |
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| 290 | void SDL_ConvertSign(SDL_AudioCVT *cvt, Uint16 format) |
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| 291 | { |
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| 292 | int i; |
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| 293 | Uint8 *data; |
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| 294 | |||
| 295 | #ifdef DEBUG_CONVERT |
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| 296 | fprintf(stderr, "Converting audio signedness\n"); |
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| 297 | #endif |
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| 298 | data = cvt->buf; |
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| 299 | if ( (format & 0xFF) == 16 ) { |
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| 300 | if ( (format & 0x1000) != 0x1000 ) { /* Little endian */ |
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| 301 | ++data; |
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| 302 | } |
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| 303 | for ( i=cvt->len_cvt/2; i; --i ) { |
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| 304 | *data ^= 0x80; |
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| 305 | data += 2; |
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| 306 | } |
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| 307 | } else { |
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| 308 | for ( i=cvt->len_cvt; i; --i ) { |
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| 309 | *data++ ^= 0x80; |
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| 310 | } |
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| 311 | } |
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| 312 | format = (format ^ 0x8000); |
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| 313 | if ( cvt->filters[++cvt->filter_index] ) { |
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| 314 | cvt->filters[cvt->filter_index](cvt, format); |
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| 315 | } |
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| 316 | } |
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| 317 | |||
| 318 | /* Toggle endianness */ |
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| 319 | void SDL_ConvertEndian(SDL_AudioCVT *cvt, Uint16 format) |
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| 320 | { |
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| 321 | int i; |
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| 322 | Uint8 *data, tmp; |
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| 323 | |||
| 324 | #ifdef DEBUG_CONVERT |
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| 325 | fprintf(stderr, "Converting audio endianness\n"); |
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| 326 | #endif |
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| 327 | data = cvt->buf; |
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| 328 | for ( i=cvt->len_cvt/2; i; --i ) { |
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| 329 | tmp = data[0]; |
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| 330 | data[0] = data[1]; |
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| 331 | data[1] = tmp; |
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| 332 | data += 2; |
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| 333 | } |
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| 334 | format = (format ^ 0x1000); |
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| 335 | if ( cvt->filters[++cvt->filter_index] ) { |
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| 336 | cvt->filters[cvt->filter_index](cvt, format); |
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| 337 | } |
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| 338 | } |
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| 339 | |||
| 340 | /* Convert rate up by multiple of 2 */ |
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| 341 | void SDL_RateMUL2(SDL_AudioCVT *cvt, Uint16 format) |
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| 342 | { |
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| 343 | int i; |
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| 344 | Uint8 *src, *dst; |
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| 345 | |||
| 346 | #ifdef DEBUG_CONVERT |
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| 347 | fprintf(stderr, "Converting audio rate * 2\n"); |
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| 348 | #endif |
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| 349 | src = cvt->buf+cvt->len_cvt; |
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| 350 | dst = cvt->buf+cvt->len_cvt*2; |
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| 351 | switch (format & 0xFF) { |
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| 352 | case 8: |
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| 353 | for ( i=cvt->len_cvt; i; --i ) { |
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| 354 | src -= 1; |
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| 355 | dst -= 2; |
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| 356 | dst[0] = src[0]; |
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| 357 | dst[1] = src[0]; |
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| 358 | } |
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| 359 | break; |
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| 360 | case 16: |
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| 361 | for ( i=cvt->len_cvt/2; i; --i ) { |
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| 362 | src -= 2; |
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| 363 | dst -= 4; |
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| 364 | dst[0] = src[0]; |
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| 365 | dst[1] = src[1]; |
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| 366 | dst[2] = src[0]; |
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| 367 | dst[3] = src[1]; |
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| 368 | } |
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| 369 | break; |
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| 370 | } |
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| 371 | cvt->len_cvt *= 2; |
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| 372 | if ( cvt->filters[++cvt->filter_index] ) { |
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| 373 | cvt->filters[cvt->filter_index](cvt, format); |
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| 374 | } |
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| 375 | } |
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| 376 | |||
| 377 | /* Convert rate down by multiple of 2 */ |
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| 378 | void SDL_RateDIV2(SDL_AudioCVT *cvt, Uint16 format) |
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| 379 | { |
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| 380 | int i; |
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| 381 | Uint8 *src, *dst; |
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| 382 | |||
| 383 | #ifdef DEBUG_CONVERT |
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| 384 | fprintf(stderr, "Converting audio rate / 2\n"); |
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| 385 | #endif |
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| 386 | src = cvt->buf; |
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| 387 | dst = cvt->buf; |
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| 388 | switch (format & 0xFF) { |
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| 389 | case 8: |
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| 390 | for ( i=cvt->len_cvt/2; i; --i ) { |
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| 391 | dst[0] = src[0]; |
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| 392 | src += 2; |
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| 393 | dst += 1; |
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| 394 | } |
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| 395 | break; |
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| 396 | case 16: |
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| 397 | for ( i=cvt->len_cvt/4; i; --i ) { |
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| 398 | dst[0] = src[0]; |
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| 399 | dst[1] = src[1]; |
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| 400 | src += 4; |
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| 401 | dst += 2; |
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| 402 | } |
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| 403 | break; |
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| 404 | } |
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| 405 | cvt->len_cvt /= 2; |
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| 406 | if ( cvt->filters[++cvt->filter_index] ) { |
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| 407 | cvt->filters[cvt->filter_index](cvt, format); |
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| 408 | } |
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| 409 | } |
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| 410 | |||
| 411 | /* Very slow rate conversion routine */ |
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| 412 | void SDL_RateSLOW(SDL_AudioCVT *cvt, Uint16 format) |
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| 413 | { |
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| 414 | double ipos; |
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| 415 | int i, clen; |
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| 416 | |||
| 417 | #ifdef DEBUG_CONVERT |
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| 418 | fprintf(stderr, "Converting audio rate * %4.4f\n", 1.0/cvt->rate_incr); |
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| 419 | #endif |
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| 420 | clen = (int)((double)cvt->len_cvt / cvt->rate_incr); |
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| 421 | if ( cvt->rate_incr > 1.0 ) { |
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| 422 | switch (format & 0xFF) { |
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| 423 | case 8: { |
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| 424 | Uint8 *output; |
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| 425 | |||
| 426 | output = cvt->buf; |
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| 427 | ipos = 0.0; |
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| 428 | for ( i=clen; i; --i ) { |
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| 429 | *output = cvt->buf[(int)ipos]; |
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| 430 | ipos += cvt->rate_incr; |
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| 431 | output += 1; |
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| 432 | } |
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| 433 | } |
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| 434 | break; |
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| 435 | |||
| 436 | case 16: { |
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| 437 | Uint16 *output; |
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| 438 | |||
| 439 | clen &= ~1; |
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| 440 | output = (Uint16 *)cvt->buf; |
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| 441 | ipos = 0.0; |
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| 442 | for ( i=clen/2; i; --i ) { |
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| 443 | *output=((Uint16 *)cvt->buf)[(int)ipos]; |
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| 444 | ipos += cvt->rate_incr; |
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| 445 | output += 1; |
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| 446 | } |
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| 447 | } |
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| 448 | break; |
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| 449 | } |
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| 450 | } else { |
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| 451 | switch (format & 0xFF) { |
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| 452 | case 8: { |
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| 453 | Uint8 *output; |
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| 454 | |||
| 455 | output = cvt->buf+clen; |
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| 456 | ipos = (double)cvt->len_cvt; |
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| 457 | for ( i=clen; i; --i ) { |
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| 458 | ipos -= cvt->rate_incr; |
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| 459 | output -= 1; |
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| 460 | *output = cvt->buf[(int)ipos]; |
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| 461 | } |
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| 462 | } |
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| 463 | break; |
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| 464 | |||
| 465 | case 16: { |
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| 466 | Uint16 *output; |
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| 467 | |||
| 468 | clen &= ~1; |
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| 469 | output = (Uint16 *)(cvt->buf+clen); |
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| 470 | ipos = (double)cvt->len_cvt/2; |
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| 471 | for ( i=clen/2; i; --i ) { |
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| 472 | ipos -= cvt->rate_incr; |
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| 473 | output -= 1; |
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| 474 | *output=((Uint16 *)cvt->buf)[(int)ipos]; |
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| 475 | } |
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| 476 | } |
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| 477 | break; |
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| 478 | } |
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| 479 | } |
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| 480 | cvt->len_cvt = clen; |
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| 481 | if ( cvt->filters[++cvt->filter_index] ) { |
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| 482 | cvt->filters[cvt->filter_index](cvt, format); |
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| 483 | } |
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| 484 | } |
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| 485 | |||
| 486 | int SDL_ConvertAudio(SDL_AudioCVT *cvt) |
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| 487 | { |
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| 488 | /* Make sure there's data to convert */ |
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| 489 | if ( cvt->buf == NULL ) { |
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| 490 | SDL_SetError("No buffer allocated for conversion"); |
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| 491 | return(-1); |
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| 492 | } |
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| 493 | /* Return okay if no conversion is necessary */ |
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| 494 | cvt->len_cvt = cvt->len; |
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| 495 | if ( cvt->filters[0] == NULL ) { |
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| 496 | return(0); |
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| 497 | } |
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| 498 | |||
| 499 | /* Set up the conversion and go! */ |
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| 500 | cvt->filter_index = 0; |
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| 501 | cvt->filters[0](cvt, cvt->src_format); |
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| 502 | return(0); |
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| 503 | } |
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| 504 | |||
| 505 | /* Creates a set of audio filters to convert from one format to another. |
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| 506 | Returns -1 if the format conversion is not supported, or 1 if the |
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| 507 | audio filter is set up. |
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| 508 | */ |
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| 509 | |||
| 510 | int SDL_BuildAudioCVT(SDL_AudioCVT *cvt, |
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| 511 | Uint16 src_format, Uint8 src_channels, int src_rate, |
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| 512 | Uint16 dst_format, Uint8 dst_channels, int dst_rate) |
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| 513 | { |
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| 514 | /* Start off with no conversion necessary */ |
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| 515 | cvt->needed = 0; |
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| 516 | cvt->filter_index = 0; |
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| 517 | cvt->filters[0] = NULL; |
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| 518 | cvt->len_mult = 1; |
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| 519 | cvt->len_ratio = 1.0; |
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| 520 | |||
| 521 | /* First filter: Endian conversion from src to dst */ |
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| 522 | if ( (src_format & 0x1000) != (dst_format & 0x1000) |
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| 523 | && ((src_format & 0xff) != 8) ) { |
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| 524 | cvt->filters[cvt->filter_index++] = SDL_ConvertEndian; |
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| 525 | } |
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| 526 | |||
| 527 | /* Second filter: Sign conversion -- signed/unsigned */ |
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| 528 | if ( (src_format & 0x8000) != (dst_format & 0x8000) ) { |
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| 529 | cvt->filters[cvt->filter_index++] = SDL_ConvertSign; |
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| 530 | } |
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| 531 | |||
| 532 | /* Next filter: Convert 16 bit <--> 8 bit PCM */ |
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| 533 | if ( (src_format & 0xFF) != (dst_format & 0xFF) ) { |
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| 534 | switch (dst_format&0x10FF) { |
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| 535 | case AUDIO_U8: |
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| 536 | cvt->filters[cvt->filter_index++] = |
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| 537 | SDL_Convert8; |
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| 538 | cvt->len_ratio /= 2; |
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| 539 | break; |
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| 540 | case AUDIO_U16LSB: |
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| 541 | cvt->filters[cvt->filter_index++] = |
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| 542 | SDL_Convert16LSB; |
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| 543 | cvt->len_mult *= 2; |
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| 544 | cvt->len_ratio *= 2; |
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| 545 | break; |
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| 546 | case AUDIO_U16MSB: |
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| 547 | cvt->filters[cvt->filter_index++] = |
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| 548 | SDL_Convert16MSB; |
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| 549 | cvt->len_mult *= 2; |
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| 550 | cvt->len_ratio *= 2; |
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| 551 | break; |
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| 552 | } |
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| 553 | } |
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| 554 | |||
| 555 | /* Last filter: Mono/Stereo conversion */ |
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| 556 | if ( src_channels != dst_channels ) { |
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| 557 | while ( (src_channels*2) <= dst_channels ) { |
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| 558 | cvt->filters[cvt->filter_index++] = |
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| 559 | SDL_ConvertStereo; |
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| 560 | cvt->len_mult *= 2; |
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| 561 | src_channels *= 2; |
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| 562 | cvt->len_ratio *= 2; |
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| 563 | } |
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| 564 | /* This assumes that 4 channel audio is in the format: |
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| 565 | Left {front/back} + Right {front/back} |
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| 566 | so converting to L/R stereo works properly. |
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| 567 | */ |
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| 568 | while ( ((src_channels%2) == 0) && |
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| 569 | ((src_channels/2) >= dst_channels) ) { |
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| 570 | cvt->filters[cvt->filter_index++] = |
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| 571 | SDL_ConvertMono; |
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| 572 | src_channels /= 2; |
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| 573 | cvt->len_ratio /= 2; |
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| 574 | } |
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| 575 | if ( src_channels != dst_channels ) { |
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| 576 | /* Uh oh.. */; |
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| 577 | } |
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| 578 | } |
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| 579 | |||
| 580 | /* Do rate conversion */ |
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| 581 | cvt->rate_incr = 0.0; |
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| 582 | if ( (src_rate/100) != (dst_rate/100) ) { |
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| 583 | Uint32 hi_rate, lo_rate; |
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| 584 | int len_mult; |
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| 585 | double len_ratio; |
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| 586 | void (*rate_cvt)(SDL_AudioCVT *cvt, Uint16 format); |
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| 587 | |||
| 588 | if ( src_rate > dst_rate ) { |
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| 589 | hi_rate = src_rate; |
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| 590 | lo_rate = dst_rate; |
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| 591 | rate_cvt = SDL_RateDIV2; |
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| 592 | len_mult = 1; |
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| 593 | len_ratio = 0.5; |
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| 594 | } else { |
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| 595 | hi_rate = dst_rate; |
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| 596 | lo_rate = src_rate; |
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| 597 | rate_cvt = SDL_RateMUL2; |
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| 598 | len_mult = 2; |
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| 599 | len_ratio = 2.0; |
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| 600 | } |
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| 601 | /* If hi_rate = lo_rate*2^x then conversion is easy */ |
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| 602 | while ( ((lo_rate*2)/100) <= (hi_rate/100) ) { |
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| 603 | cvt->filters[cvt->filter_index++] = rate_cvt; |
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| 604 | cvt->len_mult *= len_mult; |
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| 605 | lo_rate *= 2; |
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| 606 | cvt->len_ratio *= len_ratio; |
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| 607 | } |
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| 608 | /* We may need a slow conversion here to finish up */ |
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| 609 | if ( (lo_rate/100) != (hi_rate/100) ) { |
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| 610 | #if 1 |
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| 611 | /* The problem with this is that if the input buffer is |
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| 612 | say 1K, and the conversion rate is say 1.1, then the |
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| 613 | output buffer is 1.1K, which may not be an acceptable |
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| 614 | buffer size for the audio driver (not a power of 2) |
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| 615 | */ |
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| 616 | /* For now, punt and hope the rate distortion isn't great. |
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| 617 | */ |
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| 618 | #else |
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| 619 | if ( src_rate < dst_rate ) { |
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| 620 | cvt->rate_incr = (double)lo_rate/hi_rate; |
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| 621 | cvt->len_mult *= 2; |
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| 622 | cvt->len_ratio /= cvt->rate_incr; |
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| 623 | } else { |
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| 624 | cvt->rate_incr = (double)hi_rate/lo_rate; |
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| 625 | cvt->len_ratio *= cvt->rate_incr; |
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| 626 | } |
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| 627 | cvt->filters[cvt->filter_index++] = SDL_RateSLOW; |
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| 628 | #endif |
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| 629 | } |
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| 630 | } |
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| 631 | |||
| 632 | /* Set up the filter information */ |
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| 633 | if ( cvt->filter_index != 0 ) { |
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| 634 | cvt->needed = 1; |
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| 635 | cvt->src_format = src_format; |
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| 636 | cvt->dst_format = dst_format; |
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| 637 | cvt->len = 0; |
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| 638 | cvt->buf = NULL; |
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| 639 | cvt->filters[cvt->filter_index] = NULL; |
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| 640 | } |
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| 641 | return(cvt->needed); |
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| 642 | } |