Mercurial > SDL_sound_CoreAudio
annotate decoders/mpglib.c @ 271:493dd0173f3d
Added a FIXME comment.
| author | Ryan C. Gordon <icculus@icculus.org> |
|---|---|
| date | Sun, 10 Mar 2002 18:35:31 +0000 |
| parents | 9b89bb587f8f |
| children | ee6e1f8bfae9 |
| rev | line source |
|---|---|
| 261 | 1 /* |
| 2 * SDL_sound -- An abstract sound format decoding API. | |
| 3 * Copyright (C) 2001 Ryan C. Gordon. | |
| 4 * | |
| 5 * This library is free software; you can redistribute it and/or | |
| 6 * modify it under the terms of the GNU Lesser General Public | |
| 7 * License as published by the Free Software Foundation; either | |
| 8 * version 2.1 of the License, or (at your option) any later version. | |
| 9 * | |
| 10 * This library is distributed in the hope that it will be useful, | |
| 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 13 * Lesser General Public License for more details. | |
| 14 * | |
| 15 * You should have received a copy of the GNU Lesser General Public | |
| 16 * License along with this library; if not, write to the Free Software | |
| 17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
| 18 */ | |
| 19 | |
| 20 /* | |
| 21 * MPGLIB decoder for SDL_sound. This is a very lightweight MP3 decoder, | |
| 22 * which is included with the SDL_sound source, so that it doesn't rely on | |
| 23 * unnecessary external libraries. | |
| 24 * | |
| 25 * The SMPEG decoder plays back more forms of MPEGs, and may behave better or | |
| 26 * worse under various conditions. mpglib is (apparently) more efficient than | |
| 27 * SMPEG, and, again, doesn't need an external library. You should test both | |
| 28 * decoders and use what you find works best for you. | |
| 29 * | |
| 30 * mpglib is part of mpg123, which can be found in its original form at: | |
| 31 * http://www.mpg123.de/ | |
| 32 * | |
| 33 * Please see the file COPYING in the source's root directory. The included | |
| 34 * source code for mpglib falls under the LGPL, which is the same license as | |
| 35 * SDL_sound (so you can consider it a single work). | |
| 36 * | |
| 37 * This file written by Ryan C. Gordon. (icculus@clutteredmind.org) | |
| 38 */ | |
| 39 | |
| 40 #if HAVE_CONFIG_H | |
| 41 # include <config.h> | |
| 42 #endif | |
| 43 | |
| 44 #ifdef SOUND_SUPPORTS_MPGLIB | |
| 45 | |
| 46 #include <stdio.h> | |
| 47 #include <stdlib.h> | |
| 48 #include <string.h> | |
| 49 #include <assert.h> | |
| 50 #include "mpglib/mpg123_sdlsound.h" | |
| 51 #include "mpglib/mpglib_sdlsound.h" | |
| 52 | |
| 53 #include "SDL_sound.h" | |
| 54 | |
| 55 #define __SDL_SOUND_INTERNAL__ | |
| 56 #include "SDL_sound_internal.h" | |
| 57 | |
| 58 static int MPGLIB_init(void); | |
| 59 static void MPGLIB_quit(void); | |
| 60 static int MPGLIB_open(Sound_Sample *sample, const char *ext); | |
| 61 static void MPGLIB_close(Sound_Sample *sample); | |
| 62 static Uint32 MPGLIB_read(Sound_Sample *sample); | |
| 63 static int MPGLIB_rewind(Sound_Sample *sample); | |
| 64 | |
| 65 static const char *extensions_mpglib[] = { "MP3", NULL }; | |
| 66 const Sound_DecoderFunctions __Sound_DecoderFunctions_MPGLIB = | |
| 67 { | |
| 68 { | |
| 69 extensions_mpglib, | |
| 70 "MP3 decoding via internal mpglib", | |
| 71 "Ryan C. Gordon <icculus@clutteredmind.org>", | |
| 72 "http://www.icculus.org/SDL_sound/" | |
| 73 }, | |
| 74 | |
| 75 MPGLIB_init, /* init() method */ | |
| 76 MPGLIB_quit, /* quit() method */ | |
| 77 MPGLIB_open, /* open() method */ | |
| 78 MPGLIB_close, /* close() method */ | |
| 79 MPGLIB_read, /* read() method */ | |
| 80 MPGLIB_rewind /* rewind() method */ | |
| 81 }; | |
| 82 | |
| 83 | |
| 84 /* this is what we store in our internal->decoder_private field... */ | |
| 85 typedef struct | |
| 86 { | |
| 87 struct mpstr mp; | |
| 88 Uint8 inbuf[16384]; | |
| 89 Uint8 outbuf[8192]; | |
| 90 int outleft; | |
| 91 int outpos; | |
| 92 } mpglib_t; | |
| 93 | |
| 94 | |
| 95 | |
| 96 static int MPGLIB_init(void) | |
| 97 { | |
| 98 return(1); /* always succeeds. */ | |
| 99 } /* MPGLIB_init */ | |
| 100 | |
| 101 | |
| 102 static void MPGLIB_quit(void) | |
| 103 { | |
| 104 /* it's a no-op. */ | |
| 105 } /* MPGLIB_quit */ | |
| 106 | |
| 107 | |
| 108 static int MPGLIB_open(Sound_Sample *sample, const char *ext) | |
| 109 { | |
| 110 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque; | |
| 111 mpglib_t *mpg = NULL; | |
| 112 | |
| 113 /* | |
| 114 * If I understand things correctly, MP3 files don't really have any | |
| 115 * magic header we can check for. The MP3 player is expected to just | |
| 116 * pick the first thing that looks like a valid frame and start | |
| 117 * playing from there. | |
| 118 * | |
| 119 * So here's what we do: If the caller insists that this is really | |
| 120 * MP3 we'll take his word for it. Otherwise, use the same test as | |
| 121 * SDL_mixer does and check if the stream starts with something that | |
| 122 * looks like a frame. | |
| 123 * | |
| 124 * A frame begins with 11 bits of frame sync (all bits must be set), | |
| 125 * followed by a two-bit MPEG Audio version ID: | |
| 126 * | |
| 127 * 00 - MPEG Version 2.5 (later extension of MPEG 2) | |
| 128 * 01 - reserved | |
| 129 * 10 - MPEG Version 2 (ISO/IEC 13818-3) | |
| 130 * 11 - MPEG Version 1 (ISO/IEC 11172-3) | |
| 131 * | |
| 132 * Apparently we don't handle MPEG Version 2.5. | |
| 133 */ | |
| 134 if (__Sound_strcasecmp(ext, "MP3") != 0) | |
| 135 { | |
| 136 Uint8 mp3_magic[2]; | |
| 137 | |
| 138 if (SDL_RWread(internal->rw, mp3_magic, sizeof (mp3_magic), 1) != 1) | |
| 139 { | |
| 140 Sound_SetError("MP3: Could not read MP3 magic."); | |
| 141 return(0); | |
| 142 } /*if */ | |
| 143 | |
| 144 if (mp3_magic[0] != 0xFF || (mp3_magic[1] & 0xF0) != 0xF0) | |
| 145 { | |
| 146 Sound_SetError("MP3: Not an MP3 stream."); | |
| 147 return(0); | |
| 148 } /* if */ | |
| 149 | |
| 150 /* !!! FIXME: If the seek fails, we'll probably miss a frame */ | |
| 151 SDL_RWseek(internal->rw, -sizeof (mp3_magic), SEEK_CUR); | |
| 152 } /* if */ | |
| 153 | |
| 154 mpg = (mpglib_t *) malloc(sizeof (mpglib_t)); | |
| 155 BAIL_IF_MACRO(mpg == NULL, ERR_OUT_OF_MEMORY, 0); | |
| 156 mpg->outpos = mpg->outleft = 0; | |
| 157 InitMP3(&mpg->mp); | |
| 158 | |
| 159 SNDDBG(("MPGLIB: Accepting data stream.\n")); | |
| 160 | |
|
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161 /* !!! FIXME: Determine what format mpglib is spitting out... */ |
| 261 | 162 internal->decoder_private = mpg; |
| 163 sample->actual.rate = 44100; | |
| 164 sample->actual.channels = 2; | |
| 165 sample->actual.format = AUDIO_S16LSB; | |
| 166 sample->flags = SOUND_SAMPLEFLAG_NONE; | |
| 167 | |
| 168 return(1); /* we'll handle this data. */ | |
| 169 } /* MPGLIB_open */ | |
| 170 | |
| 171 | |
| 172 static void MPGLIB_close(Sound_Sample *sample) | |
| 173 { | |
| 174 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque; | |
| 175 mpglib_t *mpg = ((mpglib_t *) internal->decoder_private); | |
| 176 ExitMP3(&mpg->mp); | |
| 177 free(mpg); | |
| 178 } /* MPGLIB_close */ | |
| 179 | |
| 180 | |
| 181 static Uint32 MPGLIB_read(Sound_Sample *sample) | |
| 182 { | |
| 183 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque; | |
| 184 mpglib_t *mpg = ((mpglib_t *) internal->decoder_private); | |
| 185 Uint32 bw = 0; | |
| 186 int rc; | |
| 187 | |
| 188 while (bw < internal->buffer_size) | |
| 189 { | |
| 190 if (mpg->outleft > 0) | |
| 191 { | |
| 192 Uint16 cpysize = internal->buffer_size - bw; | |
| 193 if (cpysize > mpg->outleft) | |
| 194 cpysize = mpg->outleft; | |
| 195 memcpy(((Uint8 *) internal->buffer) + bw, | |
| 196 mpg->outbuf + mpg->outpos, cpysize); | |
| 197 bw += cpysize; | |
| 198 mpg->outpos += cpysize; | |
| 199 mpg->outleft -= cpysize; | |
| 200 continue; | |
| 201 } /* if */ | |
| 202 | |
| 203 /* need to decode more from the MP3 stream... */ | |
| 204 mpg->outpos = 0; | |
| 205 rc = decodeMP3(&mpg->mp, NULL, 0, mpg->outbuf, | |
| 206 sizeof (mpg->outbuf), &mpg->outleft); | |
| 207 if (rc == MP3_ERR) | |
| 208 { | |
| 209 sample->flags |= SOUND_SAMPLEFLAG_ERROR; | |
| 210 return(bw); | |
| 211 } /* if */ | |
| 212 | |
| 213 else if (rc == MP3_NEED_MORE) | |
| 214 { | |
| 215 rc = SDL_RWread(internal->rw, mpg->inbuf, 1, sizeof (mpg->inbuf)); | |
| 216 if (rc == -1) | |
| 217 { | |
| 218 sample->flags |= SOUND_SAMPLEFLAG_ERROR; | |
| 219 return(bw); | |
| 220 } /* if */ | |
|
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221 |
| 261 | 222 else if (rc == 0) |
| 223 { | |
| 224 sample->flags |= SOUND_SAMPLEFLAG_EOF; | |
| 225 return(bw); | |
| 226 } /* else if */ | |
| 227 | |
|
268
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228 /* make sure there isn't an ID3 tag. */ |
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229 /* |
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230 * !!! FIXME: This can fail under the following circumstances: |
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231 * First, if there's the sequence "TAG" 128 bytes from the end |
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232 * of a read that isn't the EOF. This is unlikely. |
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233 * Second, if the TAG sequence is split between two reads (ie, |
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234 * the last byte of a read is 'T', and the next read is the |
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235 * final 127 bytes of the stream, being the rest of the ID3 tag). |
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236 * While this is more likely, it's still not very likely at all. |
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237 * Still, something SHOULD be done about this. |
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238 * ID3v2 tags are more complex, too, not to mention LYRICS tags, |
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239 * etc, which aren't handled, either. Hey, this IS meant to be |
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240 * a lightweight decoder. Use SMPEG if you need an all-purpose |
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241 * decoder. mpglib really assumes you control all your assets. |
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242 */ |
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243 if (rc >= 128) |
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244 { |
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245 Uint8 *ptr = &mpg->inbuf[rc - 128]; |
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246 if ((ptr[0] == 'T') && (ptr[1] == 'A') && (ptr[2] == 'G')) |
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247 rc -= 128; /* disregard it. */ |
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248 } /* if */ |
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249 |
| 263 | 250 rc = decodeMP3(&mpg->mp, mpg->inbuf, rc, |
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251 mpg->outbuf, sizeof (mpg->outbuf), |
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252 &mpg->outleft); |
| 261 | 253 if (rc == MP3_ERR) |
| 254 { | |
| 255 sample->flags |= SOUND_SAMPLEFLAG_ERROR; | |
| 256 return(bw); | |
| 257 } /* if */ | |
| 258 } /* else if */ | |
| 259 } /* while */ | |
| 260 | |
| 261 return(bw); | |
| 262 } /* MPGLIB_read */ | |
| 263 | |
| 264 | |
| 265 static int MPGLIB_rewind(Sound_Sample *sample) | |
| 266 { | |
| 267 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque; | |
| 268 mpglib_t *mpg = ((mpglib_t *) internal->decoder_private); | |
| 269 BAIL_IF_MACRO(SDL_RWseek(internal->rw, 0, SEEK_SET) != 0, ERR_IO_ERROR, 0); | |
| 270 | |
| 271 /* this is just resetting some fields in a structure; it's very fast. */ | |
| 272 ExitMP3(&mpg->mp); | |
| 273 InitMP3(&mpg->mp); | |
| 274 mpg->outpos = mpg->outleft = 0; | |
| 275 return(1); | |
| 276 } /* MPGLIB_rewind */ | |
| 277 | |
| 278 | |
| 279 #endif /* SOUND_SUPPORTS_MPGLIB */ | |
| 280 | |
| 281 | |
| 282 /* end of mpglib.c ... */ | |
| 283 |