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comparison decoders/mpglib.c @ 261:9b6e82f7c853

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Initial add.
author Ryan C. Gordon <icculus@icculus.org>
date Thu, 21 Feb 2002 19:46:09 +0000
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260:44a4730a1e6f 261:9b6e82f7c853
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
161 internal->decoder_private = mpg;
162 sample->actual.rate = 44100;
163 sample->actual.channels = 2;
164 sample->actual.format = AUDIO_S16LSB;
165 sample->flags = SOUND_SAMPLEFLAG_NONE;
166
167 return(1); /* we'll handle this data. */
168 } /* MPGLIB_open */
169
170
171 static void MPGLIB_close(Sound_Sample *sample)
172 {
173 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
174 mpglib_t *mpg = ((mpglib_t *) internal->decoder_private);
175 ExitMP3(&mpg->mp);
176 free(mpg);
177 } /* MPGLIB_close */
178
179
180 static Uint32 MPGLIB_read(Sound_Sample *sample)
181 {
182 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
183 mpglib_t *mpg = ((mpglib_t *) internal->decoder_private);
184 Uint32 bw = 0;
185 int rc;
186
187 while (bw < internal->buffer_size)
188 {
189 if (mpg->outleft > 0)
190 {
191 Uint16 cpysize = internal->buffer_size - bw;
192 if (cpysize > mpg->outleft)
193 cpysize = mpg->outleft;
194 memcpy(((Uint8 *) internal->buffer) + bw,
195 mpg->outbuf + mpg->outpos, cpysize);
196 bw += cpysize;
197 mpg->outpos += cpysize;
198 mpg->outleft -= cpysize;
199 continue;
200 } /* if */
201
202 /* need to decode more from the MP3 stream... */
203 mpg->outpos = 0;
204 rc = decodeMP3(&mpg->mp, NULL, 0, mpg->outbuf,
205 sizeof (mpg->outbuf), &mpg->outleft);
206 if (rc == MP3_ERR)
207 {
208 sample->flags |= SOUND_SAMPLEFLAG_ERROR;
209 return(bw);
210 } /* if */
211
212 else if (rc == MP3_NEED_MORE)
213 {
214 rc = SDL_RWread(internal->rw, mpg->inbuf, 1, sizeof (mpg->inbuf));
215 if (rc == -1)
216 {
217 sample->flags |= SOUND_SAMPLEFLAG_ERROR;
218 return(bw);
219 } /* if */
220 else if (rc == 0)
221 {
222 sample->flags |= SOUND_SAMPLEFLAG_EOF;
223 return(bw);
224 } /* else if */
225
226 rc = decodeMP3(&mpg->mp, mpg->inbuf, sizeof (mpg->inbuf),
227 mpg->outbuf, sizeof (mpg->outbuf), &mpg->outleft);
228 if (rc == MP3_ERR)
229 {
230 sample->flags |= SOUND_SAMPLEFLAG_ERROR;
231 return(bw);
232 } /* if */
233 } /* else if */
234 } /* while */
235
236 return(bw);
237 } /* MPGLIB_read */
238
239
240 static int MPGLIB_rewind(Sound_Sample *sample)
241 {
242 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
243 mpglib_t *mpg = ((mpglib_t *) internal->decoder_private);
244 BAIL_IF_MACRO(SDL_RWseek(internal->rw, 0, SEEK_SET) != 0, ERR_IO_ERROR, 0);
245
246 /* this is just resetting some fields in a structure; it's very fast. */
247 ExitMP3(&mpg->mp);
248 InitMP3(&mpg->mp);
249 mpg->outpos = mpg->outleft = 0;
250 return(1);
251 } /* MPGLIB_rewind */
252
253
254 #endif /* SOUND_SUPPORTS_MPGLIB */
255
256
257 /* end of mpglib.c ... */
258