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comparison decoders/shn.c @ 86:155ab2a427ca

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Initial add.
author Ryan C. Gordon <icculus@icculus.org>
date Tue, 25 Sep 2001 22:43:09 +0000
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children 6d9fdec2f708
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85:b939258bd177 86:155ab2a427ca
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 * Shorten decoder for SDL_sound.
22 *
23 * This driver handles Shorten-compressed waveforms. Despite the fact that
24 * SHNs are generally used in online trading communities, they tend to be
25 * much bigger than MP3s. If an MP3 crunches the waveform to 10-20 percent
26 * of its original size, SHNs only go to about 50-60%. Why do the Phish fans
27 * of the world use this format then? Rabid music traders appreciate the
28 * sound quality; SHNs, unlike MP3s, do not throw away any part of the
29 * waveform. Yes, there are people that notice this, and further more, they
30 * demand it...and if they can't get a good transfer of those larger files
31 * over the 'net, they haven't underestimated the bandwidth of CDs travelling
32 * the world through the postal system.
33 *
34 * Shorten homepage: http://www.softsound.com/Shorten.html
35 *
36 * The Shorten format was gleaned from the shorten codebase, by Tony
37 * Robinson and SoftSound Limited, but none of their code was used here.
38 *
39 * Please see the file LICENSE in the source's root directory.
40 *
41 * This file written by Ryan C. Gordon. (icculus@clutteredmind.org)
42 */
43
44 #if (defined SOUND_SUPPORTS_SHN)
45
46 #include <stdio.h>
47 #include <stdlib.h>
48 #include <string.h>
49 #include <assert.h>
50 #include "SDL_sound.h"
51
52 #define __SDL_SOUND_INTERNAL__
53 #include "SDL_sound_internal.h"
54
55 static int SHN_init(void);
56 static void SHN_quit(void);
57 static int SHN_open(Sound_Sample *sample, const char *ext);
58 static void SHN_close(Sound_Sample *sample);
59 static Uint32 SHN_read(Sound_Sample *sample);
60
61 const Sound_DecoderFunctions __Sound_DecoderFunctions_SHN =
62 {
63 {
64 "SHN",
65 "Shorten-compressed audio data",
66 "Ryan C. Gordon <icculus@clutteredmind.org>",
67 "http://www.icculus.org/SDL_sound/"
68 },
69
70 SHN_init, /* init() method */
71 SHN_quit, /* quit() method */
72 SHN_open, /* open() method */
73 SHN_close, /* close() method */
74 SHN_read /* read() method */
75 };
76
77
78 static int SHN_init(void)
79 {
80 return(1); /* initialization always successful. */
81 } /* SHN_init */
82
83
84 static void SHN_quit(void)
85 {
86 /* it's a no-op. */
87 } /* SHN_quit */
88
89
90 static Uint32 mask_table[] =
91 {
92 0x00000000, 0x00000001, 0x00000003, 0x00000007, 0x0000000F, 0x0000001F,
93 0x0000003F, 0x0000007F, 0x000000FF, 0x000001FF, 0x000003FF, 0x000007FF,
94 0x00000FFF, 0x00001FFF, 0x00003FFF, 0x00007FFF, 0x0000FFFF, 0x0001FFFF,
95 0x0003FFFF, 0x0007FFFF, 0x000FFFFF, 0x001FFFFF, 0x003FFFFF, 0x007FFFFF,
96 0x00FFFFFF, 0x01FFFFFF, 0x03FFFFFF, 0x07FFFFFF, 0x0FFFFFFF, 0x1FFFFFFF,
97 0x3FFFFFFF, 0x7FFFFFFF, 0xFFFFFFFF
98 };
99
100
101 #define MAGIC_NUM 0x676B6A61 /* looks like "ajkg" as chars. */
102
103 /*
104 * Look through the whole file for a SHN magic number. This is costly, so
105 * it should only be done if the user SWEARS they have a Shorten stream...
106 */
107 static inline int extended_shn_magic_search(Sound_Sample *sample)
108 {
109 SDL_RWops *rw = ((Sound_SampleInternal *) sample->opaque)->rw;
110 Uint32 word = 0;
111 Uint8 ch;
112
113 while (1)
114 {
115 BAIL_IF_MACRO(SDL_RWread(rw, &ch, sizeof (ch), 1) != 1, NULL, -1);
116 word = ((word << 8) & 0xFFFFFF00) | ch;
117 if (SDL_SwapLE32(word) == MAGIC_NUM)
118 {
119 BAIL_IF_MACRO(SDL_RWread(rw, &ch, sizeof (ch), 1) != 1, NULL, -1);
120 return((int) ch);
121 } /* if */
122 } /* while */
123
124 return((int) ch);
125 } /* extended_shn_magic_search */
126
127
128 /* look for the magic number in the RWops and see what kind of file this is. */
129 static inline int determine_shn_version(Sound_Sample *sample)
130 {
131 SDL_RWops *rw = ((Sound_SampleInternal *) sample->opaque)->rw;
132 Uint32 magic;
133 Uint8 ch;
134
135 /*
136 * Apparently the magic number can start at any byte offset in the file,
137 * and we should just discard prior data, but I'm going to restrict it
138 * to offset zero for now, so we don't chug down every file that might
139 * happen to pass through here. If the extension is explicitly "SHN", we
140 * check the whole stream, though.
141 */
142
143 if (__Sound_strcasecmp(ext, "shn") == 0)
144 return(extended_shn_magic_search(sample);
145
146 BAIL_IF_MACRO(SDL_RWread(rw, &magic, sizeof (magic), 1) != 1, NULL, -1);
147 BAIL_IF_MACRO(SDL_SwapLE32(magic) != MAGIC_NUM, "SHN: Not a SHN file", -1);
148 BAIL_IF_MACRO(SDL_RWread(rw, &ch, sizeof (ch), 1) != 1, NULL, -1);
149 BAIL_IF_MACRO(ch > 3, "SHN: Unsupported file version", -1);
150
151 return((int) ch);
152 } /* determine_shn_version */
153
154
155 static int SHN_open(Sound_Sample *sample, const char *ext)
156 {
157 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
158 SDL_RWops *rw = internal->rw;
159 int shn_version = determine_shn_version(sample, ext);
160 int mean = MEAN_VERSION2;
161
162 BAIL_IF_MACRO(shn_version == -1, NULL, 0);
163 if (shn_version < 2) /* downgrade? */
164 mean = MEAN_VERSION0;
165
166
167
168 SNDDBG(("SHN: Accepting data stream.\n"));
169 set up sample->actual;
170 sample->flags = SOUND_SAMPLEFLAG_NONE;
171 return(1); /* we'll handle this data. */
172 } /* SHN_open */
173
174
175 static void SHN_close(Sound_Sample *sample)
176 {
177 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
178 clean up anything you put into internal->decoder_private;
179 } /* SHN_close */
180
181
182 static Uint32 SHN_read(Sound_Sample *sample)
183 {
184 Uint32 retval;
185 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
186
187 /*
188 * We don't actually do any decoding, so we read the fmt data
189 * directly into the internal buffer...
190 */
191 retval = SDL_RWread(internal->rw, internal->buffer,
192 1, internal->buffer_size);
193
194 (or whatever. Do some decoding here...)
195
196 /* Make sure the read went smoothly... */
197 if (retval == 0)
198 sample->flags |= SOUND_SAMPLEFLAG_EOF;
199
200 else if (retval == -1)
201 sample->flags |= SOUND_SAMPLEFLAG_ERROR;
202
203 /* (next call this EAGAIN may turn into an EOF or error.) */
204 else if (retval < internal->buffer_size)
205 sample->flags |= SOUND_SAMPLEFLAG_EAGAIN;
206
207 (or whatever. retval == number of bytes you put in internal->buffer).
208
209 return(retval);
210 } /* SHN_read */
211
212 #endif /* defined SOUND_SUPPORTS_SHN */
213
214 /* end of shn.c ... */
215