chiark / gitweb /
partial tests for kvp.c
[disorder] / lib / wav.c
CommitLineData
ce6c36be 1/*
2 * This file is part of DisOrder
3 * Copyright (C) 2007 Richard Kettlewell
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
18 * USA
19 */
20/** @file lib/wav.c
21 * @brief WAV file support
22 *
23 * This is used by the WAV file suppoort in the tracklength plugin and
24 * by disorder-decode (see @ref server/decode.c).
25 */
26
27/* Sources:
28 *
29 * http://www.technology.niagarac.on.ca/courses/comp530/WavFileFormat.html
30 * http://www.borg.com/~jglatt/tech/wave.htm
31 * http://www.borg.com/~jglatt/tech/aboutiff.htm
32 *
33 * These files consists of a header followed by chunks.
34 * Multibyte values are little-endian.
35 *
36 * 12 byte file header:
37 * offset size meaning
38 * 00 4 'RIFF'
39 * 04 4 length of rest of file
40 * 08 4 'WAVE'
41 *
42 * The length includes 'WAVE' but excludes the 1st 8 bytes.
43 *
44 * Chunk header:
45 * 00 4 chunk ID
46 * 04 4 length of rest of chunk
47 *
48 * The stated length may be odd, if so then there is an implicit padding byte
49 * appended to the chunk to make it up to an even length (someone wasn't
50 * think about 32/64-bit worlds).
51 *
52 * Also some files seem to have extra stuff at the end of chunks that nobody
53 * I know of documents. Go figure, but check the length field rather than
54 * deducing the length from the ID.
55 *
56 * Format chunk:
57 * 00 4 'fmt'
58 * 04 4 length of rest of chunk
59 * 08 2 compression (1 = none)
60 * 0a 2 number of channels
61 * 0c 4 samples/second
62 * 10 4 average bytes/second, = (samples/sec) * (bytes/sample)
63 * 14 2 bytes/sample
64 * 16 2 bits/sample point
65 *
66 * 'sample' means 'sample frame' above, i.e. a sample point for each channel.
67 *
68 * Data chunk:
69 * 00 4 'data'
70 * 04 4 length of rest of chunk
71 * 08 ... data
72 *
73 * There is only allowed to be one data chunk. Some people violate this; we
74 * shall encourage people to fix their broken WAV files by not supporting
75 * this violation and because it's easier.
76 *
77 * As to the encoding of the data:
78 *
79 * Firstly, samples up to 8 bits in size are unsigned, larger samples are
80 * signed. Madness.
81 *
82 * Secondly sample points are stored rounded up to a multiple of 8 bits in
83 * size. Marginally saner.
84 *
85 * Written as a single word (of 8, 16, 24, whatever bits) the padding to
86 * implement this happens at the right hand (least significant) end.
87 * e.g. assuming a 9 bit sample:
88 *
89 * | padded sample word |
90 * | 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 |
91 * | 8 7 6 5 4 3 2 1 0 - - - - - - - |
92 *
93 * But this is a little-endian file format so the least significant byte is
94 * the first, which means that the padding is "between" the bits if you
95 * imagine them in their usual order:
96 *
97 * | first byte | second byte |
98 * | 7 6 5 4 3 2 1 0 | 7 6 5 4 3 2 1 0 |
99 * | 0 - - - - - - - | 8 7 6 5 4 3 2 1 |
100 *
101 * Sample points are grouped into sample frames, consisting of as many
102 * samples points as their are channels. It seems that there are standard
103 * orderings of different channels.
104 */
105
106#include <config.h>
107#include "types.h"
108
109#include <unistd.h>
110#include <fcntl.h>
111#include <errno.h>
112#include <string.h>
113
114#include "log.h"
115#include "wav.h"
116
117static inline uint16_t get16(const char *ptr) {
118 return (uint8_t)ptr[0] + 256 * (uint8_t)ptr[1];
119}
120
121static inline uint32_t get32(const char *ptr) {
122 return (uint8_t)ptr[0] + 256 * (uint8_t)ptr[1]
123 + 65536 * (uint8_t)ptr[2] + 16777216 * (uint8_t)ptr[3];
124}
125
126/** @brief Open a WAV file
127 * @return 0 on success, an errno value on error
128 */
129int wav_init(struct wavfile *f, const char *path) {
130 int err, n;
131 char header[64];
132 off_t where;
133
134 memset(f, 0, sizeof *f);
135 f->fd = -1;
136 f->data = -1;
137 if((f->fd = open(path, O_RDONLY)) < 0) goto error_errno;
138 /* Read the file header
139 *
140 * offset size meaning
141 * 00 4 'RIFF'
142 * 04 4 length of rest of file
143 * 08 4 'WAVE'
144 * */
145 if((n = pread(f->fd, header, 12, 0)) < 0) goto error_errno;
146 else if(n < 12) goto einval;
147 if(strncmp(header, "RIFF", 4) || strncmp(header + 8, "WAVE", 4))
148 goto einval;
149 f->length = 8 + get32(header + 4);
150 /* Visit all the chunks */
151 for(where = 12; where + 8 <= f->length;) {
152 /* Read the chunk header
153 *
154 * offset size meaning
155 * 00 4 chunk ID
156 * 04 4 length of rest of chunk
157 */
158 if((n = pread(f->fd, header, 8, where)) < 0) goto error_errno;
159 else if(n < 8) goto einval;
160 if(!strncmp(header,"fmt ", 4)) {
161 /* This is the format chunk
162 *
163 * offset size meaning
164 * 00 4 'fmt'
165 * 04 4 length of rest of chunk
166 * 08 2 compression (1 = none)
167 * 0a 2 number of channels
168 * 0c 4 samples/second
169 * 10 4 average bytes/second, = (samples/sec) * (bytes/sample)
170 * 14 2 bytes/sample
171 * 16 2 bits/sample point
172 * 18 ? extra undocumented rubbish
173 */
174 if(get32(header + 4) < 16) goto einval;
175 if((n = pread(f->fd, header + 8, 16, where + 8)) < 0) goto error_errno;
176 else if(n < 16) goto einval;
177 f->channels = get16(header + 0x0A);
178 f->rate = get32(header + 0x0C);
179 f->bits = get16(header + 0x16);
180 } else if(!strncmp(header, "data", 4)) {
181 /* Remember where the data chunk was and how big it is */
182 f->data = where;
183 f->datasize = get32(header + 4);
184 }
185 where += 8 + get32(header + 4);
186 }
187 /* There had better have been a format chunk */
188 if(f->rate == 0) goto einval;
189 /* There had better have been a data chunk */
190 if(f->data == -1) goto einval;
191 return 0;
192einval:
193 err = EINVAL;
194 goto error;
195error_errno:
196 err = errno;
197error:
198 wav_destroy(f);
199 return err;
200}
201
202/** @brief Close a WAV file */
203void wav_destroy(struct wavfile *f) {
204 if(f) {
205 const int save_errno = errno;
206
207 if(f->fd >= 0)
208 close(f->fd);
209 errno = save_errno;
210 }
211}
212
213/** @brief Visit all the data in a WAV file
717ba987 214 * @param f WAV file handle
ce6c36be 215 * @param callback Called for successive blocks of data
717ba987 216 * @param u User data
ce6c36be 217 *
218 * @p callback will only ever be passed whole frames.
219 */
220int wav_data(struct wavfile *f,
221 wav_data_callback *callback,
222 void *u) {
223 off_t left = f->datasize;
224 off_t where = f->data + 8;
225 char buffer[4096];
226 int err;
227 ssize_t n;
228 const size_t bytes_per_frame = f->channels * ((f->bits + 7) / 8);
229
230 while(left > 0) {
231 size_t want = (off_t)sizeof buffer > left ? (size_t)left : sizeof buffer;
232
233 want -= want % bytes_per_frame;
234 if((n = pread(f->fd, buffer, want, where)) < 0) return errno;
235 if((size_t)n < want) return EINVAL;
236 if((err = callback(f, buffer, n, u))) return err;
237 where += n;
238 left -= n;
239 }
240 return 0;
241}
242
243/*
244Local Variables:
245c-basic-offset:2
246comment-column:40
247fill-column:79
248indent-tabs-mode:nil
249End:
250*/