1 /*
2 * libmad - MPEG audio decoder library
3 * Copyright (C) 2000-2004 Underbit Technologies, Inc.
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,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU 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 USA
18 *
19 * $Id: frame.c,v 1.29 2004/02/04 22:59:19 rob Exp $
20 */
21
22 /*# ifdef HAVE_CONFIG_H*/
23 # include "mad_config.h"
24 /*# endif*/
25
26 # include "mad_global.h"
27
28 # include <stdlib.h>
29
30 # include "mad_bit.h"
31 # include "mad_stream.h"
32 # include "mad_frame.h"
33 # include "mad_timer.h"
34 # include "mad_layer12.h"
35 # include "mad_layer3.h"
36
37 static
38 unsigned long const bitrate_table[5][15] = {
39 /* MPEG-1 */
40 { 0, 32000, 64000, 96000, 128000, 160000, 192000, 224000, /* Layer I */
41 256000, 288000, 320000, 352000, 384000, 416000, 448000 },
42 { 0, 32000, 48000, 56000, 64000, 80000, 96000, 112000, /* Layer II */
43 128000, 160000, 192000, 224000, 256000, 320000, 384000 },
44 { 0, 32000, 40000, 48000, 56000, 64000, 80000, 96000, /* Layer III */
45 112000, 128000, 160000, 192000, 224000, 256000, 320000 },
46
47 /* MPEG-2 LSF */
48 { 0, 32000, 48000, 56000, 64000, 80000, 96000, 112000, /* Layer I */
49 128000, 144000, 160000, 176000, 192000, 224000, 256000 },
50 { 0, 8000, 16000, 24000, 32000, 40000, 48000, 56000, /* Layers */
51 64000, 80000, 96000, 112000, 128000, 144000, 160000 } /* II & III */
52 };
53
54 static
55 unsigned int const samplerate_table[3] = { 44100, 48000, 32000 };
56
57 static
58 int (*const decoder_table[3])(struct mad_stream *, struct mad_frame *) = {
59 mad_layer_I,
60 mad_layer_II,
61 mad_layer_III
62 };
63
64 /*
65 * NAME: header->init()
66 * DESCRIPTION: initialize header struct
67 */
mad_header_init(struct mad_header * header)68 void mad_header_init(struct mad_header *header)
69 {
70 header->layer = 0;
71 header->mode = 0;
72 header->mode_extension = 0;
73 header->emphasis = 0;
74
75 header->bitrate = 0;
76 header->samplerate = 0;
77
78 header->crc_check = 0;
79 header->crc_target = 0;
80
81 header->flags = 0;
82 header->private_bits = 0;
83
84 header->duration = mad_timer_zero;
85 }
86
87 /*
88 * NAME: frame->init()
89 * DESCRIPTION: initialize frame struct
90 */
mad_frame_init(struct mad_frame * frame)91 void mad_frame_init(struct mad_frame *frame)
92 {
93 mad_header_init(&frame->header);
94
95 frame->options = 0;
96
97 frame->overlap = 0;
98 mad_frame_mute(frame);
99 }
100
101 /*
102 * NAME: frame->finish()
103 * DESCRIPTION: deallocate any dynamic memory associated with frame
104 */
mad_frame_finish(struct mad_frame * frame)105 void mad_frame_finish(struct mad_frame *frame)
106 {
107 mad_header_finish(&frame->header);
108
109 if (frame->overlap) {
110 free(frame->overlap);
111 frame->overlap = 0;
112 }
113 }
114
115 /*
116 * NAME: decode_header()
117 * DESCRIPTION: read header data and following CRC word
118 */
119 static
decode_header(struct mad_header * header,struct mad_stream * stream)120 int decode_header(struct mad_header *header, struct mad_stream *stream)
121 {
122 unsigned int index;
123
124 header->offset = stream->this_offset;
125 header->flags = 0;
126 header->private_bits = 0;
127
128 /* header() */
129
130 /* syncword */
131 mad_bit_skip(&stream->ptr, 11);
132
133 /* MPEG 2.5 indicator (really part of syncword) */
134 if (mad_bit_read(&stream->ptr, 1) == 0)
135 header->flags |= MAD_FLAG_MPEG_2_5_EXT;
136
137 /* ID */
138 if (mad_bit_read(&stream->ptr, 1) == 0)
139 header->flags |= MAD_FLAG_LSF_EXT;
140 else if (header->flags & MAD_FLAG_MPEG_2_5_EXT) {
141 stream->error = MAD_ERROR_LOSTSYNC;
142 return -1;
143 }
144
145 /* layer */
146 header->layer = 4 - mad_bit_read(&stream->ptr, 2);
147
148 if (header->layer == 4) {
149 stream->error = MAD_ERROR_BADLAYER;
150 return -1;
151 }
152
153 /* protection_bit */
154 if (mad_bit_read(&stream->ptr, 1) == 0) {
155 header->flags |= MAD_FLAG_PROTECTION;
156 header->crc_check = mad_bit_crc(stream->ptr, 16, 0xffff);
157 }
158
159 /* bitrate_index */
160 index = mad_bit_read(&stream->ptr, 4);
161
162 if (index == 15) {
163 stream->error = MAD_ERROR_BADBITRATE;
164 return -1;
165 }
166
167 if (header->flags & MAD_FLAG_LSF_EXT)
168 header->bitrate = bitrate_table[3 + (header->layer >> 1)][index];
169 else
170 header->bitrate = bitrate_table[header->layer - 1][index];
171
172 /* sampling_frequency */
173 index = mad_bit_read(&stream->ptr, 2);
174
175 if (index == 3) {
176 stream->error = MAD_ERROR_BADSAMPLERATE;
177 return -1;
178 }
179
180 header->samplerate = samplerate_table[index];
181
182 if (header->flags & MAD_FLAG_LSF_EXT) {
183 header->samplerate /= 2;
184
185 if (header->flags & MAD_FLAG_MPEG_2_5_EXT)
186 header->samplerate /= 2;
187 }
188
189 /* padding_bit */
190 if (mad_bit_read(&stream->ptr, 1))
191 header->flags |= MAD_FLAG_PADDING;
192
193 /* private_bit */
194 if (mad_bit_read(&stream->ptr, 1))
195 header->private_bits |= MAD_PRIVATE_HEADER;
196
197 /* mode */
198 header->mode = 3 - mad_bit_read(&stream->ptr, 2);
199
200 /* mode_extension */
201 header->mode_extension = mad_bit_read(&stream->ptr, 2);
202
203 /* copyright */
204 if (mad_bit_read(&stream->ptr, 1))
205 header->flags |= MAD_FLAG_COPYRIGHT;
206
207 /* original/copy */
208 if (mad_bit_read(&stream->ptr, 1))
209 header->flags |= MAD_FLAG_ORIGINAL;
210
211 /* emphasis */
212 header->emphasis = mad_bit_read(&stream->ptr, 2);
213
214 # if defined(OPT_STRICT)
215 /*
216 * ISO/IEC 11172-3 says this is a reserved emphasis value, but
217 * streams exist which use it anyway. Since the value is not important
218 * to the decoder proper, we allow it unless OPT_STRICT is defined.
219 */
220 if (header->emphasis == MAD_EMPHASIS_RESERVED) {
221 stream->error = MAD_ERROR_BADEMPHASIS;
222 return -1;
223 }
224 # endif
225
226 /* error_check() */
227
228 /* crc_check */
229 if (header->flags & MAD_FLAG_PROTECTION)
230 header->crc_target = mad_bit_read(&stream->ptr, 16);
231
232 return 0;
233 }
234
235 /*
236 * NAME: free_bitrate()
237 * DESCRIPTION: attempt to discover the bitstream's free bitrate
238 */
239 static
free_bitrate(struct mad_stream * stream,struct mad_header const * header)240 int free_bitrate(struct mad_stream *stream, struct mad_header const *header)
241 {
242 struct mad_bitptr keep_ptr;
243 unsigned long rate = 0;
244 unsigned int pad_slot, slots_per_frame;
245 unsigned char const *ptr = 0;
246
247 keep_ptr = stream->ptr;
248
249 pad_slot = (header->flags & MAD_FLAG_PADDING) ? 1 : 0;
250 slots_per_frame = (header->layer == MAD_LAYER_III &&
251 (header->flags & MAD_FLAG_LSF_EXT)) ? 72 : 144;
252
253 while (mad_stream_sync(stream) == 0) {
254 struct mad_stream peek_stream;
255 struct mad_header peek_header;
256
257 peek_stream = *stream;
258 peek_header = *header;
259
260 if (decode_header(&peek_header, &peek_stream) == 0 &&
261 peek_header.layer == header->layer &&
262 peek_header.samplerate == header->samplerate) {
263 unsigned int N;
264
265 ptr = mad_bit_nextbyte(&stream->ptr);
266
267 N = ptr - stream->this_frame;
268
269 if (header->layer == MAD_LAYER_I) {
270 rate = (unsigned long) header->samplerate *
271 (N - 4 * pad_slot + 4) / 48 / 1000;
272 }
273 else {
274 rate = (unsigned long) header->samplerate *
275 (N - pad_slot + 1) / slots_per_frame / 1000;
276 }
277
278 if (rate >= 8)
279 break;
280 }
281
282 mad_bit_skip(&stream->ptr, 8);
283 }
284
285 stream->ptr = keep_ptr;
286
287 if (rate < 8 || (header->layer == MAD_LAYER_III && rate > 640)) {
288 stream->error = MAD_ERROR_LOSTSYNC;
289 return -1;
290 }
291
292 stream->freerate = rate * 1000;
293
294 return 0;
295 }
296
297 /*
298 * NAME: header->decode()
299 * DESCRIPTION: read the next frame header from the stream
300 */
mad_header_decode(struct mad_header * header,struct mad_stream * stream)301 int mad_header_decode(struct mad_header *header, struct mad_stream *stream)
302 {
303 register unsigned char const *ptr, *end;
304 unsigned int pad_slot, N;
305
306 ptr = stream->next_frame;
307 end = stream->bufend;
308
309 if (ptr == 0) {
310 stream->error = MAD_ERROR_BUFPTR;
311 goto fail;
312 }
313
314 /* stream skip */
315 if (stream->skiplen) {
316 if (!stream->sync)
317 ptr = stream->this_frame;
318
319 if (end - ptr < stream->skiplen) {
320 stream->skiplen -= end - ptr;
321 stream->next_frame = end;
322
323 stream->error = MAD_ERROR_BUFLEN;
324 goto fail;
325 }
326
327 ptr += stream->skiplen;
328 stream->skiplen = 0;
329
330 stream->sync = 1;
331 }
332
333 sync:
334 /* synchronize */
335 if (stream->sync) {
336 if (end - ptr < MAD_BUFFER_GUARD) {
337 stream->next_frame = ptr;
338
339 stream->error = MAD_ERROR_BUFLEN;
340 goto fail;
341 }
342 else if (!(ptr[0] == 0xff && (ptr[1] & 0xe0) == 0xe0)) {
343 /* mark point where frame sync word was expected */
344 stream->this_offset += (ptr - stream->this_frame); /* Erez Volk */
345 stream->this_frame = ptr;
346 stream->next_frame = ptr + 1;
347
348 stream->error = MAD_ERROR_LOSTSYNC;
349 goto fail;
350 }
351 }
352 else {
353 mad_bit_init(&stream->ptr, ptr);
354
355 if (mad_stream_sync(stream) == -1) {
356 if (end - stream->next_frame >= MAD_BUFFER_GUARD)
357 stream->next_frame = end - MAD_BUFFER_GUARD;
358
359 stream->error = MAD_ERROR_BUFLEN;
360 goto fail;
361 }
362
363 ptr = mad_bit_nextbyte(&stream->ptr);
364 }
365
366 /* begin processing */
367 stream->this_offset += (ptr - stream->this_frame); /* Erez Volk */
368 stream->this_frame = ptr;
369 stream->next_frame = ptr + 1; /* possibly bogus sync word */
370
371 mad_bit_init(&stream->ptr, stream->this_frame);
372
373 if (decode_header(header, stream) == -1)
374 goto fail;
375
376 /* calculate frame duration */
377 mad_timer_set(&header->duration, 0,
378 32 * MAD_NSBSAMPLES(header), header->samplerate);
379
380 /* calculate free bit rate */
381 if (header->bitrate == 0) {
382 if ((stream->freerate == 0 || !stream->sync ||
383 (header->layer == MAD_LAYER_III && stream->freerate > 640000)) &&
384 free_bitrate(stream, header) == -1)
385 goto fail;
386
387 header->bitrate = stream->freerate;
388 header->flags |= MAD_FLAG_FREEFORMAT;
389 }
390
391 /* calculate beginning of next frame */
392 pad_slot = (header->flags & MAD_FLAG_PADDING) ? 1 : 0;
393
394 if (header->layer == MAD_LAYER_I)
395 N = ((12 * header->bitrate / header->samplerate) + pad_slot) * 4;
396 else {
397 unsigned int slots_per_frame;
398
399 slots_per_frame = (header->layer == MAD_LAYER_III &&
400 (header->flags & MAD_FLAG_LSF_EXT)) ? 72 : 144;
401
402 N = (slots_per_frame * header->bitrate / header->samplerate) + pad_slot;
403 }
404
405 /* verify there is enough data left in buffer to decode this frame */
406 if (N + MAD_BUFFER_GUARD > end - stream->this_frame) {
407 stream->next_frame = stream->this_frame;
408
409 stream->error = MAD_ERROR_BUFLEN;
410 goto fail;
411 }
412
413 stream->next_frame = stream->this_frame + N;
414
415 if (!stream->sync) {
416 /* check that a valid frame header follows this frame */
417
418 ptr = stream->next_frame;
419 if (!(ptr[0] == 0xff && (ptr[1] & 0xe0) == 0xe0)) {
420 ptr = stream->next_frame = stream->this_frame + 1;
421 goto sync;
422 }
423
424 stream->sync = 1;
425 }
426
427 header->flags |= MAD_FLAG_INCOMPLETE;
428
429 return 0;
430
431 fail:
432 stream->sync = 0;
433
434 return -1;
435 }
436
437 /*
438 * NAME: frame->decode()
439 * DESCRIPTION: decode a single frame from a bitstream
440 */
mad_frame_decode(struct mad_frame * frame,struct mad_stream * stream)441 int mad_frame_decode(struct mad_frame *frame, struct mad_stream *stream)
442 {
443 frame->options = stream->options;
444
445 /* header() */
446 /* error_check() */
447
448 if (!(frame->header.flags & MAD_FLAG_INCOMPLETE) &&
449 mad_header_decode(&frame->header, stream) == -1)
450 goto fail;
451
452 /* audio_data() */
453
454 frame->header.flags &= ~MAD_FLAG_INCOMPLETE;
455
456 if (decoder_table[frame->header.layer - 1](stream, frame) == -1) {
457 if (!MAD_RECOVERABLE(stream->error))
458 stream->next_frame = stream->this_frame;
459
460 goto fail;
461 }
462
463 /* ancillary_data() */
464
465 if (frame->header.layer != MAD_LAYER_III) {
466 struct mad_bitptr next_frame;
467
468 mad_bit_init(&next_frame, stream->next_frame);
469
470 stream->anc_ptr = stream->ptr;
471 stream->anc_bitlen = mad_bit_length(&stream->ptr, &next_frame);
472
473 mad_bit_finish(&next_frame);
474 }
475
476 return 0;
477
478 fail:
479 stream->anc_bitlen = 0;
480 return -1;
481 }
482
483 /*
484 * NAME: frame->mute()
485 * DESCRIPTION: zero all subband values so the frame becomes silent
486 */
mad_frame_mute(struct mad_frame * frame)487 void mad_frame_mute(struct mad_frame *frame)
488 {
489 unsigned int s, sb;
490
491 for (s = 0; s < 36; ++s) {
492 for (sb = 0; sb < 32; ++sb) {
493 frame->sbsample[0][s][sb] =
494 frame->sbsample[1][s][sb] = 0;
495 }
496 }
497
498 if (frame->overlap) {
499 for (s = 0; s < 18; ++s) {
500 for (sb = 0; sb < 32; ++sb) {
501 (*frame->overlap)[0][sb][s] =
502 (*frame->overlap)[1][sb][s] = 0;
503 }
504 }
505 }
506 }
507