1/* 2 * Audible AA demuxer 3 * Copyright (c) 2015 Vesselin Bontchev 4 * 5 * Header parsing is borrowed from https://github.com/jteeuwen/audible project. 6 * Copyright (c) 2001-2014, Jim Teeuwen 7 * 8 * Redistribution and use in source and binary forms, with or without modification, 9 * are permitted provided that the following conditions are met: 10 * 11 * 1. Redistributions of source code must retain the above copyright notice, this 12 * list of conditions and the following disclaimer. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 16 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 17 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR 18 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 19 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 20 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON 21 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 23 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26#include "avformat.h" 27#include "demux.h" 28#include "internal.h" 29#include "libavutil/avstring.h" 30#include "libavutil/dict.h" 31#include "libavutil/intreadwrite.h" 32#include "libavutil/tea.h" 33#include "libavutil/opt.h" 34 35#define AA_MAGIC 1469084982 /* this identifies an audible .aa file */ 36#define MAX_TOC_ENTRIES 16 37#define MAX_DICTIONARY_ENTRIES 128 38#define TEA_BLOCK_SIZE 8 39#define CHAPTER_HEADER_SIZE 8 40#define TIMEPREC 1000 41#define MP3_FRAME_SIZE 104 42 43typedef struct AADemuxContext { 44 AVClass *class; 45 uint8_t *aa_fixed_key; 46 int aa_fixed_key_len; 47 int codec_second_size; 48 int current_codec_second_size; 49 int chapter_idx; 50 struct AVTEA *tea_ctx; 51 uint8_t file_key[16]; 52 int64_t current_chapter_size; 53 int64_t content_start; 54 int64_t content_end; 55 int seek_offset; 56} AADemuxContext; 57 58static int get_second_size(char *codec_name) 59{ 60 int result = -1; 61 62 if (!strcmp(codec_name, "mp332")) { 63 result = 3982; 64 } else if (!strcmp(codec_name, "acelp16")) { 65 result = 2000; 66 } else if (!strcmp(codec_name, "acelp85")) { 67 result = 1045; 68 } 69 70 return result; 71} 72 73static int aa_read_header(AVFormatContext *s) 74{ 75 int largest_idx = -1; 76 uint32_t toc_size, npairs, header_seed = 0, start; 77 char codec_name[64] = {0}; 78 uint8_t buf[24]; 79 int64_t largest_size = -1, current_size = -1, chapter_pos; 80 struct toc_entry { 81 uint32_t offset; 82 uint32_t size; 83 } TOC[MAX_TOC_ENTRIES]; 84 uint8_t header_key[16] = {0}; 85 AADemuxContext *c = s->priv_data; 86 char file_key[2 * sizeof(c->file_key) + 1]; 87 AVIOContext *pb = s->pb; 88 AVStream *st; 89 FFStream *sti; 90 int ret; 91 92 /* parse .aa header */ 93 avio_skip(pb, 4); // file size 94 avio_skip(pb, 4); // magic string 95 toc_size = avio_rb32(pb); // TOC size 96 avio_skip(pb, 4); // unidentified integer 97 if (toc_size > MAX_TOC_ENTRIES || toc_size < 2) 98 return AVERROR_INVALIDDATA; 99 for (uint32_t i = 0; i < toc_size; i++) { // read TOC 100 avio_skip(pb, 4); // TOC entry index 101 TOC[i].offset = avio_rb32(pb); // block offset 102 TOC[i].size = avio_rb32(pb); // block size 103 } 104 avio_skip(pb, 24); // header termination block (ignored) 105 npairs = avio_rb32(pb); // read dictionary entries 106 if (npairs > MAX_DICTIONARY_ENTRIES) 107 return AVERROR_INVALIDDATA; 108 for (uint32_t i = 0; i < npairs; i++) { 109 char key[128], val[128]; 110 uint32_t nkey, nval; 111 112 avio_skip(pb, 1); // unidentified integer 113 nkey = avio_rb32(pb); // key string length 114 nval = avio_rb32(pb); // value string length 115 avio_get_str(pb, nkey, key, sizeof(key)); 116 avio_get_str(pb, nval, val, sizeof(val)); 117 if (!strcmp(key, "codec")) { 118 av_log(s, AV_LOG_DEBUG, "Codec is <%s>\n", val); 119 av_strlcpy(codec_name, val, sizeof(codec_name)); 120 } else if (!strcmp(key, "HeaderSeed")) { 121 av_log(s, AV_LOG_DEBUG, "HeaderSeed is <%s>\n", val); 122 header_seed = atoi(val); 123 } else if (!strcmp(key, "HeaderKey")) { // this looks like "1234567890 1234567890 1234567890 1234567890" 124 uint32_t header_key_part[4]; 125 av_log(s, AV_LOG_DEBUG, "HeaderKey is <%s>\n", val); 126 127 ret = sscanf(val, "%"SCNu32"%"SCNu32"%"SCNu32"%"SCNu32, 128 &header_key_part[0], &header_key_part[1], &header_key_part[2], &header_key_part[3]); 129 if (ret != 4) 130 return AVERROR_INVALIDDATA; 131 132 for (int idx = 0; idx < 4; idx++) 133 AV_WB32(&header_key[idx * 4], header_key_part[idx]); // convert each part to BE! 134 ff_data_to_hex(key, header_key, sizeof(header_key), 1); 135 av_log(s, AV_LOG_DEBUG, "Processed HeaderKey is %s\n", key); 136 } else { 137 av_dict_set(&s->metadata, key, val, 0); 138 } 139 } 140 141 /* verify fixed key */ 142 if (c->aa_fixed_key_len != 16) { 143 av_log(s, AV_LOG_ERROR, "aa_fixed_key value needs to be 16 bytes!\n"); 144 return AVERROR(EINVAL); 145 } 146 147 /* verify codec */ 148 if ((c->codec_second_size = get_second_size(codec_name)) == -1) { 149 av_log(s, AV_LOG_ERROR, "unknown codec <%s>!\n", codec_name); 150 return AVERROR(EINVAL); 151 } 152 153 /* decryption key derivation */ 154 c->tea_ctx = av_tea_alloc(); 155 if (!c->tea_ctx) 156 return AVERROR(ENOMEM); 157 av_tea_init(c->tea_ctx, c->aa_fixed_key, 16); 158 for (int i = 0; i < 6; i++) 159 AV_WB32(buf + 4 * i, header_seed + i); 160 av_tea_crypt(c->tea_ctx, buf, buf, 3, NULL, 0); 161 AV_WN64(c->file_key, AV_RN64(buf + 2) ^ AV_RN64(header_key)); 162 AV_WN64(c->file_key + 8, AV_RN64(buf + 10) ^ AV_RN64(header_key + 8)); 163 ff_data_to_hex(file_key, c->file_key, sizeof(c->file_key), 1); 164 av_log(s, AV_LOG_DEBUG, "File key is %s\n", file_key); 165 av_tea_init(c->tea_ctx, c->file_key, 16); 166 167 /* decoder setup */ 168 st = avformat_new_stream(s, NULL); 169 if (!st) 170 return AVERROR(ENOMEM); 171 sti = ffstream(st); 172 st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO; 173 if (!strcmp(codec_name, "mp332")) { 174 st->codecpar->codec_id = AV_CODEC_ID_MP3; 175 st->codecpar->sample_rate = 22050; 176 sti->need_parsing = AVSTREAM_PARSE_FULL_RAW; 177 avpriv_set_pts_info(st, 64, 8, 32000 * TIMEPREC); 178 // encoded audio frame is MP3_FRAME_SIZE bytes (+1 with padding, unlikely) 179 } else if (!strcmp(codec_name, "acelp85")) { 180 st->codecpar->codec_id = AV_CODEC_ID_SIPR; 181 st->codecpar->block_align = 19; 182 st->codecpar->ch_layout.nb_channels = 1; 183 st->codecpar->sample_rate = 8500; 184 st->codecpar->bit_rate = 8500; 185 sti->need_parsing = AVSTREAM_PARSE_FULL_RAW; 186 avpriv_set_pts_info(st, 64, 8, 8500 * TIMEPREC); 187 } else if (!strcmp(codec_name, "acelp16")) { 188 st->codecpar->codec_id = AV_CODEC_ID_SIPR; 189 st->codecpar->block_align = 20; 190 st->codecpar->ch_layout.nb_channels = 1; 191 st->codecpar->sample_rate = 16000; 192 st->codecpar->bit_rate = 16000; 193 sti->need_parsing = AVSTREAM_PARSE_FULL_RAW; 194 avpriv_set_pts_info(st, 64, 8, 16000 * TIMEPREC); 195 } 196 197 /* determine, and jump to audio start offset */ 198 for (uint32_t i = 1; i < toc_size; i++) { // skip the first entry! 199 current_size = TOC[i].size; 200 if (current_size > largest_size) { 201 largest_idx = i; 202 largest_size = current_size; 203 } 204 } 205 start = TOC[largest_idx].offset; 206 avio_seek(pb, start, SEEK_SET); 207 208 // extract chapter positions. since all formats have constant bit rate, use it 209 // as time base in bytes/s, for easy stream position <-> timestamp conversion 210 st->start_time = 0; 211 c->content_start = start; 212 c->content_end = start + largest_size; 213 214 while ((chapter_pos = avio_tell(pb)) >= 0 && chapter_pos < c->content_end) { 215 unsigned chapter_idx = s->nb_chapters; 216 uint32_t chapter_size = avio_rb32(pb); 217 if (chapter_size == 0 || avio_feof(pb)) 218 break; 219 chapter_pos -= start + CHAPTER_HEADER_SIZE * chapter_idx; 220 avio_skip(pb, 4 + chapter_size); 221 if (!avpriv_new_chapter(s, chapter_idx, st->time_base, 222 chapter_pos * TIMEPREC, 223 (chapter_pos + chapter_size) * TIMEPREC, NULL)) 224 return AVERROR(ENOMEM); 225 } 226 227 st->duration = (largest_size - CHAPTER_HEADER_SIZE * s->nb_chapters) * TIMEPREC; 228 229 avpriv_update_cur_dts(s, st, 0); 230 avio_seek(pb, start, SEEK_SET); 231 c->current_chapter_size = 0; 232 c->seek_offset = 0; 233 234 return 0; 235} 236 237static int aa_read_packet(AVFormatContext *s, AVPacket *pkt) 238{ 239 int ret; 240 AADemuxContext *c = s->priv_data; 241 uint64_t pos = avio_tell(s->pb); 242 243 // are we at the end of the audio content? 244 if (pos >= c->content_end) { 245 return AVERROR_EOF; 246 } 247 248 // are we at the start of a chapter? 249 if (c->current_chapter_size == 0) { 250 c->current_chapter_size = avio_rb32(s->pb); 251 if (c->current_chapter_size == 0) { 252 return AVERROR_EOF; 253 } 254 av_log(s, AV_LOG_DEBUG, "Chapter %d (%" PRId64 " bytes)\n", c->chapter_idx, c->current_chapter_size); 255 c->chapter_idx = c->chapter_idx + 1; 256 avio_skip(s->pb, 4); // data start offset 257 c->current_codec_second_size = c->codec_second_size; 258 } 259 260 // is this the last block in this chapter? 261 if (c->current_chapter_size / c->current_codec_second_size == 0) { 262 c->current_codec_second_size = c->current_chapter_size % c->current_codec_second_size; 263 } 264 265 ret = av_get_packet(s->pb, pkt, c->current_codec_second_size); 266 if (ret != c->current_codec_second_size) 267 return AVERROR_EOF; 268 269 // decrypt c->current_codec_second_size bytes in blocks of TEA_BLOCK_SIZE 270 // trailing bytes are left unencrypted! 271 av_tea_crypt(c->tea_ctx, pkt->data, pkt->data, 272 c->current_codec_second_size / TEA_BLOCK_SIZE, NULL, 1); 273 274 // update state 275 c->current_chapter_size = c->current_chapter_size - c->current_codec_second_size; 276 if (c->current_chapter_size <= 0) 277 c->current_chapter_size = 0; 278 279 if (c->seek_offset > c->current_codec_second_size) 280 c->seek_offset = 0; // ignore wrong estimate 281 pkt->data += c->seek_offset; 282 pkt->size -= c->seek_offset; 283 c->seek_offset = 0; 284 285 return 0; 286} 287 288static int aa_read_seek(AVFormatContext *s, 289 int stream_index, int64_t timestamp, int flags) 290{ 291 AADemuxContext *c = s->priv_data; 292 AVChapter *ch; 293 int64_t chapter_pos, chapter_start, chapter_size; 294 int chapter_idx = 0; 295 296 // find chapter containing seek timestamp 297 if (timestamp < 0) 298 timestamp = 0; 299 300 while (chapter_idx < s->nb_chapters && timestamp >= s->chapters[chapter_idx]->end) { 301 ++chapter_idx; 302 } 303 304 if (chapter_idx >= s->nb_chapters) { 305 chapter_idx = s->nb_chapters - 1; 306 if (chapter_idx < 0) return -1; // there is no chapter. 307 timestamp = s->chapters[chapter_idx]->end; 308 } 309 310 ch = s->chapters[chapter_idx]; 311 312 // sync by clamping timestamp to nearest valid block position in its chapter 313 chapter_size = ch->end / TIMEPREC - ch->start / TIMEPREC; 314 chapter_pos = av_rescale_rnd((timestamp - ch->start) / TIMEPREC, 315 1, c->codec_second_size, 316 (flags & AVSEEK_FLAG_BACKWARD) ? AV_ROUND_DOWN : AV_ROUND_UP) 317 * c->codec_second_size; 318 if (chapter_pos >= chapter_size) 319 chapter_pos = chapter_size; 320 chapter_start = c->content_start + (ch->start / TIMEPREC) + CHAPTER_HEADER_SIZE * (1 + chapter_idx); 321 322 // reinit read state 323 avio_seek(s->pb, chapter_start + chapter_pos, SEEK_SET); 324 c->current_codec_second_size = c->codec_second_size; 325 c->current_chapter_size = chapter_size - chapter_pos; 326 c->chapter_idx = 1 + chapter_idx; 327 328 // for unaligned frames, estimate offset of first frame in block (assume no padding) 329 if (s->streams[0]->codecpar->codec_id == AV_CODEC_ID_MP3) { 330 c->seek_offset = (MP3_FRAME_SIZE - chapter_pos % MP3_FRAME_SIZE) % MP3_FRAME_SIZE; 331 } 332 333 avpriv_update_cur_dts(s, s->streams[0], ch->start + (chapter_pos + c->seek_offset) * TIMEPREC); 334 335 return 1; 336} 337 338static int aa_probe(const AVProbeData *p) 339{ 340 uint8_t *buf = p->buf; 341 342 // first 4 bytes are file size, next 4 bytes are the magic 343 if (AV_RB32(buf+4) != AA_MAGIC) 344 return 0; 345 346 return AVPROBE_SCORE_MAX / 2; 347} 348 349static int aa_read_close(AVFormatContext *s) 350{ 351 AADemuxContext *c = s->priv_data; 352 353 av_freep(&c->tea_ctx); 354 355 return 0; 356} 357 358#define OFFSET(x) offsetof(AADemuxContext, x) 359static const AVOption aa_options[] = { 360 { "aa_fixed_key", // extracted from libAAX_SDK.so and AAXSDKWin.dll files! 361 "Fixed key used for handling Audible AA files", OFFSET(aa_fixed_key), 362 AV_OPT_TYPE_BINARY, {.str="77214d4b196a87cd520045fd2a51d673"}, 363 .flags = AV_OPT_FLAG_DECODING_PARAM }, 364 { NULL }, 365}; 366 367static const AVClass aa_class = { 368 .class_name = "aa", 369 .item_name = av_default_item_name, 370 .option = aa_options, 371 .version = LIBAVUTIL_VERSION_INT, 372}; 373 374const AVInputFormat ff_aa_demuxer = { 375 .name = "aa", 376 .long_name = NULL_IF_CONFIG_SMALL("Audible AA format files"), 377 .priv_class = &aa_class, 378 .priv_data_size = sizeof(AADemuxContext), 379 .extensions = "aa", 380 .read_probe = aa_probe, 381 .read_header = aa_read_header, 382 .read_packet = aa_read_packet, 383 .read_seek = aa_read_seek, 384 .read_close = aa_read_close, 385 .flags = AVFMT_NO_BYTE_SEEK | AVFMT_NOGENSEARCH, 386 .flags_internal = FF_FMT_INIT_CLEANUP, 387}; 388