3 * Copyright (c) 2015 Vesselin Bontchev
5 * Header parsing is borrowed from https://github.com/jteeuwen/audible project.
6 * Copyright (c) 2001-2014, Jim Teeuwen
8 * Redistribution and use in source and binary forms, with or without modification,
9 * are permitted provided that the following conditions are met:
11 * 1. Redistributions of source code must retain the above copyright notice, this
12 * list of conditions and the following disclaimer.
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.
28 #include "libavutil/dict.h"
29 #include "libavutil/intreadwrite.h"
30 #include "libavutil/tea.h"
31 #include "libavutil/opt.h"
33 #define AA_MAGIC 1469084982 /* this identifies an audible .aa file */
34 #define MAX_CODEC_SECOND_SIZE 3982
35 #define MAX_TOC_ENTRIES 16
36 #define MAX_DICTIONARY_ENTRIES 128
37 #define TEA_BLOCK_SIZE 8
38 #define CHAPTER_HEADER_SIZE 8
40 #define MP3_FRAME_SIZE 104
42 typedef struct AADemuxContext {
44 uint8_t *aa_fixed_key;
46 int codec_second_size;
47 int current_codec_second_size;
49 struct AVTEA *tea_ctx;
51 int64_t current_chapter_size;
52 int64_t content_start;
57 static int get_second_size(char *codec_name)
61 if (!strcmp(codec_name, "mp332")) {
63 } else if (!strcmp(codec_name, "acelp16")) {
65 } else if (!strcmp(codec_name, "acelp85")) {
72 static int aa_read_header(AVFormatContext *s)
74 int i, j, idx, largest_idx = -1;
75 uint32_t nkey, nval, toc_size, npairs, header_seed = 0, start;
76 char key[128], val[128], codec_name[64] = {0};
77 uint8_t output[24], dst[8], src[8];
78 int64_t largest_size = -1, current_size = -1, chapter_pos;
82 } TOC[MAX_TOC_ENTRIES];
83 uint32_t header_key_part[4];
84 uint8_t header_key[16] = {0};
85 AADemuxContext *c = s->priv_data;
86 AVIOContext *pb = s->pb;
90 /* parse .aa header */
91 avio_skip(pb, 4); // file size
92 avio_skip(pb, 4); // magic string
93 toc_size = avio_rb32(pb); // TOC size
94 avio_skip(pb, 4); // unidentified integer
95 if (toc_size > MAX_TOC_ENTRIES || toc_size < 2)
96 return AVERROR_INVALIDDATA;
97 for (i = 0; i < toc_size; i++) { // read TOC
98 avio_skip(pb, 4); // TOC entry index
99 TOC[i].offset = avio_rb32(pb); // block offset
100 TOC[i].size = avio_rb32(pb); // block size
102 avio_skip(pb, 24); // header termination block (ignored)
103 npairs = avio_rb32(pb); // read dictionary entries
104 if (npairs > MAX_DICTIONARY_ENTRIES)
105 return AVERROR_INVALIDDATA;
106 for (i = 0; i < npairs; i++) {
107 memset(val, 0, sizeof(val));
108 memset(key, 0, sizeof(key));
109 avio_skip(pb, 1); // unidentified integer
110 nkey = avio_rb32(pb); // key string length
111 nval = avio_rb32(pb); // value string length
112 avio_get_str(pb, nkey, key, sizeof(key));
113 avio_get_str(pb, nval, val, sizeof(val));
114 if (!strcmp(key, "codec")) {
115 av_log(s, AV_LOG_DEBUG, "Codec is <%s>\n", val);
116 strncpy(codec_name, val, sizeof(codec_name) - 1);
117 } else if (!strcmp(key, "HeaderSeed")) {
118 av_log(s, AV_LOG_DEBUG, "HeaderSeed is <%s>\n", val);
119 header_seed = atoi(val);
120 } else if (!strcmp(key, "HeaderKey")) { // this looks like "1234567890 1234567890 1234567890 1234567890"
121 av_log(s, AV_LOG_DEBUG, "HeaderKey is <%s>\n", val);
123 ret = sscanf(val, "%"SCNu32"%"SCNu32"%"SCNu32"%"SCNu32,
124 &header_key_part[0], &header_key_part[1], &header_key_part[2], &header_key_part[3]);
126 return AVERROR_INVALIDDATA;
128 for (idx = 0; idx < 4; idx++) {
129 AV_WB32(&header_key[idx * 4], header_key_part[idx]); // convert each part to BE!
131 av_log(s, AV_LOG_DEBUG, "Processed HeaderKey is ");
132 for (i = 0; i < 16; i++)
133 av_log(s, AV_LOG_DEBUG, "%02x", header_key[i]);
134 av_log(s, AV_LOG_DEBUG, "\n");
136 av_dict_set(&s->metadata, key, val, 0);
140 /* verify fixed key */
141 if (c->aa_fixed_key_len != 16) {
142 av_log(s, AV_LOG_ERROR, "aa_fixed_key value needs to be 16 bytes!\n");
143 return AVERROR(EINVAL);
147 if ((c->codec_second_size = get_second_size(codec_name)) == -1) {
148 av_log(s, AV_LOG_ERROR, "unknown codec <%s>!\n", codec_name);
149 return AVERROR(EINVAL);
152 /* decryption key derivation */
153 c->tea_ctx = av_tea_alloc();
155 return AVERROR(ENOMEM);
156 av_tea_init(c->tea_ctx, c->aa_fixed_key, 16);
157 output[0] = output[1] = 0; // purely for padding purposes
158 memcpy(output + 2, header_key, 16);
160 for (i = 0; i < 3; i++) { // TEA CBC with weird mixed endianness
161 AV_WB32(src, header_seed);
162 AV_WB32(src + 4, header_seed + 1);
164 av_tea_crypt(c->tea_ctx, dst, src, 1, NULL, 0); // TEA ECB encrypt
165 for (j = 0; j < TEA_BLOCK_SIZE && idx < 18; j+=1, idx+=1) {
166 output[idx] = output[idx] ^ dst[j];
169 memcpy(c->file_key, output + 2, 16); // skip first 2 bytes of output
170 av_log(s, AV_LOG_DEBUG, "File key is ");
171 for (i = 0; i < 16; i++)
172 av_log(s, AV_LOG_DEBUG, "%02x", c->file_key[i]);
173 av_log(s, AV_LOG_DEBUG, "\n");
176 st = avformat_new_stream(s, NULL);
178 av_freep(&c->tea_ctx);
179 return AVERROR(ENOMEM);
181 st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
182 if (!strcmp(codec_name, "mp332")) {
183 st->codecpar->codec_id = AV_CODEC_ID_MP3;
184 st->codecpar->sample_rate = 22050;
185 st->need_parsing = AVSTREAM_PARSE_FULL_RAW;
186 avpriv_set_pts_info(st, 64, 8, 32000 * TIMEPREC);
187 // encoded audio frame is MP3_FRAME_SIZE bytes (+1 with padding, unlikely)
188 } else if (!strcmp(codec_name, "acelp85")) {
189 st->codecpar->codec_id = AV_CODEC_ID_SIPR;
190 st->codecpar->block_align = 19;
191 st->codecpar->channels = 1;
192 st->codecpar->sample_rate = 8500;
193 st->codecpar->bit_rate = 8500;
194 st->need_parsing = AVSTREAM_PARSE_FULL_RAW;
195 avpriv_set_pts_info(st, 64, 8, 8500 * TIMEPREC);
196 } else if (!strcmp(codec_name, "acelp16")) {
197 st->codecpar->codec_id = AV_CODEC_ID_SIPR;
198 st->codecpar->block_align = 20;
199 st->codecpar->channels = 1;
200 st->codecpar->sample_rate = 16000;
201 st->codecpar->bit_rate = 16000;
202 st->need_parsing = AVSTREAM_PARSE_FULL_RAW;
203 avpriv_set_pts_info(st, 64, 8, 16000 * TIMEPREC);
206 /* determine, and jump to audio start offset */
207 for (i = 1; i < toc_size; i++) { // skip the first entry!
208 current_size = TOC[i].size;
209 if (current_size > largest_size) {
211 largest_size = current_size;
214 start = TOC[largest_idx].offset;
215 avio_seek(pb, start, SEEK_SET);
217 // extract chapter positions. since all formats have constant bit rate, use it
218 // as time base in bytes/s, for easy stream position <-> timestamp conversion
220 c->content_start = start;
221 c->content_end = start + largest_size;
223 while ((chapter_pos = avio_tell(pb)) >= 0 && chapter_pos < c->content_end) {
224 int chapter_idx = s->nb_chapters;
225 uint32_t chapter_size = avio_rb32(pb);
226 if (chapter_size == 0) break;
227 chapter_pos -= start + CHAPTER_HEADER_SIZE * chapter_idx;
228 avio_skip(pb, 4 + chapter_size);
229 if (!avpriv_new_chapter(s, chapter_idx, st->time_base,
230 chapter_pos * TIMEPREC, (chapter_pos + chapter_size) * TIMEPREC, NULL))
231 return AVERROR(ENOMEM);
234 st->duration = (largest_size - CHAPTER_HEADER_SIZE * s->nb_chapters) * TIMEPREC;
236 ff_update_cur_dts(s, st, 0);
237 avio_seek(pb, start, SEEK_SET);
238 c->current_chapter_size = 0;
244 static int aa_read_packet(AVFormatContext *s, AVPacket *pkt)
246 uint8_t dst[TEA_BLOCK_SIZE];
247 uint8_t src[TEA_BLOCK_SIZE];
251 uint8_t buf[MAX_CODEC_SECOND_SIZE * 2];
254 AADemuxContext *c = s->priv_data;
255 uint64_t pos = avio_tell(s->pb);
257 // are we at the end of the audio content?
258 if (pos >= c->content_end) {
262 // are we at the start of a chapter?
263 if (c->current_chapter_size == 0) {
264 c->current_chapter_size = avio_rb32(s->pb);
265 if (c->current_chapter_size == 0) {
268 av_log(s, AV_LOG_DEBUG, "Chapter %d (%" PRId64 " bytes)\n", c->chapter_idx, c->current_chapter_size);
269 c->chapter_idx = c->chapter_idx + 1;
270 avio_skip(s->pb, 4); // data start offset
272 c->current_codec_second_size = c->codec_second_size;
275 // is this the last block in this chapter?
276 if (c->current_chapter_size / c->current_codec_second_size == 0) {
277 c->current_codec_second_size = c->current_chapter_size % c->current_codec_second_size;
280 // decrypt c->current_codec_second_size bytes
281 blocks = c->current_codec_second_size / TEA_BLOCK_SIZE;
282 for (i = 0; i < blocks; i++) {
283 ret = avio_read(s->pb, src, TEA_BLOCK_SIZE);
284 if (ret != TEA_BLOCK_SIZE)
285 return (ret < 0) ? ret : AVERROR_EOF;
286 av_tea_init(c->tea_ctx, c->file_key, 16);
287 av_tea_crypt(c->tea_ctx, dst, src, 1, NULL, 1);
288 memcpy(buf + written, dst, TEA_BLOCK_SIZE);
289 written = written + TEA_BLOCK_SIZE;
291 trailing_bytes = c->current_codec_second_size % TEA_BLOCK_SIZE;
292 if (trailing_bytes != 0) { // trailing bytes are left unencrypted!
293 ret = avio_read(s->pb, src, trailing_bytes);
294 if (ret != trailing_bytes)
295 return (ret < 0) ? ret : AVERROR_EOF;
296 memcpy(buf + written, src, trailing_bytes);
297 written = written + trailing_bytes;
301 c->current_chapter_size = c->current_chapter_size - c->current_codec_second_size;
302 if (c->current_chapter_size <= 0)
303 c->current_chapter_size = 0;
305 if (c->seek_offset > written)
306 c->seek_offset = 0; // ignore wrong estimate
308 ret = av_new_packet(pkt, written - c->seek_offset);
311 memcpy(pkt->data, buf + c->seek_offset, written - c->seek_offset);
318 static int aa_read_seek(AVFormatContext *s,
319 int stream_index, int64_t timestamp, int flags)
321 AADemuxContext *c = s->priv_data;
323 int64_t chapter_pos, chapter_start, chapter_size;
326 // find chapter containing seek timestamp
330 while (chapter_idx < s->nb_chapters && timestamp >= s->chapters[chapter_idx]->end) {
334 if (chapter_idx >= s->nb_chapters) {
335 chapter_idx = s->nb_chapters - 1;
336 if (chapter_idx < 0) return -1; // there is no chapter.
337 timestamp = s->chapters[chapter_idx]->end;
340 ch = s->chapters[chapter_idx];
342 // sync by clamping timestamp to nearest valid block position in its chapter
343 chapter_size = ch->end / TIMEPREC - ch->start / TIMEPREC;
344 chapter_pos = av_rescale_rnd((timestamp - ch->start) / TIMEPREC,
345 1, c->codec_second_size,
346 (flags & AVSEEK_FLAG_BACKWARD) ? AV_ROUND_DOWN : AV_ROUND_UP)
347 * c->codec_second_size;
348 if (chapter_pos >= chapter_size)
349 chapter_pos = chapter_size;
350 chapter_start = c->content_start + (ch->start / TIMEPREC) + CHAPTER_HEADER_SIZE * (1 + chapter_idx);
353 avio_seek(s->pb, chapter_start + chapter_pos, SEEK_SET);
354 c->current_codec_second_size = c->codec_second_size;
355 c->current_chapter_size = chapter_size - chapter_pos;
356 c->chapter_idx = 1 + chapter_idx;
358 // for unaligned frames, estimate offset of first frame in block (assume no padding)
359 if (s->streams[0]->codecpar->codec_id == AV_CODEC_ID_MP3) {
360 c->seek_offset = (MP3_FRAME_SIZE - chapter_pos % MP3_FRAME_SIZE) % MP3_FRAME_SIZE;
363 ff_update_cur_dts(s, s->streams[0], ch->start + (chapter_pos + c->seek_offset) * TIMEPREC);
368 static int aa_probe(const AVProbeData *p)
370 uint8_t *buf = p->buf;
372 // first 4 bytes are file size, next 4 bytes are the magic
373 if (AV_RB32(buf+4) != AA_MAGIC)
376 return AVPROBE_SCORE_MAX / 2;
379 static int aa_read_close(AVFormatContext *s)
381 AADemuxContext *c = s->priv_data;
383 av_freep(&c->tea_ctx);
388 #define OFFSET(x) offsetof(AADemuxContext, x)
389 static const AVOption aa_options[] = {
390 { "aa_fixed_key", // extracted from libAAX_SDK.so and AAXSDKWin.dll files!
391 "Fixed key used for handling Audible AA files", OFFSET(aa_fixed_key),
392 AV_OPT_TYPE_BINARY, {.str="77214d4b196a87cd520045fd2a51d673"},
393 .flags = AV_OPT_FLAG_DECODING_PARAM },
397 static const AVClass aa_class = {
399 .item_name = av_default_item_name,
400 .option = aa_options,
401 .version = LIBAVUTIL_VERSION_INT,
404 AVInputFormat ff_aa_demuxer = {
406 .long_name = NULL_IF_CONFIG_SMALL("Audible AA format files"),
407 .priv_class = &aa_class,
408 .priv_data_size = sizeof(AADemuxContext),
410 .read_probe = aa_probe,
411 .read_header = aa_read_header,
412 .read_packet = aa_read_packet,
413 .read_seek = aa_read_seek,
414 .read_close = aa_read_close,
415 .flags = AVFMT_NO_BYTE_SEEK | AVFMT_NOGENSEARCH,