aboutsummaryrefslogtreecommitdiffstats
path: root/libavformat/aadec.c
blob: b8a5428f1f0afbecf62e016365996efda6b05333 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
/*
 * Audible AA demuxer
 * Copyright (c) 2015 Vesselin Bontchev
 *
 * Header parsing is borrowed from https://github.com/jteeuwen/audible project.
 * Copyright (c) 2001-2014, Jim Teeuwen
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "avformat.h"
#include "internal.h"
#include "libavutil/avstring.h"
#include "libavutil/dict.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/tea.h"
#include "libavutil/opt.h"

#define AA_MAGIC 1469084982 /* this identifies an audible .aa file */
#define MAX_TOC_ENTRIES 16
#define MAX_DICTIONARY_ENTRIES 128
#define TEA_BLOCK_SIZE 8
#define CHAPTER_HEADER_SIZE 8
#define TIMEPREC 1000
#define MP3_FRAME_SIZE 104

typedef struct AADemuxContext {
    AVClass *class;
    uint8_t *aa_fixed_key;
    int aa_fixed_key_len;
    int codec_second_size;
    int current_codec_second_size;
    int chapter_idx;
    struct AVTEA *tea_ctx;
    uint8_t file_key[16];
    int64_t current_chapter_size;
    int64_t content_start;
    int64_t content_end;
    int seek_offset;
} AADemuxContext;

static int get_second_size(char *codec_name)
{
    int result = -1;

    if (!strcmp(codec_name, "mp332")) {
        result = 3982;
    } else if (!strcmp(codec_name, "acelp16")) {
        result = 2000;
    } else if (!strcmp(codec_name, "acelp85")) {
        result = 1045;
    }

    return result;
}

static int aa_read_header(AVFormatContext *s)
{
    int largest_idx = -1;
    uint32_t toc_size, npairs, header_seed = 0, start;
    char codec_name[64] = {0};
    uint8_t buf[24];
    int64_t largest_size = -1, current_size = -1, chapter_pos;
    struct toc_entry {
        uint32_t offset;
        uint32_t size;
    } TOC[MAX_TOC_ENTRIES];
    uint8_t header_key[16] = {0};
    AADemuxContext *c = s->priv_data;
    char file_key[2 * sizeof(c->file_key) + 1];
    AVIOContext *pb = s->pb;
    AVStream *st;
    FFStream *sti;
    int ret;

    /* parse .aa header */
    avio_skip(pb, 4); // file size
    avio_skip(pb, 4); // magic string
    toc_size = avio_rb32(pb); // TOC size
    avio_skip(pb, 4); // unidentified integer
    if (toc_size > MAX_TOC_ENTRIES || toc_size < 2)
        return AVERROR_INVALIDDATA;
    for (uint32_t i = 0; i < toc_size; i++) { // read TOC
        avio_skip(pb, 4); // TOC entry index
        TOC[i].offset = avio_rb32(pb); // block offset
        TOC[i].size = avio_rb32(pb); // block size
    }
    avio_skip(pb, 24); // header termination block (ignored)
    npairs = avio_rb32(pb); // read dictionary entries
    if (npairs > MAX_DICTIONARY_ENTRIES)
        return AVERROR_INVALIDDATA;
    for (uint32_t i = 0; i < npairs; i++) {
        char key[128], val[128];
        uint32_t nkey, nval;

        avio_skip(pb, 1); // unidentified integer
        nkey = avio_rb32(pb); // key string length
        nval = avio_rb32(pb); // value string length
        avio_get_str(pb, nkey, key, sizeof(key));
        avio_get_str(pb, nval, val, sizeof(val));
        if (!strcmp(key, "codec")) {
            av_log(s, AV_LOG_DEBUG, "Codec is <%s>\n", val);
            av_strlcpy(codec_name, val, sizeof(codec_name));
        } else if (!strcmp(key, "HeaderSeed")) {
            av_log(s, AV_LOG_DEBUG, "HeaderSeed is <%s>\n", val);
            header_seed = atoi(val);
        } else if (!strcmp(key, "HeaderKey")) { // this looks like "1234567890 1234567890 1234567890 1234567890"
            uint32_t header_key_part[4];
            av_log(s, AV_LOG_DEBUG, "HeaderKey is <%s>\n", val);

            ret = sscanf(val, "%"SCNu32"%"SCNu32"%"SCNu32"%"SCNu32,
                   &header_key_part[0], &header_key_part[1], &header_key_part[2], &header_key_part[3]);
            if (ret != 4)
                return AVERROR_INVALIDDATA;

            for (int idx = 0; idx < 4; idx++)
                AV_WB32(&header_key[idx * 4], header_key_part[idx]); // convert each part to BE!
            ff_data_to_hex(key, header_key, sizeof(header_key), 1);
            av_log(s, AV_LOG_DEBUG, "Processed HeaderKey is %s\n", key);
        } else {
            av_dict_set(&s->metadata, key, val, 0);
        }
    }

    /* verify fixed key */
    if (c->aa_fixed_key_len != 16) {
        av_log(s, AV_LOG_ERROR, "aa_fixed_key value needs to be 16 bytes!\n");
        return AVERROR(EINVAL);
    }

    /* verify codec */
    if ((c->codec_second_size = get_second_size(codec_name)) == -1) {
        av_log(s, AV_LOG_ERROR, "unknown codec <%s>!\n", codec_name);
        return AVERROR(EINVAL);
    }

    /* decryption key derivation */
    c->tea_ctx = av_tea_alloc();
    if (!c->tea_ctx)
        return AVERROR(ENOMEM);
    av_tea_init(c->tea_ctx, c->aa_fixed_key, 16);
    for (int i = 0; i < 6; i++)
        AV_WB32(buf + 4 * i, header_seed + i);
    av_tea_crypt(c->tea_ctx, buf, buf, 3, NULL, 0);
    AV_WN64(c->file_key,     AV_RN64(buf + 2)  ^ AV_RN64(header_key));
    AV_WN64(c->file_key + 8, AV_RN64(buf + 10) ^ AV_RN64(header_key + 8));
    ff_data_to_hex(file_key, c->file_key, sizeof(c->file_key), 1);
    av_log(s, AV_LOG_DEBUG, "File key is %s\n", file_key);
    av_tea_init(c->tea_ctx, c->file_key, 16);

    /* decoder setup */
    st = avformat_new_stream(s, NULL);
    if (!st)
        return AVERROR(ENOMEM);
    sti = ffstream(st);
    st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
    if (!strcmp(codec_name, "mp332")) {
        st->codecpar->codec_id = AV_CODEC_ID_MP3;
        st->codecpar->sample_rate = 22050;
        sti->need_parsing = AVSTREAM_PARSE_FULL_RAW;
        avpriv_set_pts_info(st, 64, 8, 32000 * TIMEPREC);
        // encoded audio frame is MP3_FRAME_SIZE bytes (+1 with padding, unlikely)
    } else if (!strcmp(codec_name, "acelp85")) {
        st->codecpar->codec_id = AV_CODEC_ID_SIPR;
        st->codecpar->block_align = 19;
        st->codecpar->channels = 1;
        st->codecpar->sample_rate = 8500;
        st->codecpar->bit_rate = 8500;
        sti->need_parsing = AVSTREAM_PARSE_FULL_RAW;
        avpriv_set_pts_info(st, 64, 8, 8500 * TIMEPREC);
    } else if (!strcmp(codec_name, "acelp16")) {
        st->codecpar->codec_id = AV_CODEC_ID_SIPR;
        st->codecpar->block_align = 20;
        st->codecpar->channels = 1;
        st->codecpar->sample_rate = 16000;
        st->codecpar->bit_rate = 16000;
        sti->need_parsing = AVSTREAM_PARSE_FULL_RAW;
        avpriv_set_pts_info(st, 64, 8, 16000 * TIMEPREC);
    }

    /* determine, and jump to audio start offset */
    for (uint32_t i = 1; i < toc_size; i++) { // skip the first entry!
        current_size = TOC[i].size;
        if (current_size > largest_size) {
            largest_idx = i;
            largest_size = current_size;
        }
    }
    start = TOC[largest_idx].offset;
    avio_seek(pb, start, SEEK_SET);

    // extract chapter positions. since all formats have constant bit rate, use it
    // as time base in bytes/s, for easy stream position <-> timestamp conversion
    st->start_time = 0;
    c->content_start = start;
    c->content_end = start + largest_size;

    while ((chapter_pos = avio_tell(pb)) >= 0 && chapter_pos < c->content_end) {
        unsigned chapter_idx = s->nb_chapters;
        uint32_t chapter_size = avio_rb32(pb);
        if (chapter_size == 0 || avio_feof(pb))
            break;
        chapter_pos -= start + CHAPTER_HEADER_SIZE * chapter_idx;
        avio_skip(pb, 4 + chapter_size);
        if (!avpriv_new_chapter(s, chapter_idx, st->time_base,
                                chapter_pos * TIMEPREC,
                                (chapter_pos + chapter_size) * TIMEPREC, NULL))
            return AVERROR(ENOMEM);
    }

    st->duration = (largest_size - CHAPTER_HEADER_SIZE * s->nb_chapters) * TIMEPREC;

    avpriv_update_cur_dts(s, st, 0);
    avio_seek(pb, start, SEEK_SET);
    c->current_chapter_size = 0;
    c->seek_offset = 0;

    return 0;
}

static int aa_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    int ret;
    AADemuxContext *c = s->priv_data;
    uint64_t pos = avio_tell(s->pb);

    // are we at the end of the audio content?
    if (pos >= c->content_end) {
        return AVERROR_EOF;
    }

    // are we at the start of a chapter?
    if (c->current_chapter_size == 0) {
        c->current_chapter_size = avio_rb32(s->pb);
        if (c->current_chapter_size == 0) {
            return AVERROR_EOF;
        }
        av_log(s, AV_LOG_DEBUG, "Chapter %d (%" PRId64 " bytes)\n", c->chapter_idx, c->current_chapter_size);
        c->chapter_idx = c->chapter_idx + 1;
        avio_skip(s->pb, 4); // data start offset
        c->current_codec_second_size = c->codec_second_size;
    }

    // is this the last block in this chapter?
    if (c->current_chapter_size / c->current_codec_second_size == 0) {
        c->current_codec_second_size = c->current_chapter_size % c->current_codec_second_size;
    }

    ret = av_get_packet(s->pb, pkt, c->current_codec_second_size);
    if (ret != c->current_codec_second_size)
        return AVERROR_EOF;

    // decrypt c->current_codec_second_size bytes in blocks of TEA_BLOCK_SIZE
    // trailing bytes are left unencrypted!
    av_tea_crypt(c->tea_ctx, pkt->data, pkt->data,
                 c->current_codec_second_size / TEA_BLOCK_SIZE, NULL, 1);

    // update state
    c->current_chapter_size = c->current_chapter_size - c->current_codec_second_size;
    if (c->current_chapter_size <= 0)
        c->current_chapter_size = 0;

    if (c->seek_offset > c->current_codec_second_size)
        c->seek_offset = 0; // ignore wrong estimate
    pkt->data += c->seek_offset;
    pkt->size -= c->seek_offset;
    c->seek_offset = 0;

    return 0;
}

static int aa_read_seek(AVFormatContext *s,
                        int stream_index, int64_t timestamp, int flags)
{
    AADemuxContext *c = s->priv_data;
    AVChapter *ch;
    int64_t chapter_pos, chapter_start, chapter_size;
    int chapter_idx = 0;

    // find chapter containing seek timestamp
    if (timestamp < 0)
        timestamp = 0;

    while (chapter_idx < s->nb_chapters && timestamp >= s->chapters[chapter_idx]->end) {
        ++chapter_idx;
    }

    if (chapter_idx >= s->nb_chapters) {
        chapter_idx = s->nb_chapters - 1;
        if (chapter_idx < 0) return -1; // there is no chapter.
        timestamp = s->chapters[chapter_idx]->end;
    }

    ch = s->chapters[chapter_idx];

    // sync by clamping timestamp to nearest valid block position in its chapter
    chapter_size = ch->end / TIMEPREC - ch->start / TIMEPREC;
    chapter_pos = av_rescale_rnd((timestamp - ch->start) / TIMEPREC,
        1, c->codec_second_size,
        (flags & AVSEEK_FLAG_BACKWARD) ? AV_ROUND_DOWN : AV_ROUND_UP)
        * c->codec_second_size;
    if (chapter_pos >= chapter_size)
        chapter_pos = chapter_size;
    chapter_start = c->content_start + (ch->start / TIMEPREC) + CHAPTER_HEADER_SIZE * (1 + chapter_idx);

    // reinit read state
    avio_seek(s->pb, chapter_start + chapter_pos, SEEK_SET);
    c->current_codec_second_size = c->codec_second_size;
    c->current_chapter_size = chapter_size - chapter_pos;
    c->chapter_idx = 1 + chapter_idx;

    // for unaligned frames, estimate offset of first frame in block (assume no padding)
    if (s->streams[0]->codecpar->codec_id == AV_CODEC_ID_MP3) {
        c->seek_offset = (MP3_FRAME_SIZE - chapter_pos % MP3_FRAME_SIZE) % MP3_FRAME_SIZE;
    }

    avpriv_update_cur_dts(s, s->streams[0], ch->start + (chapter_pos + c->seek_offset) * TIMEPREC);

    return 1;
}

static int aa_probe(const AVProbeData *p)
{
    uint8_t *buf = p->buf;

    // first 4 bytes are file size, next 4 bytes are the magic
    if (AV_RB32(buf+4) != AA_MAGIC)
        return 0;

    return AVPROBE_SCORE_MAX / 2;
}

static int aa_read_close(AVFormatContext *s)
{
    AADemuxContext *c = s->priv_data;

    av_freep(&c->tea_ctx);

    return 0;
}

#define OFFSET(x) offsetof(AADemuxContext, x)
static const AVOption aa_options[] = {
    { "aa_fixed_key", // extracted from libAAX_SDK.so and AAXSDKWin.dll files!
        "Fixed key used for handling Audible AA files", OFFSET(aa_fixed_key),
        AV_OPT_TYPE_BINARY, {.str="77214d4b196a87cd520045fd2a51d673"},
        .flags = AV_OPT_FLAG_DECODING_PARAM },
    { NULL },
};

static const AVClass aa_class = {
    .class_name = "aa",
    .item_name  = av_default_item_name,
    .option     = aa_options,
    .version    = LIBAVUTIL_VERSION_INT,
};

const AVInputFormat ff_aa_demuxer = {
    .name           = "aa",
    .long_name      = NULL_IF_CONFIG_SMALL("Audible AA format files"),
    .priv_class     = &aa_class,
    .priv_data_size = sizeof(AADemuxContext),
    .extensions     = "aa",
    .read_probe     = aa_probe,
    .read_header    = aa_read_header,
    .read_packet    = aa_read_packet,
    .read_seek      = aa_read_seek,
    .read_close     = aa_read_close,
    .flags          = AVFMT_NO_BYTE_SEEK | AVFMT_NOGENSEARCH,
    .flags_internal = FF_FMT_INIT_CLEANUP,
};