MP3Extractor.cpp revision 11f8109ad8646d3acd9a0987613229cde59d52c1 
1/*
2 * Copyright (C) 2009 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17//#define LOG_NDEBUG 0
18#define LOG_TAG "MP3Extractor"
19#include <utils/Log.h>
20
21#include "include/MP3Extractor.h"
22
23#include "include/ID3.h"
24#include "include/VBRISeeker.h"
25#include "include/XINGSeeker.h"
26
27#include <media/stagefright/foundation/AMessage.h>
28#include <media/stagefright/DataSource.h>
29#include <media/stagefright/MediaBuffer.h>
30#include <media/stagefright/MediaBufferGroup.h>
31#include <media/stagefright/MediaDebug.h>
32#include <media/stagefright/MediaDefs.h>
33#include <media/stagefright/MediaErrors.h>
34#include <media/stagefright/MediaSource.h>
35#include <media/stagefright/MetaData.h>
36#include <media/stagefright/Utils.h>
37#include <utils/String8.h>
38
39namespace android {
40
41// Everything must match except for
42// protection, bitrate, padding, private bits, mode extension,
43// copyright bit, original bit and emphasis.
44// Yes ... there are things that must indeed match...
45static const uint32_t kMask = 0xfffe0cc0;
46
47// static
48bool MP3Extractor::get_mp3_frame_size(
49        uint32_t header, size_t *frame_size,
50        int *out_sampling_rate, int *out_channels,
51        int *out_bitrate) {
52    *frame_size = 0;
53
54    if (out_sampling_rate) {
55        *out_sampling_rate = 0;
56    }
57
58    if (out_channels) {
59        *out_channels = 0;
60    }
61
62    if (out_bitrate) {
63        *out_bitrate = 0;
64    }
65
66    if ((header & 0xffe00000) != 0xffe00000) {
67        return false;
68    }
69
70    unsigned version = (header >> 19) & 3;
71
72    if (version == 0x01) {
73        return false;
74    }
75
76    unsigned layer = (header >> 17) & 3;
77
78    if (layer == 0x00) {
79        return false;
80    }
81
82    unsigned protection = (header >> 16) & 1;
83
84    unsigned bitrate_index = (header >> 12) & 0x0f;
85
86    if (bitrate_index == 0 || bitrate_index == 0x0f) {
87        // Disallow "free" bitrate.
88        return false;
89    }
90
91    unsigned sampling_rate_index = (header >> 10) & 3;
92
93    if (sampling_rate_index == 3) {
94        return false;
95    }
96
97    static const int kSamplingRateV1[] = { 44100, 48000, 32000 };
98    int sampling_rate = kSamplingRateV1[sampling_rate_index];
99    if (version == 2 /* V2 */) {
100        sampling_rate /= 2;
101    } else if (version == 0 /* V2.5 */) {
102        sampling_rate /= 4;
103    }
104
105    unsigned padding = (header >> 9) & 1;
106
107    if (layer == 3) {
108        // layer I
109
110        static const int kBitrateV1[] = {
111            32, 64, 96, 128, 160, 192, 224, 256,
112            288, 320, 352, 384, 416, 448
113        };
114
115        static const int kBitrateV2[] = {
116            32, 48, 56, 64, 80, 96, 112, 128,
117            144, 160, 176, 192, 224, 256
118        };
119
120        int bitrate =
121            (version == 3 /* V1 */)
122                ? kBitrateV1[bitrate_index - 1]
123                : kBitrateV2[bitrate_index - 1];
124
125        if (out_bitrate) {
126            *out_bitrate = bitrate;
127        }
128
129        *frame_size = (12000 * bitrate / sampling_rate + padding) * 4;
130    } else {
131        // layer II or III
132
133        static const int kBitrateV1L2[] = {
134            32, 48, 56, 64, 80, 96, 112, 128,
135            160, 192, 224, 256, 320, 384
136        };
137
138        static const int kBitrateV1L3[] = {
139            32, 40, 48, 56, 64, 80, 96, 112,
140            128, 160, 192, 224, 256, 320
141        };
142
143        static const int kBitrateV2[] = {
144            8, 16, 24, 32, 40, 48, 56, 64,
145            80, 96, 112, 128, 144, 160
146        };
147
148        int bitrate;
149        if (version == 3 /* V1 */) {
150            bitrate = (layer == 2 /* L2 */)
151                ? kBitrateV1L2[bitrate_index - 1]
152                : kBitrateV1L3[bitrate_index - 1];
153        } else {
154            // V2 (or 2.5)
155
156            bitrate = kBitrateV2[bitrate_index - 1];
157        }
158
159        if (out_bitrate) {
160            *out_bitrate = bitrate;
161        }
162
163        if (version == 3 /* V1 */) {
164            *frame_size = 144000 * bitrate / sampling_rate + padding;
165        } else {
166            // V2 or V2.5
167            *frame_size = 72000 * bitrate / sampling_rate + padding;
168        }
169    }
170
171    if (out_sampling_rate) {
172        *out_sampling_rate = sampling_rate;
173    }
174
175    if (out_channels) {
176        int channel_mode = (header >> 6) & 3;
177
178        *out_channels = (channel_mode == 3) ? 1 : 2;
179    }
180
181    return true;
182}
183
184static bool Resync(
185        const sp<DataSource> &source, uint32_t match_header,
186        off64_t *inout_pos, off64_t *post_id3_pos, uint32_t *out_header) {
187    if (post_id3_pos != NULL) {
188        *post_id3_pos = 0;
189    }
190
191    if (*inout_pos == 0) {
192        // Skip an optional ID3 header if syncing at the very beginning
193        // of the datasource.
194
195        for (;;) {
196            uint8_t id3header[10];
197            if (source->readAt(*inout_pos, id3header, sizeof(id3header))
198                    < (ssize_t)sizeof(id3header)) {
199                // If we can't even read these 10 bytes, we might as well bail
200                // out, even if there _were_ 10 bytes of valid mp3 audio data...
201                return false;
202            }
203
204            if (memcmp("ID3", id3header, 3)) {
205                break;
206            }
207
208            // Skip the ID3v2 header.
209
210            size_t len =
211                ((id3header[6] & 0x7f) << 21)
212                | ((id3header[7] & 0x7f) << 14)
213                | ((id3header[8] & 0x7f) << 7)
214                | (id3header[9] & 0x7f);
215
216            len += 10;
217
218            *inout_pos += len;
219
220            LOGV("skipped ID3 tag, new starting offset is %ld (0x%08lx)",
221                 *inout_pos, *inout_pos);
222        }
223
224        if (post_id3_pos != NULL) {
225            *post_id3_pos = *inout_pos;
226        }
227    }
228
229    off64_t pos = *inout_pos;
230    bool valid = false;
231    do {
232        if (pos >= *inout_pos + 128 * 1024) {
233            // Don't scan forever.
234            LOGV("giving up at offset %ld", pos);
235            break;
236        }
237
238        uint8_t tmp[4];
239        if (source->readAt(pos, tmp, 4) != 4) {
240            break;
241        }
242
243        uint32_t header = U32_AT(tmp);
244
245        if (match_header != 0 && (header & kMask) != (match_header & kMask)) {
246            ++pos;
247            continue;
248        }
249
250        size_t frame_size;
251        int sample_rate, num_channels, bitrate;
252        if (!MP3Extractor::get_mp3_frame_size(
253                    header, &frame_size,
254                    &sample_rate, &num_channels, &bitrate)) {
255            ++pos;
256            continue;
257        }
258
259        LOGV("found possible 1st frame at %ld (header = 0x%08x)", pos, header);
260
261        // We found what looks like a valid frame,
262        // now find its successors.
263
264        off64_t test_pos = pos + frame_size;
265
266        valid = true;
267        for (int j = 0; j < 3; ++j) {
268            uint8_t tmp[4];
269            if (source->readAt(test_pos, tmp, 4) < 4) {
270                valid = false;
271                break;
272            }
273
274            uint32_t test_header = U32_AT(tmp);
275
276            LOGV("subsequent header is %08x", test_header);
277
278            if ((test_header & kMask) != (header & kMask)) {
279                valid = false;
280                break;
281            }
282
283            size_t test_frame_size;
284            if (!MP3Extractor::get_mp3_frame_size(
285                        test_header, &test_frame_size)) {
286                valid = false;
287                break;
288            }
289
290            LOGV("found subsequent frame #%d at %ld", j + 2, test_pos);
291
292            test_pos += test_frame_size;
293        }
294
295        if (valid) {
296            *inout_pos = pos;
297
298            if (out_header != NULL) {
299                *out_header = header;
300            }
301        } else {
302            LOGV("no dice, no valid sequence of frames found.");
303        }
304
305        ++pos;
306    } while (!valid);
307
308    return valid;
309}
310
311class MP3Source : public MediaSource {
312public:
313    MP3Source(
314            const sp<MetaData> &meta, const sp<DataSource> &source,
315            off64_t first_frame_pos, uint32_t fixed_header,
316            const sp<MP3Seeker> &seeker);
317
318    virtual status_t start(MetaData *params = NULL);
319    virtual status_t stop();
320
321    virtual sp<MetaData> getFormat();
322
323    virtual status_t read(
324            MediaBuffer **buffer, const ReadOptions *options = NULL);
325
326protected:
327    virtual ~MP3Source();
328
329private:
330    sp<MetaData> mMeta;
331    sp<DataSource> mDataSource;
332    off64_t mFirstFramePos;
333    uint32_t mFixedHeader;
334    off64_t mCurrentPos;
335    int64_t mCurrentTimeUs;
336    bool mStarted;
337    sp<MP3Seeker> mSeeker;
338    MediaBufferGroup *mGroup;
339
340    MP3Source(const MP3Source &);
341    MP3Source &operator=(const MP3Source &);
342};
343
344MP3Extractor::MP3Extractor(
345        const sp<DataSource> &source, const sp<AMessage> &meta)
346    : mInitCheck(NO_INIT),
347      mDataSource(source),
348      mFirstFramePos(-1),
349      mFixedHeader(0) {
350    off64_t pos = 0;
351    off64_t post_id3_pos;
352    uint32_t header;
353    bool success;
354
355    int64_t meta_offset;
356    uint32_t meta_header;
357    int64_t meta_post_id3_offset;
358    if (meta != NULL
359            && meta->findInt64("offset", &meta_offset)
360            && meta->findInt32("header", (int32_t *)&meta_header)
361            && meta->findInt64("post-id3-offset", &meta_post_id3_offset)) {
362        // The sniffer has already done all the hard work for us, simply
363        // accept its judgement.
364        pos = (off64_t)meta_offset;
365        header = meta_header;
366        post_id3_pos = (off64_t)meta_post_id3_offset;
367
368        success = true;
369    } else {
370        success = Resync(mDataSource, 0, &pos, &post_id3_pos, &header);
371    }
372
373    if (!success) {
374        // mInitCheck will remain NO_INIT
375        return;
376    }
377
378    mFirstFramePos = pos;
379    mFixedHeader = header;
380
381    size_t frame_size;
382    int sample_rate;
383    int num_channels;
384    int bitrate;
385    get_mp3_frame_size(
386            header, &frame_size, &sample_rate, &num_channels, &bitrate);
387
388    mMeta = new MetaData;
389
390    mMeta->setCString(kKeyMIMEType, MEDIA_MIMETYPE_AUDIO_MPEG);
391    mMeta->setInt32(kKeySampleRate, sample_rate);
392    mMeta->setInt32(kKeyBitRate, bitrate * 1000);
393    mMeta->setInt32(kKeyChannelCount, num_channels);
394
395    mSeeker = XINGSeeker::CreateFromSource(mDataSource, mFirstFramePos);
396
397    if (mSeeker == NULL) {
398        mSeeker = VBRISeeker::CreateFromSource(mDataSource, post_id3_pos);
399    }
400
401    int64_t durationUs;
402
403    if (mSeeker == NULL || !mSeeker->getDuration(&durationUs)) {
404        off64_t fileSize;
405        if (mDataSource->getSize(&fileSize) == OK) {
406            durationUs = 8000LL * (fileSize - mFirstFramePos) / bitrate;
407        } else {
408            durationUs = -1;
409        }
410    }
411
412    if (durationUs >= 0) {
413        mMeta->setInt64(kKeyDuration, durationUs);
414    }
415
416    mInitCheck = OK;
417}
418
419size_t MP3Extractor::countTracks() {
420    return mInitCheck != OK ? 0 : 1;
421}
422
423sp<MediaSource> MP3Extractor::getTrack(size_t index) {
424    if (mInitCheck != OK || index != 0) {
425        return NULL;
426    }
427
428    return new MP3Source(
429            mMeta, mDataSource, mFirstFramePos, mFixedHeader,
430            mSeeker);
431}
432
433sp<MetaData> MP3Extractor::getTrackMetaData(size_t index, uint32_t flags) {
434    if (mInitCheck != OK || index != 0) {
435        return NULL;
436    }
437
438    return mMeta;
439}
440
441////////////////////////////////////////////////////////////////////////////////
442
443MP3Source::MP3Source(
444        const sp<MetaData> &meta, const sp<DataSource> &source,
445        off64_t first_frame_pos, uint32_t fixed_header,
446        const sp<MP3Seeker> &seeker)
447    : mMeta(meta),
448      mDataSource(source),
449      mFirstFramePos(first_frame_pos),
450      mFixedHeader(fixed_header),
451      mCurrentPos(0),
452      mCurrentTimeUs(0),
453      mStarted(false),
454      mSeeker(seeker),
455      mGroup(NULL) {
456}
457
458MP3Source::~MP3Source() {
459    if (mStarted) {
460        stop();
461    }
462}
463
464status_t MP3Source::start(MetaData *) {
465    CHECK(!mStarted);
466
467    mGroup = new MediaBufferGroup;
468
469    const size_t kMaxFrameSize = 32768;
470    mGroup->add_buffer(new MediaBuffer(kMaxFrameSize));
471
472    mCurrentPos = mFirstFramePos;
473    mCurrentTimeUs = 0;
474
475    mStarted = true;
476
477    return OK;
478}
479
480status_t MP3Source::stop() {
481    CHECK(mStarted);
482
483    delete mGroup;
484    mGroup = NULL;
485
486    mStarted = false;
487
488    return OK;
489}
490
491sp<MetaData> MP3Source::getFormat() {
492    return mMeta;
493}
494
495status_t MP3Source::read(
496        MediaBuffer **out, const ReadOptions *options) {
497    *out = NULL;
498
499    int64_t seekTimeUs;
500    ReadOptions::SeekMode mode;
501    if (options != NULL && options->getSeekTo(&seekTimeUs, &mode)) {
502        int64_t actualSeekTimeUs = seekTimeUs;
503        if (mSeeker == NULL
504                || !mSeeker->getOffsetForTime(&actualSeekTimeUs, &mCurrentPos)) {
505            int32_t bitrate;
506            if (!mMeta->findInt32(kKeyBitRate, &bitrate)) {
507                // bitrate is in bits/sec.
508                LOGI("no bitrate");
509
510                return ERROR_UNSUPPORTED;
511            }
512
513            mCurrentTimeUs = seekTimeUs;
514            mCurrentPos = mFirstFramePos + seekTimeUs * bitrate / 8000000;
515        } else {
516            mCurrentTimeUs = actualSeekTimeUs;
517        }
518    }
519
520    MediaBuffer *buffer;
521    status_t err = mGroup->acquire_buffer(&buffer);
522    if (err != OK) {
523        return err;
524    }
525
526    size_t frame_size;
527    int bitrate;
528    for (;;) {
529        ssize_t n = mDataSource->readAt(mCurrentPos, buffer->data(), 4);
530        if (n < 4) {
531            buffer->release();
532            buffer = NULL;
533
534            return ERROR_END_OF_STREAM;
535        }
536
537        uint32_t header = U32_AT((const uint8_t *)buffer->data());
538
539        if ((header & kMask) == (mFixedHeader & kMask)
540            && MP3Extractor::get_mp3_frame_size(
541                header, &frame_size, NULL, NULL, &bitrate)) {
542            break;
543        }
544
545        // Lost sync.
546        LOGV("lost sync! header = 0x%08x, old header = 0x%08x\n", header, mFixedHeader);
547
548        off64_t pos = mCurrentPos;
549        if (!Resync(mDataSource, mFixedHeader, &pos, NULL, NULL)) {
550            LOGE("Unable to resync. Signalling end of stream.");
551
552            buffer->release();
553            buffer = NULL;
554
555            return ERROR_END_OF_STREAM;
556        }
557
558        mCurrentPos = pos;
559
560        // Try again with the new position.
561    }
562
563    CHECK(frame_size <= buffer->size());
564
565    ssize_t n = mDataSource->readAt(mCurrentPos, buffer->data(), frame_size);
566    if (n < (ssize_t)frame_size) {
567        buffer->release();
568        buffer = NULL;
569
570        return ERROR_END_OF_STREAM;
571    }
572
573    buffer->set_range(0, frame_size);
574
575    buffer->meta_data()->setInt64(kKeyTime, mCurrentTimeUs);
576    buffer->meta_data()->setInt32(kKeyIsSyncFrame, 1);
577
578    mCurrentPos += frame_size;
579    mCurrentTimeUs += frame_size * 8000ll / bitrate;
580
581    *out = buffer;
582
583    return OK;
584}
585
586sp<MetaData> MP3Extractor::getMetaData() {
587    sp<MetaData> meta = new MetaData;
588
589    if (mInitCheck != OK) {
590        return meta;
591    }
592
593    meta->setCString(kKeyMIMEType, "audio/mpeg");
594
595    ID3 id3(mDataSource);
596
597    if (!id3.isValid()) {
598        return meta;
599    }
600
601    struct Map {
602        int key;
603        const char *tag1;
604        const char *tag2;
605    };
606    static const Map kMap[] = {
607        { kKeyAlbum, "TALB", "TAL" },
608        { kKeyArtist, "TPE1", "TP1" },
609        { kKeyAlbumArtist, "TPE2", "TP2" },
610        { kKeyComposer, "TCOM", "TCM" },
611        { kKeyGenre, "TCON", "TCO" },
612        { kKeyTitle, "TIT2", "TT2" },
613        { kKeyYear, "TYE", "TYER" },
614        { kKeyAuthor, "TXT", "TEXT" },
615        { kKeyCDTrackNumber, "TRK", "TRCK" },
616        { kKeyDiscNumber, "TPA", "TPOS" },
617        { kKeyCompilation, "TCP", "TCMP" },
618    };
619    static const size_t kNumMapEntries = sizeof(kMap) / sizeof(kMap[0]);
620
621    for (size_t i = 0; i < kNumMapEntries; ++i) {
622        ID3::Iterator *it = new ID3::Iterator(id3, kMap[i].tag1);
623        if (it->done()) {
624            delete it;
625            it = new ID3::Iterator(id3, kMap[i].tag2);
626        }
627
628        if (it->done()) {
629            delete it;
630            continue;
631        }
632
633        String8 s;
634        it->getString(&s);
635        delete it;
636
637        meta->setCString(kMap[i].key, s);
638    }
639
640    size_t dataSize;
641    String8 mime;
642    const void *data = id3.getAlbumArt(&dataSize, &mime);
643
644    if (data) {
645        meta->setData(kKeyAlbumArt, MetaData::TYPE_NONE, data, dataSize);
646        meta->setCString(kKeyAlbumArtMIME, mime.string());
647    }
648
649    return meta;
650}
651
652bool SniffMP3(
653        const sp<DataSource> &source, String8 *mimeType,
654        float *confidence, sp<AMessage> *meta) {
655    off64_t pos = 0;
656    off64_t post_id3_pos;
657    uint32_t header;
658    if (!Resync(source, 0, &pos, &post_id3_pos, &header)) {
659        return false;
660    }
661
662    *meta = new AMessage;
663    (*meta)->setInt64("offset", pos);
664    (*meta)->setInt32("header", header);
665    (*meta)->setInt64("post-id3-offset", post_id3_pos);
666
667    *mimeType = MEDIA_MIMETYPE_AUDIO_MPEG;
668    *confidence = 0.2f;
669
670    return true;
671}
672
673}  // namespace android
674