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1 /*
2  * Copyright (C) 2011 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 "MPEG2PSExtractor"
19 #include <utils/Log.h>
20 
21 #include "include/MPEG2PSExtractor.h"
22 
23 #include "AnotherPacketSource.h"
24 #include "ESQueue.h"
25 
26 #include <media/stagefright/foundation/ABitReader.h>
27 #include <media/stagefright/foundation/ABuffer.h>
28 #include <media/stagefright/foundation/ADebug.h>
29 #include <media/stagefright/foundation/AMessage.h>
30 #include <media/stagefright/foundation/hexdump.h>
31 #include <media/stagefright/DataSource.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 
39 namespace android {
40 
41 struct MPEG2PSExtractor::Track : public MediaSource {
42     Track(MPEG2PSExtractor *extractor,
43           unsigned stream_id, unsigned stream_type);
44 
45     virtual status_t start(MetaData *params);
46     virtual status_t stop();
47     virtual sp<MetaData> getFormat();
48 
49     virtual status_t read(
50             MediaBuffer **buffer, const ReadOptions *options);
51 
52 protected:
53     virtual ~Track();
54 
55 private:
56     friend struct MPEG2PSExtractor;
57 
58     MPEG2PSExtractor *mExtractor;
59 
60     unsigned mStreamID;
61     unsigned mStreamType;
62     ElementaryStreamQueue *mQueue;
63     sp<AnotherPacketSource> mSource;
64 
65     status_t appendPESData(
66             unsigned PTS_DTS_flags,
67             uint64_t PTS, uint64_t DTS,
68             const uint8_t *data, size_t size);
69 
70     DISALLOW_EVIL_CONSTRUCTORS(Track);
71 };
72 
73 struct MPEG2PSExtractor::WrappedTrack : public MediaSource {
74     WrappedTrack(const sp<MPEG2PSExtractor> &extractor, const sp<Track> &track);
75 
76     virtual status_t start(MetaData *params);
77     virtual status_t stop();
78     virtual sp<MetaData> getFormat();
79 
80     virtual status_t read(
81             MediaBuffer **buffer, const ReadOptions *options);
82 
83 protected:
84     virtual ~WrappedTrack();
85 
86 private:
87     sp<MPEG2PSExtractor> mExtractor;
88     sp<MPEG2PSExtractor::Track> mTrack;
89 
90     DISALLOW_EVIL_CONSTRUCTORS(WrappedTrack);
91 };
92 
93 ////////////////////////////////////////////////////////////////////////////////
94 
MPEG2PSExtractor(const sp<DataSource> & source)95 MPEG2PSExtractor::MPEG2PSExtractor(const sp<DataSource> &source)
96     : mDataSource(source),
97       mOffset(0),
98       mFinalResult(OK),
99       mBuffer(new ABuffer(0)),
100       mScanning(true),
101       mProgramStreamMapValid(false) {
102     for (size_t i = 0; i < 500; ++i) {
103         if (feedMore() != OK) {
104             break;
105         }
106     }
107 
108     // Remove all tracks that were unable to determine their format.
109     for (size_t i = mTracks.size(); i-- > 0;) {
110         if (mTracks.valueAt(i)->getFormat() == NULL) {
111             mTracks.removeItemsAt(i);
112         }
113     }
114 
115     mScanning = false;
116 }
117 
~MPEG2PSExtractor()118 MPEG2PSExtractor::~MPEG2PSExtractor() {
119 }
120 
countTracks()121 size_t MPEG2PSExtractor::countTracks() {
122     return mTracks.size();
123 }
124 
getTrack(size_t index)125 sp<MediaSource> MPEG2PSExtractor::getTrack(size_t index) {
126     if (index >= mTracks.size()) {
127         return NULL;
128     }
129 
130     return new WrappedTrack(this, mTracks.valueAt(index));
131 }
132 
getTrackMetaData(size_t index,uint32_t flags)133 sp<MetaData> MPEG2PSExtractor::getTrackMetaData(size_t index, uint32_t flags) {
134     if (index >= mTracks.size()) {
135         return NULL;
136     }
137 
138     return mTracks.valueAt(index)->getFormat();
139 }
140 
getMetaData()141 sp<MetaData> MPEG2PSExtractor::getMetaData() {
142     sp<MetaData> meta = new MetaData;
143     meta->setCString(kKeyMIMEType, MEDIA_MIMETYPE_CONTAINER_MPEG2PS);
144 
145     return meta;
146 }
147 
flags() const148 uint32_t MPEG2PSExtractor::flags() const {
149     return CAN_PAUSE;
150 }
151 
feedMore()152 status_t MPEG2PSExtractor::feedMore() {
153     Mutex::Autolock autoLock(mLock);
154 
155     // How much data we're reading at a time
156     static const size_t kChunkSize = 8192;
157 
158     for (;;) {
159         status_t err = dequeueChunk();
160 
161         if (err == -EAGAIN && mFinalResult == OK) {
162             memmove(mBuffer->base(), mBuffer->data(), mBuffer->size());
163             mBuffer->setRange(0, mBuffer->size());
164 
165             if (mBuffer->size() + kChunkSize > mBuffer->capacity()) {
166                 size_t newCapacity = mBuffer->capacity() + kChunkSize;
167                 sp<ABuffer> newBuffer = new ABuffer(newCapacity);
168                 memcpy(newBuffer->data(), mBuffer->data(), mBuffer->size());
169                 newBuffer->setRange(0, mBuffer->size());
170                 mBuffer = newBuffer;
171             }
172 
173             ssize_t n = mDataSource->readAt(
174                     mOffset, mBuffer->data() + mBuffer->size(), kChunkSize);
175 
176             if (n < (ssize_t)kChunkSize) {
177                 mFinalResult = (n < 0) ? (status_t)n : ERROR_END_OF_STREAM;
178                 return mFinalResult;
179             }
180 
181             mBuffer->setRange(mBuffer->offset(), mBuffer->size() + n);
182             mOffset += n;
183         } else if (err != OK) {
184             mFinalResult = err;
185             return err;
186         } else {
187             return OK;
188         }
189     }
190 }
191 
dequeueChunk()192 status_t MPEG2PSExtractor::dequeueChunk() {
193     if (mBuffer->size() < 4) {
194         return -EAGAIN;
195     }
196 
197     if (memcmp("\x00\x00\x01", mBuffer->data(), 3)) {
198         return ERROR_MALFORMED;
199     }
200 
201     unsigned chunkType = mBuffer->data()[3];
202 
203     ssize_t res;
204 
205     switch (chunkType) {
206         case 0xba:
207         {
208             res = dequeuePack();
209             break;
210         }
211 
212         case 0xbb:
213         {
214             res = dequeueSystemHeader();
215             break;
216         }
217 
218         default:
219         {
220             res = dequeuePES();
221             break;
222         }
223     }
224 
225     if (res > 0) {
226         if (mBuffer->size() < (size_t)res) {
227             return -EAGAIN;
228         }
229 
230         mBuffer->setRange(mBuffer->offset() + res, mBuffer->size() - res);
231         res = OK;
232     }
233 
234     return res;
235 }
236 
dequeuePack()237 ssize_t MPEG2PSExtractor::dequeuePack() {
238     // 32 + 2 + 3 + 1 + 15 + 1 + 15+ 1 + 9 + 1 + 22 + 1 + 1 | +5
239 
240     if (mBuffer->size() < 14) {
241         return -EAGAIN;
242     }
243 
244     unsigned pack_stuffing_length = mBuffer->data()[13] & 7;
245 
246     return pack_stuffing_length + 14;
247 }
248 
dequeueSystemHeader()249 ssize_t MPEG2PSExtractor::dequeueSystemHeader() {
250     if (mBuffer->size() < 6) {
251         return -EAGAIN;
252     }
253 
254     unsigned header_length = U16_AT(mBuffer->data() + 4);
255 
256     return header_length + 6;
257 }
258 
dequeuePES()259 ssize_t MPEG2PSExtractor::dequeuePES() {
260     if (mBuffer->size() < 6) {
261         return -EAGAIN;
262     }
263 
264     unsigned PES_packet_length = U16_AT(mBuffer->data() + 4);
265     CHECK_NE(PES_packet_length, 0u);
266 
267     size_t n = PES_packet_length + 6;
268 
269     if (mBuffer->size() < n) {
270         return -EAGAIN;
271     }
272 
273     ABitReader br(mBuffer->data(), n);
274 
275     unsigned packet_startcode_prefix = br.getBits(24);
276 
277     ALOGV("packet_startcode_prefix = 0x%08x", packet_startcode_prefix);
278 
279     if (packet_startcode_prefix != 1) {
280         ALOGV("Supposedly payload_unit_start=1 unit does not start "
281              "with startcode.");
282 
283         return ERROR_MALFORMED;
284     }
285 
286     CHECK_EQ(packet_startcode_prefix, 0x000001u);
287 
288     unsigned stream_id = br.getBits(8);
289     ALOGV("stream_id = 0x%02x", stream_id);
290 
291     /* unsigned PES_packet_length = */br.getBits(16);
292 
293     if (stream_id == 0xbc) {
294         // program_stream_map
295 
296         if (!mScanning) {
297             return n;
298         }
299 
300         mStreamTypeByESID.clear();
301 
302         /* unsigned current_next_indicator = */br.getBits(1);
303         /* unsigned reserved = */br.getBits(2);
304         /* unsigned program_stream_map_version = */br.getBits(5);
305         /* unsigned reserved = */br.getBits(7);
306         /* unsigned marker_bit = */br.getBits(1);
307         unsigned program_stream_info_length = br.getBits(16);
308 
309         size_t offset = 0;
310         while (offset < program_stream_info_length) {
311             if (offset + 2 > program_stream_info_length) {
312                 return ERROR_MALFORMED;
313             }
314 
315             unsigned descriptor_tag = br.getBits(8);
316             unsigned descriptor_length = br.getBits(8);
317 
318             ALOGI("found descriptor tag 0x%02x of length %u",
319                  descriptor_tag, descriptor_length);
320 
321             if (offset + 2 + descriptor_length > program_stream_info_length) {
322                 return ERROR_MALFORMED;
323             }
324 
325             br.skipBits(8 * descriptor_length);
326 
327             offset += 2 + descriptor_length;
328         }
329 
330         unsigned elementary_stream_map_length = br.getBits(16);
331 
332         offset = 0;
333         while (offset < elementary_stream_map_length) {
334             if (offset + 4 > elementary_stream_map_length) {
335                 return ERROR_MALFORMED;
336             }
337 
338             unsigned stream_type = br.getBits(8);
339             unsigned elementary_stream_id = br.getBits(8);
340 
341             ALOGI("elementary stream id 0x%02x has stream type 0x%02x",
342                  elementary_stream_id, stream_type);
343 
344             mStreamTypeByESID.add(elementary_stream_id, stream_type);
345 
346             unsigned elementary_stream_info_length = br.getBits(16);
347 
348             if (offset + 4 + elementary_stream_info_length
349                     > elementary_stream_map_length) {
350                 return ERROR_MALFORMED;
351             }
352 
353             offset += 4 + elementary_stream_info_length;
354         }
355 
356         /* unsigned CRC32 = */br.getBits(32);
357 
358         mProgramStreamMapValid = true;
359     } else if (stream_id != 0xbe  // padding_stream
360             && stream_id != 0xbf  // private_stream_2
361             && stream_id != 0xf0  // ECM
362             && stream_id != 0xf1  // EMM
363             && stream_id != 0xff  // program_stream_directory
364             && stream_id != 0xf2  // DSMCC
365             && stream_id != 0xf8) {  // H.222.1 type E
366         CHECK_EQ(br.getBits(2), 2u);
367 
368         /* unsigned PES_scrambling_control = */br.getBits(2);
369         /* unsigned PES_priority = */br.getBits(1);
370         /* unsigned data_alignment_indicator = */br.getBits(1);
371         /* unsigned copyright = */br.getBits(1);
372         /* unsigned original_or_copy = */br.getBits(1);
373 
374         unsigned PTS_DTS_flags = br.getBits(2);
375         ALOGV("PTS_DTS_flags = %u", PTS_DTS_flags);
376 
377         unsigned ESCR_flag = br.getBits(1);
378         ALOGV("ESCR_flag = %u", ESCR_flag);
379 
380         unsigned ES_rate_flag = br.getBits(1);
381         ALOGV("ES_rate_flag = %u", ES_rate_flag);
382 
383         unsigned DSM_trick_mode_flag = br.getBits(1);
384         ALOGV("DSM_trick_mode_flag = %u", DSM_trick_mode_flag);
385 
386         unsigned additional_copy_info_flag = br.getBits(1);
387         ALOGV("additional_copy_info_flag = %u", additional_copy_info_flag);
388 
389         /* unsigned PES_CRC_flag = */br.getBits(1);
390         /* PES_extension_flag = */br.getBits(1);
391 
392         unsigned PES_header_data_length = br.getBits(8);
393         ALOGV("PES_header_data_length = %u", PES_header_data_length);
394 
395         unsigned optional_bytes_remaining = PES_header_data_length;
396 
397         uint64_t PTS = 0, DTS = 0;
398 
399         if (PTS_DTS_flags == 2 || PTS_DTS_flags == 3) {
400             CHECK_GE(optional_bytes_remaining, 5u);
401 
402             CHECK_EQ(br.getBits(4), PTS_DTS_flags);
403 
404             PTS = ((uint64_t)br.getBits(3)) << 30;
405             CHECK_EQ(br.getBits(1), 1u);
406             PTS |= ((uint64_t)br.getBits(15)) << 15;
407             CHECK_EQ(br.getBits(1), 1u);
408             PTS |= br.getBits(15);
409             CHECK_EQ(br.getBits(1), 1u);
410 
411             ALOGV("PTS = %llu", PTS);
412             // ALOGI("PTS = %.2f secs", PTS / 90000.0f);
413 
414             optional_bytes_remaining -= 5;
415 
416             if (PTS_DTS_flags == 3) {
417                 CHECK_GE(optional_bytes_remaining, 5u);
418 
419                 CHECK_EQ(br.getBits(4), 1u);
420 
421                 DTS = ((uint64_t)br.getBits(3)) << 30;
422                 CHECK_EQ(br.getBits(1), 1u);
423                 DTS |= ((uint64_t)br.getBits(15)) << 15;
424                 CHECK_EQ(br.getBits(1), 1u);
425                 DTS |= br.getBits(15);
426                 CHECK_EQ(br.getBits(1), 1u);
427 
428                 ALOGV("DTS = %llu", DTS);
429 
430                 optional_bytes_remaining -= 5;
431             }
432         }
433 
434         if (ESCR_flag) {
435             CHECK_GE(optional_bytes_remaining, 6u);
436 
437             br.getBits(2);
438 
439             uint64_t ESCR = ((uint64_t)br.getBits(3)) << 30;
440             CHECK_EQ(br.getBits(1), 1u);
441             ESCR |= ((uint64_t)br.getBits(15)) << 15;
442             CHECK_EQ(br.getBits(1), 1u);
443             ESCR |= br.getBits(15);
444             CHECK_EQ(br.getBits(1), 1u);
445 
446             ALOGV("ESCR = %llu", ESCR);
447             /* unsigned ESCR_extension = */br.getBits(9);
448 
449             CHECK_EQ(br.getBits(1), 1u);
450 
451             optional_bytes_remaining -= 6;
452         }
453 
454         if (ES_rate_flag) {
455             CHECK_GE(optional_bytes_remaining, 3u);
456 
457             CHECK_EQ(br.getBits(1), 1u);
458             /* unsigned ES_rate = */br.getBits(22);
459             CHECK_EQ(br.getBits(1), 1u);
460 
461             optional_bytes_remaining -= 3;
462         }
463 
464         br.skipBits(optional_bytes_remaining * 8);
465 
466         // ES data follows.
467 
468         CHECK_GE(PES_packet_length, PES_header_data_length + 3);
469 
470         unsigned dataLength =
471             PES_packet_length - 3 - PES_header_data_length;
472 
473         if (br.numBitsLeft() < dataLength * 8) {
474             ALOGE("PES packet does not carry enough data to contain "
475                  "payload. (numBitsLeft = %d, required = %d)",
476                  br.numBitsLeft(), dataLength * 8);
477 
478             return ERROR_MALFORMED;
479         }
480 
481         CHECK_GE(br.numBitsLeft(), dataLength * 8);
482 
483         ssize_t index = mTracks.indexOfKey(stream_id);
484         if (index < 0 && mScanning) {
485             unsigned streamType;
486 
487             ssize_t streamTypeIndex;
488             if (mProgramStreamMapValid
489                     && (streamTypeIndex =
490                             mStreamTypeByESID.indexOfKey(stream_id)) >= 0) {
491                 streamType = mStreamTypeByESID.valueAt(streamTypeIndex);
492             } else if ((stream_id & ~0x1f) == 0xc0) {
493                 // ISO/IEC 13818-3 or ISO/IEC 11172-3 or ISO/IEC 13818-7
494                 // or ISO/IEC 14496-3 audio
495                 streamType = ATSParser::STREAMTYPE_MPEG2_AUDIO;
496             } else if ((stream_id & ~0x0f) == 0xe0) {
497                 // ISO/IEC 13818-2 or ISO/IEC 11172-2 or ISO/IEC 14496-2 video
498                 streamType = ATSParser::STREAMTYPE_MPEG2_VIDEO;
499             } else {
500                 streamType = ATSParser::STREAMTYPE_RESERVED;
501             }
502 
503             index = mTracks.add(
504                     stream_id, new Track(this, stream_id, streamType));
505         }
506 
507         status_t err = OK;
508 
509         if (index >= 0) {
510             err =
511                 mTracks.editValueAt(index)->appendPESData(
512                     PTS_DTS_flags, PTS, DTS, br.data(), dataLength);
513         }
514 
515         br.skipBits(dataLength * 8);
516 
517         if (err != OK) {
518             return err;
519         }
520     } else if (stream_id == 0xbe) {  // padding_stream
521         CHECK_NE(PES_packet_length, 0u);
522         br.skipBits(PES_packet_length * 8);
523     } else {
524         CHECK_NE(PES_packet_length, 0u);
525         br.skipBits(PES_packet_length * 8);
526     }
527 
528     return n;
529 }
530 
531 ////////////////////////////////////////////////////////////////////////////////
532 
Track(MPEG2PSExtractor * extractor,unsigned stream_id,unsigned stream_type)533 MPEG2PSExtractor::Track::Track(
534         MPEG2PSExtractor *extractor, unsigned stream_id, unsigned stream_type)
535     : mExtractor(extractor),
536       mStreamID(stream_id),
537       mStreamType(stream_type),
538       mQueue(NULL) {
539     bool supported = true;
540     ElementaryStreamQueue::Mode mode;
541 
542     switch (mStreamType) {
543         case ATSParser::STREAMTYPE_H264:
544             mode = ElementaryStreamQueue::H264;
545             break;
546         case ATSParser::STREAMTYPE_MPEG2_AUDIO_ADTS:
547             mode = ElementaryStreamQueue::AAC;
548             break;
549         case ATSParser::STREAMTYPE_MPEG1_AUDIO:
550         case ATSParser::STREAMTYPE_MPEG2_AUDIO:
551             mode = ElementaryStreamQueue::MPEG_AUDIO;
552             break;
553 
554         case ATSParser::STREAMTYPE_MPEG1_VIDEO:
555         case ATSParser::STREAMTYPE_MPEG2_VIDEO:
556             mode = ElementaryStreamQueue::MPEG_VIDEO;
557             break;
558 
559         case ATSParser::STREAMTYPE_MPEG4_VIDEO:
560             mode = ElementaryStreamQueue::MPEG4_VIDEO;
561             break;
562 
563         default:
564             supported = false;
565             break;
566     }
567 
568     if (supported) {
569         mQueue = new ElementaryStreamQueue(mode);
570     } else {
571         ALOGI("unsupported stream ID 0x%02x", stream_id);
572     }
573 }
574 
~Track()575 MPEG2PSExtractor::Track::~Track() {
576     delete mQueue;
577     mQueue = NULL;
578 }
579 
start(MetaData * params)580 status_t MPEG2PSExtractor::Track::start(MetaData *params) {
581     if (mSource == NULL) {
582         return NO_INIT;
583     }
584 
585     return mSource->start(params);
586 }
587 
stop()588 status_t MPEG2PSExtractor::Track::stop() {
589     if (mSource == NULL) {
590         return NO_INIT;
591     }
592 
593     return mSource->stop();
594 }
595 
getFormat()596 sp<MetaData> MPEG2PSExtractor::Track::getFormat() {
597     if (mSource == NULL) {
598         return NULL;
599     }
600 
601     return mSource->getFormat();
602 }
603 
read(MediaBuffer ** buffer,const ReadOptions * options)604 status_t MPEG2PSExtractor::Track::read(
605         MediaBuffer **buffer, const ReadOptions *options) {
606     if (mSource == NULL) {
607         return NO_INIT;
608     }
609 
610     status_t finalResult;
611     while (!mSource->hasBufferAvailable(&finalResult)) {
612         if (finalResult != OK) {
613             return ERROR_END_OF_STREAM;
614         }
615 
616         status_t err = mExtractor->feedMore();
617 
618         if (err != OK) {
619             mSource->signalEOS(err);
620         }
621     }
622 
623     return mSource->read(buffer, options);
624 }
625 
appendPESData(unsigned PTS_DTS_flags,uint64_t PTS,uint64_t DTS,const uint8_t * data,size_t size)626 status_t MPEG2PSExtractor::Track::appendPESData(
627         unsigned PTS_DTS_flags,
628         uint64_t PTS, uint64_t DTS,
629         const uint8_t *data, size_t size) {
630     if (mQueue == NULL) {
631         return OK;
632     }
633 
634     int64_t timeUs;
635     if (PTS_DTS_flags == 2 || PTS_DTS_flags == 3) {
636         timeUs = (PTS * 100) / 9;
637     } else {
638         timeUs = 0;
639     }
640 
641     status_t err = mQueue->appendData(data, size, timeUs);
642 
643     if (err != OK) {
644         return err;
645     }
646 
647     sp<ABuffer> accessUnit;
648     while ((accessUnit = mQueue->dequeueAccessUnit()) != NULL) {
649         if (mSource == NULL) {
650             sp<MetaData> meta = mQueue->getFormat();
651 
652             if (meta != NULL) {
653                 ALOGV("Stream ID 0x%02x now has data.", mStreamID);
654 
655                 mSource = new AnotherPacketSource(meta);
656                 mSource->queueAccessUnit(accessUnit);
657             }
658         } else if (mQueue->getFormat() != NULL) {
659             mSource->queueAccessUnit(accessUnit);
660         }
661     }
662 
663     return OK;
664 }
665 
666 ////////////////////////////////////////////////////////////////////////////////
667 
WrappedTrack(const sp<MPEG2PSExtractor> & extractor,const sp<Track> & track)668 MPEG2PSExtractor::WrappedTrack::WrappedTrack(
669         const sp<MPEG2PSExtractor> &extractor, const sp<Track> &track)
670     : mExtractor(extractor),
671       mTrack(track) {
672 }
673 
~WrappedTrack()674 MPEG2PSExtractor::WrappedTrack::~WrappedTrack() {
675 }
676 
start(MetaData * params)677 status_t MPEG2PSExtractor::WrappedTrack::start(MetaData *params) {
678     return mTrack->start(params);
679 }
680 
stop()681 status_t MPEG2PSExtractor::WrappedTrack::stop() {
682     return mTrack->stop();
683 }
684 
getFormat()685 sp<MetaData> MPEG2PSExtractor::WrappedTrack::getFormat() {
686     return mTrack->getFormat();
687 }
688 
read(MediaBuffer ** buffer,const ReadOptions * options)689 status_t MPEG2PSExtractor::WrappedTrack::read(
690         MediaBuffer **buffer, const ReadOptions *options) {
691     return mTrack->read(buffer, options);
692 }
693 
694 ////////////////////////////////////////////////////////////////////////////////
695 
SniffMPEG2PS(const sp<DataSource> & source,String8 * mimeType,float * confidence,sp<AMessage> *)696 bool SniffMPEG2PS(
697         const sp<DataSource> &source, String8 *mimeType, float *confidence,
698         sp<AMessage> *) {
699     uint8_t header[5];
700     if (source->readAt(0, header, sizeof(header)) < (ssize_t)sizeof(header)) {
701         return false;
702     }
703 
704     if (memcmp("\x00\x00\x01\xba", header, 4) || (header[4] >> 6) != 1) {
705         return false;
706     }
707 
708     *confidence = 0.25f;  // Slightly larger than .mp3 extractor's confidence
709 
710     mimeType->setTo(MEDIA_MIMETYPE_CONTAINER_MPEG2PS);
711 
712     return true;
713 }
714 
715 }  // namespace android
716