ATSParser.cpp revision decd96988e495133e4a1728f612d4c9fdb4d218e 
1/*
2 * Copyright (C) 2010 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 "ATSParser"
19#include <utils/Log.h>
20
21#include "ATSParser.h"
22
23#include "AnotherPacketSource.h"
24#include "ESQueue.h"
25#include "include/avc_utils.h"
26
27#include <media/stagefright/foundation/ABitReader.h>
28#include <media/stagefright/foundation/ABuffer.h>
29#include <media/stagefright/foundation/ADebug.h>
30#include <media/stagefright/foundation/AMessage.h>
31#include <media/stagefright/foundation/hexdump.h>
32#include <media/stagefright/MediaDefs.h>
33#include <media/stagefright/MediaErrors.h>
34#include <media/stagefright/MetaData.h>
35#include <utils/KeyedVector.h>
36
37namespace android {
38
39// I want the expression "y" evaluated even if verbose logging is off.
40#define MY_LOGV(x, y) \
41    do { unsigned tmp = y; LOGV(x, tmp); } while (0)
42
43static const size_t kTSPacketSize = 188;
44
45struct ATSParser::Program : public RefBase {
46    Program(unsigned programMapPID);
47
48    bool parsePID(
49            unsigned pid, unsigned payload_unit_start_indicator,
50            ABitReader *br);
51
52    void signalDiscontinuity(bool isASeek);
53
54    sp<MediaSource> getSource(SourceType type);
55
56    int64_t convertPTSToTimestamp(uint64_t PTS);
57
58private:
59    unsigned mProgramMapPID;
60    KeyedVector<unsigned, sp<Stream> > mStreams;
61    bool mFirstPTSValid;
62    uint64_t mFirstPTS;
63
64    void parseProgramMap(ABitReader *br);
65
66    DISALLOW_EVIL_CONSTRUCTORS(Program);
67};
68
69struct ATSParser::Stream : public RefBase {
70    Stream(Program *program, unsigned elementaryPID, unsigned streamType);
71
72    void parse(
73            unsigned payload_unit_start_indicator,
74            ABitReader *br);
75
76    void signalDiscontinuity(bool isASeek);
77
78    sp<MediaSource> getSource(SourceType type);
79
80protected:
81    virtual ~Stream();
82
83private:
84    Program *mProgram;
85    unsigned mElementaryPID;
86    unsigned mStreamType;
87
88    sp<ABuffer> mBuffer;
89    sp<AnotherPacketSource> mSource;
90    bool mPayloadStarted;
91
92    ElementaryStreamQueue mQueue;
93
94    void flush();
95    void parsePES(ABitReader *br);
96
97    void onPayloadData(
98            unsigned PTS_DTS_flags, uint64_t PTS, uint64_t DTS,
99            const uint8_t *data, size_t size);
100
101    void extractAACFrames(const sp<ABuffer> &buffer);
102
103    DISALLOW_EVIL_CONSTRUCTORS(Stream);
104};
105
106////////////////////////////////////////////////////////////////////////////////
107
108ATSParser::Program::Program(unsigned programMapPID)
109    : mProgramMapPID(programMapPID),
110      mFirstPTSValid(false),
111      mFirstPTS(0) {
112}
113
114bool ATSParser::Program::parsePID(
115        unsigned pid, unsigned payload_unit_start_indicator,
116        ABitReader *br) {
117    if (pid == mProgramMapPID) {
118        if (payload_unit_start_indicator) {
119            unsigned skip = br->getBits(8);
120            br->skipBits(skip * 8);
121        }
122
123        parseProgramMap(br);
124        return true;
125    }
126
127    ssize_t index = mStreams.indexOfKey(pid);
128    if (index < 0) {
129        return false;
130    }
131
132    mStreams.editValueAt(index)->parse(
133            payload_unit_start_indicator, br);
134
135    return true;
136}
137
138void ATSParser::Program::signalDiscontinuity(bool isASeek) {
139    for (size_t i = 0; i < mStreams.size(); ++i) {
140        mStreams.editValueAt(i)->signalDiscontinuity(isASeek);
141    }
142}
143
144void ATSParser::Program::parseProgramMap(ABitReader *br) {
145    unsigned table_id = br->getBits(8);
146    LOGV("  table_id = %u", table_id);
147    CHECK_EQ(table_id, 0x02u);
148
149    unsigned section_syntax_indicator = br->getBits(1);
150    LOGV("  section_syntax_indicator = %u", section_syntax_indicator);
151    CHECK_EQ(section_syntax_indicator, 1u);
152
153    CHECK_EQ(br->getBits(1), 0u);
154    MY_LOGV("  reserved = %u", br->getBits(2));
155
156    unsigned section_length = br->getBits(12);
157    LOGV("  section_length = %u", section_length);
158    CHECK((section_length & 0xc00) == 0);
159    CHECK_LE(section_length, 1021u);
160
161    MY_LOGV("  program_number = %u", br->getBits(16));
162    MY_LOGV("  reserved = %u", br->getBits(2));
163    MY_LOGV("  version_number = %u", br->getBits(5));
164    MY_LOGV("  current_next_indicator = %u", br->getBits(1));
165    MY_LOGV("  section_number = %u", br->getBits(8));
166    MY_LOGV("  last_section_number = %u", br->getBits(8));
167    MY_LOGV("  reserved = %u", br->getBits(3));
168    MY_LOGV("  PCR_PID = 0x%04x", br->getBits(13));
169    MY_LOGV("  reserved = %u", br->getBits(4));
170
171    unsigned program_info_length = br->getBits(12);
172    LOGV("  program_info_length = %u", program_info_length);
173    CHECK((program_info_length & 0xc00) == 0);
174
175    br->skipBits(program_info_length * 8);  // skip descriptors
176
177    // infoBytesRemaining is the number of bytes that make up the
178    // variable length section of ES_infos. It does not include the
179    // final CRC.
180    size_t infoBytesRemaining = section_length - 9 - program_info_length - 4;
181
182    while (infoBytesRemaining > 0) {
183        CHECK_GE(infoBytesRemaining, 5u);
184
185        unsigned streamType = br->getBits(8);
186        LOGV("    stream_type = 0x%02x", streamType);
187
188        MY_LOGV("    reserved = %u", br->getBits(3));
189
190        unsigned elementaryPID = br->getBits(13);
191        LOGV("    elementary_PID = 0x%04x", elementaryPID);
192
193        MY_LOGV("    reserved = %u", br->getBits(4));
194
195        unsigned ES_info_length = br->getBits(12);
196        LOGV("    ES_info_length = %u", ES_info_length);
197        CHECK((ES_info_length & 0xc00) == 0);
198
199        CHECK_GE(infoBytesRemaining - 5, ES_info_length);
200
201#if 0
202        br->skipBits(ES_info_length * 8);  // skip descriptors
203#else
204        unsigned info_bytes_remaining = ES_info_length;
205        while (info_bytes_remaining >= 2) {
206            MY_LOGV("      tag = 0x%02x", br->getBits(8));
207
208            unsigned descLength = br->getBits(8);
209            LOGV("      len = %u", descLength);
210
211            CHECK_GE(info_bytes_remaining, 2 + descLength);
212
213            br->skipBits(descLength * 8);
214
215            info_bytes_remaining -= descLength + 2;
216        }
217        CHECK_EQ(info_bytes_remaining, 0u);
218#endif
219
220        ssize_t index = mStreams.indexOfKey(elementaryPID);
221#if 0  // XXX revisit
222        CHECK_LT(index, 0);
223        mStreams.add(elementaryPID,
224                     new Stream(this, elementaryPID, streamType));
225#else
226        if (index < 0) {
227            mStreams.add(elementaryPID,
228                         new Stream(this, elementaryPID, streamType));
229        }
230#endif
231
232        infoBytesRemaining -= 5 + ES_info_length;
233    }
234
235    CHECK_EQ(infoBytesRemaining, 0u);
236
237    MY_LOGV("  CRC = 0x%08x", br->getBits(32));
238}
239
240sp<MediaSource> ATSParser::Program::getSource(SourceType type) {
241    size_t index = (type == MPEG2ADTS_AUDIO) ? 0 : 0;
242
243    for (size_t i = 0; i < mStreams.size(); ++i) {
244        sp<MediaSource> source = mStreams.editValueAt(i)->getSource(type);
245        if (source != NULL) {
246            if (index == 0) {
247                return source;
248            }
249            --index;
250        }
251    }
252
253    return NULL;
254}
255
256int64_t ATSParser::Program::convertPTSToTimestamp(uint64_t PTS) {
257    if (!mFirstPTSValid) {
258        mFirstPTSValid = true;
259        mFirstPTS = PTS;
260        PTS = 0;
261    } else if (PTS < mFirstPTS) {
262        PTS = 0;
263    } else {
264        PTS -= mFirstPTS;
265    }
266
267    return (PTS * 100) / 9;
268}
269
270////////////////////////////////////////////////////////////////////////////////
271
272ATSParser::Stream::Stream(
273        Program *program, unsigned elementaryPID, unsigned streamType)
274    : mProgram(program),
275      mElementaryPID(elementaryPID),
276      mStreamType(streamType),
277      mBuffer(new ABuffer(128 * 1024)),
278      mPayloadStarted(false),
279      mQueue(streamType == 0x1b
280              ? ElementaryStreamQueue::H264 : ElementaryStreamQueue::AAC) {
281    mBuffer->setRange(0, 0);
282
283    LOGV("new stream PID 0x%02x, type 0x%02x", elementaryPID, streamType);
284}
285
286ATSParser::Stream::~Stream() {
287}
288
289void ATSParser::Stream::parse(
290        unsigned payload_unit_start_indicator, ABitReader *br) {
291    if (payload_unit_start_indicator) {
292        if (mPayloadStarted) {
293            // Otherwise we run the danger of receiving the trailing bytes
294            // of a PES packet that we never saw the start of and assuming
295            // we have a a complete PES packet.
296
297            flush();
298        }
299
300        mPayloadStarted = true;
301    }
302
303    if (!mPayloadStarted) {
304        return;
305    }
306
307    size_t payloadSizeBits = br->numBitsLeft();
308    CHECK((payloadSizeBits % 8) == 0);
309
310    CHECK_LE(mBuffer->size() + payloadSizeBits / 8, mBuffer->capacity());
311
312    memcpy(mBuffer->data() + mBuffer->size(), br->data(), payloadSizeBits / 8);
313    mBuffer->setRange(0, mBuffer->size() + payloadSizeBits / 8);
314}
315
316void ATSParser::Stream::signalDiscontinuity(bool isASeek) {
317    isASeek = false;  // Always signal a "real" discontinuity
318
319    mPayloadStarted = false;
320    mBuffer->setRange(0, 0);
321
322    mQueue.clear();
323
324    if (isASeek) {
325        // This is only a "minor" discontinuity, we stay within the same
326        // bitstream.
327
328        if (mSource != NULL) {
329            mSource->clear();
330        }
331        return;
332    }
333
334    if (mStreamType == 0x1b && mSource != NULL) {
335        // Don't signal discontinuities on audio streams.
336        mSource->queueDiscontinuity();
337    }
338}
339
340void ATSParser::Stream::parsePES(ABitReader *br) {
341    unsigned packet_startcode_prefix = br->getBits(24);
342
343    LOGV("packet_startcode_prefix = 0x%08x", packet_startcode_prefix);
344
345    CHECK_EQ(packet_startcode_prefix, 0x000001u);
346
347    unsigned stream_id = br->getBits(8);
348    LOGV("stream_id = 0x%02x", stream_id);
349
350    unsigned PES_packet_length = br->getBits(16);
351    LOGV("PES_packet_length = %u", PES_packet_length);
352
353    if (stream_id != 0xbc  // program_stream_map
354            && stream_id != 0xbe  // padding_stream
355            && stream_id != 0xbf  // private_stream_2
356            && stream_id != 0xf0  // ECM
357            && stream_id != 0xf1  // EMM
358            && stream_id != 0xff  // program_stream_directory
359            && stream_id != 0xf2  // DSMCC
360            && stream_id != 0xf8) {  // H.222.1 type E
361        CHECK_EQ(br->getBits(2), 2u);
362
363        MY_LOGV("PES_scrambling_control = %u", br->getBits(2));
364        MY_LOGV("PES_priority = %u", br->getBits(1));
365        MY_LOGV("data_alignment_indicator = %u", br->getBits(1));
366        MY_LOGV("copyright = %u", br->getBits(1));
367        MY_LOGV("original_or_copy = %u", br->getBits(1));
368
369        unsigned PTS_DTS_flags = br->getBits(2);
370        LOGV("PTS_DTS_flags = %u", PTS_DTS_flags);
371
372        unsigned ESCR_flag = br->getBits(1);
373        LOGV("ESCR_flag = %u", ESCR_flag);
374
375        unsigned ES_rate_flag = br->getBits(1);
376        LOGV("ES_rate_flag = %u", ES_rate_flag);
377
378        unsigned DSM_trick_mode_flag = br->getBits(1);
379        LOGV("DSM_trick_mode_flag = %u", DSM_trick_mode_flag);
380
381        unsigned additional_copy_info_flag = br->getBits(1);
382        LOGV("additional_copy_info_flag = %u", additional_copy_info_flag);
383
384        MY_LOGV("PES_CRC_flag = %u", br->getBits(1));
385        MY_LOGV("PES_extension_flag = %u", br->getBits(1));
386
387        unsigned PES_header_data_length = br->getBits(8);
388        LOGV("PES_header_data_length = %u", PES_header_data_length);
389
390        unsigned optional_bytes_remaining = PES_header_data_length;
391
392        uint64_t PTS = 0, DTS = 0;
393
394        if (PTS_DTS_flags == 2 || PTS_DTS_flags == 3) {
395            CHECK_GE(optional_bytes_remaining, 5u);
396
397            CHECK_EQ(br->getBits(4), PTS_DTS_flags);
398
399            PTS = ((uint64_t)br->getBits(3)) << 30;
400            CHECK_EQ(br->getBits(1), 1u);
401            PTS |= ((uint64_t)br->getBits(15)) << 15;
402            CHECK_EQ(br->getBits(1), 1u);
403            PTS |= br->getBits(15);
404            CHECK_EQ(br->getBits(1), 1u);
405
406            LOGV("PTS = %llu", PTS);
407            // LOGI("PTS = %.2f secs", PTS / 90000.0f);
408
409            optional_bytes_remaining -= 5;
410
411            if (PTS_DTS_flags == 3) {
412                CHECK_GE(optional_bytes_remaining, 5u);
413
414                CHECK_EQ(br->getBits(4), 1u);
415
416                DTS = ((uint64_t)br->getBits(3)) << 30;
417                CHECK_EQ(br->getBits(1), 1u);
418                DTS |= ((uint64_t)br->getBits(15)) << 15;
419                CHECK_EQ(br->getBits(1), 1u);
420                DTS |= br->getBits(15);
421                CHECK_EQ(br->getBits(1), 1u);
422
423                LOGV("DTS = %llu", DTS);
424
425                optional_bytes_remaining -= 5;
426            }
427        }
428
429        if (ESCR_flag) {
430            CHECK_GE(optional_bytes_remaining, 6u);
431
432            br->getBits(2);
433
434            uint64_t ESCR = ((uint64_t)br->getBits(3)) << 30;
435            CHECK_EQ(br->getBits(1), 1u);
436            ESCR |= ((uint64_t)br->getBits(15)) << 15;
437            CHECK_EQ(br->getBits(1), 1u);
438            ESCR |= br->getBits(15);
439            CHECK_EQ(br->getBits(1), 1u);
440
441            LOGV("ESCR = %llu", ESCR);
442            MY_LOGV("ESCR_extension = %u", br->getBits(9));
443
444            CHECK_EQ(br->getBits(1), 1u);
445
446            optional_bytes_remaining -= 6;
447        }
448
449        if (ES_rate_flag) {
450            CHECK_GE(optional_bytes_remaining, 3u);
451
452            CHECK_EQ(br->getBits(1), 1u);
453            MY_LOGV("ES_rate = %u", br->getBits(22));
454            CHECK_EQ(br->getBits(1), 1u);
455
456            optional_bytes_remaining -= 3;
457        }
458
459        br->skipBits(optional_bytes_remaining * 8);
460
461        // ES data follows.
462
463        if (PES_packet_length != 0) {
464            CHECK_GE(PES_packet_length, PES_header_data_length + 3);
465
466            unsigned dataLength =
467                PES_packet_length - 3 - PES_header_data_length;
468
469            CHECK_GE(br->numBitsLeft(), dataLength * 8);
470
471            onPayloadData(
472                    PTS_DTS_flags, PTS, DTS, br->data(), dataLength);
473
474            br->skipBits(dataLength * 8);
475        } else {
476            onPayloadData(
477                    PTS_DTS_flags, PTS, DTS,
478                    br->data(), br->numBitsLeft() / 8);
479
480            size_t payloadSizeBits = br->numBitsLeft();
481            CHECK((payloadSizeBits % 8) == 0);
482
483            LOGV("There's %d bytes of payload.", payloadSizeBits / 8);
484        }
485    } else if (stream_id == 0xbe) {  // padding_stream
486        CHECK_NE(PES_packet_length, 0u);
487        br->skipBits(PES_packet_length * 8);
488    } else {
489        CHECK_NE(PES_packet_length, 0u);
490        br->skipBits(PES_packet_length * 8);
491    }
492}
493
494void ATSParser::Stream::flush() {
495    if (mBuffer->size() == 0) {
496        return;
497    }
498
499    LOGV("flushing stream 0x%04x size = %d", mElementaryPID, mBuffer->size());
500
501    ABitReader br(mBuffer->data(), mBuffer->size());
502    parsePES(&br);
503
504    mBuffer->setRange(0, 0);
505}
506
507void ATSParser::Stream::onPayloadData(
508        unsigned PTS_DTS_flags, uint64_t PTS, uint64_t DTS,
509        const uint8_t *data, size_t size) {
510    LOGV("onPayloadData mStreamType=0x%02x", mStreamType);
511
512    CHECK(PTS_DTS_flags == 2 || PTS_DTS_flags == 3);
513    int64_t timeUs = mProgram->convertPTSToTimestamp(PTS);
514
515    status_t err = mQueue.appendData(data, size, timeUs);
516
517    if (err != OK) {
518        return;
519    }
520
521    sp<ABuffer> accessUnit;
522    while ((accessUnit = mQueue.dequeueAccessUnit()) != NULL) {
523        if (mSource == NULL) {
524            sp<MetaData> meta = mQueue.getFormat();
525
526            if (meta != NULL) {
527                LOGV("created source!");
528                mSource = new AnotherPacketSource(meta);
529                mSource->queueAccessUnit(accessUnit);
530            }
531        } else if (mQueue.getFormat() != NULL) {
532            // After a discontinuity we invalidate the queue's format
533            // and won't enqueue any access units to the source until
534            // the queue has reestablished the new format.
535            mSource->queueAccessUnit(accessUnit);
536        }
537    }
538}
539
540sp<MediaSource> ATSParser::Stream::getSource(SourceType type) {
541    if ((type == AVC_VIDEO && mStreamType == 0x1b)
542        || (type == MPEG2ADTS_AUDIO && mStreamType == 0x0f)) {
543        return mSource;
544    }
545
546    return NULL;
547}
548
549////////////////////////////////////////////////////////////////////////////////
550
551ATSParser::ATSParser() {
552}
553
554ATSParser::~ATSParser() {
555}
556
557void ATSParser::feedTSPacket(const void *data, size_t size) {
558    CHECK_EQ(size, kTSPacketSize);
559
560    ABitReader br((const uint8_t *)data, kTSPacketSize);
561    parseTS(&br);
562}
563
564void ATSParser::signalDiscontinuity(bool isASeek) {
565    for (size_t i = 0; i < mPrograms.size(); ++i) {
566        mPrograms.editItemAt(i)->signalDiscontinuity(isASeek);
567    }
568}
569
570void ATSParser::parseProgramAssociationTable(ABitReader *br) {
571    unsigned table_id = br->getBits(8);
572    LOGV("  table_id = %u", table_id);
573    CHECK_EQ(table_id, 0x00u);
574
575    unsigned section_syntax_indictor = br->getBits(1);
576    LOGV("  section_syntax_indictor = %u", section_syntax_indictor);
577    CHECK_EQ(section_syntax_indictor, 1u);
578
579    CHECK_EQ(br->getBits(1), 0u);
580    MY_LOGV("  reserved = %u", br->getBits(2));
581
582    unsigned section_length = br->getBits(12);
583    LOGV("  section_length = %u", section_length);
584    CHECK((section_length & 0xc00) == 0);
585
586    MY_LOGV("  transport_stream_id = %u", br->getBits(16));
587    MY_LOGV("  reserved = %u", br->getBits(2));
588    MY_LOGV("  version_number = %u", br->getBits(5));
589    MY_LOGV("  current_next_indicator = %u", br->getBits(1));
590    MY_LOGV("  section_number = %u", br->getBits(8));
591    MY_LOGV("  last_section_number = %u", br->getBits(8));
592
593    size_t numProgramBytes = (section_length - 5 /* header */ - 4 /* crc */);
594    CHECK_EQ((numProgramBytes % 4), 0u);
595
596    for (size_t i = 0; i < numProgramBytes / 4; ++i) {
597        unsigned program_number = br->getBits(16);
598        LOGV("    program_number = %u", program_number);
599
600        MY_LOGV("    reserved = %u", br->getBits(3));
601
602        if (program_number == 0) {
603            MY_LOGV("    network_PID = 0x%04x", br->getBits(13));
604        } else {
605            unsigned programMapPID = br->getBits(13);
606
607            LOGV("    program_map_PID = 0x%04x", programMapPID);
608
609            mPrograms.push(new Program(programMapPID));
610        }
611    }
612
613    MY_LOGV("  CRC = 0x%08x", br->getBits(32));
614}
615
616void ATSParser::parsePID(
617        ABitReader *br, unsigned PID,
618        unsigned payload_unit_start_indicator) {
619    if (PID == 0) {
620        if (payload_unit_start_indicator) {
621            unsigned skip = br->getBits(8);
622            br->skipBits(skip * 8);
623        }
624        parseProgramAssociationTable(br);
625        return;
626    }
627
628    bool handled = false;
629    for (size_t i = 0; i < mPrograms.size(); ++i) {
630        if (mPrograms.editItemAt(i)->parsePID(
631                    PID, payload_unit_start_indicator, br)) {
632            handled = true;
633            break;
634        }
635    }
636
637    if (!handled) {
638        LOGV("PID 0x%04x not handled.", PID);
639    }
640}
641
642void ATSParser::parseAdaptationField(ABitReader *br) {
643    unsigned adaptation_field_length = br->getBits(8);
644    if (adaptation_field_length > 0) {
645        br->skipBits(adaptation_field_length * 8);  // XXX
646    }
647}
648
649void ATSParser::parseTS(ABitReader *br) {
650    LOGV("---");
651
652    unsigned sync_byte = br->getBits(8);
653    CHECK_EQ(sync_byte, 0x47u);
654
655    MY_LOGV("transport_error_indicator = %u", br->getBits(1));
656
657    unsigned payload_unit_start_indicator = br->getBits(1);
658    LOGV("payload_unit_start_indicator = %u", payload_unit_start_indicator);
659
660    MY_LOGV("transport_priority = %u", br->getBits(1));
661
662    unsigned PID = br->getBits(13);
663    LOGV("PID = 0x%04x", PID);
664
665    MY_LOGV("transport_scrambling_control = %u", br->getBits(2));
666
667    unsigned adaptation_field_control = br->getBits(2);
668    LOGV("adaptation_field_control = %u", adaptation_field_control);
669
670    unsigned continuity_counter = br->getBits(4);
671    LOGV("continuity_counter = %u", continuity_counter);
672
673    // LOGI("PID = 0x%04x, continuity_counter = %u", PID, continuity_counter);
674
675    if (adaptation_field_control == 2 || adaptation_field_control == 3) {
676        parseAdaptationField(br);
677    }
678
679    if (adaptation_field_control == 1 || adaptation_field_control == 3) {
680        parsePID(br, PID, payload_unit_start_indicator);
681    }
682}
683
684sp<MediaSource> ATSParser::getSource(SourceType type) {
685    for (size_t i = 0; i < mPrograms.size(); ++i) {
686        sp<MediaSource> source = mPrograms.editItemAt(i)->getSource(type);
687
688        if (source != NULL) {
689            return source;
690        }
691    }
692
693    return NULL;
694}
695
696}  // namespace android
697