1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "media/mp4/track_run_iterator.h"
6
7 #include <algorithm>
8
9 #include "media/base/buffers.h"
10 #include "media/base/stream_parser_buffer.h"
11 #include "media/mp4/rcheck.h"
12
13 namespace {
14 static const uint32 kSampleIsDifferenceSampleFlagMask = 0x10000;
15 }
16
17 namespace media {
18 namespace mp4 {
19
20 struct SampleInfo {
21 int size;
22 int duration;
23 int cts_offset;
24 bool is_keyframe;
25 };
26
27 struct TrackRunInfo {
28 uint32 track_id;
29 std::vector<SampleInfo> samples;
30 int64 timescale;
31 int64 start_dts;
32 int64 sample_start_offset;
33
34 bool is_audio;
35 const AudioSampleEntry* audio_description;
36 const VideoSampleEntry* video_description;
37
38 int64 aux_info_start_offset; // Only valid if aux_info_total_size > 0.
39 int aux_info_default_size;
40 std::vector<uint8> aux_info_sizes; // Populated if default_size == 0.
41 int aux_info_total_size;
42
43 TrackRunInfo();
44 ~TrackRunInfo();
45 };
46
TrackRunInfo()47 TrackRunInfo::TrackRunInfo()
48 : track_id(0),
49 timescale(-1),
50 start_dts(-1),
51 sample_start_offset(-1),
52 is_audio(false),
53 aux_info_start_offset(-1),
54 aux_info_default_size(-1),
55 aux_info_total_size(-1) {
56 }
~TrackRunInfo()57 TrackRunInfo::~TrackRunInfo() {}
58
TimeDeltaFromRational(int64 numer,int64 denom)59 TimeDelta TimeDeltaFromRational(int64 numer, int64 denom) {
60 DCHECK_LT((numer > 0 ? numer : -numer),
61 kint64max / base::Time::kMicrosecondsPerSecond);
62 return TimeDelta::FromMicroseconds(
63 base::Time::kMicrosecondsPerSecond * numer / denom);
64 }
65
TrackRunIterator(const Movie * moov,const LogCB & log_cb)66 TrackRunIterator::TrackRunIterator(const Movie* moov,
67 const LogCB& log_cb)
68 : moov_(moov), log_cb_(log_cb), sample_offset_(0) {
69 CHECK(moov);
70 }
71
~TrackRunIterator()72 TrackRunIterator::~TrackRunIterator() {}
73
PopulateSampleInfo(const TrackExtends & trex,const TrackFragmentHeader & tfhd,const TrackFragmentRun & trun,const int64 edit_list_offset,const uint32 i,SampleInfo * sample_info,const SampleDependsOn sample_depends_on)74 static void PopulateSampleInfo(const TrackExtends& trex,
75 const TrackFragmentHeader& tfhd,
76 const TrackFragmentRun& trun,
77 const int64 edit_list_offset,
78 const uint32 i,
79 SampleInfo* sample_info,
80 const SampleDependsOn sample_depends_on) {
81 if (i < trun.sample_sizes.size()) {
82 sample_info->size = trun.sample_sizes[i];
83 } else if (tfhd.default_sample_size > 0) {
84 sample_info->size = tfhd.default_sample_size;
85 } else {
86 sample_info->size = trex.default_sample_size;
87 }
88
89 if (i < trun.sample_durations.size()) {
90 sample_info->duration = trun.sample_durations[i];
91 } else if (tfhd.default_sample_duration > 0) {
92 sample_info->duration = tfhd.default_sample_duration;
93 } else {
94 sample_info->duration = trex.default_sample_duration;
95 }
96
97 if (i < trun.sample_composition_time_offsets.size()) {
98 sample_info->cts_offset = trun.sample_composition_time_offsets[i];
99 } else {
100 sample_info->cts_offset = 0;
101 }
102 sample_info->cts_offset += edit_list_offset;
103
104 uint32 flags;
105 if (i < trun.sample_flags.size()) {
106 flags = trun.sample_flags[i];
107 } else if (tfhd.has_default_sample_flags) {
108 flags = tfhd.default_sample_flags;
109 } else {
110 flags = trex.default_sample_flags;
111 }
112
113 switch (sample_depends_on) {
114 case kSampleDependsOnUnknown:
115 sample_info->is_keyframe = !(flags & kSampleIsDifferenceSampleFlagMask);
116 break;
117
118 case kSampleDependsOnOthers:
119 sample_info->is_keyframe = false;
120 break;
121
122 case kSampleDependsOnNoOther:
123 sample_info->is_keyframe = true;
124 break;
125
126 case kSampleDependsOnReserved:
127 CHECK(false);
128 }
129 }
130
131 // In well-structured encrypted media, each track run will be immediately
132 // preceded by its auxiliary information; this is the only optimal storage
133 // pattern in terms of minimum number of bytes from a serial stream needed to
134 // begin playback. It also allows us to optimize caching on memory-constrained
135 // architectures, because we can cache the relatively small auxiliary
136 // information for an entire run and then discard data from the input stream,
137 // instead of retaining the entire 'mdat' box.
138 //
139 // We optimize for this situation (with no loss of generality) by sorting track
140 // runs during iteration in order of their first data offset (either sample data
141 // or auxiliary data).
142 class CompareMinTrackRunDataOffset {
143 public:
operator ()(const TrackRunInfo & a,const TrackRunInfo & b)144 bool operator()(const TrackRunInfo& a, const TrackRunInfo& b) {
145 int64 a_aux = a.aux_info_total_size ? a.aux_info_start_offset : kint64max;
146 int64 b_aux = b.aux_info_total_size ? b.aux_info_start_offset : kint64max;
147
148 int64 a_lesser = std::min(a_aux, a.sample_start_offset);
149 int64 a_greater = std::max(a_aux, a.sample_start_offset);
150 int64 b_lesser = std::min(b_aux, b.sample_start_offset);
151 int64 b_greater = std::max(b_aux, b.sample_start_offset);
152
153 if (a_lesser == b_lesser) return a_greater < b_greater;
154 return a_lesser < b_lesser;
155 }
156 };
157
Init(const MovieFragment & moof)158 bool TrackRunIterator::Init(const MovieFragment& moof) {
159 runs_.clear();
160
161 for (size_t i = 0; i < moof.tracks.size(); i++) {
162 const TrackFragment& traf = moof.tracks[i];
163
164 const Track* trak = NULL;
165 for (size_t t = 0; t < moov_->tracks.size(); t++) {
166 if (moov_->tracks[t].header.track_id == traf.header.track_id)
167 trak = &moov_->tracks[t];
168 }
169 RCHECK(trak);
170
171 const TrackExtends* trex = NULL;
172 for (size_t t = 0; t < moov_->extends.tracks.size(); t++) {
173 if (moov_->extends.tracks[t].track_id == traf.header.track_id)
174 trex = &moov_->extends.tracks[t];
175 }
176 RCHECK(trex);
177
178 const SampleDescription& stsd =
179 trak->media.information.sample_table.description;
180 if (stsd.type != kAudio && stsd.type != kVideo) {
181 DVLOG(1) << "Skipping unhandled track type";
182 continue;
183 }
184 size_t desc_idx = traf.header.sample_description_index;
185 if (!desc_idx) desc_idx = trex->default_sample_description_index;
186 RCHECK(desc_idx > 0); // Descriptions are one-indexed in the file
187 desc_idx -= 1;
188
189 // Process edit list to remove CTS offset introduced in the presence of
190 // B-frames (those that contain a single edit with a nonnegative media
191 // time). Other uses of edit lists are not supported, as they are
192 // both uncommon and better served by higher-level protocols.
193 int64 edit_list_offset = 0;
194 const std::vector<EditListEntry>& edits = trak->edit.list.edits;
195 if (!edits.empty()) {
196 if (edits.size() > 1)
197 DVLOG(1) << "Multi-entry edit box detected; some components ignored.";
198
199 if (edits[0].media_time < 0) {
200 DVLOG(1) << "Empty edit list entry ignored.";
201 } else {
202 edit_list_offset = -edits[0].media_time;
203 }
204 }
205
206 int64 run_start_dts = traf.decode_time.decode_time;
207 int sample_count_sum = 0;
208
209 for (size_t j = 0; j < traf.runs.size(); j++) {
210 const TrackFragmentRun& trun = traf.runs[j];
211 TrackRunInfo tri;
212 tri.track_id = traf.header.track_id;
213 tri.timescale = trak->media.header.timescale;
214 tri.start_dts = run_start_dts;
215 tri.sample_start_offset = trun.data_offset;
216
217 tri.is_audio = (stsd.type == kAudio);
218 if (tri.is_audio) {
219 RCHECK(!stsd.audio_entries.empty());
220 if (desc_idx > stsd.audio_entries.size())
221 desc_idx = 0;
222 tri.audio_description = &stsd.audio_entries[desc_idx];
223 } else {
224 RCHECK(!stsd.video_entries.empty());
225 if (desc_idx > stsd.video_entries.size())
226 desc_idx = 0;
227 tri.video_description = &stsd.video_entries[desc_idx];
228 }
229
230 // Collect information from the auxiliary_offset entry with the same index
231 // in the 'saiz' container as the current run's index in the 'trun'
232 // container, if it is present.
233 if (traf.auxiliary_offset.offsets.size() > j) {
234 // There should be an auxiliary info entry corresponding to each sample
235 // in the auxiliary offset entry's corresponding track run.
236 RCHECK(traf.auxiliary_size.sample_count >=
237 sample_count_sum + trun.sample_count);
238 tri.aux_info_start_offset = traf.auxiliary_offset.offsets[j];
239 tri.aux_info_default_size =
240 traf.auxiliary_size.default_sample_info_size;
241 if (tri.aux_info_default_size == 0) {
242 const std::vector<uint8>& sizes =
243 traf.auxiliary_size.sample_info_sizes;
244 tri.aux_info_sizes.insert(tri.aux_info_sizes.begin(),
245 sizes.begin() + sample_count_sum,
246 sizes.begin() + sample_count_sum + trun.sample_count);
247 }
248
249 // If the default info size is positive, find the total size of the aux
250 // info block from it, otherwise sum over the individual sizes of each
251 // aux info entry in the aux_offset entry.
252 if (tri.aux_info_default_size) {
253 tri.aux_info_total_size =
254 tri.aux_info_default_size * trun.sample_count;
255 } else {
256 tri.aux_info_total_size = 0;
257 for (size_t k = 0; k < trun.sample_count; k++) {
258 tri.aux_info_total_size += tri.aux_info_sizes[k];
259 }
260 }
261 } else {
262 tri.aux_info_start_offset = -1;
263 tri.aux_info_total_size = 0;
264 }
265
266 tri.samples.resize(trun.sample_count);
267 for (size_t k = 0; k < trun.sample_count; k++) {
268 PopulateSampleInfo(*trex, traf.header, trun, edit_list_offset,
269 k, &tri.samples[k], traf.sdtp.sample_depends_on(k));
270 run_start_dts += tri.samples[k].duration;
271 }
272 runs_.push_back(tri);
273 sample_count_sum += trun.sample_count;
274 }
275 }
276
277 std::sort(runs_.begin(), runs_.end(), CompareMinTrackRunDataOffset());
278 run_itr_ = runs_.begin();
279 ResetRun();
280 return true;
281 }
282
AdvanceRun()283 void TrackRunIterator::AdvanceRun() {
284 ++run_itr_;
285 ResetRun();
286 }
287
ResetRun()288 void TrackRunIterator::ResetRun() {
289 if (!IsRunValid()) return;
290 sample_dts_ = run_itr_->start_dts;
291 sample_offset_ = run_itr_->sample_start_offset;
292 sample_itr_ = run_itr_->samples.begin();
293 cenc_info_.clear();
294 }
295
AdvanceSample()296 void TrackRunIterator::AdvanceSample() {
297 DCHECK(IsSampleValid());
298 sample_dts_ += sample_itr_->duration;
299 sample_offset_ += sample_itr_->size;
300 ++sample_itr_;
301 }
302
303 // This implementation only indicates a need for caching if CENC auxiliary
304 // info is available in the stream.
AuxInfoNeedsToBeCached()305 bool TrackRunIterator::AuxInfoNeedsToBeCached() {
306 DCHECK(IsRunValid());
307 return is_encrypted() && aux_info_size() > 0 && cenc_info_.size() == 0;
308 }
309
310 // This implementation currently only caches CENC auxiliary info.
CacheAuxInfo(const uint8 * buf,int buf_size)311 bool TrackRunIterator::CacheAuxInfo(const uint8* buf, int buf_size) {
312 RCHECK(AuxInfoNeedsToBeCached() && buf_size >= aux_info_size());
313
314 cenc_info_.resize(run_itr_->samples.size());
315 int64 pos = 0;
316 for (size_t i = 0; i < run_itr_->samples.size(); i++) {
317 int info_size = run_itr_->aux_info_default_size;
318 if (!info_size)
319 info_size = run_itr_->aux_info_sizes[i];
320
321 BufferReader reader(buf + pos, info_size);
322 RCHECK(cenc_info_[i].Parse(track_encryption().default_iv_size, &reader));
323 pos += info_size;
324 }
325
326 return true;
327 }
328
IsRunValid() const329 bool TrackRunIterator::IsRunValid() const {
330 return run_itr_ != runs_.end();
331 }
332
IsSampleValid() const333 bool TrackRunIterator::IsSampleValid() const {
334 return IsRunValid() && (sample_itr_ != run_itr_->samples.end());
335 }
336
337 // Because tracks are in sorted order and auxiliary information is cached when
338 // returning samples, it is guaranteed that no data will be required before the
339 // lesser of the minimum data offset of this track and the next in sequence.
340 // (The stronger condition - that no data is required before the minimum data
341 // offset of this track alone - is not guaranteed, because the BMFF spec does
342 // not have any inter-run ordering restrictions.)
GetMaxClearOffset()343 int64 TrackRunIterator::GetMaxClearOffset() {
344 int64 offset = kint64max;
345
346 if (IsSampleValid()) {
347 offset = std::min(offset, sample_offset_);
348 if (AuxInfoNeedsToBeCached())
349 offset = std::min(offset, aux_info_offset());
350 }
351 if (run_itr_ != runs_.end()) {
352 std::vector<TrackRunInfo>::const_iterator next_run = run_itr_ + 1;
353 if (next_run != runs_.end()) {
354 offset = std::min(offset, next_run->sample_start_offset);
355 if (next_run->aux_info_total_size)
356 offset = std::min(offset, next_run->aux_info_start_offset);
357 }
358 }
359 if (offset == kint64max) return 0;
360 return offset;
361 }
362
track_id() const363 uint32 TrackRunIterator::track_id() const {
364 DCHECK(IsRunValid());
365 return run_itr_->track_id;
366 }
367
is_encrypted() const368 bool TrackRunIterator::is_encrypted() const {
369 DCHECK(IsRunValid());
370 return track_encryption().is_encrypted;
371 }
372
aux_info_offset() const373 int64 TrackRunIterator::aux_info_offset() const {
374 return run_itr_->aux_info_start_offset;
375 }
376
aux_info_size() const377 int TrackRunIterator::aux_info_size() const {
378 return run_itr_->aux_info_total_size;
379 }
380
is_audio() const381 bool TrackRunIterator::is_audio() const {
382 DCHECK(IsRunValid());
383 return run_itr_->is_audio;
384 }
385
audio_description() const386 const AudioSampleEntry& TrackRunIterator::audio_description() const {
387 DCHECK(is_audio());
388 DCHECK(run_itr_->audio_description);
389 return *run_itr_->audio_description;
390 }
391
video_description() const392 const VideoSampleEntry& TrackRunIterator::video_description() const {
393 DCHECK(!is_audio());
394 DCHECK(run_itr_->video_description);
395 return *run_itr_->video_description;
396 }
397
sample_offset() const398 int64 TrackRunIterator::sample_offset() const {
399 DCHECK(IsSampleValid());
400 return sample_offset_;
401 }
402
sample_size() const403 int TrackRunIterator::sample_size() const {
404 DCHECK(IsSampleValid());
405 return sample_itr_->size;
406 }
407
dts() const408 TimeDelta TrackRunIterator::dts() const {
409 DCHECK(IsSampleValid());
410 return TimeDeltaFromRational(sample_dts_, run_itr_->timescale);
411 }
412
cts() const413 TimeDelta TrackRunIterator::cts() const {
414 DCHECK(IsSampleValid());
415 return TimeDeltaFromRational(sample_dts_ + sample_itr_->cts_offset,
416 run_itr_->timescale);
417 }
418
duration() const419 TimeDelta TrackRunIterator::duration() const {
420 DCHECK(IsSampleValid());
421 return TimeDeltaFromRational(sample_itr_->duration, run_itr_->timescale);
422 }
423
is_keyframe() const424 bool TrackRunIterator::is_keyframe() const {
425 DCHECK(IsSampleValid());
426 return sample_itr_->is_keyframe;
427 }
428
track_encryption() const429 const TrackEncryption& TrackRunIterator::track_encryption() const {
430 if (is_audio())
431 return audio_description().sinf.info.track_encryption;
432 return video_description().sinf.info.track_encryption;
433 }
434
GetDecryptConfig()435 scoped_ptr<DecryptConfig> TrackRunIterator::GetDecryptConfig() {
436 size_t sample_idx = sample_itr_ - run_itr_->samples.begin();
437 DCHECK(sample_idx < cenc_info_.size());
438 const FrameCENCInfo& cenc_info = cenc_info_[sample_idx];
439 DCHECK(is_encrypted() && !AuxInfoNeedsToBeCached());
440
441 size_t total_size = 0;
442 if (!cenc_info.subsamples.empty() &&
443 (!cenc_info.GetTotalSizeOfSubsamples(&total_size) ||
444 total_size != static_cast<size_t>(sample_size()))) {
445 MEDIA_LOG(log_cb_) << "Incorrect CENC subsample size.";
446 return scoped_ptr<DecryptConfig>();
447 }
448
449 const std::vector<uint8>& kid = track_encryption().default_kid;
450 return scoped_ptr<DecryptConfig>(new DecryptConfig(
451 std::string(reinterpret_cast<const char*>(&kid[0]), kid.size()),
452 std::string(reinterpret_cast<const char*>(cenc_info.iv),
453 arraysize(cenc_info.iv)),
454 0, // No offset to start of media data in MP4 using CENC.
455 cenc_info.subsamples));
456 }
457
458 } // namespace mp4
459 } // namespace media
460