media/formats/mp2t/es_parser_adts.cc

   1 // Copyright 2014 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/formats/mp2t/es_parser_adts.h"
   6
   7 #include <list>
   8
   9 #include "base/basictypes.h"
  10 #include "base/logging.h"
  11 #include "base/strings/string_number_conversions.h"
  12 #include "media/base/audio_timestamp_helper.h"
  13 #include "media/base/bit_reader.h"
  14 #include "media/base/buffers.h"
  15 #include "media/base/channel_layout.h"
  16 #include "media/base/stream_parser_buffer.h"
  17 #include "media/formats/common/offset_byte_queue.h"
  18 #include "media/formats/mp2t/mp2t_common.h"
  19 #include "media/formats/mpeg/adts_constants.h"
  20
  21 namespace media {
  22
  23 static int ExtractAdtsFrameSize(const uint8* adts_header) {
  24   return ((static_cast<int>(adts_header[5]) >> 5) |
  25           (static_cast<int>(adts_header[4]) << 3) |
  26           ((static_cast<int>(adts_header[3]) & 0x3) << 11));
  27 }
  28
  29 static size_t ExtractAdtsFrequencyIndex(const uint8* adts_header) {
  30   return ((adts_header[2] >> 2) & 0xf);
  31 }
  32
  33 static size_t ExtractAdtsChannelConfig(const uint8* adts_header) {
  34   return (((adts_header[3] >> 6) & 0x3) |
  35           ((adts_header[2] & 0x1) << 2));
  36 }
  37
  38 // Return true if buf corresponds to an ADTS syncword.
  39 // |buf| size must be at least 2.
  40 static bool isAdtsSyncWord(const uint8* buf) {
  41   // The first 12 bits must be 1.
  42   // The layer field (2 bits) must be set to 0.
  43   return (buf[0] == 0xff) && ((buf[1] & 0xf6) == 0xf0);
  44 }
  45
  46 namespace mp2t {
  47
  48 struct EsParserAdts::AdtsFrame {
  49   // Pointer to the ES data.
  50   const uint8* data;
  51
  52   // Frame size;
  53   int size;
  54
  55   // Frame offset in the ES queue.
  56   int64 queue_offset;
  57 };
  58
  59 bool EsParserAdts::LookForAdtsFrame(AdtsFrame* adts_frame) {
  60   int es_size;
  61   const uint8* es;
  62   es_queue_->Peek(&es, &es_size);
  63
  64   int max_offset = es_size - kADTSHeaderMinSize;
  65   if (max_offset <= 0)
  66     return false;
  67
  68   for (int offset = 0; offset < max_offset; offset++) {
  69     const uint8* cur_buf = &es[offset];
  70     if (!isAdtsSyncWord(cur_buf))
  71       continue;
  72
  73     int frame_size = ExtractAdtsFrameSize(cur_buf);
  74     if (frame_size < kADTSHeaderMinSize) {
  75       // Too short to be an ADTS frame.
  76       continue;
  77     }
  78
  79     int remaining_size = es_size - offset;
  80     if (remaining_size < frame_size) {
  81       // Not a full frame: will resume when we have more data.
  82       es_queue_->Pop(offset);
  83       return false;
  84     }
  85
  86     // Check whether there is another frame
  87     // |size| apart from the current one.
  88     if (remaining_size >= frame_size + 2 &&
  89         !isAdtsSyncWord(&cur_buf[frame_size])) {
  90       continue;
  91     }
  92
  93     es_queue_->Pop(offset);
  94     es_queue_->Peek(&adts_frame->data, &es_size);
  95     adts_frame->queue_offset = es_queue_->head();
  96     adts_frame->size = frame_size;
  97     DVLOG(LOG_LEVEL_ES)
  98         << "ADTS syncword @ pos=" << adts_frame->queue_offset
  99         << " frame_size=" << adts_frame->size;
 100     DVLOG(LOG_LEVEL_ES)
 101         << "ADTS header: "
 102         << base::HexEncode(adts_frame->data, kADTSHeaderMinSize);
 103     return true;
 104   }
 105
 106   es_queue_->Pop(max_offset);
 107   return false;
 108 }
 109
 110 void EsParserAdts::SkipAdtsFrame(const AdtsFrame& adts_frame) {
 111   DCHECK_EQ(adts_frame.queue_offset, es_queue_->head());
 112   es_queue_->Pop(adts_frame.size);
 113 }
 114
 115 EsParserAdts::EsParserAdts(
 116     const NewAudioConfigCB& new_audio_config_cb,
 117     const EmitBufferCB& emit_buffer_cb,
 118     bool sbr_in_mimetype)
 119   : new_audio_config_cb_(new_audio_config_cb),
 120     emit_buffer_cb_(emit_buffer_cb),
 121     sbr_in_mimetype_(sbr_in_mimetype) {
 122 }
 123
 124 EsParserAdts::~EsParserAdts() {
 125 }
 126
 127 bool EsParserAdts::ParseFromEsQueue() {
 128   // Look for every ADTS frame in the ES buffer.
 129   AdtsFrame adts_frame;
 130   while (LookForAdtsFrame(&adts_frame)) {
 131     // Update the audio configuration if needed.
 132     DCHECK_GE(adts_frame.size, kADTSHeaderMinSize);
 133     if (!UpdateAudioConfiguration(adts_frame.data))
 134       return false;
 135
 136     // Get the PTS & the duration of this access unit.
 137     TimingDesc current_timing_desc =
 138         GetTimingDescriptor(adts_frame.queue_offset);
 139     if (current_timing_desc.pts != kNoTimestamp())
 140       audio_timestamp_helper_->SetBaseTimestamp(current_timing_desc.pts);
 141
 142     if (audio_timestamp_helper_->base_timestamp() == kNoTimestamp()) {
 143       DVLOG(1) << "Skipping audio frame with unknown timestamp";
 144       SkipAdtsFrame(adts_frame);
 145       continue;
 146     }
 147     base::TimeDelta current_pts = audio_timestamp_helper_->GetTimestamp();
 148     base::TimeDelta frame_duration =
 149         audio_timestamp_helper_->GetFrameDuration(kSamplesPerAACFrame);
 150
 151     // Emit an audio frame.
 152     bool is_key_frame = true;
 153
 154     // TODO(wolenetz/acolwell): Validate and use a common cross-parser TrackId
 155     // type and allow multiple audio tracks. See https://crbug.com/341581.
 156     scoped_refptr<StreamParserBuffer> stream_parser_buffer =
 157         StreamParserBuffer::CopyFrom(
 158             adts_frame.data,
 159             adts_frame.size,
 160             is_key_frame,
 161             DemuxerStream::AUDIO, 0);
 162     stream_parser_buffer->set_timestamp(current_pts);
 163     stream_parser_buffer->SetDecodeTimestamp(
 164         DecodeTimestamp::FromPresentationTime(current_pts));
 165     stream_parser_buffer->set_duration(frame_duration);
 166     emit_buffer_cb_.Run(stream_parser_buffer);
 167
 168     // Update the PTS of the next frame.
 169     audio_timestamp_helper_->AddFrames(kSamplesPerAACFrame);
 170
 171     // Skip the current frame.
 172     SkipAdtsFrame(adts_frame);
 173   }
 174
 175   return true;
 176 }
 177
 178 void EsParserAdts::Flush() {
 179 }
 180
 181 void EsParserAdts::ResetInternal() {
 182   last_audio_decoder_config_ = AudioDecoderConfig();
 183 }
 184
 185 bool EsParserAdts::UpdateAudioConfiguration(const uint8* adts_header) {
 186   size_t frequency_index = ExtractAdtsFrequencyIndex(adts_header);
 187   if (frequency_index >= kADTSFrequencyTableSize) {
 188     // Frequency index 13 & 14 are reserved
 189     // while 15 means that the frequency is explicitly written
 190     // (not supported).
 191     return false;
 192   }
 193
 194   size_t channel_configuration = ExtractAdtsChannelConfig(adts_header);
 195   if (channel_configuration == 0 ||
 196       channel_configuration >= kADTSChannelLayoutTableSize) {
 197     // TODO(damienv): Add support for inband channel configuration.
 198     return false;
 199   }
 200
 201   // TODO(damienv): support HE-AAC frequency doubling (SBR)
 202   // based on the incoming ADTS profile.
 203   int samples_per_second = kADTSFrequencyTable[frequency_index];
 204   int adts_profile = (adts_header[2] >> 6) & 0x3;
 205
 206   // The following code is written according to ISO 14496 Part 3 Table 1.11 and
 207   // Table 1.22. (Table 1.11 refers to the capping to 48000, Table 1.22 refers
 208   // to SBR doubling the AAC sample rate.)
 209   // TODO(damienv) : Extend sample rate cap to 96kHz for Level 5 content.
 210   int extended_samples_per_second = sbr_in_mimetype_
 211       ? std::min(2 * samples_per_second, 48000)
 212       : samples_per_second;
 213
 214   // The following code is written according to ISO 14496 Part 3 Table 1.13 -
 215   // Syntax of AudioSpecificConfig.
 216   uint16 extra_data_int =
 217       // Note: adts_profile is in the range [0,3], since the ADTS header only
 218       // allows two bits for its value.
 219       ((adts_profile + 1) << 11) +
 220       (frequency_index << 7) +
 221       (channel_configuration << 3);
 222   uint8 extra_data[2] = {
 223       static_cast<uint8>(extra_data_int >> 8),
 224       static_cast<uint8>(extra_data_int & 0xff)
 225   };
 226
 227   AudioDecoderConfig audio_decoder_config(
 228       kCodecAAC,
 229       kSampleFormatS16,
 230       kADTSChannelLayoutTable[channel_configuration],
 231       extended_samples_per_second,
 232       extra_data,
 233       arraysize(extra_data),
 234       false);
 235
 236   if (!audio_decoder_config.Matches(last_audio_decoder_config_)) {
 237     DVLOG(1) << "Sampling frequency: " << samples_per_second;
 238     DVLOG(1) << "Extended sampling frequency: " << extended_samples_per_second;
 239     DVLOG(1) << "Channel config: " << channel_configuration;
 240     DVLOG(1) << "Adts profile: " << adts_profile;
 241     // Reset the timestamp helper to use a new time scale.
 242     if (audio_timestamp_helper_ &&
 243         audio_timestamp_helper_->base_timestamp() != kNoTimestamp()) {
 244       base::TimeDelta base_timestamp = audio_timestamp_helper_->GetTimestamp();
 245       audio_timestamp_helper_.reset(
 246         new AudioTimestampHelper(samples_per_second));
 247       audio_timestamp_helper_->SetBaseTimestamp(base_timestamp);
 248     } else {
 249       audio_timestamp_helper_.reset(
 250           new AudioTimestampHelper(samples_per_second));
 251     }
 252     // Audio config notification.
 253     last_audio_decoder_config_ = audio_decoder_config;
 254     new_audio_config_cb_.Run(audio_decoder_config);
 255   }
 256
 257   return true;
 258 }
 259
 260 }  // namespace mp2t
 261 }  // namespace media