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.
5 #include "media/formats/mp2t/es_parser_adts.h"
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/mp2t/mp2t_common.h"
18 #include "media/formats/mpeg/adts_constants.h"
22 static int ExtractAdtsFrameSize(const uint8* adts_header) {
23 return ((static_cast<int>(adts_header[5]) >> 5) |
24 (static_cast<int>(adts_header[4]) << 3) |
25 ((static_cast<int>(adts_header[3]) & 0x3) << 11));
28 static size_t ExtractAdtsFrequencyIndex(const uint8* adts_header) {
29 return ((adts_header[2] >> 2) & 0xf);
32 static size_t ExtractAdtsChannelConfig(const uint8* adts_header) {
33 return (((adts_header[3] >> 6) & 0x3) |
34 ((adts_header[2] & 0x1) << 2));
37 // Return true if buf corresponds to an ADTS syncword.
38 // |buf| size must be at least 2.
39 static bool isAdtsSyncWord(const uint8* buf) {
40 return (buf[0] == 0xff) && ((buf[1] & 0xf6) == 0xf0);
43 // Look for an ADTS syncword.
45 // - either the byte position of the ADTS frame (if found)
46 // - or the byte position of 1st byte that was not processed (if not found).
47 // In every case, the returned value in |new_pos| is such that new_pos >= pos
48 // |frame_sz| returns the size of the ADTS frame (if found).
49 // Return whether a syncword was found.
50 static bool LookForSyncWord(const uint8* raw_es, int raw_es_size,
52 int* new_pos, int* frame_sz) {
54 DCHECK_LE(pos, raw_es_size);
56 int max_offset = raw_es_size - kADTSHeaderMinSize;
57 if (pos >= max_offset) {
58 // Do not change the position if:
59 // - max_offset < 0: not enough bytes to get a full header
60 // Since pos >= 0, this is a subcase of the next condition.
61 // - pos >= max_offset: might be the case after reading one full frame,
62 // |pos| is then incremented by the frame size and might then point
63 // to the end of the buffer.
68 for (int offset = pos; offset < max_offset; offset++) {
69 const uint8* cur_buf = &raw_es[offset];
71 if (!isAdtsSyncWord(cur_buf))
72 // The first 12 bits must be 1.
73 // The layer field (2 bits) must be set to 0.
76 int frame_size = ExtractAdtsFrameSize(cur_buf);
77 if (frame_size < kADTSHeaderMinSize) {
78 // Too short to be an ADTS frame.
82 // Check whether there is another frame
83 // |size| apart from the current one.
84 int remaining_size = raw_es_size - offset;
85 if (remaining_size >= frame_size + 2 &&
86 !isAdtsSyncWord(&cur_buf[frame_size])) {
91 *frame_sz = frame_size;
95 *new_pos = max_offset;
101 EsParserAdts::EsParserAdts(
102 const NewAudioConfigCB& new_audio_config_cb,
103 const EmitBufferCB& emit_buffer_cb,
104 bool sbr_in_mimetype)
105 : new_audio_config_cb_(new_audio_config_cb),
106 emit_buffer_cb_(emit_buffer_cb),
107 sbr_in_mimetype_(sbr_in_mimetype) {
110 EsParserAdts::~EsParserAdts() {
113 bool EsParserAdts::Parse(const uint8* buf, int size,
115 base::TimeDelta dts) {
119 // The incoming PTS applies to the access unit that comes just after
120 // the beginning of |buf|.
121 if (pts != kNoTimestamp()) {
122 es_byte_queue_.Peek(&raw_es, &raw_es_size);
123 pts_list_.push_back(EsPts(raw_es_size, pts));
126 // Copy the input data to the ES buffer.
127 es_byte_queue_.Push(buf, size);
128 es_byte_queue_.Peek(&raw_es, &raw_es_size);
130 // Look for every ADTS frame in the ES buffer starting at offset = 0
133 while (LookForSyncWord(raw_es, raw_es_size, es_position,
134 &es_position, &frame_size)) {
136 << "ADTS syncword @ pos=" << es_position
137 << " frame_size=" << frame_size;
140 << base::HexEncode(&raw_es[es_position], kADTSHeaderMinSize);
142 // Do not process the frame if this one is a partial frame.
143 int remaining_size = raw_es_size - es_position;
144 if (frame_size > remaining_size)
147 // Update the audio configuration if needed.
148 DCHECK_GE(frame_size, kADTSHeaderMinSize);
149 if (!UpdateAudioConfiguration(&raw_es[es_position]))
152 // Get the PTS & the duration of this access unit.
153 while (!pts_list_.empty() &&
154 pts_list_.front().first <= es_position) {
155 audio_timestamp_helper_->SetBaseTimestamp(pts_list_.front().second);
156 pts_list_.pop_front();
159 base::TimeDelta current_pts = audio_timestamp_helper_->GetTimestamp();
160 base::TimeDelta frame_duration =
161 audio_timestamp_helper_->GetFrameDuration(kSamplesPerAACFrame);
163 // Emit an audio frame.
164 bool is_key_frame = true;
166 // TODO(wolenetz/acolwell): Validate and use a common cross-parser TrackId
167 // type and allow multiple audio tracks. See https://crbug.com/341581.
168 scoped_refptr<StreamParserBuffer> stream_parser_buffer =
169 StreamParserBuffer::CopyFrom(
170 &raw_es[es_position],
173 DemuxerStream::AUDIO, 0);
174 stream_parser_buffer->SetDecodeTimestamp(current_pts);
175 stream_parser_buffer->set_timestamp(current_pts);
176 stream_parser_buffer->set_duration(frame_duration);
177 emit_buffer_cb_.Run(stream_parser_buffer);
179 // Update the PTS of the next frame.
180 audio_timestamp_helper_->AddFrames(kSamplesPerAACFrame);
182 // Skip the current frame.
183 es_position += frame_size;
186 // Discard all the bytes that have been processed.
187 DiscardEs(es_position);
192 void EsParserAdts::Flush() {
195 void EsParserAdts::Reset() {
196 es_byte_queue_.Reset();
198 last_audio_decoder_config_ = AudioDecoderConfig();
201 bool EsParserAdts::UpdateAudioConfiguration(const uint8* adts_header) {
202 size_t frequency_index = ExtractAdtsFrequencyIndex(adts_header);
203 if (frequency_index >= kADTSFrequencyTableSize) {
204 // Frequency index 13 & 14 are reserved
205 // while 15 means that the frequency is explicitly written
210 size_t channel_configuration = ExtractAdtsChannelConfig(adts_header);
211 if (channel_configuration == 0 ||
212 channel_configuration >= kADTSChannelLayoutTableSize) {
213 // TODO(damienv): Add support for inband channel configuration.
217 // TODO(damienv): support HE-AAC frequency doubling (SBR)
218 // based on the incoming ADTS profile.
219 int samples_per_second = kADTSFrequencyTable[frequency_index];
220 int adts_profile = (adts_header[2] >> 6) & 0x3;
222 // The following code is written according to ISO 14496 Part 3 Table 1.11 and
223 // Table 1.22. (Table 1.11 refers to the capping to 48000, Table 1.22 refers
224 // to SBR doubling the AAC sample rate.)
225 // TODO(damienv) : Extend sample rate cap to 96kHz for Level 5 content.
226 int extended_samples_per_second = sbr_in_mimetype_
227 ? std::min(2 * samples_per_second, 48000)
228 : samples_per_second;
230 // The following code is written according to ISO 14496 Part 3 Table 1.13 -
231 // Syntax of AudioSpecificConfig.
232 uint16 extra_data_int =
233 // Note: adts_profile is in the range [0,3], since the ADTS header only
234 // allows two bits for its value.
235 ((adts_profile + 1) << 11) +
236 (frequency_index << 7) +
237 (channel_configuration << 3);
238 uint8 extra_data[2] = {
239 static_cast<uint8>(extra_data_int >> 8),
240 static_cast<uint8>(extra_data_int & 0xff)
243 AudioDecoderConfig audio_decoder_config(
246 kADTSChannelLayoutTable[channel_configuration],
247 extended_samples_per_second,
249 arraysize(extra_data),
252 if (!audio_decoder_config.Matches(last_audio_decoder_config_)) {
253 DVLOG(1) << "Sampling frequency: " << samples_per_second;
254 DVLOG(1) << "Extended sampling frequency: " << extended_samples_per_second;
255 DVLOG(1) << "Channel config: " << channel_configuration;
256 DVLOG(1) << "Adts profile: " << adts_profile;
257 // Reset the timestamp helper to use a new time scale.
258 if (audio_timestamp_helper_) {
259 base::TimeDelta base_timestamp = audio_timestamp_helper_->GetTimestamp();
260 audio_timestamp_helper_.reset(
261 new AudioTimestampHelper(samples_per_second));
262 audio_timestamp_helper_->SetBaseTimestamp(base_timestamp);
264 audio_timestamp_helper_.reset(
265 new AudioTimestampHelper(samples_per_second));
267 // Audio config notification.
268 last_audio_decoder_config_ = audio_decoder_config;
269 new_audio_config_cb_.Run(audio_decoder_config);
275 void EsParserAdts::DiscardEs(int nbytes) {
276 DCHECK_GE(nbytes, 0);
280 // Adjust the ES position of each PTS.
281 for (EsPtsList::iterator it = pts_list_.begin(); it != pts_list_.end(); ++it)
284 // Discard |nbytes| of ES.
285 es_byte_queue_.Pop(nbytes);