Mpeg2 TS stream parser for media source.

media/mpeg2/es_parser_adts.cc

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "media/mpeg2/es_parser_adts.h"
+
+#include <list>
+
+#include "base/basictypes.h"
+#include "base/logging.h"
+#include "base/strings/string_number_conversions.h"
+#include "media/base/audio_decoder_config.h"
+#include "media/base/bit_reader.h"
+#include "media/base/channel_layout.h"
+#include "media/base/stream_parser_buffer.h"
+#include "media/mpeg2/mpeg2ts_common.h"
+
+namespace {
+// Adts header is at least 7 bytes (can be 9 bytes).
+const int kAdtsHeaderMinSize = 7;
+
+const int adts_frequency_table[16] = {
+  96000,
+  88200,
+  64000,
+  48000,
+  44100,
+  32000,
+  24000,
+  22050,
+  16000,
+  12000,
+  11025,
+  8000,
+  7350,
+  0,
+  0,
+  0,
+};
+const int kExplicitFrequencyIndex = 15;
+
+media::ChannelLayout adts_channel_layout[8] = {
+  media::CHANNEL_LAYOUT_NONE,
+  media::CHANNEL_LAYOUT_MONO,
+  media::CHANNEL_LAYOUT_STEREO,
+  media::CHANNEL_LAYOUT_SURROUND,
+  media::CHANNEL_LAYOUT_4_0,
+  media::CHANNEL_LAYOUT_5_0_BACK,
+  media::CHANNEL_LAYOUT_5_1_BACK,
+  media::CHANNEL_LAYOUT_7_1,
+};
+
+// Number of samples per frame.
+const int kNumberSamplesPerAACFrame = 1024;
+const int kNumberSamplesPerHeAACFrame = 2048;
+const int kNumberSamplesPerAACLcFrame = 960;
+
+int ExtractAdtsFrameSize(const uint8* adts_header) {
+  int frame_size =
+      (static_cast<int>(adts_header[5]) >> 5) |
+      (static_cast<int>(adts_header[4]) << 3) |
+      ((static_cast<int>(adts_header[3]) & 0x3) << 11);
+  return frame_size;
+}
+
+int ExtractAdtsFrequencyIndex(const uint8* adts_header) {
+  int frequency_index =
+      (adts_header[2] >> 2) & 0xf;
+  return frequency_index;
+}
+
+int ExtractAdtsChannelConfig(const uint8* adts_header) {
+  int channel_config =
+      ((adts_header[3] >> 6) & 0x3) |
+      ((adts_header[2] & 0x1) << 2);
+  return channel_config;
+}
+
+// Look for an ADTS syncword.
+bool LookForSyncWord(const std::vector<uint8>& buf,
+                     int pos,
+                     int* new_pos, int* frame_sz) {
+  int max_offset = buf.size() - kAdtsHeaderMinSize;
+  if (max_offset < 0) {
+    max_offset = 0;
+  }
+
+  for (int offset = pos; offset < max_offset; offset++) {
+    const uint8* cur_buf = &buf[offset];
+
+    if ((cur_buf[0] != 0xff) || ((cur_buf[1] & 0xf6) != 0xf0)) {
+      // The first 12 bits must be 1.
+      // The layer field (2 bits) must be set to 0.
+      continue;
+    }
+
+    int frequency_index = ExtractAdtsFrequencyIndex(cur_buf);
+    if (frequency_index == kExplicitFrequencyIndex) {
+      // 15 is a forbidden value.
+      continue;
+    }
+
+    int frame_size = ExtractAdtsFrameSize(cur_buf);
+    if (frame_size < kAdtsHeaderMinSize) {
+      // Too short to be an ADTS frame.
+      continue;
+    }
+
+    // Check whether there is another frame
+    // |size| apart from the current one.
+    int remaining_size = buf.size() - offset;
+    if (remaining_size >= frame_size + 2) {
+      if ((cur_buf[frame_size] != 0xff) ||
+          (cur_buf[frame_size + 1] & 0xf6) != 0xf0) {
+        continue;
+      }
+    }
+
+    *new_pos = offset;
+    *frame_sz = frame_size;
+    return true;
+  }
+
+  *new_pos = max_offset;
+  return false;
+}
+
+}  // namespace
+
+namespace media {
+namespace mpeg2ts {
+
+EsParserAdts::EsParserAdts(
+    NewAudioConfigCB new_audio_config_cb,
+    EmitBufferCB emit_buffer_cb)
+  : first_frame_(true),
+    new_audio_config_cb_(new_audio_config_cb),
+    emit_buffer_cb_(emit_buffer_cb),
+    is_audio_config_known_(false),
+    sampling_frequency_(0),
+    channel_configuration_(0) {
+}
+
+EsParserAdts::~EsParserAdts() {
+}
+
+void EsParserAdts::Parse(const uint8* buf, int size,
+                         bool is_pts_valid, base::TimeDelta pts,
+                         bool is_dts_valid, base::TimeDelta dts) {
+  // The incoming PTS applies to the access unit that comes just after
+  // the beginning of |buf|.
+  if (is_pts_valid) {
+    pts_list_.push_back(EsPts(raw_es_.size(), pts));
+  }
+
+  // Copy the input data to the ES buffer.
+  int old_size = raw_es_.size();
+  raw_es_.resize(old_size + size);
+  memcpy(&raw_es_[old_size], buf, size);
+
+  // Look for every ADTS frame in the ES buffer starting at offset = 0
+  int es_position = 0;
+  int frame_size;
+  while (LookForSyncWord(raw_es_, es_position,
+                         &es_position, &frame_size)) {
+    VLOG(LOG_LEVEL_ES) << "ADTS syncword @ pos=" << es_position
+                       << " frame_size=" << frame_size;
+    VLOG(LOG_LEVEL_ES) << "ADTS header: "
+                       << base::HexEncode(&raw_es_[es_position], 7);
+
+    // Do not process the frame if this one is a partial frame.
+    int remaining_size = raw_es_.size() - es_position;
+    if (frame_size > remaining_size) {
+      break;
+    }
+
+    // Update the audio configuration if needed.
+    DCHECK_GE(frame_size, kAdtsHeaderMinSize);
+    UpdateAudioConfiguration(&raw_es_[es_position]);
+
+    // Get the PTS of this access unit.
+    base::TimeDelta current_pts = estimated_pts_;
+    while (!pts_list_.empty() &&
+           pts_list_.front().first <= es_position) {
+      current_pts = pts_list_.front().second;
+      pts_list_.pop_front();
+    }
+    VLOG(LOG_LEVEL_ES)
+        << "Current PTS: " << current_pts.InMilliseconds()
+        << " Estimated PTS: " << estimated_pts_.InMilliseconds();
+
+    // Verify that PTS is increasing.
+    if (!first_frame_ && current_pts < last_frame_pts_) {
+      LOG(WARNING) << "ADTS: pts not monotonic";
+    }
+    first_frame_ = false;
+    last_frame_pts_ = current_pts;
+
+    // Emit an audio frame.
+    bool is_key_frame = true;
+    scoped_refptr<StreamParserBuffer> stream_parser_buffer =
+        StreamParserBuffer::CopyFrom(
+            &raw_es_[es_position],
+            frame_size,
+            is_key_frame);
+    stream_parser_buffer->SetDecodeTimestamp(current_pts);
+    stream_parser_buffer->set_timestamp(current_pts);
+    emit_buffer_cb_.Run(stream_parser_buffer);
+
+    // Update the PTS of the next frame.
+    base::TimeDelta frame_duration =
+        base::TimeDelta::FromMicroseconds(
+            (1000000 * kNumberSamplesPerAACFrame) / sampling_frequency_);
+    estimated_pts_ = current_pts + frame_duration;
+
+    // Skip the current frame.
+    es_position += frame_size;
+  }
+
+  // Discard all the bytes that have been processed.
+  DiscardEs(es_position);
+}
+
+void EsParserAdts::Flush() {
+  // All the complete frames have been emitted,
+  // so just clear the ES buffer.
+  raw_es_.clear();
+  pts_list_.clear();
+}
+
+void EsParserAdts::UpdateAudioConfiguration(const uint8* adts_header) {
+  int frequency_index = ExtractAdtsFrequencyIndex(adts_header);
+  if (frequency_index > 12) {
+    // Frequency index 13 & 14 are reserved
+    // while 15 means that the frequency is explicitly written
+    // (not supported).
+    return;
+  }
+  int samples_per_second = adts_frequency_table[frequency_index];
+
+  int channel_configuration = ExtractAdtsChannelConfig(adts_header);
+  int adts_profile = (adts_header[2] >> 6) & 0x3;
+
+#if 0
+  // TODO(damienv): support HE-AAC frequency doubling (SBR)
+  if (adts_profile == kAdtsProfileHeAAC) {
+    samples_per_second *= 2;
+  }
+#endif
+
+  if (!is_audio_config_known_ ||
+      sampling_frequency_ != samples_per_second ||
+      channel_configuration_ != channel_configuration) {
+    is_audio_config_known_ = true;
+    sampling_frequency_ = samples_per_second;
+    channel_configuration_ = channel_configuration;
+
+    LOG(INFO) << "Sampling frequency: " << samples_per_second;
+    LOG(INFO) << "Channel config: " << channel_configuration;
+    LOG(INFO) << "Adts profile: " << adts_profile;
+    AudioDecoderConfig audio_decoder_config(
+        kCodecAAC,
+        kSampleFormatS16,
+        adts_channel_layout[channel_configuration],
+        samples_per_second,
+        NULL, 0,
+        false);
+    new_audio_config_cb_.Run(audio_decoder_config);
+  }
+}
+
+void EsParserAdts::DiscardEs(int nbytes) {
+  if (nbytes <= 0) {
+    return;
+  }
+
+  // Adjust the ES position of each PTS.
+  EsPtsList::iterator it = pts_list_.begin();
+  for (; it != pts_list_.end(); ++it) {
+    it->first -= nbytes;
+  }
+
+  // Discard |nbytes| of ES.
+  int old_size = raw_es_.size();
+  int new_size = old_size - nbytes;
+  CHECK_LE(nbytes, old_size);
+  if (new_size > 0) {
+    memmove(&raw_es_[0], &raw_es_[nbytes], new_size);
+  }
+  raw_es_.resize(new_size);
+}
+
+}  // namespace mpeg2ts
+}  // namespace media