Add HE AAC support to ISO BMFF.

media/mp4/aac.cc

+// Copyright (c) 2012 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/mp4/aac.h"
+
+#include "base/logging.h"
+#include "media/base/bit_reader.h"
+#include "media/mp4/rcheck.h"
+
+// The following conversion table is extracted from ISO 14496 Part 3 -
+// Table 1.16 - Sampling Frequency Index.
+static const uint32 kFrequencyMap[] = {
+  96000, 88200, 64000, 48000, 44100, 32000, 24000,
+  22050, 16000, 12000, 11025, 8000, 7350
+};
+
+static ChannelLayout GetChannelLayout(uint8 channel_config) {
+  switch (channel_config) {
+    case 1:
+      return CHANNEL_LAYOUT_MONO;
+    case 2:
+      return CHANNEL_LAYOUT_STEREO;
+    case 3:
+      return CHANNEL_LAYOUT_SURROUND;
+    case 4:
+      return CHANNEL_LAYOUT_4_0;
+    case 5:
+      return CHANNEL_LAYOUT_5_0;
+    case 6:
+      return CHANNEL_LAYOUT_5_1;
+    case 8:
+      return CHANNEL_LAYOUT_7_1;
+    default:
+      break;
+  }
+
+  return CHANNEL_LAYOUT_UNSUPPORTED;
+}
+
+namespace media {
+
+namespace mp4 {
+
+AAC::AAC()
+    : profile_(0), frequency_index_(0), channel_config_(0), frequency_(0),
+      channel_layout_(CHANNEL_LAYOUT_UNSUPPORTED) {
+}
+
+AAC::~AAC() {
+}
+
+bool AAC::Parse(const std::vector<uint8>& data) {
+  BitReader reader(&data[0], data.size());
+  uint8 extension_type = 0;
+  bool ps_present = false;
+  uint8 extension_frequency_index;
+
+  profile_ = 0;
+  frequency_index_ = 0;
+  frequency_ = 0;
+  channel_config_ = 0;
+
+  // The following code is written according to ISO 14496 Part 3 Table 1.13 -
+  // Syntax of AudioSpecificConfig.
+
+  // Read base configuration
+  RCHECK(reader.ReadBits(5, &profile_));
+  RCHECK(reader.ReadBits(4, &frequency_index_));
+  if (frequency_index_ == 0xf)
+    RCHECK(reader.ReadBits(24, &frequency_));
+  RCHECK(reader.ReadBits(4, &channel_config_));
+
+  extension_frequency_index = frequency_index_;
+
+  // Read extension configuration
+  if (profile_ == 5 || profile_ == 29) {
+    ps_present = (profile_ == 29);
+    extension_type = 5;
+    RCHECK(reader.ReadBits(4, &extension_frequency_index));
+    if (extension_frequency_index == 0xf)
+      RCHECK(reader.ReadBits(24, &frequency_));
+    RCHECK(reader.ReadBits(5, &profile_));
+  }
+
+  RCHECK(SkipDecoderGASpecificConfig(&reader));
+  RCHECK(SkipErrorSpecificConfig());
+
+  // Read extension configuration again
+  if (extension_type != 5 && reader.NumBitsLeft() >= 16) {

[Ami GONE FROM CHROMIUM, 2012/07/17 23:22:18]

What does it mean if extension_type != 5 but NumBitsLeft()==15?  Isn't that a
malformed stream that should return false from this method?

[xiaomings, 2012/07/19 00:16:32]

Remove the check and let the underlying code to check if it is valid.

+    uint16 sync_extension_type;
+    uint8 sbr_present_flag;
+    uint8 ps_present_flag;
+
+    RCHECK(reader.ReadBits(11, &sync_extension_type));
+
+    if (sync_extension_type == 0x2b7) {
+      RCHECK(reader.ReadBits(5, &extension_type));
+
+      if (extension_type == 5) {
+        RCHECK(reader.ReadBits(1, &sbr_present_flag));
+
+        if (sbr_present_flag) {
+          RCHECK(reader.ReadBits(4, &extension_frequency_index));
+
+          if (extension_frequency_index == 0xf)
+            RCHECK(reader.ReadBits(24, &frequency_));
+
+          RCHECK(reader.ReadBits(11, &sync_extension_type));
+
+          if (sync_extension_type == 0x548) {
+            RCHECK(reader.ReadBits(1, &ps_present_flag));
+            ps_present = ps_present_flag != 0;
+          }
+        }
+      }
+    }
+  }
+
+  if (frequency_ == 0) {
+    RCHECK(extension_frequency_index < arraysize(kFrequencyMap));
+    frequency_ = kFrequencyMap[extension_frequency_index];
+  }
+
+  // When Parametric Stereo is on, mono will be played as stereo.
+  if (ps_present && channel_config_ == 1)
+    channel_layout_ = GetChannelLayout(channel_config_ + 1);
+  else
+    channel_layout_ = GetChannelLayout(channel_config_);
+
+  return frequency_ != 0 && channel_layout_ != CHANNEL_LAYOUT_UNSUPPORTED &&
+      profile_ >= 1 && profile_ <= 4 && frequency_index_ != 0xf &&
+      channel_config_ <= 7;
+}
+
+uint32 AAC::frequency() const {
+  return frequency_;
+}
+
+ChannelLayout AAC::channel_layout() const {
+  return channel_layout_;
+}
+
+bool AAC::ConvertEsdsToADTS(std::vector<uint8>* buffer) const {
+  size_t size = buffer->size() + 7;
+
+  DCHECK(profile_ >= 1 && profile_ <= 4 && frequency_index_ != 0xf &&
+         channel_config_ <= 7);
+
+  // ADTS header uses 13 bits for packet size.
+  if (size > (1 << 13) - 1)
+    return false;
+
+  std::vector<uint8>& adts = *buffer;
+
+  adts.insert(buffer->begin(), 7, 0);
+  adts[0] = 0xff;
+  adts[1] = 0xf1;
+  adts[2] = ((profile_ - 1) << 6) + (frequency_index_ << 2) +
+      (channel_config_ >> 2);
+  adts[3] = ((channel_config_ & 0x3) << 6) + (size >> 11);
+  adts[4] = (size & 0x7ff) >> 3;
+  adts[5] = ((size & 7) << 5) + 0x1f;
+  adts[6] = 0xfc;
+
+  return true;
+}
+
+// Currently this function only support GASpecificConfig defined in
+// ISO 14496 Part 3 Table 4.1 - Syntax of GASpecificConfig()
+bool AAC::SkipDecoderGASpecificConfig(BitReader* bit_reader) const {
+  switch (profile_) {
+    case 1:
+    case 2:
+    case 3:
+    case 4:
+    case 6:
+    case 7:
+    case 17:
+    case 19:
+    case 20:
+    case 21:
+    case 22:
+    case 23:
+      return SkipGASpecificConfig(bit_reader);
+    default:
+      break;
+  }
+
+  return false;
+}
+
+bool AAC::SkipErrorSpecificConfig() const {
+  switch (profile_) {
+    case 17:
+    case 19:
+    case 20:
+    case 21:
+    case 22:
+    case 23:
+    case 24:
+    case 25:
+    case 26:
+    case 27:
+      return false;
+    default:
+      break;
+  }
+
+  return true;
+}
+
+// The following code is written according to ISO 14496 part 3 Table 4.1 -
+// GASpecificConfig.
+bool AAC::SkipGASpecificConfig(BitReader* bit_reader) const {
+  uint8 extension_flag = 0;
+  uint8 depends_on_core_coder;
+
+  RCHECK(bit_reader->SkipBits(1));  // frameLengthFlag
+  RCHECK(bit_reader->ReadBits(1, &depends_on_core_coder));
+  if (depends_on_core_coder == 1)
+    RCHECK(bit_reader->SkipBits(14));  // coreCoderDelay
+
+  RCHECK(bit_reader->ReadBits(1, &extension_flag));
+  RCHECK(channel_config_ != 0);
+
+  if (profile_ == 6 || profile_ == 20)
+    RCHECK(bit_reader->SkipBits(3));
+
+  if (extension_flag) {
+    if (profile_ == 22) {
+      RCHECK(bit_reader->SkipBits(5));
+      RCHECK(bit_reader->SkipBits(11));
+    }
+
+    if (profile_ == 17 || profile_ == 19 || profile_ == 20 || profile_ == 23) {
+      RCHECK(bit_reader->SkipBits(1));
+      RCHECK(bit_reader->SkipBits(1));
+      RCHECK(bit_reader->SkipBits(1));
+    }
+
+    RCHECK(bit_reader->SkipBits(1));
+  }
+
+  return true;
+}
+
+}  // namespace mp4
+
+}  // namespace media