267 lines
8.0 KiB
C++
267 lines
8.0 KiB
C++
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "packager/media/codecs/aac_audio_specific_config.h"
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#include <algorithm>
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#include "packager/base/logging.h"
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#include "packager/media/base/bit_reader.h"
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#include "packager/media/base/rcheck.h"
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namespace {
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// Sampling Frequency Index table, from ISO 14496-3 Table 1.16
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static const uint32_t kSampleRates[] = {96000, 88200, 64000, 48000, 44100,
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32000, 24000, 22050, 16000, 12000,
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11025, 8000, 7350};
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// Channel Configuration table, from ISO 14496-3 Table 1.17
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const uint8_t kChannelConfigs[] = {0, 1, 2, 3, 4, 5, 6, 8};
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} // namespace
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namespace shaka {
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namespace media {
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AACAudioSpecificConfig::AACAudioSpecificConfig() {}
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AACAudioSpecificConfig::~AACAudioSpecificConfig() {}
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bool AACAudioSpecificConfig::Parse(const std::vector<uint8_t>& data) {
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if (data.empty())
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return false;
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BitReader reader(&data[0], data.size());
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uint8_t extension_type = AOT_NULL;
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uint8_t extension_frequency_index = 0xff;
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sbr_present_ = false;
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ps_present_ = false;
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frequency_ = 0;
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extension_frequency_ = 0;
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// The following code is written according to ISO 14496 Part 3 Table 1.13 -
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// Syntax of AudioSpecificConfig.
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// Read base configuration.
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// Audio Object Types specified in ISO 14496-3, Table 1.15.
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RCHECK(reader.ReadBits(5, &audio_object_type_));
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// Audio objects type >=31 is not supported yet.
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RCHECK(audio_object_type_ < 31);
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RCHECK(reader.ReadBits(4, &frequency_index_));
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if (frequency_index_ == 0xf)
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RCHECK(reader.ReadBits(24, &frequency_));
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RCHECK(reader.ReadBits(4, &channel_config_));
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// Read extension configuration.
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if (audio_object_type_ == AOT_SBR || audio_object_type_ == AOT_PS) {
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sbr_present_ = audio_object_type_ == AOT_SBR;
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ps_present_ = audio_object_type_ == AOT_PS;
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extension_type = AOT_SBR;
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RCHECK(reader.ReadBits(4, &extension_frequency_index));
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if (extension_frequency_index == 0xf)
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RCHECK(reader.ReadBits(24, &extension_frequency_));
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RCHECK(reader.ReadBits(5, &audio_object_type_));
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// Audio objects type >=31 is not supported yet.
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RCHECK(audio_object_type_ < 31);
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}
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RCHECK(SkipDecoderGASpecificConfig(&reader));
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RCHECK(SkipErrorSpecificConfig());
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// Read extension configuration again
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// Note: The check for 16 available bits comes from the AAC spec.
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if (extension_type != AOT_SBR && reader.bits_available() >= 16) {
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uint16_t sync_extension_type;
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uint8_t sbr_present_flag;
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uint8_t ps_present_flag;
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if (reader.ReadBits(11, &sync_extension_type) &&
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sync_extension_type == 0x2b7) {
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if (reader.ReadBits(5, &extension_type) && extension_type == 5) {
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RCHECK(reader.ReadBits(1, &sbr_present_flag));
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sbr_present_ = sbr_present_flag != 0;
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if (sbr_present_flag) {
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RCHECK(reader.ReadBits(4, &extension_frequency_index));
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if (extension_frequency_index == 0xf)
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RCHECK(reader.ReadBits(24, &extension_frequency_));
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// Note: The check for 12 available bits comes from the AAC spec.
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if (reader.bits_available() >= 12) {
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RCHECK(reader.ReadBits(11, &sync_extension_type));
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if (sync_extension_type == 0x548) {
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RCHECK(reader.ReadBits(1, &ps_present_flag));
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ps_present_ = ps_present_flag != 0;
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}
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}
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}
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}
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}
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}
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if (frequency_ == 0) {
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RCHECK(frequency_index_ < arraysize(kSampleRates));
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frequency_ = kSampleRates[frequency_index_];
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}
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if (extension_frequency_ == 0 && extension_frequency_index != 0xff) {
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RCHECK(extension_frequency_index < arraysize(kSampleRates));
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extension_frequency_ = kSampleRates[extension_frequency_index];
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}
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RCHECK(channel_config_ < arraysize(kChannelConfigs));
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num_channels_ = kChannelConfigs[channel_config_];
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return frequency_ != 0 && num_channels_ != 0 && audio_object_type_ >= 1 &&
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audio_object_type_ <= 4 && frequency_index_ != 0xf &&
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channel_config_ <= 7;
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}
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bool AACAudioSpecificConfig::ConvertToADTS(std::vector<uint8_t>* buffer) const {
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size_t size = buffer->size() + kADTSHeaderSize;
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DCHECK(audio_object_type_ >= 1 && audio_object_type_ <= 4 &&
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frequency_index_ != 0xf && channel_config_ <= 7);
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// ADTS header uses 13 bits for packet size.
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if (size >= (1 << 13))
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return false;
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std::vector<uint8_t>& adts = *buffer;
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adts.insert(buffer->begin(), kADTSHeaderSize, 0);
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adts[0] = 0xff;
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adts[1] = 0xf1;
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adts[2] = ((audio_object_type_ - 1) << 6) + (frequency_index_ << 2) +
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(channel_config_ >> 2);
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adts[3] = ((channel_config_ & 0x3) << 6) + static_cast<uint8_t>(size >> 11);
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adts[4] = static_cast<uint8_t>((size & 0x7ff) >> 3);
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adts[5] = static_cast<uint8_t>(((size & 7) << 5) + 0x1f);
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adts[6] = 0xfc;
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return true;
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}
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AACAudioSpecificConfig::AudioObjectType
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AACAudioSpecificConfig::GetAudioObjectType() const {
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if (ps_present_)
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return AOT_PS;
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if (sbr_present_)
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return AOT_SBR;
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return audio_object_type_;
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}
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uint32_t AACAudioSpecificConfig::GetSamplesPerSecond() const {
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if (extension_frequency_ > 0)
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return extension_frequency_;
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if (!sbr_present_)
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return frequency_;
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// The following code is written according to ISO 14496 Part 3 Table 1.11 and
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// Table 1.22. (Table 1.11 refers to the capping to 48000, Table 1.22 refers
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// to SBR doubling the AAC sample rate.)
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DCHECK_GT(frequency_, 0u);
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return std::min(2 * frequency_, 48000u);
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}
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uint8_t AACAudioSpecificConfig::GetNumChannels() const {
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// Check for implicit signalling of HE-AAC and indicate stereo output
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// if the mono channel configuration is signalled.
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// See ISO-14496-3 Section 1.6.6.1.2 for details about this special casing.
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if (sbr_present_ && channel_config_ == 1)
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return 2; // CHANNEL_LAYOUT_STEREO
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// When Parametric Stereo is on, mono will be played as stereo.
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if (ps_present_ && channel_config_ == 1)
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return 2; // CHANNEL_LAYOUT_STEREO
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return num_channels_;
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}
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// Currently this function only support GASpecificConfig defined in
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// ISO 14496 Part 3 Table 4.1 - Syntax of GASpecificConfig()
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bool AACAudioSpecificConfig::SkipDecoderGASpecificConfig(BitReader* bit_reader) const {
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switch (audio_object_type_) {
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case 1:
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case 2:
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case 3:
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case 4:
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case 6:
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case 7:
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case 17:
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case 19:
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case 20:
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case 21:
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case 22:
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case 23:
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return SkipGASpecificConfig(bit_reader);
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default:
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break;
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}
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return false;
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}
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bool AACAudioSpecificConfig::SkipErrorSpecificConfig() const {
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switch (audio_object_type_) {
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case 17:
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case 19:
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case 20:
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case 21:
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case 22:
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case 23:
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case 24:
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case 25:
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case 26:
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case 27:
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return false;
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default:
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break;
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}
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return true;
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}
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// The following code is written according to ISO 14496 part 3 Table 4.1 -
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// GASpecificConfig.
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bool AACAudioSpecificConfig::SkipGASpecificConfig(BitReader* bit_reader) const {
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uint8_t extension_flag = 0;
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uint8_t depends_on_core_coder;
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uint16_t dummy;
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RCHECK(bit_reader->ReadBits(1, &dummy)); // frameLengthFlag
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RCHECK(bit_reader->ReadBits(1, &depends_on_core_coder));
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if (depends_on_core_coder == 1)
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RCHECK(bit_reader->ReadBits(14, &dummy)); // coreCoderDelay
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RCHECK(bit_reader->ReadBits(1, &extension_flag));
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RCHECK(channel_config_ != 0);
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if (audio_object_type_ == 6 || audio_object_type_ == 20)
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RCHECK(bit_reader->ReadBits(3, &dummy)); // layerNr
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if (extension_flag) {
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if (audio_object_type_ == 22) {
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RCHECK(bit_reader->ReadBits(5, &dummy)); // numOfSubFrame
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RCHECK(bit_reader->ReadBits(11, &dummy)); // layer_length
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}
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if (audio_object_type_ == 17 || audio_object_type_ == 19 ||
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audio_object_type_ == 20 || audio_object_type_ == 23) {
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RCHECK(bit_reader->ReadBits(3, &dummy)); // resilience flags
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}
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RCHECK(bit_reader->ReadBits(1, &dummy)); // extensionFlag3
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}
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return true;
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}
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} // namespace media
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} // namespace shaka
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