The Tor Browser: content/media/fmp4/demuxer/aac.cc@a63d609f5ebe (annotated)

content/media/fmp4/demuxer/aac.cc@a63d609f5ebe (annotated)

content/media/fmp4/demuxer/aac.cc

Thu, 15 Jan 2015 15:55:04 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 15 Jan 2015 15:55:04 +0100
branch: TOR_BUG_9701
changeset 9: a63d609f5ebe
permissions: -rw-r--r--

Back out 97036ab72558 which inappropriately compared turds to third parties.

 // 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 "mp4_demuxer/aac.h"
 #include <algorithm>
 #include "mp4_demuxer/bit_reader.h"
 namespace mp4_demuxer {
 // The following conversion table is extracted from ISO 14496 Part 3 -
 // Table 1.16 - Sampling Frequency Index.
 static const int kFrequencyMap[] = {
 , 88200, 64000, 48000, 44100, 32000, 24000,
 , 16000, 12000, 11025, 8000, 7350
 };
 static ChannelLayout ConvertChannelConfigToLayout(uint8_t 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;
 }
 AAC::AAC()
     : profile_(0), frequency_index_(0), channel_config_(0), frequency_(0),
       extension_frequency_(0), channel_layout_(CHANNEL_LAYOUT_UNSUPPORTED) {
 }
 AAC::~AAC() {
 }
 bool AAC::Parse(const std::vector<uint8_t>& data) {
   if (data.empty())
     return false;
   BitReader reader(&data[0], data.size());
   uint8_t extension_type = 0;
   bool ps_present = false;
   uint8_t extension_frequency_index = 0xff;
   frequency_ = 0;
   extension_frequency_ = 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_));
   // 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, &extension_frequency_));
     RCHECK(reader.ReadBits(5, &profile_));
   }
   RCHECK(SkipDecoderGASpecificConfig(&reader));
   RCHECK(SkipErrorSpecificConfig());
   // Read extension configuration again
   // Note: The check for 16 available bits comes from the AAC spec.
   if (extension_type != 5 && reader.bits_available() >= 16) {
     uint16_t sync_extension_type;
     uint8_t sbr_present_flag;
     uint8_t ps_present_flag;
     if (reader.ReadBits(11, &sync_extension_type) &&
         sync_extension_type == 0x2b7) {
       if (reader.ReadBits(5, &extension_type) && 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, &extension_frequency_));
           // Note: The check for 12 available bits comes from the AAC spec.
           if (reader.bits_available() >= 12) {
             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(frequency_index_ < arraysize(kFrequencyMap));
     frequency_ = kFrequencyMap[frequency_index_];
   }
   if (extension_frequency_ == 0 && extension_frequency_index != 0xff) {
     RCHECK(extension_frequency_index < arraysize(kFrequencyMap));
     extension_frequency_ = kFrequencyMap[extension_frequency_index];
   }
   // When Parametric Stereo is on, mono will be played as stereo.
   if (ps_present && channel_config_ == 1)
     channel_layout_ = CHANNEL_LAYOUT_STEREO;
   else
     channel_layout_ = ConvertChannelConfigToLayout(channel_config_);
   audio_specific_config_.insert(audio_specific_config_.begin(), data.begin(), data.end());
   return frequency_ != 0 && channel_layout_ != CHANNEL_LAYOUT_UNSUPPORTED &&
       profile_ >= 1 && profile_ <= 4 && frequency_index_ != 0xf &&
       channel_config_ <= 7;
 }
 const std::vector<uint8_t>& AAC::AudioSpecificConfig() const
 {
   return audio_specific_config_;
 }
 int AAC::GetOutputSamplesPerSecond(bool sbr_in_mimetype) const {
   if (extension_frequency_ > 0)
     return extension_frequency_;
   if (!sbr_in_mimetype)
     return frequency_;
   // The following code is written according to ISO 14496 Part 3 Table 1.11 and
   // Table 1.22. (Table 1.11 refers to the capping to 48000, Table 1.22 refers
   // to SBR doubling the AAC sample rate.)
   // TODO(acolwell) : Extend sample rate cap to 96kHz for Level 5 content.
   DCHECK_GT(frequency_, 0);
   return std::min(2 * frequency_, 48000);
 }
 ChannelLayout AAC::GetChannelLayout(bool sbr_in_mimetype) const {
   // Check for implicit signalling of HE-AAC and indicate stereo output
   // if the mono channel configuration is signalled.
   // See ISO-14496-3 Section 1.6.6.1.2 for details about this special casing.
   if (sbr_in_mimetype && channel_config_ == 1)
     return CHANNEL_LAYOUT_STEREO;
   return channel_layout_;
 }
 bool AAC::ConvertEsdsToADTS(std::vector<uint8_t>* buffer) const {
   size_t size = buffer->size() + kADTSHeaderSize;
   DCHECK(profile_ >= 1 && profile_ <= 4 && frequency_index_ != 0xf &&
          channel_config_ <= 7);
   // ADTS header uses 13 bits for packet size.
   if (size >= (1 << 13))
     return false;
   std::vector<uint8_t>& adts = *buffer;
   adts.insert(buffer->begin(), kADTSHeaderSize, 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_t extension_flag = 0;
   uint8_t depends_on_core_coder;
   uint16_t dummy;
   RCHECK(bit_reader->ReadBits(1, &dummy));  // frameLengthFlag
   RCHECK(bit_reader->ReadBits(1, &depends_on_core_coder));
   if (depends_on_core_coder == 1)
     RCHECK(bit_reader->ReadBits(14, &dummy));  // coreCoderDelay
   RCHECK(bit_reader->ReadBits(1, &extension_flag));
   RCHECK(channel_config_ != 0);
   if (profile_ == 6 || profile_ == 20)
     RCHECK(bit_reader->ReadBits(3, &dummy));  // layerNr
   if (extension_flag) {
     if (profile_ == 22) {
       RCHECK(bit_reader->ReadBits(5, &dummy));  // numOfSubFrame
       RCHECK(bit_reader->ReadBits(11, &dummy));  // layer_length
     }
     if (profile_ == 17 || profile_ == 19 || profile_ == 20 || profile_ == 23) {
       RCHECK(bit_reader->ReadBits(3, &dummy));  // resilience flags
     }
     RCHECK(bit_reader->ReadBits(1, &dummy));  // extensionFlag3
   }
   return true;
 }
 }  // namespace mp4_demuxer

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content/media/fmp4/demuxer/aac.cc@a63d609f5ebe (annotated)

content/media/fmp4/demuxer/aac.cc