125 lines
4.0 KiB
C++
125 lines
4.0 KiB
C++
// Copyright 2014 Google Inc. All rights reserved.
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//
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file or at
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// https://developers.google.com/open-source/licenses/bsd
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#include "packager/media/formats/mp2t/adts_header.h"
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#include "packager/media/base/bit_reader.h"
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#include "packager/media/base/bit_writer.h"
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#include "packager/media/formats/mp2t/mp2t_common.h"
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namespace {
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const size_t kAdtsHeaderMinSize = 7;
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// The following conversion table is extracted from ISO 14496 Part 3 -
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// Table 1.16 - Sampling Frequency Index.
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const int kAdtsFrequencyTable[] = {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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const size_t kAdtsFrequencyTableSize = arraysize(kAdtsFrequencyTable);
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// The following conversion table is extracted from ISO 14496 Part 3 -
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// Table 1.17 - Channel Configuration.
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const int kAdtsNumChannelsTable[] = {0, 1, 2, 3, 4, 5, 6, 8};
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const size_t kAdtsNumChannelsTableSize = arraysize(kAdtsNumChannelsTable);
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} // namespace
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namespace shaka {
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namespace media {
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namespace mp2t {
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bool AdtsHeader::IsSyncWord(const uint8_t* buf) const {
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return (buf[0] == 0xff) && ((buf[1] & 0xf6) == 0xf0);
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}
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size_t AdtsHeader::GetMinFrameSize() const {
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return kAdtsHeaderMinSize + 1;
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}
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size_t AdtsHeader::GetSamplesPerFrame() const {
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const size_t kSamplesPerAacFrame = 1024;
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return kSamplesPerAacFrame;
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}
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bool AdtsHeader::Parse(const uint8_t* adts_frame, size_t adts_frame_size) {
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CHECK(adts_frame);
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if (adts_frame_size < kAdtsHeaderMinSize)
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return false;
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BitReader frame(adts_frame, adts_frame_size);
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// Verify frame starts with sync bits (0xfff).
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uint32_t sync;
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RCHECK(frame.ReadBits(12, &sync));
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RCHECK(sync == 0xfff);
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// Skip MPEG version and layer.
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RCHECK(frame.SkipBits(3));
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RCHECK(frame.ReadBits(1, &protection_absent_));
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RCHECK(frame.ReadBits(2, &profile_));
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RCHECK(frame.ReadBits(4, &sampling_frequency_index_));
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RCHECK(sampling_frequency_index_ < kAdtsFrequencyTableSize);
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// Skip private stream bit.
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RCHECK(frame.SkipBits(1));
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RCHECK(frame.ReadBits(3, &channel_configuration_));
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RCHECK(channel_configuration_ < kAdtsNumChannelsTableSize);
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// Skip originality, home and copyright info.
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RCHECK(frame.SkipBits(4));
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RCHECK(frame.ReadBits(13, &frame_size_));
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// Skip buffer fullness indicator.
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RCHECK(frame.SkipBits(11));
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uint8_t num_blocks_minus_1;
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RCHECK(frame.ReadBits(2, &num_blocks_minus_1));
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if (num_blocks_minus_1) {
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NOTIMPLEMENTED() << "ADTS frames with more than one data block "
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"not supported.";
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return false;
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}
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return true;
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}
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size_t AdtsHeader::GetHeaderSize() const {
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const size_t kCrcSize = sizeof(uint16_t);
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return kAdtsHeaderMinSize + (protection_absent_ ? 0 : kCrcSize);
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}
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size_t AdtsHeader::GetFrameSize() const {
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return frame_size_;
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}
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size_t AdtsHeader::GetFrameSizeWithoutParsing(const uint8_t* data,
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size_t num_bytes) const {
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DCHECK_GT(num_bytes, static_cast<size_t>(5));
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return ((static_cast<int>(data[5]) >> 5) | (static_cast<int>(data[4]) << 3) |
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((static_cast<int>(data[3]) & 0x3) << 11));
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}
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void AdtsHeader::GetAudioSpecificConfig(std::vector<uint8_t>* buffer) const {
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DCHECK(buffer);
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buffer->clear();
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BitWriter config(buffer);
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config.WriteBits(GetObjectType(), 5);
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config.WriteBits(sampling_frequency_index_, 4);
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config.WriteBits(channel_configuration_, 4);
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config.Flush();
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}
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uint8_t AdtsHeader::GetObjectType() const {
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return profile_ + 1;
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}
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uint32_t AdtsHeader::GetSamplingFrequency() const {
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DCHECK_LT(sampling_frequency_index_, kAdtsFrequencyTableSize);
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return kAdtsFrequencyTable[sampling_frequency_index_];
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}
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uint8_t AdtsHeader::GetNumChannels() const {
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DCHECK_LT(channel_configuration_, kAdtsNumChannelsTableSize);
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return kAdtsNumChannelsTable[channel_configuration_];
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}
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} // namespace mp2t
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} // namespace media
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} // namespace shaka
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