115 lines
3.3 KiB
C++
115 lines
3.3 KiB
C++
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// 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 "adts_header.h"
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#include "media/base/bit_reader.h"
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#include "media/formats/mp2t/mp2t_common.h"
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#include "media/formats/mpeg/adts_constants.h"
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namespace media {
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namespace mp2t {
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AdtsHeader::AdtsHeader()
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: valid_config_(false),
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profile_(0),
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sampling_frequency_index_(0),
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channel_configuration_(0) {}
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size_t AdtsHeader::GetAdtsFrameSize(const uint8* data, size_t num_bytes) {
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if (num_bytes < 6)
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return 0;
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return ((static_cast<int>(data[5]) >> 5) |
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(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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size_t AdtsHeader::GetAdtsHeaderSize(const uint8* data, size_t num_bytes) {
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if (num_bytes < 2)
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return 0;
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if (data[1] & 0x01)
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return kAdtsHeaderMinSize;
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return kAdtsHeaderMinSize + sizeof(uint16); // Header + CRC.
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}
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bool AdtsHeader::Parse(
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const uint8* adts_frame, size_t adts_frame_size) {
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CHECK(adts_frame);
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valid_config_ = 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 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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// Get "protection absent" flag.
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bool protection_absent;
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RCHECK(frame.ReadBits(1, &protection_absent));
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// Get profile.
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RCHECK(frame.ReadBits(2, &profile_));
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// Get sampling frequency.
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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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// Get number of audio channels.
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RCHECK(frame.ReadBits(3, &channel_configuration_));
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RCHECK((channel_configuration_ > 0) &&
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(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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// Verify that the frame size matches input parameters.
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uint16 frame_size;
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RCHECK(frame.ReadBits(13, &frame_size));
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RCHECK(frame_size == adts_frame_size);
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// Skip buffer fullness indicator.
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RCHECK(frame.SkipBits(11));
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uint8 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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valid_config_ = true;
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return true;
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}
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bool AdtsHeader::GetAudioSpecificConfig(
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std::vector<uint8>* buffer) const {
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DCHECK(buffer);
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if (!valid_config_)
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return false;
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buffer->resize(2);
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(*buffer)[0] = ((profile_ + 1) << 3) | (sampling_frequency_index_ >> 1);
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(*buffer)[1] = ((sampling_frequency_index_ & 1) << 7) |
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(channel_configuration_ << 3);
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return true;
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}
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uint8 AdtsHeader::GetObjectType() const {
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return profile_ + 1;
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}
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uint32 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 AdtsHeader::GetNumChannels() const {
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DCHECK_GT(channel_configuration_, 0);
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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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